Steve,

   Where did you measured 220 C ?
   Install termocouples at uncured locations and process the board again.
Being the board very complex, there is a change of uneven thermal
distribution during peak reflow, this occur due differential temperatures
just before the rise to reflow, this difference becomes greater at
accelerate ramp up ( this is normal ) and can give peak to peak temperatures
as bigger to avoid reflow with some parts.
   The trick is make the pre-heating ( the flat part of the reflow curve )
more longer in order to get all temperatures stabilized with small
temperatures differences to avoid bigg differences at peak reflow. This will
be more time consuming but since the board is complex I believe the volume
production is not so high for that addicional time be a problem.
   This is my 2 cents ...

Jorge Dourado de Santana
Maintenance / Process Engr
Microtec - Brazil



> -----Original Message-----
> From: Steve Collins [SMTP:[log in to unmask]]
> Sent: 24 de Fevereiro de 2000 15:17
> To:   [log in to unmask]
> Subject:      [TN] Resonator soldering problem
>
> I have this Resonator part that is very large and sets on the top of the
> PCB and
> goes through our convection reflow oven at 220 C. Board is very complex
> and the
> problem we are having is that only the edges are being soldered and when
> we
> cross-section to inspect solder under part it is still uncured. We
> discovered
> this problem when parts started falling off PCB.
>
> Any and all comments welcomed. What we would like to know is if any one
> else is
> using this part and have they solved this problem..
>
> Steve
>
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