Author Topic: Cleaning up solder from a stubborn thruhole  (Read 13118 times)

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Offline lpc32

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Cleaning up solder from a stubborn thruhole
« on: November 12, 2014, 10:33:32 pm »
I've desoldered a capacitor, which wasn't that difficult, and am now trying to clean up the holes. One was easy enough. The other (the positive), not at all. So far it resisted: manual sucker, braid, flux, adding solder, all of the above on both sides, and temperatures at least up to 450C (I think more). It was partially unclogged after one of the cleaning attempts but after adding solder I can't even get the solder on the side opposite the iron to melt.

It's on an old low-end graphics card, I don't think there are too many layers.

Edit: Photos in a later post.
« Last Edit: November 16, 2014, 03:08:36 pm by lpc32 »
 

Offline krivx

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Re: Cleaning up solder from a stubborn thruhole
« Reply #1 on: November 12, 2014, 10:35:53 pm »
Sometimes force is the only thing that can work. A de-soldering station with vacuum pump would probably clear it. If you don't have one you could try heating it and poking out the solder with something like a toothpick before it solidifies.
 

Offline kxenos

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Re: Cleaning up solder from a stubborn thruhole
« Reply #2 on: November 12, 2014, 10:39:06 pm »
1. Take an unused resistor and while heating from one side push the lead from the other and don't stop moving the resistor until the pad gets cold
2. while heating the pad blow air with a high pressure air gun if you have one
3. Don't do anything, and when you place the new part just keep this pad melted so the new part will slide through
 

Online Alex Eisenhut

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Offline AG6QR

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Re: Cleaning up solder from a stubborn thruhole
« Reply #4 on: November 13, 2014, 12:33:43 am »
kxenos has some very good suggestions.  I'll add one more that has worked for me.

Use that copper braid you had been using, but before you start, put some rosin flux on it.  Sometimes that will make the difference and help the braid to suck up the solder.
 

Offline BradC

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Re: Cleaning up solder from a stubborn thruhole
« Reply #5 on: November 13, 2014, 01:06:37 am »
If you take tip no 1 from kxenos above and substitute a stainless steel sewing needle for the resistor lead you'll get great results. Solder won't touch the stainless steel and it just pushes the solder out of the way. I used to do that when replacing caps on 8 layer boards with big ground planes before I bought a desoldering gun.

The tip from AG6QR about the extra flux is a winner too. Flux always makes things easier.
 


Online Alex Eisenhut

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Re: Cleaning up solder from a stubborn thruhole
« Reply #7 on: November 13, 2014, 01:15:03 am »
http://www.ebay.com/itm/61-80-MICRO-MINI-PIN-NUMBER-WIRE-SIZES-NUMBERED-DRILL-BIT-TOOL-SET-KIT-INDEX-/320886280065?pt=LH_DefaultDomain_0&hash=item4ab6500f81

I would be careful with these - they can take out the through-hole plating

The solder is far softer than the copper. Use a bit just over the size of the cap's lead and use a hand tool. You just get a nice little spiral of solder coming out, there you go. No heat, flux, or braid.
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Offline krivx

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Re: Cleaning up solder from a stubborn thruhole
« Reply #8 on: November 13, 2014, 01:20:45 am »
http://www.ebay.com/itm/61-80-MICRO-MINI-PIN-NUMBER-WIRE-SIZES-NUMBERED-DRILL-BIT-TOOL-SET-KIT-INDEX-/320886280065?pt=LH_DefaultDomain_0&hash=item4ab6500f81

I would be careful with these - they can take out the through-hole plating

The solder is far softer than the copper. Use a bit just over the size of the cap's lead and use a hand tool. You just get a nice little spiral of solder coming out, there you go. No heat, flux, or braid.

Yep sure, I've done it with a pin vice and that same micro drill kit. Just have to make sure the size is right.
 

Offline Rasz

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Re: Cleaning up solder from a stubborn thruhole
« Reply #9 on: November 13, 2014, 03:05:28 am »
no no nooooo
use a thin Hypodermic needle - they are made out of steel so solder wont adhere to it.

You melt the solder and quickly puncture it, stop heating it up while still moving the needle around. Done.


It also sounds like you might want to look into hot air stations.
and if you plan to do multilayer boards wit heavy ground planes more often  buy a preheater.
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Offline Dave Turner

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Re: Cleaning up solder from a stubborn thruhole
« Reply #10 on: November 13, 2014, 07:30:21 pm »
I agree with the stainless steel needle but would advise imbedding the blunt end into a cork, holding it in a pin vice or even wrapping it with insulating tape to improve handling accuracy and reduce the chance of a burn.
 

Online nfmax

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Re: Cleaning up solder from a stubborn thruhole
« Reply #11 on: November 13, 2014, 07:39:50 pm »
I use a stainless steel dental pick for this sort of job. For some reason, these used to appear regularly on the second hand tool-tat stalls that populate the market area of steam rallies round these parts. I've no idea if they still do...
 

Offline AndyC_772

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Re: Cleaning up solder from a stubborn thruhole
« Reply #12 on: November 13, 2014, 07:56:25 pm »
I once resorted to a very short piece of stiff copper wire held in a drill chuck, with just a few mm poking out. The sharp edges from where the wire was cut act like the teeth of a drill bit, and the copper is hard enough to chew away the solder without damaging the plating.

