Copper Shims in Reflow Jobs, Yes or No?

[Rosabonita]

I'm working on a couple of reflow repair jobs atm and have come across a technique previously unknown to me: the use of copper shims on top of thermal paste to reduce future defect rates. From experience, I know that there is a chance that a reflow job won't 'stick' so to speak. For example, when repairing fat PS3 YLOD, I make it a point to run the systems at least over night. Most pass this basic test fine, but every once in a while I have a system fail which I need to subject to a re-reflow. Atm, I am working on a HP Pavilion dv7 who, despite several attempts, still crashes during graphics benchmarks from over heating.

 

While chatting with other enthusiasts at a local restore, the advice was given that a copper shim should be added between the thermal paste on the gpu and the head sink (in this case, the cpu will also need one to maintain a level heat sink). I am not able to find definitive information on this method online and would like to know before I make the attempt whether anyone has had success with this method. In addition, what size copper shim should be employed? The type I ordered is slightly smaller than the gpu/heatsink block, but I am under the assumption that this is acceptable. Is this the case?

 

 

[sushisharkjl]

I have not encountered this nor tried it, but from intuition I think that a thinner piece would be better, around 1/8 or 1/16 inch. 

 

Would it not be easier just to have the entire heatsink base made of copper? Or do they not make those anymore?

[Rosabonita]

It is, but the apparent difficulty is with the quality of the sodder. Being poor, even after the reflow they fail at a higher rates that systems which haven't failed. As I understand it, the copper shim not only provides additional thermal benefits, but adds additional pressure which helps solidifies the connections. Or, so I have been told.