Electronics Forum | Wed Jul 22 13:50:49 EDT 1998 | Justin Medernach
| My firm has just begun it's first PCB that will use BGA packaging. I have been reading up on the processes involved with BGAs and was wondering if you need to apply solder paste to the pads prior to applying heat and mounting the part to the board
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 | 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 | 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 | Mon Jan 26 03:45:37 EST 2004 | Vinny
Hi All, We are producing a veriety of RF related PCBAs in which we see Unsolder/Mislaigned on a regular basis. In these baords usually one of the pad is connected to a signal trace and the other pad is connected to very huge ground plane. This gro
Electronics Forum | Wed Jan 28 20:58:16 EST 2004 | davef
Vinny: From a thermal standpoint, your choices are: * Get your customer to design thermal relief in the board. * Set your thermal recipe to assure that the grounded pad reaches reflow temperature. This may require a long soak at a single temperature
Electronics Forum | Mon Jan 26 04:13:48 EST 2004 | patthemack
First of all, did you profile this board with a mole, such as a KIC? Is the solder flowing, or just not wetting to the part or pad? I work with RF boards as well, but the main problem is tombstoning due to the ground plane side being larger because o
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 | 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
