Electronics Forum | Thu Jan 29 06:58:40 EST 2004 | davef
Ramp / Soak: Tombstoning is occuring during reflow. You need to get more heat into the ground plane. Obviously a ramp aint gettin' it done. Further, without intending to disrespect your internal discussion, if a linear profile improved the situati
Electronics Forum | Wed Jan 28 20:26:32 EST 2004 | Vinny
Hi Guys, Really need your help to suggest how to tackle this situation.
Electronics Forum | Thu Jan 29 00:10:17 EST 2004 | Vinny
Hi Dave, Thanks for your reply. I have tried getting the design changed from the customer but they cannot provide thermal relief as this changes the RF performance and they cannot afford to do that. As for profile it does reach the reflow tempera
Electronics Forum | Tue Feb 10 15:13:06 EST 2004 | patthemack
Hey Vinny, Sorry I haven't looked at this for a while. 3 things to try: Tombstoning- The ground plane side is larger because the solder mask allows for a little slop at the board shop (clearance around a pad of a few mils). Since there is not a defi
Electronics Forum | Mon Jan 26 21:10:36 EST 2004 | Vinny
I have done acurate profiling which meets the solder paste specifications. The point I am trying to highlight here is also due to the ground plane side being much larger causing the tombstone defect. I have even tried doing a linear profile, it hel
Electronics Forum | Thu Jan 29 18:01:20 EST 2004 | davef
Rethinking to Ramp / Soak: Yano, staying with ramp might not be all that bad after all, just decrease the ramp / slow-down the conveyor.
Electronics Forum | Thu Feb 24 20:13:22 EST 2022 | dwl
They don't look that bad, especially for SN100. There is evidence of wetting on the toe and the paste on the pad seems to have reflowed properly. What does the heal look like? That's the more critical part of the solder joint for Gull leaded parts.
Electronics Forum | Thu Oct 15 11:04:28 EDT 2009 | spitkis2
Thanks Jim. Pressing the QFN into paste was what I thought of, just wasn't sure if it would cause solder paste to be pressed outside the pad area and possibly bridge with an adjacent pad. Do you recall the ratio of paste coverage to the pad area?
Electronics Forum | Fri Oct 16 14:11:16 EDT 2009 | davef
thermal and pad
Electronics Forum | Wed Sep 30 13:10:49 EDT 2009 | spitkis2
Hi guys, Can someone please clarify whether adjustment of Z axis travel is a critical parameter during placement of QFN devices. If so, to within what tolerance? In other words, should a pick and place machine position a QFN down on the board so t
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