Need help with SMD soldering

[dhowland]

I feel a little silly about posting to the beginner's section as I am actually a professional in the field, however I certainly qualify as beginner level when it comes to soldering.

I recently took up a project that requires building a board with a microcontroller.  I chose an AVR with USB in a TQFP-44 package.  Designing the board was delightfully simple but actually constructing it is turning out to be deviously hard.

I knew I needed to upgrade my tools, so I got myself a Weller WES51 with a nice small screwdriver tip, some Kester 245 at 0.020", a good flux pen, thin desoldering braid and some nice Wiha ESD tweezers.  Combined with the excellent tutorials that can be found on YouTube (including Dave's), I thought I couldn't lose.  After all, I mastered through-hole soldering many years ago...

In a way I feel like I was tricked.  Everywhere I was told that surface mount soldering is no trouble at all... anyone can do it... it's a breeze!  Well it isn't, it's difficult.

No matter what I do I seem to leave far too much solder on everything, even knowing that I'm doing so.  Simply tacking a 0603 resister in place to start soldering it is a task that my hands do not seem steady enough for.  I seem to short every fifth lead on my TQFP-44, and desoldering braid is unable to pick it up even after using so much heat that entire part is oxidized and useless.  On the tutorials I watched, the solder reflows perfectly and the parts seem to magically settle on to the pad once heat is applied.  Well that doesn't happen for me, it doesn't happen at all.

Most frustratingly, these fancy new tips oxidize so quickly that I'm at a loss to understand how they could be used professionally.  I tinned my tip as I've been doing for years, but after only one use (about 30 mins), the tip has become useless.  I only used it at about 450-550 degrees.  When I took it out for the second round, attempts to re-tin the tip only result in a ball forming at the end of my solder strand.  It doesn't look so bad but it is obviously oxidized.  These are genuine Weller tips, what on earth is going on?  I can't afford to keep buying these at 4-7 bucks a pop, and SMD soldering is futile if I can't hold solder at the tip.  I ordered some tip tinner that hasn't arrived yet.  Will that clean it enough to let me keep using it?

Please tell me what I'm doing wrong!  Thanks for any help.
-d

[jaqie]

a few questions...
is the desoldering braid prefluxed? if not apply flux to it first.
is the solder multicore flux?
are you soldering with a rohs tip? are you using rohs solder? preferably not in both cases.
are you using some brass wool sponge stuff to clean off your tip after use? wet sponges don't cut it anymore.
are you using the same type of flux manual applied, in the solder, and on the wick? if not fix that.
It may not be best but its better than throwing tips away, are you using a fine emery paper to clean off the tips when they get like that, inbetween uses?  it's what I do, it lengthens their life considerably.

[ftransform]

Maybe you are being a bit neurotic with your tips? Dave does it with a hakko and I don't think he replaces his tips every often.
Then again a pin every milimeter is pretty damn close when doing it by hand. Perhaps you should consider a hot air rework station or microscope.

[IanB]

OK...

Firstly, 450-550 degrees? What are you trying to do, incinerate your solder and start a bonfire? 325-350 C (625-650 F), please.
[Edit: I got confused here. At first I assumed 450-550 was in Celsius, but maybe it's Fahrenheit? If so 450-550 F is not likely to be hot enough to produce good results.]

Secondly, make sure you are not using lead free solder. That stuff is not useful for hand soldering. Use 63/37 Sn/Pb alloy.

Thirdly, don't try to use desoldering braid to clean up bridges. Just touch the bridge with a clean solder tip to suck up the excess. Wipe and repeat as necessary.

Fourthly, 30 mins between tip cleaning and tinning? WTF? I hope you don't mean that. You have to clean and tin your tip between each use, every 30 seconds or so. Have a good damp sponge or brass tip cleaner handy and use it often.

Fifthly, have you (a) scrupulously cleaned the pads on the board before soldering, and (b) do you have a good solder mask in place? Solder mask is almost essential to prevent bridges forming with SMD chips.

[dhowland]

Maybe you are being a bit neurotic with your tips? Dave does it with a hakko and I don't think he replaces his tips every often.
Then again a pin every milimeter is pretty damn close when doing it by hand. Perhaps you should consider a hot air rework station or microscope.

Well, not neurotic.  When solder actively avoids sticking to your tip, you can't get much done.  I have a 10x jeweler's magnifier.

[dhowland]

a few questions...
is the desoldering braid prefluxed? if not apply flux to it first.
is the solder multicore flux?
are you soldering with a rohs tip? are you using rohs solder? preferably not in both cases.
are you using some brass wool sponge stuff to clean off your tip after use? wet sponges don't cut it anymore.
are you using the same type of flux manual applied, in the solder, and on the wick? if not fix that.
It may not be best but its better than throwing tips away, are you using a fine emery paper to clean off the tips when they get like that, inbetween uses?  it's what I do, it lengthens their life considerably.

