Hi Toby - I am not a big proponent of assessing a situation without
understanding as much of the case as possible as one can sometimes go down
the wrong road but per your request, I'll try to provide some help.

1. Adding a small amount of flux to solder paste is contaminating the
solder, and not allowing it to flow.

*** The adding of flux to solder paste can cause issues due to the
incompatibility of the added flux with the flux materials in the solder
paste. Testing needs to be conducted to determine that no compatibility
issues exist. Adding flux to solder paste does not contaminate the solder
metal as any flux would be burned off when the solder is in its molten
state.

2. Soldering battery terminals with a selective solder machine adds too
much solder that when the low power device is turned on, the solder swells
causing a short from the positive battery terminal to the ground plane
underneath.

*** Solder swells because it has current flowing thru it? Humm, if that
were true then we would have a whole lot of electronics that have issues.
It is true that metals expand as they are heated and running current thru
solder can heat it up but it would take a unique situation/configuration
for such a failure mechanism as you described to be in effect. Not
impossible but not probable.

3. Using Electro-Wash to clean flux residue from a PCB is contaminating
the PCB and solder joints, which causes failures of the circuits.

*** My understanding is that electro-wash is a chemical formulation that
can be used for cleaning printed wiring assemblies. If the electro-wash is
being used per the formulation supplier technical data sheet then I would
not expect it to cause failures.

Dave Hillman
Rockwell Collins
[log in to unmask]




Toby Carrier <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
01/11/2012 10:04 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Toby Carrier    <[log in to unmask]>


To
<[log in to unmask]>
cc

Subject
[TN] Contamination of Solder






All,

I would like to know what you think about some contamination causes that
were stated on an low volume, high yield electronics manufacturing floor:

1. Adding a small amount of flux to solder paste is contaminating the
solder, and not allowing it to flow.

2. Soldering battery terminals with a selective solder machine adds too
much solder that when the low power device is turned on, the solder swells
causing a short from the positive battery terminal to the ground plane
underneath.

3. Using Electro-Wash to clean flux residue from a PCB is contaminating
the PCB and solder joints, which causes failures of the circuits.

I do not agree to these, and would like input as to why I might be right
or wrong.

Thanks,

Toby Carrier

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 16.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
For additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------



______________________________________________________________________
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]
______________________________________________________________________

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 16.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------