It is not the pictures that will be interesting, it is who is going to eat
some PCBs that will be interesting.
Let me guess, did anyone say it was an ENIG finish on the board?
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carl VanWormer
Sent: Monday, September 19, 2011 5:33 PM
To: [log in to unmask]
Subject: Re: [TN] large parts falling off finished surface mount board
assemblies
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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