TECHNET Archives

August 2014

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
TAYLOR Paul R <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, TAYLOR Paul R <[log in to unmask]>
Date:
Fri, 1 Aug 2014 07:39:14 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (67 lines)
One simple word (or words!)  Ionic Contamination

This will be probably due to using 'towns water' during the wash at some point in the process. We use a 'spray wash' with built in ionic metering because of issues like this in house, but controlling what CM's do usually ends up with you specifying exactly the wash process, ignore this point at your peril!!.

As far as the relays go: check out the specification very carefully, you might find (as we did ) that a certain relay manufactures glue that held the relay base to the cover was affected by the wash chemicals.
Pots: we don't have any on boards and only have panel mount so can't comment
Optos: I'm interested in you failure mode, we use opto couplers...do you mean this type of device

Regards
Paul




Paul Taylor
Alstom Grid | R&D | Post Design Service Team Leader
Phone: +44 (0) 1785 223251 (x2014) | Mobile: +44 (0) 7827 312568 | E-mail: [log in to unmask]
Office address: St Leonards Avenue, Stafford, ST17 4LX
Site: www.alstom.com
** Please consider the environment before printing this e-mail **

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Nutting, Phil
Sent: 31 July 2014 15:38
To: [log in to unmask]
Subject: [TN] component failures due to post wave/reflow washing

Over the past years we have had relays, optos and pots fail due to corrosion being found inside the parts after post soldering wash.  The quick solutions have been to use other manufacturer's parts or install after wash with hand solder "no-clean" cored flux.  One manufacturer said it was because of halides in the flux.  Our primary CM's and our flux contains halides, but we haven't seen as many failures with in-house processed PTH boards as with CM built boards.  Recent pot failures have been explained  by component manufacturers as too much wash pressure or bad flow direction from the wash jets.  Opto failures were similarly diagnosed.

Our in-house process, all PTH, is foam flux with OA flux, wave solder with 63/37 or SC995e followed by a closed loop DI wash with no chemicals.  This has been a great process since 2006 when we switched from a no-clean foam flux, 63/37 wave and terpene/alcohol wash to our listed system above.

We do not dictate flux/wash process to our CMs, but we do specify cleanliness to J-STD-001 C-22 using the 1.56 ėgm / cm2 NaCl equivalent contamination value.  Forcing the CM to change fluxes for our product met great resistance and added cost so no change in flux was made.

Our business is high voltage from 30 kV to 240 kV so clean with NO residue is very important.  The DI wash has provided that in-house.

We are using different CMs going forward, but not necessarily for this reason.

Is this a problem unique to us or do other suffer from similar problems?

Phil Nutting  |  HVP Development Engineer   |  Excelitas Technologies Corp

Lab: +1 978.224.4332   |  Office: +1 978.224.4152
35 Congress St, Salem, MA  01970 USA
[log in to unmask]<mailto:[log in to unmask]>
www.excelitas.com<http://www.excelitas.com/>


[Description: Excelitas R_emailsig]


Please consider the environment before printing this e-mail.
________________________________
This email message and any attachments are confidential and proprietary to Excelitas Technologies Corp. If you are not the intended recipient of this message, please inform the sender by replying to this email or sending a message to the sender and destroy the message and any attachments. Thank you.


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________

________________________________
CONFIDENTIALITY : This e-mail and any attachments are confidential and may be privileged. If you are not a named recipient, please notify the sender immediately and do not disclose the contents to another person, use it for any purpose or store or copy the information in any medium.

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

ATOM RSS1 RSS2