Proud of what I did? Not really. Got the job done without damaging the board? Sure!

Offline krivx

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Re: Cleaning up solder from a stubborn thruhole
« Reply #13 on: November 13, 2014, 08:44:56 pm »
Hey, if it got the job done you should be proud.
 

Offline AndyC_772

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Re: Cleaning up solder from a stubborn thruhole
« Reply #14 on: November 13, 2014, 08:48:04 pm »
 :-+

Offline DmitryL

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Re: Cleaning up solder from a stubborn thruhole
« Reply #15 on: November 13, 2014, 09:33:38 pm »
I've desoldered a capacitor, which wasn't that difficult, and am now trying to clean up the holes. One was easy enough. The other (the positive), not at all. So far it resisted: manual sucker, braid, flux, adding solder, all of the above on both sides, and temperatures at least up to 450C (I think more). It was partially unclogged after one of the cleaning attempts but after adding solder I can't even get the solder on the side opposite the iron to melt.
It's on an old low-end graphics card, I don't think there are too many layers.

[sigh] put some flux into that thruhole, take a big blob of a normal _leaded_ solder on a a tip of a _proper_ temperature controlled soldering iron (it should be > 50 Watts).
Fill that hole with solder, it should be liquid, that's why you need a high power soldering iron with controlled temperature. From the opposite side stick something like a bamboo toothpick into this hole.
 

Offline German_EE

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Re: Cleaning up solder from a stubborn thruhole
« Reply #16 on: November 14, 2014, 01:20:16 pm »
I have been known to use a sharpened pencil, nothing sticks to pencil lead and the wooden shaft means that you do not burn your fingers.
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Offline GreyWoolfe

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Re: Cleaning up solder from a stubborn thruhole
« Reply #17 on: November 14, 2014, 01:43:32 pm »
I use a stainless steel dental pick for this sort of job. For some reason, these used to appear regularly on the second hand tool-tat stalls that populate the market area of steam rallies round these parts. I've no idea if they still do...

On this side of the pond, you can find boxes of dental picks at the local flea markets.  I have used the dental pick method in the past.  Now I have a ZD-985 that was a Christmas gift from SWMBO ;D.
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Offline lpc32

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Re: Cleaning up solder from a stubborn thruhole
« Reply #18 on: November 14, 2014, 10:21:54 pm »
Thanks everyone.

I tried what I could of the above. I can't push anything through because at no point the solder melts all the way through the hole. Tried more flux on the board, flux on the braid, another type of braid (new, but fishy), another type of solder (known good and new). The soldering iron is good. Tried up to 480C.

The best I could get is shallow depressions in both sides of the hole, but the middle remained blocked. I suspect something blocks heat transfer in the middle. Is that a common occurrence, and any idea what and why that might be?

Those drill bits, what range of mm sizes is useful for this?

BTW, in some cases when touching the iron to the hole something creaked. Maybe the board, but not sure. Common thing? A bad sign? :)
 

Offline Dave Turner

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Re: Cleaning up solder from a stubborn thruhole
« Reply #19 on: November 14, 2014, 11:43:44 pm »
Let's see some pictures
 

Offline KJDS

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Re: Cleaning up solder from a stubborn thruhole
« Reply #20 on: November 15, 2014, 06:29:27 am »
What soldering iron and bit are you using?

Offline Richard Head

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Re: Cleaning up solder from a stubborn thruhole
« Reply #21 on: November 15, 2014, 09:14:00 am »
Try using an iron with a large flat bit. Place a short length of silicone tube (silicone wire insulation) over the end of your solder sucker. This allows you to get a very good seal on the board when you suck. Then, place the iron on the side of the board with the groundplane while simultaneously placing the solder sucker over the pad on the opposite side of the board and suck. This generally works with stubborn THP holes but not always. If all else fails use the stainless steel needle method. If that fails drill the bloody thing out and use one of the inserts to repair the THP.
Dick
 


Offline DTJ

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Re: Cleaning up solder from a stubborn thruhole
« Reply #23 on: November 15, 2014, 11:39:22 am »
Something else that can be used to poke through a hole and clear solder is a stainless steel hypodermic needle. The solder doesn't stick to it. Dirt cheap at your local chemist or vet, available in lots of sizes. Perhaps not quite as nice as the Hakko desoldering gun.
 

Offline GreyWoolfe

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Re: Cleaning up solder from a stubborn thruhole
« Reply #24 on: November 15, 2014, 01:56:34 pm »
When I have had to use a dental pick, I heat the pick not the solder.  Did you try it this way?  The heat will probably soften the pick and warp it, but just keep it for opening the holes up only.
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Offline atferrari

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Re: Cleaning up solder from a stubborn thruhole
« Reply #26 on: November 15, 2014, 11:39:26 pm »
Sometimes force is the only thing that can work. A de-soldering station with vacuum pump would probably clear it. If you don't have one you could try heating it and poking out the solder with something like a toothpick before it solidifies.

I have always kind of a toothpick around for those cases.  :-+
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Offline kxenos

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Re: Cleaning up solder from a stubborn thruhole
« Reply #27 on: November 16, 2014, 02:57:53 am »
Thanks everyone.

