I'm getting more and more anxious to see how much that "guessing game" might contribute to finding the root cause. There are simply not enough data to solve the puzzle.
Leland,
If you don't have capabilities to do proper analysis, you can send samples to us.
Regards,
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: "Amol Kane (Asteelflash,US)" <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Wed, 28 Mar 2012 05:36:43
To: <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
"Amol Kane (Asteelflash,US)"
<[log in to unmask]>
Subject: Re: [TN] Rework Concern and Question
Leland,
Have you tried preheating the assembly while doing the rework? If it’s a RoHS compliant laminate, you can preheat it to 120-130C and try the rework then.
Amol Kane
Process Engineer
AsteelFlash US East Corp
Tel: (607) 687.7669 x349 (O)
www.asteelflash.com
This e-mail and any attachments are confidential. It is intended for the recipient only. If you have received this e-mail in error, please immediately notify the sender by replying to this e-mail and delete the e-mail and all copies from your computer. Although the sender and AsteelFlash have taken every reasonable precaution, the e-mail and attachments may have some errors or omissions and may contain viruses. We cannot accept liability for any damage that you sustain as a result of that.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Tuesday, March 27, 2012 5:03 PM
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question
Bob,
At this point, we don't know what has happened nor how high we'll have to go to achieve release from the board. Thus far we've stayed within our set standards of 700 degrees F. We'll experiment tomorrow and should know something then.
Gee, I'll never make a reference to 200C again. Learned my lesson on that one.
Leland
-----Original Message-----
From: Robert Kondner [mailto:[log in to unmask]]
Sent: Tuesday, March 27, 2012 4:24 PM
To: 'TechNet E-Mail Forum'; Leland Woodall
Subject: RE: [TN] Rework Concern and Question
Leland,
So you are suggesting Si defused into the solder and raised its melting point by 200C ?
Did I get that right?
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Tuesday, March 27, 2012 4:14 PM
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question
George,
It's been a long day, and maybe I'm not making myself too clear.
We're not being able to achieve a liquidus state with a 700 degree F soldering iron. We're not trying to melt the lead, just the solder that's holding it to the PCB. We're not accomplishing that with the new component, so I'm thinking something has mixed with the solder joint and has raised the resultant reflow temperature.
Leland
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
Sent: Tuesday, March 27, 2012 4:10 PM
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question
Leland,
Am I missing something? I don't think it really matter that the lead base material or lead surface finish is. What matters is the solder used to attach the lead to the board. When you desolder a lead you don't melt the lead you melt the solder.
Regards,
George
George M. Wenger
Senior Principal Reliability / FMA Engineer Andrew Corporation - Wireless Network Solutions
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 Office (732) 309-8964 Mobile
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Tuesday, March 27, 2012 4:05 PM
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question
Hi Leland - I recommend you find out the lead base metal composition. If you shot an SEM-EDS of the lead toe, you could be getting the Si from the base metal composition and not part of the solder alloy composition.
Dave Hillman
Rockwell Collins
[log in to unmask]
Leland Woodall <[log in to unmask]> Sent by: TechNet <[log in to unmask]>
03/27/2012 02:52 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to Leland Woodall <[log in to unmask]>
To
<[log in to unmask]>
cc
Subject
Re: [TN] Rework Concern and Question
Vladimir,
We analyzed raw components straight out of the tape and reel packaging.
The site selection was on the bottom side of the leads at the toe.
Leland
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of vladimir Igoshev
Sent: Tuesday, March 27, 2012 3:12 PM
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question
Sorry Ben, it doesn't.
Leland,
What you are saying sounds strange. What does it mean: "We've analyzed the lead material beneath the SEM and it returns 98% tin and 2% silicone"? Did you analyzed leads or solder? Where the analysis was taken from? Did you analyzed leads with pads ripped off?
Regards,
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: "Gumpert, Ben" <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Tue, 27 Mar 2012 18:58:21
To: <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
"Gumpert, Ben"
<[log in to unmask]>
Subject: Re: [TN] Rework Concern and Question
Leland,
I won't claim to be an expert, but this website seems to imply something along those lines.
http://resource.npl.co.uk/mtdata/phdiagrams/sisn.htm
Ben
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Tuesday, March 27, 2012 2:18 PM
To: [log in to unmask]
Subject: EXTERNAL: [TN] Rework Concern and Question
Folks,
We've ran across a strange incident and I'd like a little advice from the group.
We recently underwent a component vendor change, and part of the first group of boards were misbuilt due to incorrect polarity (the part marking was misinterpreted by the vision operator).
Anyway, an attempt to remove the part by our Repair group resulted in lifted pads on 10 of the first 12 boards. We've analyzed the lead material beneath the SEM and it returns 98% tin and 2% silicone. The old style component comes off quite easily (within 3 seconds), and an analysis of its leads shows to be 100% tin. It's a 6 pin diode with very little mass.
What's going on here? Does a 2% silicone mix raise the melting point of solder by 200 degrees C?
Please help me understand.
Thanks,
Leland
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