| | Our spec on voids is 30% ball diameter in the center. On the component to ball and pad to ball interface, we use 25%. To determine this spec, we asked around. I don't know of any studies that have been done to verify if this is OK | | | | Regards | | Jim | | | | | I saw the problem of void in solder bump on in lead less component or some BGA. But I didn't have standard specification of that void is accept or reject? Do any body have the better idea or suggestion of the criteria ? | | | | | | Thank you, | | | Wirat S. / Jan 15, 99 | | | | | For those of you that want specific guidelines please send me e-mail containing the customer and I will get back to you on the exact void allowance. I would post it here but there is not enough room! If this does not work the customer would be more than greatful to give you dimension acceptabilities for each product you build. | | Hope I can help | | | | | Dear Sir,
Thank you for every feedback, I think in the range of 20% - 25% of void in solder are acceptable, it depend to our products application and component packaging type. Right now, i saw problem of lead less SMD size very close to Tant-C, saw a little small void around the solder join. But other SMD component in the same assembly was good, no viod.
I'm very interested to see the result of study with ESS. It may give us a guide line to revised our specification again. I am looking for the result of ESS study.
Since the specification of void in solder is not the concrete yet. Can I change a question ? Instead of specification of void solder to what is the root cause and how to eliminate or minimize the problem in our assembly process ?
I assembly PCBA FR4 with PBGA or Lead less component, with clean solder paste (water soluble paste) type 2, PBGA was in the second reflow. Reflow with hot oven. I used to baking PCB FAB 1-2 Hrs at 120 C +/- 5 degree C and PBGA baking at 125 C =/- 5 degree C. But x-ray after second reflow still saw a little void in solder. Why did it coming from? - PCB FR4 Multilayer was out gasing during reflow? - Moisture in the component or PCB? - Incomplete melting of solder paste? or flux residue? - Wrong reflow profile? PBGA require special profile? Appreciate every input from your experience.
Best Regards, Wirat S. / Jan 16, 99 email : wiratsr@gssthai.com
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