Todd

"Its a long shot Chuck, but it might just work."

When you say "The profile was also tweaked" do you mean that the temp/ramp
was increased.

If this is the case try slowing down the ramp.

The basic problem arises with a temperature difference between the top and
bottom of the board causing the board to warp (bow up to the hot side -
watch the next time you put an oven tray onto the sink). I could bore you
with the details of the formula but I would suggest you try slowing down the
conveyor instead.

Happy Hogmany (New Years Eve) to all

Finlay Buchan
Chief Propellerhead
Datum Dynamics


> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Todd Ness
> Sent: 14 December 1998 16:42
> To: [log in to unmask]
> Subject: [TN] Fine-Pitch Soldering Problem
>
>
> Technetters,
>
> We are currently having soldering problems with a QFP 100 package
> part. The part is a TI microprocessor component with a 0.0196" pitch.
> The problem we are having with this part is we are getting
> intermittent opens with corner leads. Other fine-pitch components on
> this board solder fine. We have been building these boards for about 1
> 1/2  years in production with no problems until the last three months.
> I found out that TI recently switched the lead plating for this part
> from Tin/Lead to Nickel/Palladium. The solder paste we were using was
> Kester OA 596. However, due to the inability of this paste to solder
> to palladium parts, we switched to Kester OA 598. The profile was also
> tweeked per Kester's recommendations for soldering to palladium leads.
> All leads for this component and all other components on the board are
> soldering fine with the new paste and new profile, except for some
> intermittent opens on corner leads of the TI part with
> Nickel/Palladium leads. Component leads for this part were inspected
> prior to pick and place for coplanarity. Does anyone have any ideas of
> what may be happening and any recommendations for eliminating this
> problem.
>
> Happy Holidays
>
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