Electronics Forum | Sun May 19 23:38:57 EDT 2013 | shrikant_borkar
We are EMS. Later revisions and Other models are get Modified. Now we have some remain Stock of Pcbs abd there end also. We have taken trial with Reduction in Apparatuses. But even small amount of solder paste at thermal Pad is causing QFN lift up.
Electronics Forum | Fri Nov 09 10:37:38 EST 2007 | devajj
We have started using QFN packages in large volume and are having problems with no-solders. We are using 6mil stencil with 1x1 paste print to pad. These also have thermal pads with thru vias that we reduce the stencil aperture by 1/4. Board also ha
Electronics Forum | Fri May 31 12:50:42 EDT 2013 | spoiltforchoice
Is this a "thermal balance" issue? In the 2nd image you have a group of pads blobbed together as one giant pad. IMHO this is a bad idea, QFN's rely heavily on the magic of your paste and good PCB design to get good alignment. When your solder paste i
Electronics Forum | Fri Jul 27 09:47:20 EDT 2018 | davef
Adding to Rob's suggestions ... One of the theories about voiding in thermal / ground pads of BTC is: Solder starts melting at the edge of the pad and moves inward towards the center of the solder mass. This traps flux volatilizes. So, there needs t
Electronics Forum | Thu Nov 06 07:54:50 EST 2003 | davef
First, skewing is a perfectly acceptable condition, providing the amount of skewing is not excessive. A-610 provides guidance. Second, this part is a land grid device. Land grid devices [ie, BCC�, LGA, QFN, MicroLeadFrame�, etc] are essentially BGA
Electronics Forum | Sat Nov 10 22:45:06 EST 2007 | realchunks
1. What is the body size? Who cares. 2. What is the pitch? Doesn't amtter. 3. What is the terminal size? Doesn't matter 4. What is the land pattern size? Really doesn't matter. 5. The Thermal square pad in the middle, with how many vias? If you
Electronics Forum | Mon Nov 12 09:22:41 EST 2007 | devajj
BTW, The surrounded QFN fine pitch terminals > should have the normal aperture reduction of 7 % > in case of RoHS Senju solder paste. This works > for our Telecom customer. > > The vias in the > ground pad will be somewhat filled with solder >
Electronics Forum | Fri Dec 22 16:04:26 EST 2006 | mika
Hi, This Not so easy as one wuold think. Has the thermal pad of yours vias? How many? What's the via's dia? What is the pcb thickness? If the the pcb has a "ground layer" connected (vias) to the pcb thermal pad, it could sometimes be a little bit tri
Electronics Forum | Sat Dec 02 10:23:47 EST 2017 | tomh
Have you ever heard of "Solder Mask Defined Thermal Pads"? I wrote a short blurb on this here - https://www.pcblibraries.com/forum/ipc7093a-btc-qfn-solder-mask-defined-thermal-pad_topic2154.html This technology saves fabrication costs by not havi
Electronics Forum | Thu Oct 26 10:29:03 EDT 2006 | Mike
First, Voiding under thermal pad is unavoidable(pardon the pun), unless you can find a way to add sufficient amount of solder paste to cover the area, and match that solder volume on your terminal leads. I build HVM qty's of "QFN" components w/ therm
