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Flex PCB through production

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#83592

Flex PCB through production | 17 October, 2019

We've been getting more and more flex and rigid-flex assemblies.

Making carriers for mounting the boards to go through printer and pick & place is becoming more challenging with the size of some of the arrays.

Normally we use a pair of pins that are ground down to half the board thickness to hold the board and keep placement consistent. That really isn't possible with the thickness of FLEX.

The challenge is finding a method to secure the board that doesn't stick up higher than the board to interfere with stencil contact.

What are you using? Photos of fixtures would be great, even if it's a custom made thing.

We are making multiple carriers, that all have to be identical and consistent in board placement.

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#83593

Flex PCB through production | 17 October, 2019

It's the printing part that's the most challenge, right? You can print it correctly, then you should able to run it with PnP. You might need to have one "print" fixture only for screen printing, then transfer the printed board to SMT fixtures which you can use the tooling pins. Whenever the pins are not possible, then try to use the tacsil to holds the array down. You would need to send an array sample to the fixture tooling house to have the precision cuts if you want things to get it right.

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#83606

Flex PCB through production | 18 October, 2019

I found TACSIL tape, but I can't figure out how to buy it? None of the websites seem to have sales. Just info.

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#83611

Flex PCB through production | 18 October, 2019

Check with the tooling house where you get the fixture from. They should able to help out on that subject. At least they should know have some idea where you can purchase TACSIL from. Tip: when you dealing with flex cable PCB, always ask tooling house to add TACSIL tape underneath the "flex" section to ensure it's not going to shift around.

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#83614

Flex PCB through production | 19 October, 2019

For volume we used machined pocket durastone pallets, machined to the thickness of the flex to allow flat printing, with pockets machined for components placed on side 1. We held them down with 3M spray mount.

For low volumes we used flat durastone and held them with Kapton tape.

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SMTA-Davandran

#83617

Flex PCB through production | 19 October, 2019

There is double sided adhesive that able to withstand high temperature during reflow. `keep the adhesive minimum and appropriate location for securing the FPC on pallet during entire SMT process and easier for release of FPC after reflow process. Take note the FPC shall release during pallet is still warm.

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#83618

Flex PCB through production | 19 October, 2019

Can be customized?

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#83636

Flex PCB through production | 23 October, 2019

We are making our own fixture, so I don't have that resource to ask.

Is there not a way to buy the tape direct?

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#83666

Flex PCB through production | 30 October, 2019

Yo Ho! I'm a little late to the party, sorry! Flex can be a simple PCB to process through Screen, Pick & Place & Reflow, if the card is designed properly. 4 symmetrical tooling holes .125" diameter and 5mm in on each corner of the card. Wedge Effect: Using two tapered tooling pins on one end, two below surface puller mechanisms on the opposite 2 holes, will create the gentle tension needed to locate & secure the flex against the tapered tooling pins, to the pallet. There are other tricks that can be done to the pallet that helps in heat transfer, but I gotta keep some trade secrets!

Pallet Guy, Out!

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SMTA-Tony

#83752

Flex PCB through production | 14 November, 2019

Very late but here's my 2 cents. Will require a custom fixture for every flex or semi-rigid flex. Depending on panel thickness; use 2 tooling hole to fixture on one axis, other tooling holes will have pullers to ensure proper placement. Even with the pullers etc, always secure panel with the thinnest kapton tape in the fixture. Kapton will remain holding panel in place until after reflow. Depending on volume, might require 20 fixtures. Ensure fixtures are cool before reusing. We run flex & semi-rigid all the time.

This message was posted via the Electronics Forum @ SMTASMTA

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SMTA-Bob

#83764

Flex PCB through production | 15 November, 2019

We covered this in a past webinar on flexible and thin board assembly I presented. The webinar is available from my archive of recordings

Its also covered in the Joe Fjelstad's book on flexible circuits which is free online if you do a search. I wrote the assembly section and two different methods are shown. I have used fixed pallets from Germany and sticky pallets from Japan with my flex test circuits for my hands on workshops. We used them in the Lead Free Experience production features I organised in the past at exhibitions

Finally if you could post images on the forum I would send you a couple. Alternatively here is a direct link to two images

https://www.bobwillis.co.uk/wp-content/uploads/2019/11/DSC01629.jpg

https://www.bobwillis.co.uk/wp-content/uploads/2019/11/Flex-Pallet-VP.jpg

Bob Willis bob@bobwillis.co.uk

This message was posted via the Electronics Forum @ SMTASMTA

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#83765

Flex PCB through production | 15 November, 2019

Bob, where can I find that webinar? I did a search but it doesn't come up.

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#83767

Flex PCB through production | 15 November, 2019

Flexible circuits assembly is different from rigid board assembly. For some manfacturers, fpc assembly are some things more painful because the assembly quality is unstable. Recommend to check and hope these 2 blogs are helpful. Flexible Circuit Assembly: https://pcbboardassembly.com/flexible-circuit-assembly-services/ SMT Carrier: https://pcbboardassembly.com/all-about-smt-pallet-and-carrier/

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