Clearing blocked holes in PCB's

[Hewitson]

Hi all,

I have here a PCB which I would like to repair. It seems someone has diagnosed one of the 6116 RAM's as faulty and removed it, but some material (definitely NOT solder) has been left in some of the through holes. I have tried to flush it out with resoldering and desoldering but I can't get it to budge, the only idea I have is to drill it out very carefully with an 0.6mm drill bit I have...

If anyone has any better suggestions, I'd love to hear them as I really don't want to damage this board!

Thanks

 

[Nick C.]

It sounds like the part might have been cut off of the board, leaving some of the leads in the holes. Depending on the size of the pads, I would drill as a last resort, as it would be very easy to damage the board (imagine trying to drill out a nail that's in a piece of plywood). Have you tried pushing out the obstruction while the solder is flowing - maybe with something like a resistor lead? A hot air soldering station would simplify this, if you are so equipped. And preheating the board sure wouldn't hurt either.

Whatever you decide to do, I would suggest replicating the problem on a scrap PCB and working out your technique on that first.

Best of luck, and let us know how you make out.

Nick C.

 

[dick_freebird]

I have a similar problem with a batch of boards, where it
looks like the solder mask got all into my plated through
holes and made then unsolderable.

Does anyone know what eats solder mask but not the
FR-4?

 

[KJ6EAD]

One technique that works sometimes is to load the bottom of the hole with molten solder on the iron while pushing a sharp stainless steel pick through from the top side. With a curved pick you can do it the opposite way (iron on top, pick on bottom).

 

[KHALEDRAHNAMA]

If I was you, I never drill any board ,My suggestion : Use plenty of flux. Then try to heat the remained lead with your iron.

For whom that do not know when and where use flux:

1- If you want to melt a solder that had been melt before .

2- Used with some board or any materials that doesn't accept the solder easily.

 

[nandhu015]

I have a similar problem with a batch of boards, where it
looks like the solder mask got all into my plated through
holes and made then unsolderable.

Does anyone know what eats solder mask but not the
FR-4?

Thinner will do the job. But i dont know which thinner to use.

 

[Raza]

Is that a Double Sided PCB or single sided. If it is double sided then the possibility is that the Electroplating (some time known as Wells) of the holes is damaged while removing the IC and those are stuck in the holes. First please use the Amplifying Glass to make sure the residue in the holes. As you said it is definitely not solder then it is the only possibility left.
Good Luck.