Author Topic: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!  (Read 24744 times)

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Offline bitwelder

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #25 on: December 01, 2014, 06:11:17 pm »
As an example, you can find on the adafruit repository
https://github.com/adafruit/DS1307-breakout-board

the png output. ds1307.png
But I see also that the .png last commit is 4 years ago, while every other file (.sch, .brd) is 4 months ago.
I would wonder if the png is still up-to-date and still trustable picture of the current project status.
 

Offline digitdroid

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #26 on: December 01, 2014, 07:09:31 pm »
Instead of use "patented" ChipQuick kit you always may use https://en.wikipedia.org/wiki/Rose%27s_metal
Retail price for this alloy is about $3 for 100g pack (Russia).

Do you have any link where to buy it?

I think it should be available from local stores/suppliers. Export from Russia is expensive.
I see several lots on ebay (from Eastern Europe countries), but price not so good.
http://www.ebay.com/itm/Roses-metall-100g-Roses-metal-alloy-Rose-Legierung-bismut-wismut-Zinn-Blei-/221249414876?pt=Labor_Zubeh%C3%B6r&hash=item33837e26dc
 

Offline Tonkabot

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #27 on: December 01, 2014, 07:11:39 pm »
A few things I noticed here:

#1  the footprint on the circuit board was generated from a crappy library - it probably had an english to metric unit conversion done, and the rounding errors add up.  Note how the pad for pin 1 is offset a little high, and as you get down to pin 12 (or whatever the bottom pin on the same side is) the pad offsets are now on the low side.     I experienced this once using a library that came with Eagle, the 100 pin QFP footprint was 1/2 a pad (.025 at least) off on a .050 pin pitch part.   Now I always make my own footprints, and I use Altium.  Start in metric or english, whatever the part is natively (usually metric) when making the footprint. 

#2  I would first use solder wick on all the pins, maybe with a little extra flux on the solderwick.   
      Then I would apply the iron to a pad (not pin), and use the tip of an exact-o to pry that pin up.
      Repeat til done.  With practice, it is pretty fast.

#3   Also using a dremal to chop off the pins will allow desoldering them individually with little chance of pad damage.

Although seeing how easy the chipquick worked, I think I'll be getting some in the future.
 

Offline Agent24

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #28 on: December 01, 2014, 07:39:46 pm »
Although seeing how easy the chipquick worked, I think I'll be getting some in the future.

I think you will find hot air is cheaper in the long run.
 

Offline open loop

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #29 on: December 01, 2014, 08:53:42 pm »

Dremel + diamond disc + very gentle force applied will do.

Good idea! but the standard abrasive cut off discs will cut the leads much better than diamond plated discs.

Did a repair on a Samsung tab3, looked like a 3 year old had tried to insert something pointy into the micro USB, result?

Mashed connector  :'(

I had two issues:
looks like the Tab 3 uses a non standard usb connector (found on ebay) and the old connector was a mongrel to remove.

Tried chip quick , did not budge surprising given I use a lot of chip quick and have used it successfully on removing connectors, ICs etc. Used hot air and it still did not move, got the board really hot and was beginning to melt the captan tape that was used to mask some small SMT caps.  :wtf: never had this before as the board was very thin so there can't have been much thermal mass to the small board. Did not want wreck the board so....

In the end I used a Dremmel, I was really careful and just ended up cutting the connector to bits and removing by piece meal. Got the new connnector soldered on ok and the tab3 is working again :)

The problem was the the connector casing was soldered to the ground plane in three places, two sides and the Middle not to mention the fine connections for the socket as it was dead easy to rip the pads on that thing. Dip SMT ICs are far easier to shift.
 

