Your note suggests that ALL components may become surface mount, but as far
as the connector is concerned, perhaps this design may be an "ideal"
candidate for intrusive reflow:  keeping the connector as a through hole
component processed through a reflow environment.  The decision may be based
on what type of connector this is.

Do you have a shielded I/O connector (higher mating/unmating forces)?  Is it
a high pin count (higher mating/unmating forces)?  Is it a tin (versus gold)
interface (higher mating/unmating forces)?  Is it a "right angle" board
connector (higher shear stress)?  All of these will affect the stress/strain
on the solder joints.  If you do go the surface mount route, I'd keep some
hold downs on the design.

Martha Rupert
AMP Incorporated
email:[log in to unmask]


> -----Original Message-----
> From: Michael Lang [SMTP:[log in to unmask]]
> Sent: Sunday, June 28, 1998 9:35 PM
> To:   [log in to unmask]
> Subject:      [TN] HELP: Cracking Discretes on PCB's
>
> Hello Technetters,
>
> I have a PCBA which has been built in PTH configuration with great
> success for years.  However, due to the need for increased functionality
> in the same form factor, it seems that it is time to convert the PCBA to
> SMT format.
>
> My main concern relates to PCB flex and solder joint integrity...
>
> The PCBA is about 4" x 6".  It is held along its 4" sides in a rack.  A
> cable is plugged into the card via a connector along the top 6" side of
> the PCB (NOT a card edge connector, but PTH connector which means you
> push against the FACE of the PCBA.  I do not know the force, but the PCB
> DOES flex significantly.  Plus, since this is a home / contractor
> product, it does not get handled gingerly...
>
> THE PRIMARY CONCERN: Inducing cracks in either the components or solder
> joints of leadless surface mount components.
>
> What information exists with respect to this subject?
>
>
> What testing makes sense?  What has been done already by others?
>
>
> Any help is appreciated.
>
> Thanks,
>
> Michael Lang
> [log in to unmask]
>
>
> ps. Hi RH!
>
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