I tried what I could of the above. I can't push anything through because at no point the solder melts all the way through the hole. Tried more flux on the board, flux on the braid, another type of braid (new, but fishy), another type of solder (known good and new). The soldering iron is good. Tried up to 480C.

The best I could get is shallow depressions in both sides of the hole, but the middle remained blocked. I suspect something blocks heat transfer in the middle. Is that a common occurrence, and any idea what and why that might be?

Those drill bits, what range of mm sizes is useful for this?

BTW, in some cases when touching the iron to the hole something creaked. Maybe the board, but not sure. Common thing? A bad sign? :)

I'm afraid the next suggestion will suggest a kitchen oven...  ;)
 

Offline pickle9000

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Re: Cleaning up solder from a stubborn thruhole
« Reply #28 on: November 16, 2014, 03:26:05 am »
If you can melt the solder use these:

http://www.ebay.ca/itm/Hollow-needles-desoldering-tool-for-electronic-components-/370723601236?pt=LH_DefaultDomain_0&hash=item5650d93b54

If you can't melt the solder measure the diameter of the wire of the replacement component. 

Get a pin vise http://www.ebay.ca/sch/i.html?_from=R40&_sacat=0&LH_BIN=1&_nkw=pin+vise&rt=nc&_pppn=r1&LH_FS=1

Get some bits http://www.ebay.ca/sch/i.html?_odkw=pcb+drill+bits&_from=R40|R40&LH_BIN=1&LH_FS=1&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313&_nkw=pcb+drill+bits+set&_sacat=0

I prefer plain old hss twist bits. Manually drill the hole, be gentle. Take 3 minutes or so . For things like caps you can flush cut with snips and leave the lead in place. The trick is not to use a large bit, even if you destroy part of the thru hole the small bit keeps most of it intact. Having said that if you have the hole partially clear and can't get the lead through this method should not be used. The bit can screw in and detach the plating. Better to fill the hole and drill it out.

Stuff like this is always handy to have on the bench, of course a preheater is also an option.
 

Offline BradC

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Re: Cleaning up solder from a stubborn thruhole
« Reply #29 on: November 16, 2014, 04:19:49 am »
The soldering iron is good. Tried up to 480C.

Actually the problem is your iron. If your iron was any good and had a real 480C at the tip when you had it buried in the hole you'd push right through. Your iron is either
A) Lying to you (never seen a properly calibrated whoflungpoo iron out of the box)
B) having sufficient thermal resistance between the heater and the tip that the board is sucking the heat out faster than the iron can keep up (ie crap iron/tip)
C) Woefully undersized

Now, you can either preheat the board (I use an Aoyue hot air gun held in a chemistry retort stand and clamp for positioning) or get a better iron. None of the suggested fixes will work until you can properly melt _all_ the solder.

If your iron is a JBC, Hakko or Metcal then you are using it wrong. If it's not then it's likely too small or badly engineered. I have 3 irons here, all cheap Aoyue handles. One of them has had the heater replaced with a genuine Hakko unit, and all have genuine Hakko tips on them. The upgraded unit is far better at thermal conductivity than the others and sees the most use. I have the extras as at $17 each it's easier to swap irons than tips, so I have irons ready with all the other tips I commonly use.

Take another long hard look at your iron.
 

Offline G7PSK

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Re: Cleaning up solder from a stubborn thruhole
« Reply #30 on: November 16, 2014, 09:43:45 am »
Nozzle cleaners (for gas torches) are very good for cleaning through holes in PCB's Start small and work up to the correct size and unless you are very brutal there is no damage to the copper plating.

http://www.ebay.co.uk/itm/1-X-NOZZLE-CLEANER-SET-SPECIAL-OFFER-/180468427507?pt=LH_DefaultDomain_3&hash=item2a04c1aaf3
 

Offline dfmischler

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Re: Cleaning up solder from a stubborn thruhole
« Reply #31 on: November 16, 2014, 12:33:05 pm »
A) Lying to you (never seen a properly calibrated whoflungpoo iron out of the box)
B) having sufficient thermal resistance between the heater and the tip that the board is sucking the heat out faster than the iron can keep up (ie crap iron/tip)
C) Woefully undersized
D) Not moving heat because it is not properly tinned.
 

Offline lpc32

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Re: Cleaning up solder from a stubborn thruhole
« Reply #32 on: November 16, 2014, 03:04:09 pm »
Let's see some pictures


(How's that for guerrilla marketing? :))

Iron and tip: Hakko FX-888D with probably T18-D16 (chisel, ~1.5mm). It's tinned, etc.

If your iron is a JBC, Hakko or Metcal then you are using it wrong.
It's not an Apple iron. But yes, anything's possible, though it worked mostly okay for other holes.

If you can melt the solder use these:

http://www.ebay.ca/itm/Hollow-needles-desoldering-tool-for-electronic-components-/370723601236
Why hollow, less heat loss? Will the handles stand the needles being heated directly?

Quote
I prefer plain old hss twist bits.
As opposed to what other types?


Silicone tube: Where do you get it?

Nozzle cleaners: Are these just variable-size needles?

Pin vise: Any recommend/not recommended types? Will these hold most drill bit types?