- The braid is marked as "no-clean" so I'm pretty sure it's fluxed. (MG Chemicals 400-NS)
- I don't believe Kester 245 is multicore but it is flux core
- Weller ET series, I don't know if it is RoHS.
- I'm using the sponge that comes with the WES51 station, but I do retin the tip after using it.
- I have no idea if the flux in the solder is the same as the pen, but they are different brands.  Why would I have to use all the same?  Does anyone else do that?
- I have not tried to sand it off, perhaps I'll try that.

[dhowland]

OK...

Firstly, 450-550 degrees? What are you trying to do, incinerate your solder and start a bonfire? 325-350 F, please.

Secondly, make sure you are not using lead free solder. That stuff is not useful for hand soldering. Use 63/37 Sn/Pb alloy.

Thirdly, don't try to use desoldering braid to clean up bridges. Just touch the bridge with a clean solder tip to suck up the excess. Wipe and repeat as necessary.

Fourthly, 30 mins between tip cleaning and tinning? WTF? I hope you don't mean that. You have to clean and tin your tip between each use, every 30 seconds or so. Have a good damp sponge or brass tip cleaner handy and use it often.

Fifthly, have you (a) scrupulously cleaned the pads on the board before soldering, and (b) do you have a good solder mask in place? Solder mask is almost essential to prevent bridges forming with SMD chips.

1 - I started with a lower temp, but I wasn't getting enough heat transfer.  I will lower it next time, thanks.  One of the tutorials I saw mentioned using 650 degrees which struck me as high but I'm the beginner here.

2 - My solder is 60/40.  I know enough not to use lead-free for my home projects.

3 - I tried that, it didn't work.  The solder wasn't moving.  Reheating it was something I saw in a tutorial, so I did try it, but it wanted to stick to the pin more than it wanted to stick to my tip.  there was just too much.

4 - I meant I used it to solder for 30 mins.  I came back at a later time to work some more and it was useless.

5a - I used 70% isopropyl alcohol to clean board and of course the flux pen just prior to soldering.
5b - My prototype boards to not have the mask layer.  However the bridges were on the pins, well above the surface of the board.

[cwalex]

don't be afraid to use flux. heaps of it! The 450degC will explain the oxidisation for sure. Adding plenty of flux and going over it again with the iron will help clear bridges, it there is way too much solder remove it with the with (did I mention use heaps of flux?).

Starting smt work with 0603 might be a bit too much of a challenge. 0805 would be better for practicing.

Having a bit too much solder on a joint won't matter in a prototype as long as you can see that there is a good connection.

Also use some flux 

[IanB]

OK, so flux is where I was going to go next, but Alex beat me to it.

Copious flux is essential. Try the liquid type and brush it on liberally. Without flux solder will form an oxide layer on the surface and ball up so it refuses to flow or stick to anything.

Your iron tip should always be shiny before you try to use it. Just before you switch off the iron, clean it on the damp sponge and flow liberal amounts of fresh solder over it just before letting it cool. The tip should then cool with a clean coating of solder all over it ready for use next time.

If ever your tip will not wick up solder it has become useless     Work on it with tip tinner/cleaner compound until it is repaired, or discard it. You can avoid it getting into this state by frequent cleaning and re-tinning during use.

[nukie]

I use a damp sponge and I have no care for thermal shock damage, I have tips in use made several thousands of solder joints they are all fine no issues at all. Even if they develop an issue it will be a few years down the road and not instantly. Unleaded soldering temperatures will cause more damage than thermal shock. As far as I know there's only one manufacturer which has conducted thermal shock test and demonstrated damage? on their tips and yet still supply wet sponge with their station as a means of tip cleaning.

If you have tips that last less than a month then you are seriously over the temperature. You are not only burning the tip but also oxidizing the flux which helps with soldering. Adjust the temperature if possible.

I dont like brass wool they don't clean well enough for me. I am used to the wiping action of me tips on damp sponge always return shiny tips ready for action. Wipe when required, wipe when you finish a joint, wipe before you start, wipe frequently, wipe when you don't feel right. I don't get any problem with that.

The Kester 245 solder in 0.020" that you have is a eutectic solder. And I google 0.020" it seems to be equal to 0.50mm. I suggest 0.30mm you get less control due to weak thin wire that increases frustrution but once you master it you can control the amount of solder deposit on a joint. It will be much easier than 0.020".

Regarding eutectic solder, I never like them, not one bit, regardless brand name or not. They don't produce the same shiny joint as 60/40. In my experience, they don't flow well enough without additional flux. Quality 60/40 0.30mm solder will flow nicely with just the flux core.

[nukie]

Your iron tip should always be shiny before you try to use it. Just before you switch off the iron, clean it on the damp sponge and flow liberal amounts of fresh solder over it just before letting it cool. The tip should then cool with a clean coating of solder all over it ready for use next time.

