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SMT on Flexible circuits

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#47647

SMT on Flexible circuits | 15 February, 2007

Hi all

have anyone has experiance in SMT on fexible circuits.

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CL

#47649

SMT on Flexible circuits | 15 February, 2007

vshan,

Good Morning. I used to work for a flex house and was responsible for the SMT assembly area. What is your question?

Thanks

Chris

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#47652

SMT on Flexible circuits | 15 February, 2007

I didn't pose the question -- but have some: As the substrate is flexible -- how do you hold the flex substrate flat for paste application and then flat enough for larger (>1" long SMT components to be placed without coplanarity issues> Also, what types of finishes are common for the flex;i.e, ENIG, immersion Ag, etc.?

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#47653

SMT on Flexible circuits | 15 February, 2007

Jim,

In a previous life, we built some flex circuits for a customer. The configuration was a flex cable, with a circuit at one end of it. We had fixtures made out of the same material that we had selective wave solder fixtures made from. Cut an indention in the material in the shape of the flex circuit, and included a clip to hold the circuit securely in place.

I didn't work on it personally, but it seemed to work through screening, pick/place, and reflow (conveyorized line).

cheers ..rob

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#47686

SMT on Flexible circuits | 15 February, 2007

Hi Chris Good Day!!!!

well we are running flex panel(150x270) with one connector(3 pin legs both sides) insert. Each panel consists of 28 parts and its used for disk drive industries. We are having a pallet to support with the top cover design such away the connector area is open and each open area a bridge are crossing to hold the connector. Im using lead free type(brand avantec) 1) facing problem on leg shifted 2) solder fillet

by the way do you think that aqueous cleaning system is playing important role??

tx

rgd vshan

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#47688

SMT on Flexible circuits | 15 February, 2007

Hi Jim Good Day

yes we are using a pallet bottom support as well as top cover. The top cover are design such a way that the solder paste area is open. the type of solder is lead free type(Avantec-ecorel free) in one panel consists of 28 parts and each parts consists of one 3leg connector. main problem is the leg shifted and solder fillet.

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#47689

SMT on Flexible circuits | 15 February, 2007

Hi Rob and all

the type of pallet we are using is durastone. how can we immediately cool the panel so that the throughput time at flex loading is faster. Currently we are directing the normal air using air gun to cool down but yet not fast, it takes >45sec to cool down

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Rob

#47705

SMT on Flexible circuits | 16 February, 2007

Hi Vshan,

Have more pallets made, and don't stack them - lay them flat on a trolley and move them back to the start of the line.

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CL

#47707

SMT on Flexible circuits | 16 February, 2007

vshan,

We were using pallets (delmat with cavities for the flex) We put stips of double sided Kapton tape in the critical areas. The tape held up to the heat and kept the circuit flat for the QFP's and BGA's. We based our assembly process for this circuit around the carrier pallet. After the circuit was loaded, we used the pallet for printing (Manual), placement and reflow. We then removed the circuit and ran through an in-line aqueous cleaner in a basket with spring clips to secure the circuit to prevent damage.

We also had some applications where we used a vacuum table to secure the circuit for placement but you need to maintain planarity throughout the entire process through reflow or you will see the same sort of problems.

I think every application has different requirements but we found that utilizing a carrier thoughout the process eliminated quite a few problems.

Please let me know if you would like to discuss this further.

Good Luck

Chris

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#47852

SMT on Flexible circuits | 20 February, 2007

Hi Chris Good day!!!

could you please let me know what kind of basket yu r using. Currrently we are using 30 by 40cm stainless steel carrier. Top n bottom design with square type. The area of connectors are open so that the water hits the connetor directly. Problem encountered i) its heavy ii) creating dent on flex due to open area on the carrier

by the way do you know how to attach images so that its easier for you to look at it

rgd vshan

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#47853

SMT on Flexible circuits | 20 February, 2007

Hi Rob Good Day!!!

yes im aware that more pallets will help. What im trying to do is that with the current pallets any other way of cooling the pallet

pls let me know

rgd vshan

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