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 | Fri Sep 12 09:10:23 EDT 2003 | Norm Morikawa
Around 1989 I had this probelmm with a SMT CCA that would not solder in one area consistently. I had it cross sectioned by the bare board supplier and found that under their metallurgical microscope the thickness of this HASL bare board could not be
Electronics Forum | Fri Sep 17 03:03:29 EDT 2010 | grahamcooper22
Hi Gani, looking at the HASL icture and the poor wetting of the solder over the pads I would imagine that the HASL coating is very thin on the pads and in actual fact isn't 'solder' but is tin /copper intemetallic and this has poor solderability. It
Electronics Forum | Mon May 18 13:30:15 EDT 1998 | Earl Moon
| 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 solde
Electronics Forum | Fri Mar 26 15:48:31 EDT 2021 | grahamcooper22
Leaded HASL on small pads can be quite difficult to print on...the HASL tends to be domed rather than flat..and that can affect print quality...you really need a perfectly flat pcb pad to print paste on when you are assembling 0.5mm QFPs. If the pcb
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 | Tue Aug 03 17:13:41 EDT 2010 | bradlanger
Craig, If it is LF Hasl it sounds like it applied too thin exposing the intermetallic layer wich is not solderable. We call out a minimum thickness of 80 microinches and have good results. We have had shops in the past that did not control the Hasl
Electronics Forum | Fri Sep 17 07:33:56 EDT 2010 | scottp
Based on the last few pictures in the report, the root cause is lousy HASL. In fact, you don't have HASL - you've got SnCu intermetallic. Don't mess with your reflow profile, change paste, or monkey with anything else in your process. Have the boar
Electronics Forum | Mon Jun 15 16:51:05 EDT 2020 | emeto
Tin/Lead has 183C melting point and probably around 220 peak temperature at reflow. Tin has 232C melting point. I would assume that based on this information you would understand why intermetallic joint is questionable. Go to any flat finish. HASL wi