Preheater: I'm not doing it often enough to warrant getting the gear. I assume it SHOULD be possible to somehow do it without.

I'll try making a hot-needle implement; but where are all the corks when you need them...

By the way, I had a go at another board and most annoyingly I'm stuck at about the same point. 3 caps removed, 4 holes cleaned, 1 hole open but too narrow, 1 hole blocked. Like the first board, cap removal and all initial holes went mostly smooth.
 

Online Alex Eisenhut

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Re: Cleaning up solder from a stubborn thruhole
« Reply #33 on: November 16, 2014, 04:51:48 pm »
sigh

http://www.ebay.com/itm/21pc-Mini-Micro-Drill-Bits-Set-Index-61-80-w-Blue-Aluminum-Drill-Handle-CHIDB003-/371180845759?pt=LH_DefaultDomain_0&hash=item566c1a3abf

Just drill it out. The amount of time and energy you have invested so far you could have drilled for oil by now!

I almost feel like making a video now, and I've never done that before!
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Offline dfmischler

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Re: Cleaning up solder from a stubborn thruhole
« Reply #34 on: November 16, 2014, 04:54:51 pm »
I also have a Hakko FX-888D.  I like the 3.2mm chisel tip for recapping because it moves a lot more heat than the 1.6mm chisel tip that comes with the iron.

As for the suggestion to drill out the hole: that will work for getting the new cap into the hole, but what makes you think he will be able to melt the solder all the way through once it is in place?
 

Offline pickle9000

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Re: Cleaning up solder from a stubborn thruhole
« Reply #35 on: November 16, 2014, 05:05:14 pm »
@ lpc32

Stainless Needles:

No reason for the hollow tips as far as I know. The linked pins in the post are fairly crappy in terms of finish but they work just fine. Basically the procedure is to apply fresh solder and while it is still smoking (resin still present) poke a needle through. Use the smallest one you can get away with otherwise the solder will harden. Holding the needle on the tip will help. Remember heat will destroy the throughole plating and PCB itself if applied too long. If you can't do it in under 3-4 seconds then there is potential for damage.

Drill bits

Many bits are actually router bits they tend to wander when hand drilling. The tin or tin/lead solder is very soft so twist bits will pull a nice curl from the hole. Any hss twist bit is my pick and will stay on center.

Any pin vise will work I have a few. My preference is for one like this (narrow body):

http://www.ebay.ca/itm/Double-End-Pin-Vise-Tong-For-Jewelry-Craft-Hobby-Tools-/310602618746?pt=LH_DefaultDomain_2&hash=item48515bd77a

Pin vises and small drill bits can normally be found at a local hobby shop that sells electric train sets.


- Your picture shows a slight bowl on the bottom side this is a perfect place hand drill. The drill will autocenter on this point.   
 

Offline pickle9000

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Re: Cleaning up solder from a stubborn thruhole
« Reply #36 on: November 16, 2014, 05:23:43 pm »
I also have a Hakko FX-888D.  I like the 3.2mm chisel tip for recapping because it moves a lot more heat than the 1.6mm chisel tip that comes with the iron.

As for the suggestion to drill out the hole: that will work for getting the new cap into the hole, but what makes you think he will be able to melt the solder all the way through once it is in place?

I have done it this way many times over the years. The main issue with solder removal is that the device being used to remove or poke through the solder will have a heatsink effect and solidify the solder. This holds true for solder suckers as well. I'm talking about the marginal heating ability of any system, in some cases this can be your soldering iron / system. It could also be a simply massive ground plane on an 8 layer board with a large FET or other device on it. I have used a grinder to remove components, and the sucked out the pins after, saving a large expensive pcb can be worth it. 

For myself I often opt for drilling when I feel the end user has any chance of seeing the rework. Drilling preserves the "look" of the board. 

When it comes to time spent. I would normally solder suck holes and then just drill the one or two that need it. I could use a preheater, pins and such (I have them) but drilling is very time efficient when doing just one or two holes.
 

Online Alex Eisenhut

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Re: Cleaning up solder from a stubborn thruhole
« Reply #37 on: November 16, 2014, 05:25:15 pm »
I also have a Hakko FX-888D.  I like the 3.2mm chisel tip for recapping because it moves a lot more heat than the 1.6mm chisel tip that comes with the iron.

As for the suggestion to drill out the hole: that will work for getting the new cap into the hole, but what makes you think he will be able to melt the solder all the way through once it is in place?

It doesn't have to melt all the way through unless he's going for an IPC certified and inspected repair. And in any case you can use two irons to bring the heat to a stubborn joint. It's far easier than using two irons and braid or whatever to unsolder.

And if he can't melt the solder, then insisting on trying to clean the hole with heat will do far more damage than a simple drill.

I mean we're at how many soldering or desoldering irons, different tips, braid, flux, stainless steel needles, or pins now?

And the holes are still plugged.

Just drill them out. It's done in 5 seconds. No heat. No flux. No needles, pins, chisel tips, braid, or mechanical engineering treatises.
*Except AC/DC adapters on eBay. Avoid them all!
 

Offline lpc32

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Re: Cleaning up solder from a stubborn thruhole
« Reply #38 on: November 16, 2014, 05:49:15 pm »
Just drill it out. The amount of time and energy you have invested so far you could have drilled for oil by now!
These eBay drills are 2 to 8 weeks away. Assuming it is possible to clean the hole with "normal" methods, isn't that an overall safer or cleaner choice?

