Matthew

Don't forget that, if you clean after reflowing, the criteria imposed by
your cleaning process: this is sometimes contradictory to the reflow and
a compromise becomes necessary. The designer should always work with the
production guys (concurrent engineering).

Brian

Matthew Lamkin wrote:
>
> Hi there folks, can I get some experience on the best component placement &
> orientation directions for
> when designing an SMT board for use with a convection reflow oven to design
> for minimum defects.
>
> All orientations in relation to the direction of flow through the oven.
>
> 1) Electrolytic capacitors.
>     Should these be placed so that they are perpendicular to the direction
> of flow through the oven, so that there is
>     equal heating on both pads and none are shadowed during reflow.
> Naff ASCII picture follows.
> FLOW         _____\
>                                  /
>          P            = PAD
>          O            = BODY OF CAP
>          P            = PAD
>
> 2) Shadowing?
>      How do I calculate the area that may cause shadowing problems?
>      Given that I know the height & width of the component, what other
> factors do I need to know?
>      Where on the web can I find some documentation on this?
>
> 3)  Where (on the web) can I find some good documentation on how
> "convection" reflow ovens work?
>       Most documents that I can find mention IR. & VP reflow but not
> convection (which our old QUAD oven is).
>
> Many thanks in advance for any helpful replies.
> Matthew Lamkin
> Printed Circuitboard Draughtsman
> Protec Fire Detection PLC.
> Email matthew.lamkinATprotec-fire-detection.plc.uk
>
> [log in to unmask]
>
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