Hi Phil
You can replace BGAs that have been parylene coated - but you really,
really have to want to. Not a recommended activity.
And I have to disagree with Bogert as well. Shadowing is a known part
of the process, any drawing that does not specify special techniques or
materials can expect to have no coating under BGAs, as well as other low
profile parts. Do you have any vias under QFPs? They won't be
coated...
regards,
Graham Collins
Process Engineer,
L-3 Communications Electronic Systems Inc.
Halifax
(902) 873-2000 ext 6215
>>> [log in to unmask] 11/20/06 07:43PM >>>
i'm sorry, i just can't help myself. parylene is a great coating, but
i
don't think you'll be removing and replacing any bga's that have been
conformally coated with parylene. just another engineering tradeoff
to
consider.
phil
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Monday, November 20, 2006 3:27 PM
To: [log in to unmask]
Subject: Re: [TN] BGA and conformal coating
Hi Bogert! Sorry but I respectfully disagree. If the contract requires
the assembly to be conformal coating and provides no other process
guidance then I would process the assembly in accordance with best
industry practice/accepted material process practice for the
particular
conformal coating material specified. As other TechNettees have
documented, intentionally forcing AR or UR conformal coating under a
component is not standard conformal coating practice as the such an
action results in degraded component/product integrity due to CTE
mismatch for many use environments. However, if I was using a
paralyene
conformal coating, standard material process practice is quite the
opposite - paralyene conformal coating is design to coat all pwa
surfaces. The application process for each conformal coating material
dictates how/where it should be applied unless there are specific
instruction that deviate from standard practice (such as a specific
exclusion area for RF, etc.).
Dave
- Bogert
<[log in to unmask]>
Sent by: TechNet
To
<[log in to unmask]> [log in to unmask]
cc
11/20/2006 03:52
Subject
PM Re: [TN] BGA and conformal
coating
Please respond to
TechNet E-Mail
Forum
<[log in to unmask]>
; Please respond
to
- Bogert
<[log in to unmask]>
If the contract assembly drawing requires the assembly to be conformal
coated, unless it also allows the area under the BGA to be free of
coating, then you are in violation of the contract drawing regardless
of
what 610 says or does not say.
----- Original Message -----
From: David D. Hillman<mailto:[log in to unmask]>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Monday, November 20, 2006 2:20 PM
Subject: Re: [TN] BGA and conformal coating
Hi Joe - Your statement......." type AR or type UR does not coat the
BGA
solder balls/solder connections located under the BGA so you are
violating
the acceptability requirements in IPC-A-610" has me some confused.
What
IPC-A-610 requirement is violated?
Dave Hillman
Rockwell Collins
[log in to unmask]<mailto:[log in to unmask]>
"Macko, Joe @
IEC"
<joe.macko@L-3COM<mailto:joe.macko@L-3COM>
To
.COM> [log in to unmask]<
mailto:[log in to unmask]>
Sent by: TechNet
cc
<[log in to unmask]<mailto:[log in to unmask]>>
Subject
Re: [TN] BGA and conformal
coating
11/20/2006 12:47
PM
Please respond to
TechNet E-Mail
Forum
<[log in to unmask]<mailto:[log in to unmask]>>
; Please respond
to
"Macko, Joe @
IEC"
<joe.macko@L-3COM<mailto:joe.macko@L-3COM>
.COM>
Vered,
I would start with IPC-A-610 and J-STD-001 documents. One item that
is
over
looked is that spraying a board with for example type AR or type UR
does
not
coat the BGA solder balls/solder connections located under the BGA
so
you
are violating the acceptability requirements in IPC-A-610!
Good luck,
- Joe
-----Original Message-----
From: Vered BS [mailto:[log in to unmask]]
Sent: Monday, November 20, 2006 8:40 AM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: [TN] BGA and conformal coating
looking for reviews/articles or case studies regarding conformal
coating on
BGA
for military/aerospace environment
Appreciate any comment or sharing your experiance
Thanks
Vered
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