Regards, Jim > -------- Original Message -------- > Subject: Re: [EE]: SMD soldering question > From: Mike Hord > Date: Thu, May 19, 2011 10:15 am > To: "Microcontroller discussion list - Public." >=20 >=20 > Is it the bond failing, or is the pad being levered off the board? ANS: The parts is coming loose from the pad. The pad is staying attached to the baord. >=20 > Does your CM do any kind of pre-placement solder paste inspection > to ensure that sufficient deposits of paste are being left? ANS: I just called them and they said yes, they do a 100% preplacement inspection, and a=20 sample post placement inspection. And a final inspection after reflow. >=20 > Is it always the same pad, or does it vary? ANS: It varies >=20 > Can you increase the pad size? ANS: No. Not easily. Due to connector design, and lack of real estate on the PCB. =20 >=20 > Mike H >=20 > On Thu, May 19, 2011 at 9:58 AM, wrote: >=20 > > > When these boards go through our production testing, which includes > > > several cycles of hot (85C) and cold (-40C) temperatures, we find > > > that the solder bond between the PCB pad and the connector pin fails, > > > which in turn causes the unit under test to fail. > > > > My first question would be what sort of strain relief is there in the l= ead. > > It sounds to me like it is not the solder joint at fault, more that whe= n the > > metal lead shrinks as it cools it pulls the lead off the pad. If there = is no > > loop in the lead to give it some expansion/contraction ability the faul= t you > > are seeing is exactly what I would expect. > > > > For space qualified assembly work all leads like you mention should hav= e > > some form of Z strain relief in them. The sort of temperature range you= are > > testing to is the non-operating survival temp range we would use. > > > > > > -- > > Scanned by iCritical. > > > > -- > > http://www.piclist.com PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > --=20 > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .