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johnorun
Joined: 04 Apr 2008
Posts: 3364
Location: Chicago, IL- US
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 Posted: Fri Apr 25, 2008 8:28 pm Post subject: Any way to remove solder from legs of pulled chips? |
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I have solder residue on legs of chips that I have de-soldered from PC boards.
Can anyone tell me how to remove solder OR where to find out how to do it?
Some have Gold legs, others have steel.
Thanks 
John |
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chip68
Joined: 19 Oct 2004
Posts: 1024
Location: Central Pennsylvania
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| Posted: Fri Apr 25, 2008 9:20 pm Post subject: |
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Solder sucker or solder wick.
- CMW |
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chip68
Joined: 19 Oct 2004
Posts: 1024
Location: Central Pennsylvania
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| Posted: Fri Apr 25, 2008 9:23 pm Post subject: |
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Or, you could heat the pins up and quickly wipe them clean with a wet sponge.
- CMW |
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donutty
Joined: 16 Feb 2008
Posts: 1122
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| Posted: Sun Apr 27, 2008 11:33 am Post subject: |
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Yes, I do it the same as Chip68, but with cotton buds (what you Pennsylvanians know as Q-tips).
1] Heat legs with hot air gun (SMD rework tool)
2] Swab off the majority of solder with buds / cloth
3] More accurately rub off the solder each leg at a time whilst still heating. Replace the bud when it gets too scorched by the hot air gun
Your chips will look almost indistinguishable from new / pulled ones! (well, from the outside unless you want to repeat on the back of the legs) |
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Tredsaw12
Joined: 21 Apr 2008
Posts: 14
Location: Blackstone Valley, MA
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| Posted: Sun Apr 27, 2008 12:05 pm Post subject: |
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Wow, you guys have a lot of time on your hands. I just soak them in HCL, (hydrochloric acid). You can find it in the hardware store as Muriatic acid. HCL will dissolve solder but will not harm gold or copper. It may take about 24 hours or more depending on how much solder is on the legs.
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debs3759
Joined: 18 Jan 2006
Posts: 9477
Location: Northampton, Divided Kingdom
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| Posted: Sun Apr 27, 2008 12:13 pm Post subject: |
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| Tredsaw12 wrote: | | Wow, you guys have a lot of time on your hands. I just soak them in HCL, (hydrochloric acid). You can find it in the hardware store as Muriatic acid. HCL will dissolve solder but will not harm gold or copper. It may take about 24 hours or more depending on how much solder is on the legs. |
Can you show any before and after pics of some chips cleaned this way? It sounds like a great method if it really works and doesn't damage anything else on the chips...
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johnorun
Joined: 04 Apr 2008
Posts: 3364
Location: Chicago, IL- US
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donutty
Joined: 16 Feb 2008
Posts: 1122
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| Posted: Mon Apr 28, 2008 3:11 pm Post subject: |
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Acid! Wow... you had better be careful! What strength are we talking about here? 30% ? higher?
How about the print? And for epoxy encapsulated chips? I know for sure that conc. sulphuric acid (especially hot) will break down the epoxy plastic of chips. |
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wepwawet
Joined: 18 Mar 2004
Posts: 3019
Location: Seligenstadt - Germany
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| Posted: Thu May 01, 2008 5:47 am Post subject: |
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This is my result with pretty low concentrated HCL (a drop on the tounge doesn't realy hurt:-)
though it seems not being "dangerous" be careful when you mean it doesn't harm your chip...
btw, there was pretty much solder on the pins before, so far HCL works perfect.
I guess it is more or less a question of concentration and exact timing.
HCL can't be much more concentrated than little over 30 %. |
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donutty
Joined: 16 Feb 2008
Posts: 1122
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| Posted: Mon May 05, 2008 2:39 pm Post subject: |
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I tried also with hot 37% HCl on a TMS2516JL (gold leg / cap EPROM). Bubbles were produced around the solder, which was mainly removed, leaving it similar appearance as the photo above, but it also removed the print. So I would say, it is not worth doing because it still leaves a tarnished appearance.
Maybe something worth doing to prepare it for re-plating though. |
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vinthewrench
Joined: 08 Apr 2008
Posts: 20
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| Posted: Mon May 05, 2008 3:45 pm Post subject: |
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google found
http://www.sicsb.com/list_chemical.html
| Quote: | 7. SS500 - Immersion Solder Stripper
Use to strip off copper without attack copper base material.
SS500 is an acidic liquid material specially formulated for immersion stripping of solder and other tin-lead alloys from copper. SS500 does not attack copper. In addition, it will not etch nickel, gold, and iron which may be immersed into the stripping solution as part of the work being processed. It supplied as a ready to-use liquid and used at room temperature.
Oily, greasy, or heavily soiled products should be cleaned in a mild alkaline cleaner prior to immersion in the SS500 solution. Stripping is accomplished by simple immersion of the part in the SS500 solution. A new SS500 solution strips tin-lead from copper at a rate of approximately 100 micro ins per minute. As the solution is used, the stripping rate falls off slightly.
Mechanical agitation of the solution with a plastic stirrer will increase the stripping rate. SS500 leaves the copper substrate with a clean appearance. For printed circuit applications, where mechanical scrubbing is performed after the solder is stripped, no post-strip treatment is necessary prior to electroplating. However, if mechanical scrubbing procedures are not used, a mild acid bright dip may be used to make sure optimum adhesion of subsequent electroplated deposits. |
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wepwawet
Joined: 18 Mar 2004
Posts: 3019
Location: Seligenstadt - Germany
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| Posted: Mon May 05, 2008 4:01 pm Post subject: |
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Hm, how get some milliliters from a chemical plant in Malaysia?
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Kevinposton
Guest
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| Posted: Fri Jul 01, 2016 7:05 pm Post subject: Acid Gold recovery |
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| 2 parts hydrogen peroxide and one part muriatic acid. Takes a week or so, depending on quantity of metals, stir it daily. I've seen best results when done in a glass container. I use a coffee pot and filter in coffee filter and reuse. Keep covered when not in use. If you want to dispose it, throw in some baking soda it will neatralize it for disposal. |
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