Why does baking the board  reduce
the reliability and life expectancy of the board?


> -----Original Message-----
> From: Alain Savard [SMTP:[log in to unmask]]
> Sent: Tuesday, October 26, 1999 8:51 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] HELP!!! - flow solder problems RT
>
> Hi Richard,
>
> Now you know why some assemblers request test coupons.
> For the age of the boards, you might have a DATE CODE on
> the board. It's usually 4 digits, 2 of them are the week number
> and the other 2 are the fabrication year. (example: 99-12 or
> 12-99 represent the 12th week of 1999).
>
> Boards older then 6 months may start to have a substantial
> amount of water absorbed into the laminate. They may also
> have a fair amount of oxidised tin forming on the surface of
> traces and inside the PTH.
>
> Do NOT bake the boards unless necessary, it slightly reduces
> the reliability and life expectancy of the board.
>
> You might have to sacrifice a board to microsection it and see
> any problems with the internal structure (mostly the plating).
>
> If you are scrapping any boards, use the area affected.
>
> If the failures are always at the same component, the batch of
> components may need to be looked at for solderability.
>
> Finally check the wave and preheat temperature. (You could do
> this first actually).
>
> Good luck,
>
> Alain Savard, B.Sc.
> Chemical Process Analyst
> CAE Electronics Ltd.
> e-mail: [log in to unmask]
>
> -----Original Message-----
>
> Hello Richard,
>
> HELLO ALAIN
>
> A few things to look at:
> - Did you perform a solderability test on the test coupons?
> NO COUPONS WERE SUPPLIED.
>
> - How old are these boards?
> NOT ENTIRELY SURE - WE GET THEM FROM AN EXTERNAL SUPPLIER.
>
> - Did you verify plating thickness and voiding in the test coupons?
> NO COUPONS SUPPLIED.
>
> - are your components pre-tinned?
> NOT BY US. FITTED AS SUPPLIED.
>
> RICHARD TILBROOK
>
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