Electronics Forum | Fri Jan 03 02:03:58 EST 2020 | sssamw
What's your target for voiding? I cannot see it violate 25% of solder joint area. Process setting and PCB design can impact the voiding, many factors, such as PCB pad, stencil aperture and thickness, re-flow profile, solder paste, etc.
Electronics Forum | Fri Jan 03 12:48:23 EST 2020 | cyber_wolf
Besides correct stencil design, solder paste chemistry can have a profound effect on voiding. People will tell you reflow profiles. I have never in my career seen a reflow profile have any effect on voiding unless it is grossly off.
Electronics Forum | Fri Jan 18 14:39:07 EST 2013 | davef
Main issues with LGA voiding are: * Design * Material selection * Thermal recipe For design, loo here http://blogs.smtnet.com/smt/other/qfn-btc-design-guidelines-thermal-pads-etc/ BR, davef
Electronics Forum | Tue Jan 14 12:20:33 EST 2020 | cyber_wolf
If you are using standard alloy and flux types and you are within the ballpark of 30-90 seconds above liquidous you should be fine. As I said above unless your profile is grossly off, it is not the cause of your voids.
Electronics Forum | Thu Jan 02 10:30:42 EST 2020 | emeto
thank you Steve, when you mention Stencil design, what do you refer to? How about the Reflow profile? Any specifics that I should look for. Everything is in my process window, but some detail towards this package might be very helpful.
Electronics Forum | Sat Jan 11 08:57:26 EST 2020 | jakapratama
Hi Evtimov, Could you share your current reflow profile setting, and also your part technical datasheet on its heat tolerance? It might as well help other engineers to review and give their opinions.
Electronics Forum | Tue Jan 14 16:57:52 EST 2020 | emeto
Still considering going from 5mil to 4mil stencil. Concern is the 50mm part might have issues with contact on the outside rows.
Electronics Forum | Thu Jan 02 22:09:15 EST 2020 | Zack
Hello, Can you give more detail on LGA parts in question? is 50 mm x 50 mm is overall size of the parts? What about pad pitch and how big is the pads individually? I assume that 50x50 mm is overall size. How about the stencil opening for the LGA pad
Electronics Forum | Sun Jan 05 20:10:16 EST 2020 | sssamw
Yes, you may need tell us how the PCB designed, how it re-flow(even it's Indium voiding formula), how stencil is. The void ratio means area ratio, not diameter ratio, so you need calculate it. If you have high ratio void, show its picture.
Electronics Forum | Tue Dec 31 17:05:20 EST 2019 | slthomas
Assuming you've already looked at optimizing your profile and stencil design, have you looked at metal load in the paste? I hadn't, but just read that increased metal load (associated with reduced powder size, i.e., moving from T3 to T4) has been sh
