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September 2011

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Subject:
From:
Carl VanWormer <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Carl VanWormer <[log in to unmask]>
Date:
Mon, 19 Sep 2011 14:32:31 -0700
Content-Type:
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text/plain (247 lines)
To test this possibility, I wedged the X-Acto blade under the plastic
package of a SOT-23 transistor.  A pin lifted up.  I held that pin down
with a fingernail, re-inserted the blade, and the other two pins popped
off the board.  All 3 pins had solder blobs the shape of the pads, and
all 6 surfaces were uniformly granular. 

Does anybody want to see some pictures?  If so, I can try to get some to
Steve.

Thanks,
Carl


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Goodyear, Patrick
Sent: Monday, September 19, 2011 2:29 PM
To: [log in to unmask]
Subject: Re: [TN] large parts falling off finished surface mount board
assemblies

I'm with Phil, sounds to me like the thermal mass on the component was
too large for the 'BIG' components to fully heat and they never actually
got a melt or good reflow, due to too short a dwell time, the only thing
that was holding the component on was the binder in the flux in the
paste which had slightly solidified with a minor melt.  But that is just
a guess.  

Pat
Pacific Gas and Electric  

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro
Sent: Monday, September 19, 2011 1:52 PM
To: [log in to unmask]
Subject: Re: [TN] large parts falling off finished surface mount board
assemblies

I might have missed something but are you sure the solder actually
melted?  It almost sounds as if the bottom side heaters in the reflow
were off and you only got topside heat applied.  You should not have
been able to see any yellowish metal beneath the solder connections.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carl VanWormer
Sent: Monday, September 19, 2011 1:23 PM
To: [log in to unmask]
Subject: Re: [TN] large parts falling off finished surface mount board
assemblies

The Gold looks good and shiny.  Using my trusty X-Acto blade, I scraped
the granular solder that was left on the board.  I could imagine that
after removal of a layer of solder, I could see the Gold, then, with
more scraping, I convinced myself that I was seeing Copper.  Is there
any additional (easy) testing that I can do in my environment before I
contact either the PCB assembly house or the PC board fabricator with my
whining complaints?

Thanks,
Carl

-----Original Message-----
From: vladimir Igoshev [mailto:[log in to unmask]]
Sent: Monday, September 19, 2011 1:10 PM
To: TechNet E-Mail Forum; Carl VanWormer
Subject: Re: [TN] large parts falling off finished surface mount board
assemblies

Hi Carl, it sound like you got a problem with your ENIG board. I'm not
going to spell the "famous" BP word as saw a case with exact same
symptoms and it nothing to do with BP.  

The best you can do is to have the assembly analyzed. You can contact me
off line if you want us to do it.
Vladimir

SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca

-----Original Message-----
From: Carl VanWormer <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Mon, 19 Sep 2011 12:48:23
To: <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
        Carl VanWormer <[log in to unmask]>
Subject: [TN] large parts falling off finished surface mount board
assemblies

A surface mount PC board assembly (made by a local assembly house and
passed by our outgoing test) was returned from the end user, along with
an electrolytic capacitor that they had "knocked off" the board.  After
looking at the assembly and component under a microscope, I noticed that
the "gold plated" PC board (Lead free) had a fine granular solder
appearance (much smaller grain than solder paste balls) on the pads
newly exposed, with the whole "melted solder" blobs (in the shape of the
pads) attached to the capacitor leads (with a similar granular
appearance).  After minor scraping of various parts, I had come to no
brilliant conclusions, so I pressed my finger nail against an inductor
that was of similar size to the capacitor.  It popped off the board with
the same symptoms as the capacitor.  After recovering from my surprise,
I realized that I have no clue about the causes or cures for my
component adhesion problem.  Can any of the more experienced members of
this fine group direct me to some key words that might lead me to a
quick education (and solution)?

 

Thanks,
Carl

 

 

 

Carl Van Wormer, P.E., AE7GD

Senior Hardware Engineer

Cipher Systems

1800 NW 169th Place, Suite B-100

Beaverton, OR  97006

Cipher Systems (503) 617-7447 x 5163

Direct Line (503) 425-5163

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