Electronics Forum | Sat Jan 30 21:04:32 EST 1999 | Sidharth
Hi all, i'm researching information on fluxless solder bumping of flip-chip by either : 1. electroplating AuSn bumps 2. electroless Ni on Al pads in an autocatalysis process. could anyone point me in the direction of more information ? partic
Electronics Forum | Tue Apr 27 21:24:14 EDT 2021 | kwalker
No, you're correct. Nickel oxidation can be difficult to remove
Electronics Forum | Thu Apr 15 19:58:40 EDT 2021 | jimpat
In addition to confirming that the pad temperatures reach above the melting point of the preforms, consider checking the O2 PPM concentration.
Electronics Forum | Tue Apr 27 07:46:14 EDT 2021 | jeremy_leaf
I have tried cleaning the pads. That was our first step. Ultrasonic cleaning in acetone and IPA, and also tried etching in a 10% HCL solution. Our board is definitely achieving the correct temperature.
Electronics Forum | Tue Apr 27 07:50:09 EDT 2021 | jeremy_leaf
@KWalker I think that could be the case. Though I read somewhere a while back that nickel oxidation can be quite tough to remove, even with flux. Am I wrong about that?
Electronics Forum | Tue Apr 27 19:08:04 EDT 2021 | emeto
Jerry, just out of curiosity, why can't you use flux? Flux is essential part of soldering and it is there for multiple reasons. Flux we can also clean afterwords - even No Clean.
Electronics Forum | Tue Apr 27 21:22:57 EDT 2021 | kwalker
The fact that your cleaning didn't really help reinforces that it probably is oxidation. Cleaning won't remove that.
Electronics Forum | Wed Apr 28 15:51:52 EDT 2021 | duchoang
Could you share some pictures? Without any flux or paste, how could you place preforms on pads? SMT Pick and Place ?
Electronics Forum | Wed Apr 28 06:26:15 EDT 2021 | jeremy_leaf
@Evtimov I can't use flux as the components being soldered can't cope with any contamination whatsoever. Even an ultra low solids no-clean flux will be too much. I also can't clean the boards after soldering due to any residual contamination from the
Electronics Forum | Mon May 17 13:21:45 EDT 2021 | SMTA-64387881
PWB Bake out or other elevated temperture processes can cause issues with oxidation of that Nickel layer. The gold porosity can vary from batch to batch, but also process changes can contribute. Are you baking the boards or have previous reflow pro
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