Thanks Grant,
it's also with 0805s that I'm fighting.
What did you do about it?
Ioan
> -----Original Message-----
> From: Grant Emandien [SMTP:[log in to unmask]]
> Sent: Thursday, August 30, 2001 11:02 AM
> To: [log in to unmask]
> Subject: Re: [TN] Component skew after reflow
>
> Ioan,
>
> You're explaining a similar problem (on 0805's) we had recently (also on
> ENIG boards) - what we noticed was that the applied paste at times was
> offset to one end and further exacerbated by the component being placed
> off-centre to the other end, hence the apparant randomness. Inspection
> prior
> to reflow indicated fractional or no contact between the solder and the
> end.
> This condition resulted in 2 types of defects after reflow i.e. not
> soldered
> at one end (as you mentioned), as well as the more obvious tombstones when
> the tension really gets angry.
>
> Regards
> Grant
>
> -----Original Message-----
> From: Tempea, Ioan [mailto:[log in to unmask]]
> Sent: Thursday, August 30, 2001 4:51 PM
> To: [log in to unmask]
> Subject: [TN] Component skew after reflow
>
>
> Hi Technos,
>
> I have an intriguing one.
>
> I find passive components that are not soldered at one end after reflow.
> These components show very good joints at one extremity while the other
> end
> is not soldered at all. The not soldered end is usually outside of the
> pad,
> at the mercy of the surface tension, but sometimes it touches the
> respective
> pad, being untouched by the solder, that forms nice bumps on the pad.
>
> We're on no-clean paste, the board finish is ENIG. The assembly has being
> running for a long time, we built tenths of thousands without this
> problem.
> But all of a sudden... The problem appears randomly, not always on the
> same
> component, not always at the same place. The frequency is let's say one
> occurence every 50 boards. The assembly is not so populated, barely about
> 50
> parts.
>
> I checked the insertion, it is good. I even offset manually some parts
> before the reflow, but got good soldering on them. The reflow profile is
> the
> same, I even ran the profiler. The paste is OK, good date code, same
> printing conditions, paste height OK. The land patterns are adequate, they
> haven't changed.
>
> First, my instinct told me it's the parts, maybe they're too old. I
> checked
> the reels and the manufacturer's date codes (not the broker's) are between
> mid 2000 until june 2001. Not that old, are they?
>
> What could it be? The board? What and how to check, since the pads are
> very
> well wet? The parts? Anything else?
>
> Thanks for any input,
> Ioan
>
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