TECHNET Archives

June 2013

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:
Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Joyce Koo <[log in to unmask]>
Date:
Thu, 20 Jun 2013 16:08:31 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (1 lines)
Few things to be aware of:
(1) although PEG or similar stuff are limited or not existence in the west, but some are still used in far east (or other not our neck of the woods places).  
(2) combine with poor process control and poor quality of the solder mask, (e.g. on HASL board), it could be more problematic.  Extraction or omega meter reading using time limited condition usually gave false security, especially, for the board that being sit around for a while (not easy to extract ionics out if it somewhat got oxidized).  
(3) know your vendor/process is the key.  My 1.94 cents. 

Joyce Koo
Researcher
Materials Interconnect Lab
Office: (519) 888-7465 79945
BlackBerry: (226) 220-4760

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Thursday, June 20, 2013 11:59 AM
To: [log in to unmask]
Subject: [TN]

I'm afraid that some of what you say may be misleading. Frank Zado's 
paper, at the Anaheim and Philadelphia Nepcon conferences in 1979, 
explored mainly Carbowax (polyethylene glycol. PEG) of specific ranges 
of MW. Although he did some tests with polypropylene and higher glycols, 
these proved to be of much reduced effect. This was also specific to 
wave soldering. Also the effect was not due to an epoxy-OH bond; it was 
a hydrogen bond, exacerbated by the structural surface of the epoxy, 
left by the copper treatment. It could be described as a 
chemi-physico-adsorption. However, PEG fell largely into disuse in the 
1980s, except for some tin-lead reflow and HASL processes in the FAB 
side. Of course, it was your famous OH group that potentially created 
any hydrophilic characteristics at the other end of the molecule!

More particularly, as I have propounded many times since 1969 
(Inter-Nepcon), in my book and other publications, in lectures and in my 
swansong paper in Circuit World, the water-break test is absolutely 
meaningless, with easily produced false negatives and false positives. 
IMO, anyone who uses it as determinant of any specific reliability 
conditions needs his head examining. The only valid way of determining 
the presence of hydrophilic surface phenomena is by non-biased, low 
voltage 50/90 or 85/85 SIR qualification tests. The oracle hath spoken! :)

Brian

On 20.06.2013 17:21, greg wrote:
> It is true that WS flux should be removed in the cleaning process.
>
> However, many glycols actually bond to FR-4 epoxy through their -OH groups. Hence the surface after soldering and cleaning is hydrophillic. (Frank Zado showed this back in the early 80s.)
>
> An easy test is take a board that is clean but not WS soldered and drop DI water on it. It should bead up.
>
> If after WS soldering and cleaning a drop of DI spreads you have glycols bonded to the epoxy.
>
> Adding a no-clean (with dibasic acids) to a hydrophobic mix may be an iffy proposition.
>
> Better to use a Bellcore compliant flux for your final soldering.
>
>
>>   -------Original Message-------
>>   From: Steven Kelly <[log in to unmask]>
>>   To: [log in to unmask]
>>   Subject: [TN]
>>   Sent: 20 Jun '13 09:02
>>
>>   Thanks Dave - customer has not done any testing and for years we have only used no-clean for both operations so now I have some parts to be done one way and some another for Class 3 medical. Not good in my 2 cent opinion. Regards Steve Kelly
>>
>>   From: [log in to unmask] [mailto:[log in to unmask]]
>>   Sent: June-20-13 9:15 AM
>>   To: TechNet E-Mail Forum; Steven Kelly
>>   Cc: TechNet
>>   Subject: Re: [TN] Mixing solders,
>>
>>   Hi Steve - I'll have to pay Doug and use his tag line - "It depends"! Anytime you mix two different flux systems, especially a water soluble and a low residue (aka no clean), there may be an issue of incompatibility that could result in a really hard lacquer (best case) or a really cool corrosion cell (worst case).��My recommendation would be to advise the customer that the mixing of the two flux systems would not be advised unless some testing can be conducted to ensure no detrimental reactions would occur. A second option would be to check with the flux supplier to see if they have any compatibility data. If the fluxes come from two different suppliers, don't waste your time asking that question as they won't have the answer. Good Luck.
>>
>>   Dave Hillman
>>   Rockwell Collins
>>   [log in to unmask]<mailto:[log in to unmask]>
>>
>>
>>
>>   From:��������Steven Kelly <[log in to unmask]<mailto:[log in to unmask]>>
>>   To:��������<[log in to unmask]<mailto:[log in to unmask]>>
>>   Date:��������06/20/2013 08:02 AM
>>   Subject:��������[TN] Mixing solders,
>>   Sent by:��������TechNet <[log in to unmask]<mailto:[log in to unmask]>>
>>   ________________________________
>>
>>
>>
>>   Hi All,
>>   I have been looking in the archives but can't seem to find what I want an answer to . I have a customer who wants us to use water soluble RoHS for the SMT process but wants no-clean RoHS for the touch-up. Is this recommended? Regards Steve Kelly
>>
>>
>>   If the recipient to whom this e-mail is sent has an NDA with PFC Flexible Circuits Limited this e-mail is considered confidential and is subject to any NDA agreements between the respective parties.
>>
>>   See PFC on "How It's Made`` coming soon on the Discovery Channel!
>>
>>
>>   ______________________________________________________________________
>>   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]<mailto:[log in to unmask]>
>>   ______________________________________________________________________
>>
>>
>>   ______________________________________________________________________
>>   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]
>>   ______________________________________________________________________
>>
>
> ______________________________________________________________________
> 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]
> ______________________________________________________________________
>

______________________________________________________________________
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] 
______________________________________________________________________

---------------------------------------------------------------------
This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. Any use of this information by anyone other than the intended recipient is prohibited. If you have received this transmission in error, please immediately reply to the sender and delete this information from your system. Use, dissemination, distribution, or reproduction of this transmission by unintended recipients is not authorized and may be unlawful.

______________________________________________________________________
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