Doug,
Are you talking about baking board after wash to dry the water under
low standoff parts? Management is driving us to a no-clean process
specifically to address this issue. Is no clean your preference? Or
water wash with additional drying options? (Some CSP's may demand no clean
anyway, but that's beside the point).
Thanks
Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]
> -----Original Message-----
> From: Douglas Pauls [SMTP:[log in to unmask]]
> Sent: Thursday, June 08, 2000 2:25 PM
> To: [log in to unmask]
> Subject: Re: [TN] question about pre-heat & SIR
>
> In a message dated 06/08/2000 2:35:48 PM US Eastern Standard Time,
> [log in to unmask] writes:
>
> > Does pre-heat temperature influence SIR test results?
>
> I'll give my favorite answer - It Depends. If you are talking about flux
> residues, running too cold will increase the likelihood that you have
> unreacted or unactivated flux residues, which tend to be more conductive,
> especially around humidity. As such, SIR would tend to be lower, all
> other
> factors being equal. On the other hand, if you run the preheats too hot,
> you
> run the risk of taking any benign flux residues and causing them to
> thermally
> break down (pyrolize). Such residues are generally corrosive and cause
> SIR
> failures. Most flux manufacturers that I know of, during product
> development, will run SIR on flux samples that are nominal temp,
> nominal-20C,
> and nominal+20C to examine the window.
>
> If you are talking about bake operations, I would recommend them if you
> are
> doing aqueous cleaning and have low standoff parts. I have seen IPC-B-36
> boards with 4 LCCs on them (5 mil standoff) go past three 15 HP blower
> motors
> and still have water under them. Such water shoots SIR immediately.
> Prebakes are a good idea.
>
> Doug Pauls
> CSL
>
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