Hi technet! We've got a customer working with high power transistors, they want to use solder pre-forms to solder a heatsink on top of a row of transistors. So the stackup will be PCB - transistor - preform - heatsink, where the heatsink will span a row of 5 transistors. The question is how do we establish that this is working OK and isn't full of voids? This is at the "ok, we think this will work but we need to qualify the attachment method" stage. I've come up with a couple of options: 1) tear / grind it off and look for anomalies - not very sure to find issues. 2) x-ray it - we don't have a 3-d x-ray so I'm not confident in our abilities to find voiding. We do have a nice static x-ray though and will try it to see how well it can see. 3) Sonoscan it to look for voids? Would have to be outsourced. Am I missing any obvious options? -- Graham Collins Senior Process Engineer Sunsel Systems (902) 444-7867