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July 2006

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Subject:
From:
Paul Edwards <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Paul Edwards <[log in to unmask]>
Date:
Fri, 14 Jul 2006 09:01:33 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (160 lines)
Steve,

I would bet you are right about the shorting...

I have seen shorting in similar conditions due to 2 conditions...
1) Contamination of the adhesive structures around the traces by the
material manufacturing process and fabrication process
2) The adhesive structure is incorrect for the high temp and humidty
environment...i.e.  TCE is too high, adhesive is microcracking and
absorbing moisture, or the adhesive is too hydroscopic...

If the adhesive is the problem, you might try baking the assembly to see
if this extends the MTTF...

I don't know of a good way to determine if it is a contamination
problem....


Paul Edwards
Process/Quality Engineering
[log in to unmask]
Tel: 408-433-4700
FAX: 408-433-9988
Surface Art Engineering
81Bonaventura Dr.
San Jose, CA 95134
DUNS: 944740570
CAGE/NCAGE: 1XZ48
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Kelly
Sent: Friday, July 14, 2006 7:31 AM
To: [log in to unmask]
Subject: [TN] Flex Circuit Voltage Failures

Good Morning,

I apologize for this long e-mail but I thought it best to try and
provide as
much info as possible.

We have a customer who is experiencing voltage failures on the following
build :

S/M

.0007 Copper (pads layer)

.008 FR-4 (Isola 410)

.0007 Copper (pads layer)

.001 DuPont Acrylic adhesive (bag layer)

.001 DuPont FR Kapton (bag layer)

1080 pre-preg

.0005 DuPont kapton

.0005 DuPont Adhesive

.0007 Copper (signals)

.001 Kapton

.0007 Copper (signals)

.0005 adhesive

.0005 kapton

.0005 adhesive

.0007 copper (signals)

.001 kapton

.0007 copper (signals)

.0005 adhesive

.0005 kapton

1080 pre-preg

.001 kapton

.001 adhesive

.0007 copper (pads layer)

.008 FR-4

.0007 copper (pads layer)

S/M

 

Finish ENIG

 

Lines are .004-.005 and spaces .008. 

 

The part is run at 75 C , 90 % RH, with 300 volts run on line 1 , 0 on
line
2 etc. Failures start to occur after approx. 48 hours and we think it is
track to track.

Any thoughts or suggestions would be appreciated.

 

 

 

 

Steve Kelly

PH: (416) 750-8433

FAX: (416) 750-0016

CELL: (416) 577-8433

 


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