Electronics Forum | Mon Nov 06 10:29:28 EST 2000 | Dean Stadem
All of the replies have merit. Here is another one. Because the cause of the tombstoning is wetting forces that are imbalanced, and one end wets faster or more readily than the other, the 0402 lifts up on that end easily because of its low mass. Incr
Electronics Forum | Thu Feb 08 12:09:06 EST 2001 | BLNorman
Potting compounds and conformal coatings. Any 1 or 2 component liquid thermoset material.
Electronics Forum | Fri Dec 17 16:23:22 EST 1999 | Mike Naddra
Hello Henry, Tombstoning is caused (In most cases) by a force imbalance on either side of the component. As the solder becomes liquidous the surface tension of the liquid will pull the component to the center of the liquidous area. To solve the probl
Electronics Forum | Mon Jun 11 21:27:43 EDT 2001 | procon
Way to go CPI! This is a classic example of design. Many people experience this when the have an 0402 close to a QFP or other large components. The pad closest to the larger component will become liquidous later than the pad farthest. Hence, a new t
Electronics Forum | Tue Dec 17 18:37:18 EST 2002 | davef
As a starting point, consider that these component leads may not be getting hot enough. Measure the temperature profile on the leads that do not solder well to be sure: * Heating and cooling ramps are within the paste supplier's recommendations. * C
Electronics Forum | Wed Oct 09 20:52:27 EDT 2002 | davef
Russ, Be careful on how you determine your liquidous point. Sure 205-210�C is fine if your paste and the solderability protection on pads and component leads are near eutectic solder and things worked according to plan, but in real life it doesn't
Electronics Forum | Thu May 04 17:14:11 EDT 2000 | Boca
Solder 'follows' heat, sounds like the fab is heating up faster than the component. Or the components are solderability 'chanllenged' and the paste turns liquid, and would rather spead out on the land than wet to the component termination. Are thes
Electronics Forum | Wed Jan 18 09:18:49 EST 2006 | samir
I had the same exact problem recently. I did exactly as the gentlemen said, and reduced the B/S zones 20 or so degrees, AND changed to medium convection. I'd like to point out that the B/S components still go liquidous (such is the Physics of convec
Electronics Forum | Thu May 04 13:20:55 EDT 2023 | tommy_magyar
We do the same as dontfeedphils, with the difference being that it goes through a drying program too after stencil wash program (3 mins @ 90 degrees air spray) to dry out the via holes and any trapped liquid from under the components.
Electronics Forum | Tue Dec 28 12:59:34 EST 1999 | Justin Medernach
Edmund, Check your "Air Amp" settings or the equivalent on your oven. Sounds to me like they are probably turned up too high in the reflow zone and you are blowing the components off of the board when the solder goes liquidous. Regards, Justin
