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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