Thomas,

Is this a new problem, meaning they ran fine on previous builds, or is this the first
build of this assembly?  We had a similar problem on a new product that we tracked to
not enough solder to form a joint.  The parts were varied, not specific to any one part
like you are describing so this may not apply.  But, we were able to get solder to flow
up on to the leads of these parts in touch-up.  Have you confirmed that solder does not
flow onto the leads to rule out solderability yet?  We ended up changing the apetures
sizes on our stencil to increase the volume of paste deposited on the affected parts
and our problem went away.  You have to be careful not to cause bridging though.  Good
luck.

blm

Thomas Han wrote:

> Hi all,
>
> I have been noticing on our last batch of boards that we ran, some of the
> tsop flash chips were not reflowing properly.  I am not getting very good
> toe fillets on the chips and some appear as though they are just sitting on
> top of the reflowed solder.  This board has a good component mix(i.e. BGA,
> QFPs, PLCCsocket, SOICs, total(325-350)).  Other components reflow fine,
> but for some reason these TSOPS are not.  Is there something that we are
> overlooking?
>
> Your input would be greatly appreciated.  Thanks in advance
>
> Tom
>
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