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July 2007

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Subject:
From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 11 Jul 2007 07:38:36 -0500
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Hi folks! I can add some additional detail to Guy's observations. The dull 
solder joint appearance that Guy correlated to the fresh DI beds is a 
result of the solder joint surfaces being slightly etched. The "fresh DI 
beds" result in a water pH that is slightly more acidic in nature than 
"old DI beds". This change in water pH results in a preferential etch of 
the tin in the tin/lead solder joint surfaces thus the dull visual 
appearance. A number of years ago, I ran into a situation where a number 
of printed wiring assemblies had been subjected to an excess number of 
saponified cleaning cycles. The solder joints surfaces were soo etched 
that the pwas looked "purple" - we dubbed the pwas "Barney boards" in 
honor of the purple dinosaur cartoon show! This dull solder joint 
discussion again demonstrates the visual appearance has very little to do 
with the overall solder joint integrity.

Dave Hillman
Rockwell Collins
[log in to unmask]




Guy Ramsey <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
07/10/2007 09:10 AM
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Subject
Re: [TN] Dull SnPb solder joints






With fresh DI beds we get duller joints for a day or two. It was more
pronounced with the flux formula we used a year ago. We switched to get
better control of the foam fluxer and got shiner joints, more like the
joints from our reflow process. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Amol (349)
Sent: Tuesday, July 10, 2007 9:22 AM
To: [log in to unmask]
Subject: [TN] Dull SnPb solder joints

Dear Technetters,
We are seeing dull SMT solder joints near some TH parts that go over the
wave. The board top side temp is getting to 110C. using OA flux at wave 
and
SMT. The boards are immediately put thru an aqueous wash. The SMT joints
were shiny coming out of SMT. The customer is noticing this because other
areas of the board (except near the TH parts) look shiny.
There are no residues on the joints as I tried to manually clean a joint
with water and IPA and did not have any flux residue on the Q-tip.

Has anybody else noticed this phenomenon?......the only literature I could
find on dull SnPb joints says the dull appearance could be due to a "cold"
joint, which I know is not the case. Even though this is not a defect I 
want
to know the reason for this to happen.

Could the wave flux cause this issue?

Amol

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Tuesday, July 10, 2007 8:19 AM
To: [log in to unmask]
Subject: Re: [TN] Injury by array

Jeff,
Two other possibilities (both costing $) are:
1) automatic board handler
2) gloves

I don't like either one, but there they are.
Bev
RIM

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of McGlaughlin, Jeffrey A
Sent: Tuesday, July 10, 2007 7:23 AM
To: [log in to unmask]
Subject: [TN] Injury by array

Oh wise and wonderful members of tech net -

We have had to incidents in the past six months where assemblers have been
cut while handling assembly arrays (2-up panels) for one of our products.
This has elevated the issue to "Panic Mode" due to the involvement of 
EHS&Q
(environmental health, safety and quality). As the designer of the array I
have been given ownership of the issue and am task with resolving it. 
After
20+years of handling boards and arrays I have never been cut, so I am 
unsure
as to what if any corrective action can be taken to prevent future 
injuries.

The specifics on the arrays -
10.5" [267mm] x 12.0" [305mm] x 0.062" [1.6mm] thick
2 - up for 4.7"[119.3mm] x 9.2" [233.6mm] PCB Minimum rail 0.38"[9.5mm] 
Tab
Route and Retain (mouse bite) Injuries occurred during loading of the 
solder
printer and during slide line operations for post reflow assembly.

Any suggestions on what to tell our production group?

Jeffrey McGlaughlin, CID
Engineering Designer
Battelle
505 King Avenue
Columbus Ohio 43201-2693
(614)424-7582 Phone
(614)458-7582 Fax
PS Don't you just love all those  management buzzwords (underlined.)
>;-D

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