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April 2011

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Subject:
From:
Ioan Tempea <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ioan Tempea <[log in to unmask]>
Date:
Fri, 8 Apr 2011 12:05:38 -0400
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Hi Richard,

How would the Hakko preheater fare against the Zephyrtronics airbath, see http://www.zeph.com/mega_grid.html , as I am sure you have tested them all?

As a downside regarding the Hakko preheater I see the IR, requiring the operators to be more on their toes, in order to avoid burning the PCB. On the other hand, the Airbath is double the price, for a much smaller active area.

Thanks,

Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] 
W | www.digico.cc

N'imprimer que si nécessaire - Print only if you must


-----Message d'origine-----
De : Stadem, Richard D. [mailto:[log in to unmask]] 
Envoyé : April-08-11 11:24 AM
À : [log in to unmask]
Objet : Re: [TN] Cracked ceramic capacitors

Option 1 will probably not flush out anything, and may cause other issues, very high risk versus little return.
Option 2 poses good probability of finding at least 90% of cracked caps with a good inspector and a good 30x microscope, and poses very little risk IF THE CORRECT REWORK METHOD IS USED.
Option 3 depends on the fallout percentage from Option 2. If you visually screen 10 boards and find a single cracked cap amongst those 500 caps (50 caps x 10 boards = 500 caps screened) then Option 3 would not appear to be a good choice. Option 3 would then represent unnecessary rework, with little return versus very high risk.

Use a Hakko FR1012B bottom preheater and a Hakko FR802 hot air wand to perform any rework : 
http://www.hakkousa.com/detail.asp?CID=51&PID=2414&Page=1
http://www.hakkousa.com/detail.asp?CID=51,261&PID=4754&Page=1

You may not need the pre-heater, but you want to avoid large temperature gradients across the board. That is where the pre-heater helps.    
I'll think of you when I am up north fishing this weekend. Have fun!

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rivera, Raye
Sent: Friday, April 08, 2011 9:55 AM
To: [log in to unmask]
Subject: [TN] Cracked ceramic capacitors

Hello Technetters,

We had an issue with cracked SMT ceramic capacitors causing boards to fail functional test. We isolated the problem to a reel of parts that contained some cracked caps and purged these. Problem solved.

My question is about what to do with boards built with these capacitors before we purged. The boards pass functional test. The concern is that a cracked cap was loaded, but has not yet failed. The range of actions proposed here are:

- Temperature cycle the boards between -5 C and 55 C a few times. The theory is that this will flush out any latent defects.

- Visually inspect for defects.

- Manually change out all the suspect caps, about 50 per board.

Does anyone have thoughts on what would be the best method or another idea? We don't have ICT capability.

Thanks!

Raye Rivera



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