Offline janengelbrecht

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #30 on: December 01, 2014, 09:04:11 pm »
Does anyone else find these half-complete repairs really frustrating?
I need closure!  :scared:

I dont find it frustating. I saw a soldering method. Done. If the circuit was working after this or not is a matter of interest for the owner :P Not my shit :)
Dave has in the past made long repair videos where the subject is trouble shooting...this time i think it was soldering...so my needs were satisfied  :P

Offline Rasz

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #31 on: December 01, 2014, 09:53:40 pm »
Tried chip quick , did not budge surprising given I use a lot of chip quick and have used it successfully on removing connectors, ICs etc. Used hot air and it still did not move, got the board really hot and was beginning to melt the captan tape that was used to mask some small SMT caps.  :wtf:

WTF indeed considering Kapton melts >250'C, you arent supposed to burn off solder, just melt it
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Offline Unixon

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #32 on: December 01, 2014, 10:14:11 pm »
I find it much easier and precise to glue the chip down with rosin flux and then solder pins while the chip is fixed on the board. This way is it possible to precisely place the part while the flux is slowly getting viscous as its solvent evaporates. After precise placement just push it on the top a little bit and after that you can't accidentally move it with iron tip, provided, everything is done carefully.
 

Offline open loop

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #33 on: December 01, 2014, 10:17:22 pm »
Tried chip quick , did not budge surprising given I use a lot of chip quick and have used it successfully on removing connectors, ICs etc. Used hot air and it still did not move, got the board really hot and was beginning to melt the captan tape that was used to mask some small SMT caps.  :wtf:

WTF indeed considering Kapton melts >250'C, you arent supposed to burn off solder, just melt it

Totally agree ! The trick is when things are not going smoothly. STOP! You are probably doing it wrong   :palm: got there in the end though and the board was not scorched or damaged :phew:

 

Offline magetoo

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #34 on: December 02, 2014, 03:53:34 am »
This is a common missunderstanding is what git actually is. Git is a source control tool, it is not designed to track binary files. It is very commonly frowned upon to publish a binary/compiled file into the actual source repository

All true.  Problem is that Github has become a project hosting platform, and therefore a place where people do expect to find rendered output / tarballs / whatever as well.

I don't think that's what was intended from the beginning when Github started to offer a place to host opensource repos, but it happened, and we're seeing the collision of two separate ways of doing things here.  There's no obvious correct solution.  (Other than setting up a "conventional" website as well.)


Edit: I should add that this isn't isn't intended as criticism in any way, just wanted to add something.  (You never know how people are going to read something that's clear and unambiguous inside one's own head, as we've seen.)
« Last Edit: December 02, 2014, 05:43:21 am by magetoo »
 

Offline Fungus

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #35 on: December 02, 2014, 10:50:11 am »
Don't forget the enamelled wire trick!



That looks like it will rip the last pad off the PCB with incredible ease. Watch again the part of the video where he reaches the last pin, I don't know how the pad stays on the board (maybe it didn't...!)

Compared to chip-quick? No thanks...

« Last Edit: December 02, 2014, 10:56:21 am by Fungus »
 

Offline Kjelt

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #36 on: December 02, 2014, 01:42:38 pm »
Just wondering, was there any particular reason why cutting off the pins of that chip was not an option?
I forgot to mention that's another option. Have mentioned that in previous videos.
It's possible, but because of the fine pin pitch you'd have to cut them with a knife and that can put stress on the pads.
Don't use a knife use the specialized tools for it, like the Erem Miniature angle cutter for delicate cutting applications, it costs €60 a piece but it is a beauty for cutting smd pins under a microscope, just don't use it for anything hard or above AWG24 or it will be damaged which is how I ended up owing one for free (with a dent in it)  :D
Best is, there is no excessive heat to the pcb so zero chance of doing damage to the pads. The chipquick looks nice but the same as mixing up leaded with unleaded solder you need a lot of time (if you want to do it right) to clean it up and make sure nothing is left. I would only use that if I needed the chip itself again alive.
 

Offline Tonkabot

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #37 on: December 02, 2014, 10:12:32 pm »
I just checked the KiCad board file for the display board located at https://github.com/shackspace/bttf/blob/master/display/Uhr_Modul.brd
and just as I suspected, it has a crappy footprint.   using KiCad I measured, and the pads for the part Dave replaces are located on 0.653796mm centers.
(I measured from the top edge of pad 1 to the top edge of Pad 11, and divided by 10. )
Not the 0.65 mm centers I suspect the Data Sheet says.

