Electronics Forum | Fri May 15 10:04:59 EDT 2009 | aj
Hi all, Is there any standard for percentage voiding on the center thermal pad on a QFN? We use the dot matrix array for paste to allow for outgassing etc, but we have had a couple of xray inspection "fails" for voiding on this pad , in or around 3
Electronics Forum | Mon Dec 07 14:55:41 EST 2015 | clydestrum
So I have an issue coming up that I'm not too sure how to handle. A board was designed with the wrong footprint for a 3-lead transistor in which the single-lead side has a much larger (think thermal pad for qfn) copper land than what is meant for the
Electronics Forum | Fri Feb 27 11:33:32 EST 2004 | Bryan
Very strange question,but interesting.Is there anyone who have conducted any experiments to figure out the results?I made a profile board,one thermal couple on pad and other one drilled into the ball of BGA.the 2 points are perpendicular to conveyor
Electronics Forum | Thu Aug 13 14:10:01 EDT 2015 | markhoch
Hi Sam, I have a feeling that what you're trying to communicate is that your DPAK's are skewing off the pad during reflow. This is caused by a thermal "mismatch" where the solder paste on one side of the DPAK becomes molten before the other, then th
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 | 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 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 May 12 07:53:28 EDT 2004 | solderpro
Lets make it easy on the poor guy, some are correct, check you profile but remember one thing most do not apply, it is important to match the type of paste you are using with the style of oven and configuration. send a direct email and I will give so
Electronics Forum | Tue Jun 04 20:34:28 EDT 2002 | russ
Jason, Excessive thermal ramp rates, misprints, improper pad design, paste type, placement pressure, all can cause solderballs. Do the pads on this board meet IPC 782 criterias? I have found that too much pad underneath component can cause this. A
