Jim,
Sometimes the best solution to a problem is the simplest (or at least the
one immediately at hand), especially for those of us who occasionally
support non-production R&D activities. When you rarely fab the same circuit
twice, it just doesn't make sense to invest in specialized holding fixtures,
etc. for every new job. I'm unaware of Vishy's specific application, but if
it's low volume production, the 3M tape works well. I'm not trying to sell
my company's services to members of the the TechNet; rather, I'm honestly
relating my experiences in the hope that some may benefit (as I have). It's
a big world out there, and we're not all mass producing $5 clock radios. If
you don't find my suggestions useful, please ignore them, don't disparage
them. After all, you never know when you might alienate a potential
customer.
Kent
P.S. Can you supply me with the precise part number for that carpet tape? I
may have a use for it in my next project.
-----Original Message-----
From: jim <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Saturday, March 13, 1999 8:22 AM
Subject: Re: [TN] Flex circuit flatness - Is the solution out there ?
>Along these lines, ACE hardware has double sided carpet tape that won't let
>you even budge the part but comes off quickly with a little laquer thinner.
>Jim Gleason
>-----Original Message-----
>From: Kent S. Asmus <[log in to unmask]>
>To: [log in to unmask] <[log in to unmask]>
>Date: Saturday, March 13, 1999 9:50 AM
>Subject: Re: [TN] Flex circuit flatness - Is the solution out there ?
>
>
>>Vishy,
>>
>>I have had success mounting single-sided flexible circuits on FR-4 using
3M
>>high-temperature acrylic double-sided tape. The OVERSIZED flex substrate
is
>>placed face-down on a smooth table and stretched taut and smooth, holding
>>the edges with single-sided polyester tape (or similar). A strip (0.5" to
>1"
>>wide) of the 3M acrylic double-sided tape is placed around the edge of the
>>FR-4 board, and the board is placed on the back of the circuit. A sharp
>>blade is then used to cut around the perimeter of the board, releasing the
>>circuit from the table. The circuit is now held taut to the FR-4 board by
>>the strip of 3M acrylic tape around the outer edges of the board. In this
>>way, no adhesive residue contaminates the backside of the circuit. After
>>processing, the circuit is removed from the carrier by cutting within the
>>tape perimeter.
>>
>>As you can imagine, this process is not suitable for high-volume
>>applications, but it works well for low volume. I have successfully
>>performed SMT printing, placement and reflow with circuits mounted in this
>>fashion. The 3M tape is very aggressive and has no problem taking the
>reflow
>>temperature.
>>
>>Good luck,
>>
>>Kent
>>
>>-----Original Message-----
>>From: Narayana Vishy-CVN002 <[log in to unmask]>
>>To: [log in to unmask] <[log in to unmask]>
>>Date: Thursday, March 11, 1999 11:17 PM
>>Subject: [TN] Flex circuit flatness - Is the solution out there ?
>>
>>
>>>Hi Technet pals :
>>>
>>>Flexible circuits have this natural tendency to be flexible . They tend
to
>>>springup , bend ,kink & warp due to natural flexibility & handling .
>>>
>>>This behaviour is a major headache for the manufacturing engineers during
>>>the assembly process of these circuits - Defects & more defects !
>>>The non-flat nature of these circuits is the root cause of numerous
>defects
>>>like misaligned , unflush and unsoldered components . Processes such as
>>>solder paste printing,component placement & reflow oven are not very
>>>resistant to such flexible , warped & bent surfaces . Keeping these
>ciruits
>>>perfectly flat (like a PCB ) during these processes is key to
eliminating
>>>many of the defects mentioned.
>>>
>>>Not to mention that much of conventional automation strategies are not
>>>easily applicable on flex ciruit assembly manufacturing - For example,
>>>automated vision isnpection is an entirely different ball game when it
>>comes
>>>to flexible circuits.
>>>
>>>Now the questions :
>>>
>>>1) Is there anybody out there who knows techniques of holding the
flexible
>>>circuits down real flat ?
>>>2) Are there technologies/vendors in the market who have adhesives
>>>(sheets/sprays/liquids) which can :
>>> a. hold down flexible circuit panels flat on a solid pallet
>>>(carrier)
>>> b. withstand the reflow oven temperature (max 290 deg
>>>centigrade)
>>> c. be peelable/detachable from the flexible circuit panel
w/o
>>>causing cosmetic defects on the flex circuit after the reflow process .
>>>
>>>Any clues ?
>>>
>>>
>>>Thanks in advance,
>>>Vishy.
>>>
>>>################################################################
>>>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV
1.8c
>>>################################################################
>>>To subscribe/unsubscribe, send a message to [log in to unmask] with
>following
>>text in the body:
>>>To subscribe: SUBSCRIBE TechNet <your full name>
>>>To unsubscribe: SIGNOFF TechNet
>>>################################################################
>>>Please visit IPC's web site (http://www.ipc.org) "On-Line Services"
>section
>>for additional information.
>>>For technical support contact Hugo Scaramuzza at [log in to unmask] or
>>847-509-9700 ext.312
>>>################################################################
>>>
>>
>>################################################################
>>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
>>################################################################
>>To subscribe/unsubscribe, send a message to [log in to unmask] with
following
>text in the body:
>>To subscribe: SUBSCRIBE TechNet <your full name>
>>To unsubscribe: SIGNOFF TechNet
>>################################################################
>>Please visit IPC's web site (http://www.ipc.org) "On-Line Services"
section
>for additional information.
>>For technical support contact Hugo Scaramuzza at [log in to unmask] or
>847-509-9700 ext.312
>>################################################################
>>
>
>################################################################
>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
>################################################################
>To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in the body:
>To subscribe: SUBSCRIBE TechNet <your full name>
>To unsubscribe: SIGNOFF TechNet
>################################################################
>Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section
for additional information.
>For technical support contact Hugo Scaramuzza at [log in to unmask] or
847-509-9700 ext.312
>################################################################
>
################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe: SUBSCRIBE TechNet <your full name>
To unsubscribe: SIGNOFF TechNet
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################
|