Quote
I almost feel like making a video now, and I've never done that before!
That could be interesting. But difficult to shoot. I haven't found videos that go into detail on trouble holes, just generic "use sucker/wick" where everything works.

Many bits are actually router bits they tend to wander when hand drilling. ... Any hss twist bit is my pick and will stay on center.
How do you tell them apart?

Anyway, I've tried heating up a needle. No go. It helped to increase the hole size of an open but too narrow hole (another PCB), but not open a blocked one. Hopefully the widened hole is not damaged.



« Last Edit: November 16, 2014, 05:55:50 pm by lpc32 »
 

Online Alex Eisenhut

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Re: Cleaning up solder from a stubborn thruhole
« Reply #39 on: November 16, 2014, 06:08:22 pm »
Just drill it out. The amount of time and energy you have invested so far you could have drilled for oil by now!

These eBay drills are 2 to 8 weeks away. Assuming it is possible to clean "normally", isn't that an overall safer or cleaner method?

How many weeks away is a new Hakko 707? (That's the one I have, it's old but it's a beast.)

Quote
I almost feel like making a video now, and I've never done that before!
There could be interesting. But difficult to shoot.

Anyway, I've tried heating up a needle. No go. It helped to increase the hole size of an open but too narrow hole (another PCB), but not open a block one. Hopefully the widened hole is not damaged.

Fair enough. I didn't want to have to do it, but here goes:

Get a BIC pen. Take out the innards and the endcap. Now you have a nice blowgun. Heat the joint with fresh solder and make sure you have a nice plug of as hot as possible solder going. While you are still heating the joint, move the iron away from the hole but still on the copper, now bring the BIC pen to the hole and blow as hard as you can. Of course do this as one quick move. And needless to say: don't inhale!

The best way is to have a board holder, heat the joint from beneath, and look at top of the joint, when it's liquid you blow it out! The advantage is that the iron only needs to heat the joint and not any additional stuff like braid or a pin.

Of course there's the danger of a hot slug of solder flying all over the place, but there you go.

And if the other side of the joint looks like a dying T-1000, that's far easier to fix now that the solder is out of the hole.
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Offline pickle9000

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Re: Cleaning up solder from a stubborn thruhole
« Reply #40 on: November 16, 2014, 06:17:00 pm »
For ID here are a couple images.

Regular twist drills are easy to spot, same diameter all the way along. You should be able to get these from a local hobby shop.

Items with the fat shank are the ones to stay away from. It is possible to find bits of the correct type in this format it's just easier to get the other ones.
 

Online Alex Eisenhut

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Re: Cleaning up solder from a stubborn thruhole
« Reply #41 on: November 16, 2014, 06:32:11 pm »
For ID here are a couple images.

Regular twist drills are easy to spot, same diameter all the way along. You should be able to get these from a local hobby shop.

Items with the fat shank are the ones to stay away from. It is possible to find bits of the correct type in this format it's just easier to get the other ones.

That's not a routing bit, it's a carbide twist drill for drilling PCBs. It's far too brittle for routing or hand-drilling.

http://en.wikipedia.org/wiki/Drill_bit#PCB_through-hole_drill_bits
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Offline pickle9000

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Re: Cleaning up solder from a stubborn thruhole
« Reply #42 on: November 16, 2014, 06:37:09 pm »
For ID here are a couple images.

Regular twist drills are easy to spot, same diameter all the way along. You should be able to get these from a local hobby shop.

Items with the fat shank are the ones to stay away from. It is possible to find bits of the correct type in this format it's just easier to get the other ones.

That's not a routing bit, it's a carbide twist drill for drilling PCBs. It's far too brittle for routing or hand-drilling.

http://en.wikipedia.org/wiki/Drill_bit#PCB_through-hole_drill_bits

I know, it's an example shape of what to avoid.
 

Offline lpc32

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Re: Cleaning up solder from a stubborn thruhole
« Reply #43 on: November 17, 2014, 04:53:37 pm »
heat the joint from beneath, and look at top of the joint, when it's liquid you blow it out!
But this too needs the same basic requirement: having the whole joint liquid.

As for the suggestion to drill out the hole: that will work for getting the new cap into the hole, but what makes you think he will be able to melt the solder all the way through once it is in place?
A good question. I'm assuming part of the problem is the old (leadfree?) solder, or something mechanical blocking heat transfer, but I don't know. The only trivial thing I can think of next is to try drilling.

Though, I'm unhappy about not being able to clean it up normally, or even know for sure why it doesn't work.

With only an iron, manual sucker, and wick, how common do you get holes that need drilling? In the two boards I have here it's 2 (or 3 with the narrow hole) out of 12, not a good ratio.
 

Offline AG6QR

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Re: Cleaning up solder from a stubborn thruhole
« Reply #44 on: November 17, 2014, 05:28:40 pm »
With only an iron, manual sucker, and wick, how common do you get holes that need drilling? In the two boards I have here it's 2 (or 3 with the narrow hole) out of 12, not a good ratio.