And if you do this with the wrong type of flux core you are going to be sorry. Even mild acid solder will eat away the plating slowly.

[dhowland]

Regarding eutectic solder, I never like them, not one bit, regardless brand name or not. They don't produce the same shiny joint as 60/40. In my experience, they don't flow well enough without additional flux. Quality 60/40 0.30mm solder will flow nicely with just the flux core.

You're right it's actually 67/37.  This is the highest quality solder I could find.  What would you suggest instead?  I can't find anything at the diameter that you suggested except for the Kester offering.

Edit: Looks like if I want to go with 60/40 below 0.020", I'd have to get RA core instead of No-clean.  I'm under the impression that for hobbyist use, No-clean is the way to go.  Is that correct?

[dhowland]

And if you do this with the wrong type of flux core you are going to be sorry. Even mild acid solder will eat away the plating slowly.

Well what do you guys use?  Help me out here.

[cwalex]

Disagree with seanb. 63/37 solder with RMA flux core is the best I have used and I have used many except never used the ROHS stuff. 0.5mm should be fine! you aren't looking to solder individual pads on a high density chip, you just want to flood it with solder and or drag solder and use heaps of good flux either way. more to clean up after but I get better results that way!

## dislcaimer! I am not an ee or technician per se. My advice should be taken as any on the inter webs and corroborated with other info from more experienced guys I just love soldering and joining in these discussions is great fun for me, hopefully helpful for all the lurkers out there struggling like I did.

Warmest Regards

Alex

[cwalex]

Oh, and I forgot to mention. If you don't already, get some acid brushes like thses :http://www.ebay.com/itm/12-2-Acid-Brushes-6-1-2-wide-Bristles-Solder-Flux-Contact-Cement-etc-/170958610746?pt=LH_DefaultDomain_0&hash=item27cded613a

Just cut the bristles off close to the bad and that makes it a nice stiff brush you can use with alcohol or flux cleaning solution to easily scrub off stubborn flux residues. I have been using methylated spirits for cleaning and it is working very well so far. I have a can of flux off but I haven't used it yet.

cheers and good luck 

Alex

[nanofrog]

Well what do you guys use?  Help me out here.

The Kester 245 is fine, as is their 44 or 186 (R & RMA respectively).

For SMD, you need plenty of flux as others have said (boston bottle with needle for dispensing liquid flux or a good pen). Makes a mess vs. just using what's in the solder, but the solder flows much better, so the additional effort in cleanup is worth it (though technically speaking, you can skip this with the No Clean flux). I'm also more of a fan of 63/37 than 60/40, but either would work.

Make sure your pads are clean before beginning to solder though, as it can wreak havoc if they're oxidized. Pencil eraser can work wonders.

As per cleaning up your existing tip, try a brass bristle brush (don't scrub at it too hard).

I have a different Weller station and use 2x different series of tips (NT & LT). Unfortunately, Weller's QC isn't that wonderful these days, so the tip tinner you have on order should really help when it shows up (stuff can work wonders).

[IanB]

Your iron tip should always be shiny before you try to use it. Just before you switch off the iron, clean it on the damp sponge and flow liberal amounts of fresh solder over it just before letting it cool. The tip should then cool with a clean coating of solder all over it ready for use next time.

And if you do this with the wrong type of flux core you are going to be sorry. Even mild acid solder will eat away the plating slowly.

I'm not sure why that would happen? I've been doing it for years and never had a tip wear out. I just tin the iron tip thoroughly with clean solder, wipe off the excess on the damp sponge and immediately power off. The tip cools down shiny and is ready for the next use.

[IanB]

Regarding eutectic solder, I never like them, not one bit, regardless brand name or not. They don't produce the same shiny joint as 60/40. In my experience, they don't flow well enough without additional flux. Quality 60/40 0.30mm solder will flow nicely with just the flux core.

You're right it's actually 67/37.  This is the highest quality solder I could find.  What would you suggest instead?  I can't find anything at the diameter that you suggested except for the Kester offering.

Edit: Looks like if I want to go with 60/40 below 0.020", I'd have to get RA core instead of No-clean.  I'm under the impression that for hobbyist use, No-clean is the way to go.  Is that correct?

With solder you can experiment a bit. Not all solder wires are the same and some definitely work better than others. Recently I've been having good success with MG Chemicals 63/37 or 60/40 alloy with 2.2% RA flux: http://www.mgchemicals.com/products/solder/leaded/sn63-pb37-4880/

The 23 gauge 0.025" wire seems fine enough for small work.

You can use no clean flux, but since you ought to clean up the flux residues anyway you may as well use RA flux.

