Polyimide is more hygroscopic, as you know, than epoxy resin systems. I
bake, when required, for 3 hours at 250 F. within 24 hours of assembly.
Earl Moon
----- Original Message -----
From: Louis, Edwin @ CSE <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, August 17, 1999 12:00 PM
Subject: Re: [TN] Baking out PCBs?
> What are the bake out conditions for Polyimide?
>
> -----Original Message-----
> From: Blomberg, Rainer (FL51) [mailto:[log in to unmask]]
> Sent: Tuesday, August 17, 1999 10:44 AM
> To: [log in to unmask]
> Subject: Re: [TN] Baking out PCBs?
>
>
> Mr. Talbert,
>
> In response to your questions,
> 1) Boards in Florida (and most other places except Arizona) acquire
moisture
> over a short time that causes measeling when suddenly exposed to high
heat.
> The moisture turns to vapor and seeks to escape. The moisture content also
> causes dimensional changes that can cause warp and bow of boards with
> integral heatsinks.
>
> 2)We use polyamide boards of 9 to 16 layers. The baking spec I provided
> just happened to be from the wave solder process. The bake-out for manual
> processing is the same. Master Interconnect Boards (MIB) of up to 16
layers
> are vacuum baked longer (16 hours).
>
> 3) The process was developed from our experience and process development
> experiments.
>
> Hope this is helpful.
> R. G. Blomberg
> Honeywell -SASSO
> Staff Production Engineer
>
>
>
>
> -----Original Message-----
> From: Talbert, Marvin [mailto:[log in to unmask]]
> Sent: Monday, August 16, 1999 4:03 PM
> To: [log in to unmask]
> Subject: FW: [TN] Baking out PCBs?
>
>
> Hello Mr. Blomberg,
>
> This is interesting. We take similar precautions for moisture sensitive
> packages but not for the boards.
>
> What is your concern with the bare board? What type of board material did
> you have the problems on? How many layer and can you tell me who the
vendor
> is?
>
> You said specifically wave but not reflow. Why?
>
> Did you devise these specs yourself or were these taken from MIL-SPECs?
>
> Marvin Talbert
> Data General PCB Engineer
> 919-387-5134 Direct
> 919-387-5292 Fax
> 919-871-6598 Beeper
> The most successful people in life are generally those who have the best
> information. [Benjamin Disraeli]
>
> > -----Original Message-----
> > From: Blomberg, Rainer (FL51) [SMTP:[log in to unmask]]
> > Sent: Friday, August 13, 1999 11:47 AM
> > To: [log in to unmask]
> > Subject: Re: [TN] Baking out PCBs?
> >
> > Here's a cut out of our process spec: "Prior to wave soldering, the
boards
> > shall be baked in a vacuum oven (28.5 inches of mercury, minimum) at
95?C
> ?
> > 5?C for six hours minimum. The boards shall be soldered within 4 days
> after
> > removal from the oven or maintained at 54?C ? 5?C minimum or stored in a
> dry
> > nitrogen box. If these conditions are not maintained, the baking cycle
> > shall be repeated." The cleaning method is up to you, but we use Axarel
> 32
> > in an ECD batch cleaner followed by water and IPA rinse then oven drying
@
> > 150 deg. F. for 2 hours.
> >
> > Rainer G. Blomberg
> > Staff Production Engineer
> >
> > -----Original Message-----
> > From: Rick Thompson [mailto:[log in to unmask]]
> > Sent: Friday, August 13, 1999 10:28 AM
> > To:
> > Subject: [TN] Baking out PCBs?
> >
> >
> > Hi,
> >
> > As a small contract manufacturer, we receive a lot of bare PCBs
consigned
> > from our customers. Many times these PCBs are of questionable
cleanliness
> > and the storage conditions are unknown to us, so we routinely wash and
> bake
> > these boards out overnight. My question is this: Are there any
industry
> > specifications or recommendations for this type of process? Anybody care
> to
> > share how they handle this? I've looked in IPC-A-600, IPC-6011 and
> IPC-6012
> > and don't find anything specific to this topic.
> >
> > Thanks in advance.
> >
> >
> > Rick Thompson
> > Ventura Electronics Assembly
> > 2665A Park Center Dr.
> > Simi Valley, CA 93065
> >
> > +1 (805) 584-9858 voice
> > +1 (805) 584-1529 fax
> > [log in to unmask]
> >
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