Based on your limited description I would suspect that your contract
manufacturer is having problems withsolder joint quality.
A few questions:
Was the solder paste changed?
        Different heating process can cause extreme changes in solder
joint characteristics/quality. The flux and solvent characteristics,
especialy with no-clean and water soluble fluxes are often very
different for IR and Convection systems.
Was the profile duplicated from one system to the other?
        Infra red heating affects metals before organic material.
replicating an infrared system profile on a convection system will cause
much higher ramping rates and absolute temperature. Duplicating the
board profile will minimize the differences between systems.
The impact of design on performance of a reflow system is "unusual" to
say the least.
I know for a fact that designs that work in IR reflow systems also work
in convection relow systems.
I would continue to have conversations with your contractor as to the
cause of the problems, over and above changing the physical design of
your PCB surface mount pads.
Good Luck.


> -----Original Message-----
> From: Stefan Pollmeier [SMTP:[log in to unmask]]
> Sent: Thursday, June 04, 1998 3:29 PM
> To:   [log in to unmask]
> Subject:      [TN] Reflow soldering: forced gas vs. infra-red
>
> Dear TechNetters,
>
> a contract manufacturer has problems in controlling the soldering
> process after switching to forced gas (from infra-red).
>
> One idea was letting us change land patterns ("my experience: oval
> works
> better than rectangular"). Any experience reports, hints, literature
> regarding land patterns _and_ soldering process would be welcome.
>
> Any hints on process optimization we could forward to our contract
> manufacturer are also welcome (is there a "top ten faults in forced
> gas
> convection soldering"?).
>
> Thank you very much in advance.
>
> Best regards
>
> Stefan Pollmeier
>
> --
> Stefan Pollmeier                 [log in to unmask]
>
> ESR Pollmeier GmbH               Tel. +49 6167 9306-0
> Lindenstr. 20                    Fax  +49 6167 9306-77
>
> D-64372 Ober-Ramstadt, Germany
>
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