[JuKu]

My take on the issues:
-Flux is done several times already.
-Temperature: Contrary to what others have said, don't be _too_ shy with heat. You want to have enough heat that the flux reacts fast and that you have enough heat left on a thin tip after the cooling effect of evaporating flux, solder melting and heat transfer to the PCB and the component. I use 330C setting (although I have no idea what the real temp is), but I like to work fast. At that temp, a solder joint takes a couple of seconds, and I have enough experience not to burn boards or parts.
-0603's are difficult by hand. You do need a microscope (or a very good loupe or mag. glass, although I haven't found any that are good enough for my old eyes). When you can really see what's happening, the hand movements get smaller. No caffeine! Have at least three to four hours without coffee before trying to do 0603 or smaller. Seriously.
-You solder (0.5mm) is too thick. As you noted, you can't melt small enough amount from that thick bar. You want to have the thinnest solder you can find, 0.2mm or smaller.

But there is something fundamentally wrong in your setup. The way you describe it is not what should happen. sadly, nowadays you can't rely that the stuff in your flux pen or solder is what the label claims it to be. You said your tips are genuine. I wouldn't rule out that your flux, braid or tin have some nasty ingredients that should not be there. On the other hand, if your 450-550 deg. setting is in C, that would destroy ordinary tips while you watch. You would know when you really need that ('soldering' pure silver).

[IanB]

-Temperature: Contrary to what others have said, don't be _too_ shy with heat. You want to have enough heat that the flux reacts fast and that you have enough heat left on a thin tip after the cooling effect of evaporating flux, solder melting and heat transfer to the PCB and the component. I use 330C setting (although I have no idea what the real temp is), but I like to work fast. At that temp, a solder joint takes a couple of seconds, and I have enough experience not to burn boards or parts.

On re-reading my earlier post I realized I got muddled between temperatures in C and F. I thought dhowland was saying 450-550 C, which is much too hot. But maybe this was meant to be read as 450-550 F?

An optimum tip temperature for Sn/Pb alloys and common fluxes is 600-650 F, 325-350 C. I've tried soldering at 500 F and it is unsuccessful. You have to activate the flux on the component leads to clean them enough so the solder will flow, and to do that requires a good amount of heat transfer from the iron. If the iron is too cold it won't work. Exactly what JuKu says here.

[jaqie]

. . . . No caffeine! Have at least three to four hours without coffee before trying to do 0603 or smaller. Seriously.

Something of note - caffeine is a calming agent to some people, I am bouncing off the walls and shaky-ADHD without it, it works great to get me on a calm, even keel and keep me there provided I keep the right amount in my system.  Too much and I find myself falling asleep.

[HackedFridgeMagnet]

Quote from: IanB on Today at 15:48:24

    Your iron tip should always be shiny before you try to use it. Just before you switch off the iron, clean it on the damp sponge and flow liberal amounts of fresh solder over it just before letting it cool. The tip should then cool with a clean coating of solder all over it ready for use next time.

And if you do this with the wrong type of flux core you are going to be sorry. Even mild acid solder will eat away the plating slowly.

When I'm finished I put some fresh solder on and dont even clean it before switching off, this seems to work. My tips are quite old. But I'm not soldering every day.
I used to clean it on a sponge every time before turning off but I found it oxidised the tip, I think I cleaned it too much, I had symptoms like the OP seems to have.

[dhowland]

Thanks for the advice guys.  I am a Yankee so I am using units in degrees F.  I will specify in the future.  I am going to try 625 degF as described in the data sheet for the solder.

I'm going to stick with my Kester 245 for now.  I will really get liberal with the flux next time.  I'm pretty confident in the brand (MG chemicals)  but I may also try some of the thick tacky stuff.

[nanofrog]

Thanks fot the advice guys.  I am a Yankee so I am using units in F.  I will specify in the future.  I am going to try 625degF as described in the data sheet for the solder.

I'm going to stick with my Kester 245 for now.  I will really get liberal with the flux next time.  I'm pretty confident in the brand (MG chemicals)  but I may also try some of the thick tacky stuff.

Kester and MG Chemicals both make very good soldering supplies, so no need to second guess yourself on this. 

[nukie]

Your iron tip should always be shiny before you try to use it. Just before you switch off the iron, clean it on the damp sponge and flow liberal amounts of fresh solder over it just before letting it cool. The tip should then cool with a clean coating of solder all over it ready for use next time.

And if you do this with the wrong type of flux core you are going to be sorry. Even mild acid solder will eat away the plating slowly.

I'm not sure why that would happen? I've been doing it for years and never had a tip wear out. I just tin the iron tip thoroughly with clean solder, wipe off the excess on the damp sponge and immediately power off. The tip cools down shiny and is ready for the next use.

Try it with acidic flux core solder. I never had pitting on my tips until I tried a corrosive flux core solder and it messed up the tips the next day, the plating was gone and it was beyond repair. All I could do was to file it down.