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June 2011

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Subject:
From:
Don McFarland <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Don McFarland <[log in to unmask]>
Date:
Thu, 16 Jun 2011 10:33:15 -0600
Content-Type:
text/plain
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text/plain (274 lines)
Michael, 

I believe that you can push back pretty hard on this one.

Section 5.2.7.3 is referring to solder webbing and splash criteria only. In fact, the cited requirements states "Visual inspection for SOLDER SPLASHES shall be done without magnification". Feel free to disagree here, but splashes and solder balls are very different in appearance and cause. The criteria for solder balls/fines (including residual paste FOD)is found in 5.2.7.1 and doesn't provide any caveat for inspection magnification reduction. Therefore, in my humble opinion, solder ball/fine inspection shall be performed at magnifications detailed in table 1-2 and 1-3. 

Again, residual paste powder on the board from a aqueous process is not a normal condition. There are a number of good articles and white papers that detail ways to eliminate this through stencil design (foil thickness, aperture design, etc). Ultimately, it would be good for your CM to fix their process and stop pushing back on potential reliability concerns...especially when their position is this silly!

Another avenue, that may be applicable, is a statement within the defect condition of 5.2.7.1 that says if solder balls become dislodged in the normal service environment, they are still bad. I mention this because some products with unique service environments (e.g. vibration, temp cycling, exposure) may not be permitted to have any solder balls, even if they are entrapped, encapsulated or attached. 

I hope this didnt confuse anyone. 

Don


----- Original Message -----
From: "Michael Forrester (H USA)" <[log in to unmask]>
To: [log in to unmask]
Sent: Thursday, June 16, 2011 9:50:50 AM
Subject: Re: [TN] PCBA Inspection for Solder Balls/Splashes

MaryJane,

        The problem is that we procure these assemblies from a
subcontractor and they are stating that it is not an issue per
IPC-A-610E so no action will be taken on their part.  I don't want to
have to spell out on every PCBA print that " any solder anomalies not
entrapped in flux is considered a defect"
against the wording in the standard and have all of our subcontractors
agree to meet higher than standard (IPC-A-610E) specifications across
the board.  
Until IPC put the statement:

                "Inspection for solder splashes shall be done without
magnification." 

this would have been a defect.  This statement is new to Rev E of the
standard.

Best Regards,
 
Michael Forrester
Sr. Product Engineer
CSMTPE
 
Siemens Healthcare Diagnostics
101 Silvermine Rd.
Brookfield, CT  06804
PH: (203) 740-6452

-----Original Message-----
From: MaryJane Chism [mailto:[log in to unmask]] 
Sent: Thursday, June 16, 2011 11:36 AM
To: TechNet E-Mail Forum; Forrester, Michael (H USA)
Subject: RE: PCBA Inspection for Solder Balls/Splashes

Michael,

Two things that you can do when using the IPC-A-610E; you can interpret
it "literally" or you can use it as a "guide" when manufacturing
electronic assemblies.  

I prefer to use it as a reference guide as well as I think our company
does.  Common sense tells us that even though the slivers were not
visible without magnification, once we have seen them and they are not
entrapped, get rid of them.  



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Forrester, Michael
(H USA)
Sent: Thursday, June 16, 2011 11:06 AM
To: [log in to unmask]
Subject: Re: [TN] PCBA Inspection for Solder Balls/Splashes

1st sentence in section 5.2.7.3 Soldering Anomalies - Excess Solder-
Solder Webbing/Splashes:

        "Inspection for solder splashes shall be done without
        magnification." 


Best Regards,
 
Michael Forrester
Sr. Product Engineer
CSMTPE
 
Siemens Healthcare Diagnostics
101 Silvermine Rd.
Brookfield, CT  06804
PH: (203) 740-6452

-----Original Message-----
From: Joyce Koo [mailto:[log in to unmask]] 
Sent: Thursday, June 16, 2011 10:36 AM
To: 'TechNet E-Mail Forum'; Forrester, Michael (H USA)
Subject: RE: PCBA Inspection for Solder Balls/Splashes

I thought table 1-2 and 1-3 specified Mag.  I didn't know anything about
no-mag.  

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Forrester, Michael
(H USA)
Sent: Thursday, June 16, 2011 10:24 AM
To: [log in to unmask]
Subject: [TN] PCBA Inspection for Solder Balls/Splashes

I have a question about solder balls/splashes on PCBAs.  in IPC-A-610E
section 5.2.7.1 it mentions that solder balls and "fines" that are NOT
encapsulated in flux is a defect.
Section 5.2.7.3 mentions that the inspection for said solder anomalies
shall be done with NO magnification.  We have an SMT assembly that is
manufactured with water soluble flux and has two SMT parts hand soldered
to the board with No-Clean.  In reviewing the rework under
magnification, we discovered solder slivers entrapped in the No-Clean
flux that did not violate the minimal electrical clearance.  So far so
good.  I have several assemblies where there are unmelted solder balls
from the paste and solder slivers (4-5 mils) spread all over the PCB NOT
entrapped in any flux.  I can not see them without magnification, so
does that mean that they pass the IPC-A-610E specification?  In thinking
about this, in theory, once the board is put into service all of the
solder anomalies, not entrapped in flux, could shake loose, converge and
create a short?  So hence my confusion between section 5.2.7.1 and
5.2.7.3.  Any thoughts would be appreciated.  Thank you.
 
Best Regards,
 
Michael Forrester
Sr. Product Engineer
CSMTPE
 
Siemens Healthcare Diagnostics
101 Silvermine Rd.
Brookfield, CT  06804
PH: (203) 740-6452
 

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