About 80% of the holes I try come clean the first time using only an iron and wick (sometimes with flux added).  Every one of the remaining ones has come clean using a little piece of resistor lead, and heating the hole and lead with an iron while pushing the lead through the hole.  That technique was mentioned in the second reply on this thread. 

I've never tried any of the other techniques mentioned on this thread, not because I think there's something wrong with them, but because wick and a resistor lead have always worked.  I can't count the number of holes I've cleaned up that way, but it's a lot.
 

Offline Smith

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Re: Cleaning up solder from a stubborn thruhole
« Reply #45 on: November 17, 2014, 06:10:59 pm »
Most will do fine when adding some new solder.
I occasionally use a heat plate aka second hand 500W kitchen warming plate when the ground plane is just to large. Heating the board to 100/125 degrees does wonders.
Trying is the first step towards failure
 

Offline dfmischler

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Re: Cleaning up solder from a stubborn thruhole
« Reply #46 on: November 18, 2014, 11:45:08 am »
With only an iron, manual sucker, and wick, how common do you get holes that need drilling? In the two boards I have here it's 2 (or 3 with the narrow hole) out of 12, not a good ratio.

I have never had a hole that I had to drill because I couldn't heat it up enough to suck it out, but I use a much larger tip on my iron, and I have a Weller iron, heat gun and hot air station that I could use as well.  I even have a 100 watt soldering gun that I could use if really necessary, but I can't ever remember using it on a PC board.

Hints: leaded solder (e.g. 63/37) melts at a lower temperature than unleaded.  Adding leaded solder to the joint can help by reducing the melting temperature.  Unless you have really top-of-the-line equipment a bigger tip generally moves more heat.
 

Offline nanofrog

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Re: Cleaning up solder from a stubborn thruhole
« Reply #47 on: November 18, 2014, 07:17:16 pm »
I occasionally use a heat plate aka second hand 500W kitchen warming plate when the ground plane is just to large. Heating the board to 100/125 degrees does wonders.
+1  :-+

Adding more heat via an electric skillet has been mentioned in another thread the OP started. Not sure if he's ignoring it or missed it.  :-// Even a hair dryer could help (trying to think of something that may be on-hand or purchased locally to finish the job same day).
 

Online nali

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Re: Cleaning up solder from a stubborn thruhole
« Reply #48 on: November 18, 2014, 08:07:37 pm »
I've used before one of those 500W yard floodlights that you can buy in DIY superstores for £5 or so to preheat boards.. which has the advantage of not needing direct contact for heat transfer. Warning: Use a dimmer or make sure you switch it off when the board gets to temperature or you'll get lots of smoke & molten solder!  :palm:
 

Offline tiago

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Re: Cleaning up solder from a stubborn thruhole
« Reply #49 on: November 18, 2014, 09:06:09 pm »
Heat the pad and whack the board against the table.

Crude but effective.
 

Offline lpc32

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Re: Cleaning up solder from a stubborn thruhole
« Reply #50 on: November 18, 2014, 10:58:58 pm »
Drilling is a last ditch effort at best, as you run a real risk of destroying the hole you're trying to clear.
Sounds like it's used regularly by some of the people here. Maybe less risk when using narrow bits?

It's possible to remove a part if the solder reaches it's plastic range and sufficient mechanical force is applied
That's an interesting point. The capacitors weren't terribly difficult to remove. Partially pull one lead, the other, back to the first... and after a few rounds it's out. Even assuming partial melting, if it was possible to pull the cap out won't it be similarly possible to later mechanically push the solder out?

But this bring me to what AG6QR said...
the remaining ones has come clean using a little piece of resistor lead, and heating the hole and lead with an iron while pushing the lead through the hole.
Do you specifically mean that component leads are better heat conductors than needles? I guess the end is wider, at the very least.

FWIW, even the best irons need a preheater if the PCB has enough layers sucking off the heat.
If it works well enough for some of the people here, on similar boards, using similar basic gear, I do wonder what's different.

I don't dismiss preheating entirely, but I would rather go for the minimalistic approach if possible. I don't think I have anything suitable handy, and it looks awkward for larger things, but I'll read up more and see how it works.

Heat the pad and whack the board against the table.
Even in cases when that can work, I wouldn't want to be brutal to the poor boards. ;D
 

Offline AG6QR

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Re: Cleaning up solder from a stubborn thruhole
« Reply #51 on: November 18, 2014, 11:21:57 pm »
the remaining ones has come clean using a little piece of resistor lead, and heating the hole and lead with an iron while pushing the lead through the hole.
Do you specifically mean that component leads are better heat conductors than needles? I guess the end is wider, at the very least.

I haven't used needles, so my experience is limited.  All I know for certain is that component leads have been good enough in my experience.  Also, they're cheaper for me, since I'm always clipping them off and I always have a bunch around that I'm about to throw in the trash anyway.  But I do know that, if you look up the material properties, copper's heat conductivity is much better than stainless steel.  Steel needles would probably be more rigid and better suited to applying force, though.

Also, for getting good heat transfer, it's useful to wet the tip of the soldering iron with plenty of molten solder to provide a good contact area.  I am certain that molten solder conducts heat a LOT better than air.  When you have a dry iron contacting a dry circuit board, with a dry needle or dry component lead, you'll only have a couple of points of solid contact, almost zero area.  You can improve the heat conduction hugely if you fill all of the air gaps up with molten solder.  This factor is much more important than steel needle versus copper component lead. 
 

