soppcb
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I'm curious as to what technology they are using on their boards. For SMD design based products and from two recent PCB designer get togethers* ENIG was the finish of choice, but this was standard small BGA QFN (bottom terminated components). HASL is no good for QFNs and numerous other SMD compnents today, especialy 0.5mm pitch QFP's. As I have said for PTH and SOIC type SMD, you can probably get away with HASL, tin/lead HASL has many advantages (ie we've always used this finish, blah bal balh, which is why quite a few mill designs still use it cos they are dinasours), BUT if you use modern SMD (0603, BGA QFN) then one of the flat surface finishes is a requirement, be it ENIG, Immersion silver, OSD. You cant even screen small components properly with HASL's meniscus.
Anyway what I would reccomend is that if you are members of the IPC, have a look at their website and the amount of research that has been done on surface finishes for PCBs. They also have data from the majority of the world PCB manufacturers. They are the ultimate resource for any information regarding any aspect of PCB design. Also the solder paste screen printing research done with various surface finishes. And the SMTA is another source of info, oh and NASSA, and the SMART group in the UK.
Tin whiskers is not related to surface finish (unless it is tin), it is more to do with lead free components having matt tin terminations, and lead free solders. Funnily adding about 3% lead to tin stops the dendritic growth of tin whiskers. The best source for info is NSSA:
NASA Goddard Tin Whisker Homepage
For the record I have been studying surface finishes for both tin/lead, lead free, and lead free components with tin/lead solder for over 10 years. From my research and numerous high tech, low tech boards the best all round surface finish is ENIG, it dosn't lead every category, but when you look at all the other knock on effects it comes out top, though ENIPIG will probably overtake it.
Shelf life and storage conditions,solderability, high speed, screen printing, cost, reliability (a cheap finish is no good if you get solder defects, the cost of one duff board will usualy pay for a better finish on a few 100-1000 boards).
*One was a military only on flex and felx rigid design.
Yes, I used HASL for many years, the crossover was between 1998 to 2002, where some designs were HASL and some were ENIG,. And even now I get to see jobs with HASL. Some like immersion silver, for very high speed and GHz RF its the best finish as it gives the best solder joint in terms of resistance.
Others like organic finishes, and others tin!
Without discussions and debate though we would not be aware of other finishes, and in my case it prompts me to re-read my documentation and also look for new documentation.
What I would reccomend is signing up to this, its a great source of PCB related news:
https://www.pcbupdate.com/
Hi...
you can also try in this..
Praveen
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