A possible way to make reflows/reballs last longer?

[Th3_uN1Qu3]

I happened to stumble upon the wikipedia page for BGA. And look what i found...

Mechanical stress issues can be overcome by bonding the devices to the board through a process called "under filling", which injects an epoxy mixture under the device after it is soldered to the PCB, effectively gluing the BGA device to the PCB. There are several types of under fill materials in use with differing properties relative to workability and thermal transfer. An additional advantage of under fill is that it limits tin whisker growth.

Could anything like this be done using commonly available materials? It sounds like a really good idea to me. After all, if it's glued, it can't move, and if it can't move, it can't break.

[c_hegge]

Re: A possible way to make reflows/reballs last longer?

^
It certainly didn't work for nVidia.

[severach]

Re: A possible way to make reflows/reballs last longer?

So all it takes to beat differential thermal expansion is a little glue?

nVidia chips also crack at the die bumps where the glue has no effect.

[Th3_uN1Qu3]

Re: A possible way to make reflows/reballs last longer?

At least it would alleviate ONE of the stress points. Any ideas on how this could be done at hobbyist level?

[tom66]

Re: A possible way to make reflows/reballs last longer?

Probably would involve removing the BGA, applying the glue (via an inverse stencil, glue where the balls aren't) and soldering the BGA back on.

[kikkoman]

Re: A possible way to make reflows/reballs last longer?

squeeze some thin epoxy through a needle under the thing?
it would have to have very low shrinkage, obviously.
no idea what kind the red stuff is they mostly use.

i sooo wish they had good glues (look at DuPont stuff for instance!!!!) at large hardware stores... nope. nothing. i mean the real good nasty chemical stuff.
the average joe must be kept away from such complicated and dangerous things.
arrgh!

[kikkoman]

Re: A possible way to make reflows/reballs last longer?

on a side note, on of the hardware chains over here now sells a UV hardening urethane glue (comes with needle tip and UV lamp). Interesting stuff although it has its downsides e.g. no chemical bonding.

[Th3_uN1Qu3]

Re: A possible way to make reflows/reballs last longer?

squeeze some thin epoxy through a needle under the thing?

That's exactly what i was thinking.

[marcellodj]

Re: A possible way to make reflows/reballs last longer?

Personally, i don t think glue will help...(think to epoxy you should remove when reflowing Dv serie...) but you can take a look here..

http://www.toolsfix.com/list/pro_cate75_2.html

[Joun]

Re: A possible way to make reflows/reballs last longer?

^
It certainly didn't work for nVidia.

That is so true..I have seen that red glue only on Nvidia chips and never on ATI.
We all know who breaks more often.On a side note something I have found the hard way: That glue makes it very hard to remove BGA chip when it fails..
The hard way means "by destroying laptop mainboards"..

[mattbrad2]

Re: A possible way to make reflows/reballs last longer?

That is so true..I have seen that red glue only on Nvidia chips and never on ATI.
We all know who breaks more often.On a side note something I have found the hard way: That glue makes it very hard to remove BGA chip when it fails..
The hard way means "by destroying laptop mainboards"..

I hate the glue stuff. It just makes my job more difficult. Take the xbox for example. They don't use glue but instead mount a heatsink with the force of a concrete block. Of course we all know how that turned out. The problem is more flexing of the solder balls themselves via ROHS solder and the micro-fractures between the solder pads.