Electronics Forum | Thu Sep 11 16:50:18 EDT 2003 | davef
Sure it's conceivable that thin HASL can cause tombstoning. Harkening back to the ample discussion in the fine SMTnet Archives, tombstoning is caused by an imbalance in solder surface tension between the two pads of SMT component. The source of thi
Electronics Forum | Fri Sep 12 13:14:33 EDT 2003 | Mark Kostinovsky
A little adition to Norm's statement: Sn-Pb intermettalic compounds do not accept solder as they are (even without being oxidized).
Electronics Forum | Tue Sep 09 18:07:18 EDT 2003 | davef
We would be very wary of allowing 50 uinches, because this will likely result in reduced shelf life due to intermetallic growth. As a guesstimate, at least 10 uinches of that 50 uinches, and maybe more, is already intermetallic when you receive the b
Electronics Forum | Wed Sep 10 12:56:09 EDT 2003 | davef
Intermetallic compounds [IMC]: * Form during the alloying process of some metals. In soldering these are Sn, Ni, Ag, Cu, Au. * Do not accept solder. * Increase in depth in logarithmic proportion to both time and temperature. [So during the solder
Electronics Forum | Thu Mar 02 13:04:22 EST 2006 | Chunks
0603 parts at .2mm spacing is pretty easy. But are there any other parts, like fine pitch QFPs? Is your board HASL or something else? Is there resist/mask between all pads? If it's just 0603's at .2mm, then you can probably go 7 mils and get good
Electronics Forum | Tue Sep 16 10:58:03 EDT 2003 | swagner
I am currently having a discussion with a pcb supplier about inadequate hasl thickness, we are measuring below 40 microinches of hasl when our spec calls for 100 microinches as the minimum. Our supplier came back with the statement the entire indust
Electronics Forum | Wed Sep 17 10:49:48 EDT 2003 | davef
We agree. Colin Lea showed that HASL less than 2 microns [80 uin] thick has limited shelf life and that shelf life gets worse as the HASL gets thinner. Unless you do not need shelf life, consider sticking with 100 to 500 uin. There is nothing wrong
Electronics Forum | Tue Sep 16 15:09:23 EDT 2003 | russ
Maybe trying to get a flatter HASL PCB. But i am unaware of the "entire industry" trying to go thinner. Russ
Electronics Forum | Mon May 18 13:18:25 EDT 1998 | Chrys
I'm reviewing my board fab spec. It calls for a minimum SnPb thickness of 50 microinches on HASL PWB's. I've looked at other specs that call out anything from 30 to 80 microinches, and others that just say the copper pad must be covered and soldera
Electronics Forum | Wed Nov 17 07:39:20 EST 2010 | jax
Most PCB manufacturers should be able to fall between 1.25um-5.00um for Pb-Free HASL. I doubt you will get anyone to agree to anything higher. If you are going to require an average thickness, make sure you also state "No Copper exposure allowed".
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