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SMT electronics assembly manufacturing forum.

RoHS Issues

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RoHS Issues | 13 April, 2007

Hello All,

I am working with a Mid Sized PCBA Manufacturer as a process Engineer. We have recently moved 1 of our customers to RoHS(Silver Immersion) boards. We are seeing a lagre number of issues Blowholes, allignment issues, board quality etc. We have route caused all of these but I am just wondering are the roadblocks we are encountering being seen across the industry or is it our qualification process that needs tweaking. It just seems to me that we are encountering alot of (independent)issues. Is everyone seeing these.

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RoHS Issues | 13 April, 2007

We have already started to ship ROHS products to our customer since mid of last year. So far, I do not encounter any problems that you describe. Have to check with your flux manufacturer, is it for leadfree process?

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RoHS Issues | 18 April, 2007

Check with your PCB supplier who the manufacturer of your I-Ag is. This makes a world of difference with regards to solderability.

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RoHS Issues | 19 April, 2007

Welcome to RoHS. Or, at least, to the version of RoHS that I've had to deal with since I started with my current company.

Blowholes and pinholes seem to be common in PB-free manufacturing. At least, they have for me here. I also note that IPC has listed some anomalies in pb-free assembling that most of us would have thought previously rejectable conditions. Check out the 610D for lead free solder joint differences.

We are using SN100 solder, and have experienced a higher rate of blowholes. We've been soldering with a static pot, and haven't found much to resolve our issues. I've recently purchased a pb-free wave machine, and am hoping I can address the issues there with different heating/fluxing capabilities, as well as an active wave rather than a static pot.

One thing that seemed to improve blow-hole creation for us was board finish. White-tin and tin-immersion finishes seemed to cause a lot of problems in our process, while ENIG finishes reduced a lot of those problems. I know that with white-tin finishes, the boards must be given an alcohol bath before processing; it's the only thing we've been able to find that improves soldering.

In surface mount soldering, we've observed a higher rate of mis-aligned parts. This is due, in part, to the shorter TAL during reflow. And, apparently, a difference in surface tension during reflow. The parts do not center themselves nearly as well as they do with regular tin-lead solder. How to fix this issue? Make sure your machines are placing the parts as close to dead-nuts center as possible. Since the pb-free paste/reflow won't center the parts as well as tin-lead did, less slop is allowable during smt placement.

cheers ..rob

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