It doesn't sound like much, but it accumulates, and will be a problem on higher pin count parts (like I said before, quoted below).
It was off by enough for me to see while watching Dave's video.

I tend to not trust libraries that I didn't create.   I trust but verify the Altium ones.

A few things I noticed here:

#1  the footprint on the circuit board was generated from a crappy library - it probably had an english to metric unit conversion done, and the rounding errors add up.  Note how the pad for pin 1 is offset a little high, and as you get down to pin 12 (or whatever the bottom pin on the same side is) the pad offsets are now on the low side.     I experienced this once using a library that came with Eagle, the 100 pin QFP footprint was 1/2 a pad (.025 at least) off on a .050 pin pitch part.   Now I always make my own footprints, and I use Altium.  Start in metric or english, whatever the part is natively (usually metric) when making the footprint. 

 

Offline EEVblogTopic starter

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #38 on: December 02, 2014, 10:30:43 pm »
Does anyone else find these half-complete repairs really frustrating?
I need closure!  :scared:
I dont find it frustating. I saw a soldering method. Done. If the circuit was working after this or not is a matter of interest for the owner :P Not my shit :)
Dave has in the past made long repair videos where the subject is trouble shooting...this time i think it was soldering...so my needs were satisfied  :P

This video was never meant to be a repair troubleshooting video. It was supposed to be a video about replacing the chip and the technique used.
The unit was fully expected to work after this repair. It didn't for some as yet unknown reason.
I have since shot some troubleshooting video which the original designer has seen and he's scratching his head too.
I still haven't finished that video and it's already 22 minutes long edited. Could take another hour of edited footage to find out what's wrong at this stage.
The original repair video stands on it's own and IMO is very useful. I'm not going to hold off on that and make some super ridiculously long video just because a few people bitch that I didn't get it going in the one video.
Some video bloggers do that, hold off on a video until it's all done and dusted, and then edit it to make it look like it was an easy fix, but I don't do that. If I think a video has enough material to be useful in it's own right, then I release it.
 

Offline EEVblogTopic starter

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #39 on: December 02, 2014, 10:33:00 pm »
It doesn't sound like much, but it accumulates, and will be a problem on higher pin count parts (like I said before, quoted below).
It was off by enough for me to see while watching Dave's video.

Interesting, I got that same vibe. I thought it was just me going a bit wonky...
 

Offline muffenme

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #40 on: December 03, 2014, 05:19:33 am »
I though of way to easy remove some ic chip with a small clearance. use a magnetic wire. feed wire between two middle pins and lightly pull up while heating the pins on the the ic chip like Dave show in the video.

Can you check if green isn't requiring more voltage/amperage that the other 2 need. All 3 should be at the same brightness, there could be a problem with SS0P24 ic chip on the green one.

Have you check to if you Arduino unit too verify it OK.

Have you though about just take a Breadboard and see if there nothing wrong with how wired.
 

Offline Rasz

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Re: EEVblog #689 - How To Rework Solder SMD Chips - BTTF Time Circuits Repair!
« Reply #41 on: December 03, 2014, 10:11:04 pm »
I though of way to easy remove some ic chip with a small clearance. use a magnetic wire. feed wire between two middle pins and lightly pull up while heating the pins on the the ic chip

and pull that pad of the pcb
Amazing, no matter how many times you tell people to NOT USE ANY FORCE, especially together with high temperature, they keep insisting on inventing new ways to break something :(  :palm:


muffenme copper tracks are 'glued' to pcb, they are easy to rip off to begin with. When you heat up pads they become even more fragile. There really is no need to innovate here, just heat all the pins at the same time, wait for solder to melt and lift whole part (using vacuum picker or tweezers).

Those 'easier' homemade methods end up more time consuming and potentially destructive, and all because people are afraid of SMD and/or dont have hotair. Its only ~$40 (for the cheapest chinese hotair, the one Dave tested some time ago for example), just buy one already and enter wonderful world of no hassle smd rework.
Who logs in to gdm? Not I, said the duck.
My fireplace is on fire, but in all the wrong places.
 


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