Electronics Forum | Thu Jun 07 18:09:21 EDT 2007 | stephan
We noticed unsufficient soldering on some 0805 chips located between pins from a plastic bloc connector . All chips are soldered with 45� angle. Flux quantity , preheating , contact time and PCB quality was checked. Do you know any international stan
Electronics Forum | Fri Oct 16 14:11:16 EDT 2009 | davef
thermal and pad
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 14:45:58 EDT 2009 | cyber_wolf
Many pick and place platforms rely on nozzle spring pressure to determine how hard a part is getting pushed into the paste.
Electronics Forum | Fri Oct 09 00:57:05 EDT 2009 | jjmag921612000
SteveO, I had personal experience with this using a Panasonic MPAV2B. It took a while, but I believe the end result was to have some additional "Z" travel to press the QFN into the paste. Also, the design of the paste on the ground was key to keep t
Electronics Forum | Wed Oct 21 08:06:06 EDT 2009 | scottp
I agree with Dave. If the device has a lot of power we'll put thermal vias between the solder deposits with annular rings of soldermask to keep solder out of the holes. We've never had to mess with placement pressure. We've been using QFNs for yea
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
Electronics Forum | Wed Sep 15 04:12:11 EDT 2010 | headlad
We had a similar problem so we shrunk the thermal and extended the pads. This allowed us to ensure solder resist was applied to the track in between. It fixed our problem.
Electronics Forum | Thu Sep 16 08:47:39 EDT 2010 | headlad
I extended the pads to help ensure the component locates correctly and to allow for easier re-work should problems occur. I reduced the thermal by 5% but you may want to speak to your fabricator and ask what they require to ensure that the resist is
Electronics Forum | Wed Sep 15 10:59:12 EDT 2010 | asksmt
Thanks for the valueable feedback, I have two questions 1. why do you have to extend the pad size ? is it okay if i keep pad size 2. I am currently using thermal pad size recommended in datasheet max value 4.2mm x 4.2mm, how much should i shrink