Hi Tom - your email address bounced on my end so I am routing my response
through TechNet to get it to you.

Dave Hillman
Rockwell Collins
---------------------- Forwarded by David D
Hillman/CedarRapids/Collins/Rockwell on 01/20/98 06:13 AM
---------------------------


David D Hillman
01/20/98 06:11 AM

To:   [log in to unmask]
cc:
Subject:  Re: [TN] Overheated solder joints  (Document link not converted)

Hi Tom - I would look at two issues - what is the use environment the
boards are going to be used in and how "good" is the rework process the
assemblies would be subjected too. A majority of the industry would say
that a reworked solder joint is less reliable than a as processed solder
joint. That doesn't mean that a reworked solder joint is going to
necessarily fail but only that you use up some of the service life due to
the rework process stressing the board, growing a bit more intermetallic,
etc. If you don't feel that the rework process is going to have good
repeatibility and reproducibility then I would look at the use environment
and evaluate if the assemblies will preform (despite being classified "less
than what was originally intended") adequately. Typically 'grainy' solder
joints are a visual issue and don't impact reliability. Look to see what
the wetting angles are and talk with you customer on how the boards would
interact with the use environment. Good Luck,

Dave



[log in to unmask] on 01/20/98 05:39:28 AM

Please respond to [log in to unmask]

To:   David D Hillman/CedarRapids/Collins/Rockwell
cc:
Subject:  Re: [TN] Overheated solder joints




David
I agree with you on both accounts. We have adjusted the solder temp and are
working with the customer, it's his design, to redesign the thermals on th
board pads.
Unfortunately, three of the boards have already moved to the point of
production where rework becomes difficult. Would these boards need to be
reworked under class 2 criteria?
Thanks again for your help.
Tom Moore
David D Hillman wrote:
> Hi Tom - "grainy" solder joints can be caused by three sources: excess
> soldering heat, printed wiring board features and gold finishes. The
excess
> soldering heat results in the lead phase growth that causes surface
relief
> that looks 'grainy'. Some printed wiring board internal design features
> result in thermal sinks which results in grainy solder joints due to slow
> solidification. Soldering to gold finishes can result in the formation of
> gold-tin intermetallic phases in the solder joints which cause surface
> relief also. I would suspect that you have grainy solder joints due to
the
> excess soldering heat phenomena. Unfortunately the assembly you are
trying
> to solder is a tough one thus the reason for the temperatures you are
> using. You might investigate turning the temperatures down and/or looking
> at the board design to see if you can get some improvement. Good Luck.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> [log in to unmask] on 01/16/98 03:20:30 PM
>
> Please respond to [log in to unmask]
>
> To:   [log in to unmask]
> cc:    (bcc: David D Hillman/CedarRapids/Collins/Rockwell)
> Subject:  Re: [TN] Overheated solder joints
>
> I've been asked to give some more information on this defect and how it
> occurred.
> First the defect: The solder joints of the effected areas are grainy and
> crystalline. Distribution is numerous and random, on the solder side
> only. On the component side flow through is great( this is a multi-layer
> board with a large ground plane and weird thermal relief that we have
> struggle in the past to get decent flow thru). Vias and PTHs without
> components are effected as well.
> The description of this as an "overheated solder joint" comes not only
> frrom my DOD-2000 training (defect code A117) but also the conditions
> which produced the "defect."
> The conditions: We are using a Novastar 16FD wave solder machine that is
> under two years old (we bought it about 3 months ago). We use an RMA
> flux and clean the boards by hand with "Reliasol". Preheaters were set
> at 430 C (unchanged from previous run of same PWA), but the wave
> temperature was raised 250 C to 260 C to address the bridging.
> Thanks again for your help.
> Tom Moore
> Tom Moore wrote:
> >
> > Technetters,
> > In an attempt to reduce solder bridging between P-T-H leads one of
> > our employees raised the temperature on the solder pot of our wave
> > solder
> > machine. While this did alleviate most of the bridging effecting the
> > boards,on one board type, a multi-layer board, we ended up with
numerous
> > overheated joints. Unfortunately it effected 27 boards, which for our
> > small shop would be a large amount of rework.
> >
> > Reviewing both A-610 and J-STD-001 we didn't see anything that called
> > this out as a defect to rework or even a process indicator. Is this
> > correct?
> > Thanks for your help.
> > Tom Moore
> ##############################################################
> TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> ##############################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
following
> text in the body:
> To subscribe:   SUBSCRIBE TECHNET <your full name>
> To unsubscribe:   SIGNOFF TECHNET
> ##############################################################
> Please visit IPC web site (-610http://www.ipc.org/html/forum.htm) for
> additional information.
> For the technical support contact Dmitriy Sklyar at [log in to unmask] or
> 847-509-9700 ext.311
> ##############################################################

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################