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In a message dated 09/06/2000 11:43:51 AM Central Daylight Time,
[log in to unmask] writes:
> Thechneters,
>
> I'd like to know if there are special design rules for the solder mask on
> PCB.
> Most of PCBs I have seen have pads surrended with a gap and solder mask.
> In our case I have got a PCB with solder mask on the periphery of BGA pads
> (to prevent bridging according to the customer).
> It seems to me that the solder mask on the periphery of pads is not so
> efficient as expected to prevent bridging and it seems to be also
> responsible of the poor mechanical properties of the joint.
> Does anybody have experience with this weird technique (solder mask on the
> periphery of pads)?
>
> Thanks in advance,
>
>
> Walter Horaud
Hi Walter!
I believe you're referring to Solder mask defined pads vs. Non Solder mask
defined pads. You're right when you say that it reduces reliabilty of a BGA
solder joint. Go to:
http://extra.ivf.se/ngl/E-BGA/ChapterE2.htm
and you'll find an article that addresses that very issue. The article also
states that there maybe an occasion in which it is better to use a solder
mask defined pad on the PCB, that is if the BGA device has solder mask
defined pads to which the balls are attached.
-Steve Gregory-
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