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TIP: A simple and safe way to desolder SMD SOICS etc

I discovered this via needing to isolate Vcc of a SOIC where the trace is under the IC and a multilayer board. I have a reel of 0.08mm diameter tungsten wire , tungsten probably not critical and diameter only needs to be small enough to go under SOIC pins. I've since tried, pin by pin, of an 8p SOIC on a scrap board with a success rate of 8 out of 8 isolating each pin , first time. Leaded solder, PbF situation not tried yet

Feed length of the wire under a pin , long enough to grab hold of both ends. Pull outwards and slightly upward while quick soldering iron melt of the pin solder. The wire pulls through, but surprisingly , 8 out out

8 times so far, the solder has not rejoined across the gap. Then a sliver of mica under the pin , in my Vcc situation, to fully isolate for testing purposes. But of course where hot air is out of the question , the IC is required for salvaged re-use etc, this method pin by pin could be used even in restricted space, to salvage a whole SMD IC. I wonder if a single loop per side of a DIL or quad footprint IC , and progressive single pin melting , would work with 8 or more pins in one operation - worth trying some time
Reply to
N_Cook
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Surface-mounted stuffs are not supposed to be repaired as traditional chips, right? :)

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Reply to
Mr. Man-wai Chang

I'd try to break the trace leading from the pad first.

Reply to
dave

I believe he was describing a diagnostic procedure, not a chip repair.

Reply to
dave

Not accessible in tnis case, its buried inside the board somewhere unknown. While at it for traces that are accessible. Sometimes in those sets of Cintride/"diamond" abrasive addons for Dremmels, a diabolo shaped one. Like 2 cones back-to-back, the 3mm or so diameter outermost cone base is excellent for cutting neat + tight slots in fine pcb copper traces.

I will try kevlar fibre from an optical data link instead of tungsten wire, to see if that works also

Reply to
N_Cook

A twist of kevlar fibres works if you can get the cord under and around the pin

Reply to
N_Cook

That sounds like the 30 AWG wire that used to be used to wrap wire backplanes. I have several rolls of solid wire in that size that is tinned, and has a thermoplastic insulator, commonly used for ECOs (Engineering Change Order)

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Reply to
Michael A. Terrell

I believe he was being humorous. (note smiley...)

Reply to
notme

or even just plain old wire-wrap wire, it has to be strong enough to be pulled tight over those square corners of the pins without fracturing. If I can remember where it is I'll dig out some of it and see how solderable it is and whether it works for this SOIC removal purpose

Reply to
N_Cook

Tried some ancient Bicc-Vero wire-wrap wire (Kynar sleeving stated on the drum, order code faded with age), surprisingly as made just down the road from me, stated as 30AWG. I don't know how to strip off long lengths of the sleeving but for 6 inch length, grab stripped wire end in pliers and compress by pushing with fingernail+finger, the Kynar/ptfe? along and off the wire. Incidently , by heating and stretching this , in effect sleeving, will form even finer spaghetti tube. The wire does take solder and I can confirm can be used for SMD SOIC removal

Reply to
N_Cook

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