Nah, he was either an idiot or a really bad liar... a good liar would
have told you they were engineering evaluation samples or something like
that...
regards,
- Graham
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Thursday, March 29, 2012 1:33 PM
To: [log in to unmask]
Subject: Re: [TN] Does YOUR company ever screw up rework?
Correct,
And so many sales guys will tell customer "We are 100% accurate in what
goes out the door. Our final QC misses nothing."
Funny Story:
I was visiting a perspective assembly shop once, I asked the guy about
his % first pass yield. "Oh, 100%." He was absolutely confident in that
number.
So we walk a little further and there was a small pile of boards
sitting up on a self so I asked what those were. "Oh, they failed test."
He was still confident he had 100% first past yield.
So the guy was either an idiot or a really good liar. I still have yet
to decide which one.
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Glidden, Kevin
Sent: Thursday, March 29, 2012 12:12 PM
To: [log in to unmask]
Subject: Re: [TN] Does YOUR company ever screw up rework?
If the company were perfect there would be no rework in the first place!
-----Original Message-----
From: Robert Kondner [mailto:[log in to unmask]]
Sent: Thursday, March 29, 2012 12:02 PM
To: [log in to unmask]
Subject: [TN] Does YOUR company ever screw up rework?
Rex,
Absolutely Correct.
Simple Solution: No doubt in my mind, it is a squirm to avoid
responsibility for messing up a board.
Here is my question:
Is it reasonable to promise NOT to damage a board during rework? I
suggest no. Even if people are perfect materials would not be perfect.
(I would suggest materials are more consistent than people.)
So let's hear for all the sales guys on this list that sell
assembly/rework
services: Does your company ever screw up boards?
Bob K.
-----Original Message-----
From: Rex Waygood [mailto:[log in to unmask]]
Sent: Thursday, March 29, 2012 10:13 AM
To: [log in to unmask]
Subject: RE: [TN] Rework Concern and Question - SEM EDX Results Posted
See Occam's Razor.
:-)
Rex
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: 28 March 2012 18:42
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question - SEM EDX Results Posted
George,
Sure, measuring the melting point of the folder is fine. But look at
what we are suggesting here:
1. Either the solder used when the component was mounted has magically
increased in melting temp.
Or
2. Someone pulled the part off the board before the solder melted.
<---
My Choice
I have seen and done enough rework to have seen and pulled a few pads.
Rework is not easy. But pointing the finger of blame to the board house
or component? And using some high-tech erroneous SEM results as proof?
Come on.
It sounds like some rework shop trying to squirm out of screwing up a
board.
Bob
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
Sent: Wednesday, March 28, 2012 1:14 PM
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question - SEM EDX Results Posted
Bob,
That would be my first guess but rather than guessing I think it would
be prudent to measure the melting temperature. That could be done
crudely on a hot plate with thermocouples or you could take samples of
the solder from the good and part parts and do DSC analysis which I
don't think is necessary.
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: Robert Kondner [mailto:[log in to unmask]]
Sent: Wednesday, March 28, 2012 12:42 PM
To: 'TechNet E-Mail Forum'; Wenger, George M.
Subject: RE: [TN] Rework Concern and Question - SEM EDX Results Posted
So are we back to the point of:
"Someone pulled off the part before the solder melted?"
Much simpler concept than Si or SEM results?
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
Sent: Wednesday, March 28, 2012 12:03 PM
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question - SEM EDX Results Posted
Hi Leland,
SEM/EDX has its purpose but whenever we have problems with component
soldering we always do XRF measurements to not only see what the surface
finish is but to also measure the thickness of the surface finish. What
we've found is that SEM/EDX is great for surface analysis but if you
want to use it for bulk analysis you need to cross section samples and
do measurements at several locations. I have two suggestions: 1st). I
would do XRF measurements on an old "good" part and compare the results
to XRF measurement on a new "bad" part and 2nd). I would take a board
with a soldered new "bad" part and put it on a hot plate and monitor the
temperature as the board heats and record the temperature at which the
solder melts.
If you don't have access to XRF I would be happy to make XRF
measurements for you. Just put one old "good" and one new "bad" part in
an envelope and send it to the address in my email signature block
below. The measurements would only take a couple of minutes.
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: Wednesday, March 28, 2012 11:49 AM
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question - SEM EDX Results Posted
Hi Leland - do you have any photos of the "bad" parts after removal from
the pwa? Looking at the SEM EDX, I agree with Stewart, that Si peak
could be a misidentification issue.
Dave
Leland Woodall <[log in to unmask]> Sent by: TechNet
<[log in to unmask]>
03/28/2012 10:26 AM
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 - SEM EDX Results Posted
I've also added the SEM photos and EDX results to the folder at
http://ipc-technet.groupsite.com/file_cabinet.
Leland
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Wednesday, March 28, 2012 11:18 AM
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question
Everyone,
Thanks for all your responses. To answer a few of the items brought up
between yesterday afternoon and this morning:
The solder did indeed reflow and formed what visually appear to be good
joints. There is no evidence of dewetting or nonwets. I see no
difference between the joints on the old versus the new components.
The EDX analysis was performed on two leads of the old component and two
leads of the new component. Both of the samples were taken directly out
of the tape and reel packaging with tweezers, placed near each other on
kapton tape upside down, and analyzed within minutes of each other. The
old component returned two readings of 100% tin, the new component
returned two readings of 98% tin and 2% silicon.
When examined beneath a microscope at high magnification, the original
part leads are somewhat dull and grainy in appearance on the bottom.
The leads on the new component are very shiny and smooth.
I've taken a few photos and posted them to
http://ipc-technet.groupsite.com/gallery/22905.
I'll look through the SEM results from yesterday and see if there's
anything worth posting as well.
Leland
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of vladimir Igoshev
Sent: Wednesday, March 28, 2012 9:18 AM
To: [log in to unmask]
Subject: Re: [TN] Rework Concern and Question
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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