Offline nanofrog

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Re: Cleaning up solder from a stubborn thruhole
« Reply #52 on: November 19, 2014, 04:18:26 am »
Sounds like it's used regularly by some of the people here. Maybe less risk when using narrow bits?
Unlike blunt needles and wire, drill bits are designed to cut. If sized properly (same size as the hole, so will barely clear it) any misalignment, and you'll end up removing some or all of the copper from the hole itself. Possibly tearing a pad off as it exits. Not the best odds, so not good practice generally speaking.

Even assuming partial melting, if it was possible to pull the cap out won't it be similarly possible to later mechanically push the solder out?
Possible? Yes.

It depends on the temp and force applied after inserting some tool (tool can conduct heat away). So you could insert the tool, say a piece of wire or component leg, and it solidify rather than clear the hole out (you're boned without more heat if this happens). Even as it enters the plastic range, use too much force and you'll damage the board (lifted or torn traces). It's a balancing act to pull off, as you're flirting with the absolute minimal heat requirement for the given conditions, and there's considerable risk involved.

Simple solution is more heat.

Hair dryer, electric skillet, heat gun, or oven can help you with this, and you don't need to get anywhere near melting point. As mentioned before, 100C will do wonders. Just work quickly so it doesn't cool off too much if you can't apply preheating while soldering or desoldering.  ;)

But this bring me to what AG6QR said...
the remaining ones has come clean using a little piece of resistor lead, and heating the hole and lead with an iron while pushing the lead through the hole.
Do you specifically mean that component leads are better heat conductors than needles? I guess the end is wider, at the very least.

FWIW, even the best irons need a preheater if the PCB has enough layers sucking off the heat.
If it works well enough for some of the people here, on similar boards, using similar basic gear, I do wonder what's different.
I think you're missing a critical point, and that's that the solder is fully molten when using wire, component leads, needles, probe tips as needles, and so on that's pushing a stick through a hole.

The one exception as I read it, are those that have used drills to clear holes they couldn't get the solder to melt. Unmolten solder = insufficient heat. Its really that simple. The causality can be more complicated (tip size, molten solder on the tip, and so on, that are all related to thermal transfer <get the iron's heat into the joint>).

I don't dismiss preheating entirely, but I would rather go for the minimalistic approach if possible. I don't think I have anything suitable handy, and it looks awkward for larger things, but I'll read up more and see how it works.
Assuming you've an appropriate tip size, have enough molten solder on the tip, sufficient flux, and possibly adding a lower melting point solder as previously discussed for best thermal transfer for the particular joint & equipment used, the proper approach is more heat.

This ^ is where I'm assuming you're at.

So adding heat is the minimalistic approach with this particular board with your equipment and techniques. Any other means without adding heat under these conditions, is risking damage to the board.
 

Offline neuraxon77

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Re: Cleaning up solder from a stubborn thruhole
« Reply #53 on: November 19, 2014, 10:47:04 am »
I've seen suck mentioned but I haven't seen blow (didn't read every post though), so try blowing it our with compressed air or perhaps pressurized electrical cleaner:

Lay the board down on news paper and put on safety glasses. Tape around the area if you're concerned about solder blowout, preferably kapton and not too close to the hole.
Add flux to the hole (if you have it).
Add solder.
Add heat.
Melt the solder through.
While molten, blow the hole out with compressed air or electrical cleaner.
Repeat on the other side if necessary.
Clean any mess with solder wick or the tip of an iron.
If the thru-hole plating is still intact it should come out clean, if not, you'll need to drill or as a very last resort poke it out while being careful not to lift tracks.
 

Online Alex Eisenhut

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Re: Cleaning up solder from a stubborn thruhole
« Reply #54 on: November 19, 2014, 03:34:22 pm »
Sounds like it's used regularly by some of the people here. Maybe less risk when using narrow bits?
Unlike blunt needles and wire, drill bits are designed to cut. If sized properly (same size as the hole, so will barely clear it) any misalignment, and you'll end up removing some or all of the copper from the hole itself. Possibly tearing a pad off as it exits. Not the best odds, so not good practice generally speaking.

Then it's not properly sized. I don't know what you think people are doing, but no one is suggesting using a drill press. The solder is far softer than the copper and the drill bit will simply bite into the solder.

I don't understand the resistance to a simple and effective solution. I think trying all these different heat-based approaches are the risky ones.

No one is tearing off pads or removing copper with a #61 wire drill twisted by hand. And even if they are so clumsy, you can see the color of the tailings change.

This is in the repair section, not the IPC-approved NASA man-rated PCB assembly section.

I don't get it.
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Offline pickle9000

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Re: Cleaning up solder from a stubborn thruhole
« Reply #55 on: November 19, 2014, 04:26:13 pm »
Sounds like it's used regularly by some of the people here. Maybe less risk when using narrow bits?
Unlike blunt needles and wire, drill bits are designed to cut. If sized properly (same size as the hole, so will barely clear it) any misalignment, and you'll end up removing some or all of the copper from the hole itself. Possibly tearing a pad off as it exits. Not the best odds, so not good practice generally speaking.

