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.
>>
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