Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

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via hole plugging

Chris Nuttall

#11426

via hole plugging | 19 May, 1999

We care currently running into problems during our plug via process: At the moment we plug prior to soldermask (LPISM) using epoxy resin - plugging takes place from the component side - however we are seeing solderballs after solder level.This is causing a bit of pain for those involved. I believe the solder pick up / balls is due to not plugging the via deep enough - leaving a recess only visible on the solder side for the solder to adhere. We are toying with the idea of plugging both sides to ensure that we get no recesses.

But I am open to any suggestions that may make my life a little bit easier with regard to via hole plugging.

Many thanks, Chris Nuttall - quality engineering

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#11427

Re: via hole plugging | 19 May, 1999

| We care currently running into problems during our plug via process: | At the moment we plug prior to soldermask (LPISM) using epoxy resin - plugging takes place from the component side - however we are seeing solderballs after solder level.This is causing a bit of pain for those involved. | I believe the solder pick up / balls is due to not plugging the via deep enough - leaving a recess only visible on the solder side for the solder to adhere. | We are toying with the idea of plugging both sides to ensure that we get no recesses. | | But I am open to any suggestions that may make my life a little bit easier with regard to via hole plugging. | | Many thanks, | Chris Nuttall - quality engineering | | Chris: Two things:

1 Let's hear more about your second side hot air leveling process, the board finish, and the extent of the problem. 2 Resist your temptation to plug both sides of the board. It's your "evil twin" trying to get you to do this. The heat of reflow or wave soldering during your customer's processing will cause the little air packet between the top and bottom plugs to expand and fire little epoxy ex-plugs across the room.

Good luck

Dave

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Chris Nuttall

#11428

Re: via hole plugging | 20 May, 1999

| | We care currently running into problems during our plug via process: | | At the moment we plug prior to soldermask (LPISM) using epoxy resin - plugging takes place from the component side - however we are seeing solderballs after solder level.This is causing a bit of pain for those involved. | | I believe the solder pick up / balls is due to not plugging the via deep enough - leaving a recess only visible on the solder side for the solder to adhere. | | We are toying with the idea of plugging both sides to ensure that we get no recesses. | | | | But I am open to any suggestions that may make my life a little bit easier with regard to via hole plugging. | | | | Many thanks, | | Chris Nuttall - quality engineering | | | | | Chris: Two things: | | 1 Let's hear more about your second side hot air leveling process, the board finish, and the extent of the problem. | 2 Resist your temptation to plug both sides of the board. It's your "evil twin" trying to get you to do this. The heat of reflow or wave soldering during your customer's processing will cause the little air packet between the top and bottom plugs to expand and fire little epoxy ex-plugs across the room. | | Good luck | | Dave | Dave,

We are using a CEMCO horizontal solder level which gives us an excellent HASL finish. However on we are seeing a hell of a lot of pick up on the solder side, and it seems to be where the registration of the resin plugging is not so good - smudging of the resin can be seen on the holes on the adjacent side to the solder pick up. As such we are trying to optimise the registration of the screen printer in an attempt to avaiod this - as we believe that if the registration is improved then we will be able to fill the hole a lot better. Regarding your comments on the "evil twin" trying to get me to plug from both sides, if the via is plugged for both sides (say about 50 - 75% plugged) then do you believe that the small amount of trapped air will cause the plugs to "fire out"? Remember that the resin wil shrink a little (sometimes the surface looks slightly concave due to shrinkage) giving a little bit more room between the 2 plugs - I think that this may reduce the effects of pressure build up. Please note however that I have limited exposure to via hole plugging, so please excuse me if this is not strictly true - any advice warmly welcome. Perhaps we should set up direct e-mail discussions for this one? Let me know.

Many thanks,

Chris.

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