Then it's not properly sized. I don't know what you think people are doing, but no one is suggesting using a drill press. The solder is far softer than the copper and the drill bit will simply bite into the solder.

I don't understand the resistance to a simple and effective solution. I think trying all these different heat-based approaches are the risky ones.

No one is tearing off pads or removing copper with a #61 wire drill twisted by hand. And even if they are so clumsy, you can see the color of the tailings change.

This is in the repair section, not the IPC-approved NASA man-rated PCB assembly section.

I don't get it.

When drilling (by hand) the correct procedure is to have the bit matched to the lead size (of the component to be installed) and NOT the hole size (which is much larger). The plating may be nicked true but not to an extent that it will be removed.

If excessive heat has been used then any method used has the potential to destroy the through hole plating as the support structure may be weakened. 

Choosing a bit that matches the hole size will remove the plating and is not a correct in any circumstance.

If after drilling it is decided that more solder must be removed (hole too small). Great care must be taken if using another slightly larger drill bit. In this case the bit can grab an detach the through hole. I normally apply fresh solder try to suck or wick it out from the ground plane side. If that fails I use a slightly larger, still smaller than the hole but big enough to fit the new component. Drill only a hole filled completely with solder and be gentle, solder is soft.

The main issue with this type of repair is this. While it can be done well, there is a potential that if done several times the through hole will be at least degraded, at most destroyed. Keeping good records is important. With double sided boards even if the through plating is destroyed it can be fixed, multi-layer boards are another story.


 

Offline lpc32

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Re: Cleaning up solder from a stubborn thruhole
« Reply #56 on: November 21, 2014, 12:44:27 am »
Ultimately, I made progress on the 2nd board (not the one photoed) after replacing the needle with a cut lead. While heating the lead, I push it into the hole and pulled it out. I repeated it a few times, most of which resulted in the hole closing after the lead was removed, but once or twice it did leave some hole, though too narrow. I followed with repeated wicking and reapplying solder to the hole. In the end it was wide enough, though still not as nicely cleaned as the easier holes.

The board seems functional, but it didn't undergo as much work as the other one.

On the 1st board, pushing a lead into the molten hole also wasn't too difficult, but once the lead was removed it never left a hole, not even a narrow one. This board's holes are wider, I'm not sure if it's a factor.

What's the expected result with this lead poking technique? It didn't push enough solder out, and the extra solder I had to add (to heat the lead) tended to counter the some that was removed from the hole. Do you push it in one direction, or push then pull back? What do you use to handle the lead with?

Regarding just leaving the old solder there and sliding in the new component; is the only reason to clean holes to make it easy to insert new components, or are there advantages to actual removal of the old solder?
« Last Edit: November 21, 2014, 03:58:44 am by lpc32 »
 

Offline pickle9000

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Re: Cleaning up solder from a stubborn thruhole
« Reply #57 on: November 21, 2014, 02:46:32 am »
- As a general rule solder should be removed. This is the best practice. You may then use your own mix.
- If not as much as possible should be removed. And the joint should be finished with solder of the same type and flux.

As for the stainless pin, hollow pin / needle. As far as I have seen and done myself. Cut the lead to be removed in such a way that the inside of the needle can be slipped over the lead. Apply fresh solder and heat until you have pushed the stainless out through the other side of the pcb. At this point the lead will be inside the tube. Remove the heat while rotating the tube left to right while the solder solidifies. Once hardened try to pull the lead from the needle. If that fails, snip the lead from the component side and remove the needle. The solder won't stick to the outside needle, the solder will often prevent the lead from being removed from the needle.

In my experience needles are removed once the solder has cooled.

 
 

Offline lpc32

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Re: Cleaning up solder from a stubborn thruhole
« Reply #58 on: November 21, 2014, 04:09:20 am »
What's the reason for removal being preferred? By "solder of the same type", do you mean just the distinction between leaded and leadfree?

I might try these hollow pins later on; maybe it's a combination of the best properties of needles and component leads. I do wonder if the lead worked for me (partially anyway), unlike the needle, because of the wider end or because of the material. Or both.
 

Offline pickle9000

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Re: Cleaning up solder from a stubborn thruhole
« Reply #59 on: November 21, 2014, 05:05:58 am »
There are many variations / formulations when it comes to solder. Pre-leadfree the rules where the same. There is no way of knowing either the quality, environmental conditions or how the solder will react over time. Remove as much of the original as reasonable and use the best you have and trust.

The solder issue is important but for consumer gear a quality brand name solder will probably do everything you need.

 

Offline kaindub

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Re: Cleaning up solder from a stubborn thruhole
« Reply #60 on: December 03, 2014, 11:42:01 am »
I only saw one mention of this method.
I had similar problems of clearing holes until I tried this method.

I get a solder sucker, but you need the build type because you want to blow the solder clear through the hole.
Apply a little solder to the pad so the solder is slightly above the surface.
Then heat the solder and blow through the hole with the solder sucker.
Works most of the time. There may be a little tail left on the reverse side of the board

Robert
 

Offline digital

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Re: Cleaning up solder from a stubborn thruhole
« Reply #61 on: December 04, 2014, 08:19:32 am »
Use a pin vise and a twist drill the same diameter as the component lead and just be careful and it will work,be gentle.
 


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