Electronics Forum | Sun Jan 20 21:03:34 EST 2002 | peterson
Hello everyone! We just completed some 16-layer boards and noticed (after wave soldering) that there are some unique, white-ish discolorations. It looks as if someone layed their finger at weird angles on the groundplane areas. It is NOT finger prin
Electronics Forum | Mon Mar 24 08:57:20 EST 2003 | russ
I don't know if I would call it a "blow hole". what I believe happens (I don't have a camera to watch spheres during the reflow process) is that when the flux starts heating up, expansion, bubbling, or something physically displaces the balls. We fo
Electronics Forum | Thu Sep 11 23:50:51 EDT 2003 | Dean
Epoxy is hydroscopic. A cavity will form when the cure furnace reaches the boiling point of water. The steam expansion creates the pocket. It can be large enough to be filled with molten solder from the wave machine and cause a hard short under th
Electronics Forum | Mon Jun 28 22:12:24 EDT 2004 | davef
Things to consider are: * Thermal expansion characteristics of you flex and your pallet should be better matched. We use G-10. * Placement of your two sided tape should be better, more uniformly distributed. We run strips the length of the flex that
Electronics Forum | Wed Jan 12 10:15:43 EST 2005 | davef
We conformal coat our boards and get pretty good coverage along the edges of BGA. If you need coverage along the edges and are not getting it, your supplier may be able to recommend a different material or application method. Most often, underfill
Electronics Forum | Mon Aug 15 04:02:38 EDT 2005 | Rob
Purely out of interest & to satisfy my curiosity: Fact: China has been importing huge amounts of SMT equipment due to it's rapid expansion, bringing in used equipment from Europe, US & just about everywhere else, at a not insignificant cost. Questi
Electronics Forum | Sun Sep 25 11:18:16 EDT 2005 | CS
Hi! I'm facing a strange problem where PCB expanded in X & Y-axis after bottom-side reflow. When the PCB send for Top-side printing process, it is abvious that the printing alignment on the PCB's pads are out. With the problem mentioned above, I am
Electronics Forum | Mon Sep 26 10:06:06 EDT 2005 | stepheniii
Make sure the stencil lined up perfectly in the middle all along the width of the board. Everytime someone has told me that a stencil doesn't match the board, they were not critical enough on alignment. Usually they would say one corner is perfect b
Electronics Forum | Tue May 02 14:56:57 EDT 2006 | Tim
8.2.5.5 Flat Ribbon, L, and Gull Wing Leads, Maximum Heel Fillet Height (E). For class 3 the heel fillet cannot touch the body of a plastic component, except for SOICs and SOTs. Why is my question? What type of failure will be the result of solder
Electronics Forum | Tue May 02 16:37:57 EDT 2006 | bhall
I have experienced the exact same problem with excess solder touching the plastic component body. The solution in my case was simply to replace the stencil. I was using a reusable stencil frame that had been worn out. I replaced the stencil with a so
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