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March 2008

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Subject:
From:
Graham Collins <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Thu, 13 Mar 2008 12:50:08 -0300
Content-Type:
text/plain
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text/plain (112 lines)
Phil,
Fair enough.  Can you poll the possible CMs with respect to their
capabilities / limitations?  Get an idea of how familiar they are with
using partial wave fixtures and/or do they have selective solder
machines?  A good CM will work with you on the design - it's in their
best interests to ensure it can be built by them... if the design is
going to be a challenge you may want to / need to pre-select who will
build it based on capabilities (AKA going with "best value" instead of
"best price"...)??

good luck!

regards,
 - Graham

-----Original Message-----
From: Phil Nutting [mailto:[log in to unmask]] 
Sent: Thursday, March 13, 2008 12:35 PM
To: Collins, Graham (FN) @ ESI; TechNet E-Mail Forum
Subject: RE: [TN] SMT layout

Graham,

OK.  I forgot to add that these will be built by a CM.  Depending on
which CM it goes to may vary how the boards are soldered.

Phil

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, March 13, 2008 11:30 AM
To: TechNet E-Mail Forum; Phil Nutting
Subject: RE: [TN] SMT layout

Hi Phil
I don't do layout, but our design guys can attest that I spend _lots_ of
time bugging them about it.  Enough so that they've adopted the "get him
to review it first" attitude, which I really appreciate.

With respect to your issue (10 lbs in 5 lb bag), we'd look at doing
partial wave (using a selective soldering pallet for the wave solder
operation).  If you can do that, the restriction on the bottom side SMT
parts are:
- max height ~ .200"
- need a margin around all through-hole parts to allow for the vertical
wall on the pallet.
- the through-hole parts can't block all access to SMT parts.

Of course, if you've got a selective soldering machine then you've got
even more flexibility, almost anything on the bottom should be OK.

Hope that helps a bit.

regards,
 - Graham

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Nutting
Sent: Thursday, March 13, 2008 12:19 PM
To: [log in to unmask]
Subject: [TN] SMT layout

Hi folks,

Disclaimer: I'm a neophyte at SMT board layout.

That being said, we have a board that equates to 10 pounds in a 5 pound
bag.  Is there a recommended layout with reference to which components
should be on the component side versus the solder side?  I assume it is
partially affected by the method of processing, reflow or wave for
solder side.  Put passive parts on the solder side and the active parts
on the component side?

Thanks in advance,

Phil

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Note: All the information contained in this e-mail and its attachments
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