Thanks for all the (varied) opinions!  No consensus here.

We are a build to print shop, so I'm not responsible to dictate how to put it on - my obligation is to point out the issue and recommend a solution.  I'm going to recommend the "attach last by hand using no-clean flux" method, it will work on this application as the module has castellation terminations, accessible by hand.  If it was bottom terminations only I'd be facing a bigger problem, in that case I would recommend the "wash and bake".

cheers,

 Graham

regards,

Graham Collins
Senior Process Engineer
Sunsel Systems
(902) 444-7867

On 12/1/2017 4:37 PM, Richard Kraszewski wrote:

Ditto  to Bob's thought. Localized clean if need be.

Rich  Kraszewski
Senior Staff Process Engineer
Plexus Engineering Solutions

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Wettermann
Sent: Friday, December 01, 2017 12:28 PM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: [TN] board wash / non-washable modules - the dilemma

My vote because this is what we have done for small Proto builds is to leave the module off, build and wash w water soluble flux then install the RF module using the no-clean?

Bob Wettermann
BEST Inc
Your BEST source for PCB Rework/Repair, Training and Tools
847-767-5745




On Dec 1, 2017, at 10:15 AM, Tom Brendlinger <[log in to unmask]><mailto:[log in to unmask]> wrote:

I have heard many times that in high humidity environments with very
small amounts of condensing humidity, no clean flux can become
re-activated. This paper discusses some options:
https://link.springer.com/article/10.1007/s11664-014-3609-0

In my opinion, reach out to the part manufacturer and see if you can
perform cleaning in a particular way to not risk having issues.

Tom

On Fri, Dec 1, 2017 at 1:05 PM, Robert Kondner
<[log in to unmask]><mailto:[log in to unmask]>
wrote:



I would go for wash and bake but I worry that washing will "Wash Crud Into"
the shielded areas and the rinse will not rinse it out.

Are your concerns about no clean flux in a marine environment really
justified or is it hog wash from somewhere?

Bob K.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
Sent: Friday, December 01, 2017 10:09 AM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: [TN] board wash / non-washable modules - the dilemma

Hello Technet!

Wondering what other people are doing with this dilemma.

We have had several customers design in pre-built RF modules on their
boards.  I totally get why, it is a pre-built, FCC approved, easy
solution
-
the fastest way to get a good Wi-Fi or bluetooth solution.

Where things go off the rails for me are where this is used in a high
humidity application (e.g. a marine setting).  We strongly prefer to
wash boards, we can build no-clean if needed but I'd prefer not to
for an on the water use.  But the part a customer has designed in
specifically says not to wash it (it has an EMI shield, so they are
properly concerned with water entrapment).

So - would you:

- build it no-clean?
- leave the part off, build and wash as usual, install RF module
later using no-clean?
- wash it (and maybe bake it to dry it out)?
- ????

--
regards,

Graham Collins
Senior Process Engineer
Sunsel Systems
(902) 444-7867