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How to install FBGA ICs on both sides of Flex boards with no stiffeners ?

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#80863

How to install FBGA ICs on both sides of Flex boards with no stiffeners ? | 9 August, 2018

Hello,

My name is John Kim and I am working for a Contract Manufacturer located in Fremont, California. Sometimes, I receive flex boards as a consignment part. Today, I received a consignment job, but decided to return the kit to the customer. The reason is that the flex PCB is too thin (I measured the thickness and it is 4.5 mil with no stiffeners) and on both sides there are components including FBGA components.

To prevent any more Kit returning, I’d like to ask you some advice how to build those difficult assemblies. Q1> Is there any special machines/equipment which are able to install FBGA parts on the very thin flex boards for Printing, Pick & Place, and Reflow ? Q2> Is there any Fixture house who can offer fixtures to enable SMT processes for those assemblies ? Q3> Or do you have any advices to solve my issue at different angles ?

Your advice will be very highly appreciated.

Best regards, John Kim

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#80866

How to install FBGA ICs on both sides of Flex boards with no stiffeners ? | 9 August, 2018

To me the most challenge would be the printing step. If you can print it, you should able to run it with SMT. We ran similar thickness flex boards before. But it's long flex with small stiffener at both ends, and it was 10up array. You need fixture with "special double-sided tape" to hold the array board down with minimum flex allowed. It's difficult to get it right. But once you get hang of it, it's still doable, but just be prepared, fail rate will be high.

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#80869

How to install FBGA ICs on both sides of Flex boards with no stiffeners ? | 9 August, 2018

Hi Thomas,

Thank you for your posting and I agree with you that Printing is the most difficult one.

BTW, after you ran the one side (let's say Bottom side), my engineer worries about the distortion of flex board because of the thickness. In that case, the surface may be not even, and it caused bad Printing quality for fine pitches.

Also, I think that the component installed on Bottom side disturbs the flatness of Top side surface as well.

If you have any idea and/or know a good fixture house to prevent my concerning, please advise once again. And everybody is welcome to teach me to solve this issue.

Thanks, John

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#80871

How to install FBGA ICs on both sides of Flex boards with no stiffeners ? | 9 August, 2018

A good set of fixtures are what you need to get it done right. Since we are in the same area, I would recommend give ATD (Advance Tooling Design)a try, they located in San Jose. We been using fixtures from them for years. We build thousands of Flex cable I mentioned earlier with the fixture from them. Just provide them the Array Gerber, BOM, and actual Array board as sample would be your best bet. They would able to find out how the height of the components (per BOM) to make the best cut possible for the fixture.

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#80874

How to install FBGA ICs on both sides of Flex boards with no stiffeners ? | 10 August, 2018

Hi Thomas,

Thank you for your advice. BTW, unfortunately, I received negative answer from the Fixture house same as below.

=========== We have an issue here. Your board is too thin. It is fine to make the fixture for first side.

But when you run the second side, you can not have full support because the fixture have to clear for the component on the other side.

It is not feasible to make the fixture for this board.

Sorry for the inconvenience. ===========

Does anyone know the better Houses or other solutions ?

Still I need advice from experienced people...

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#80875

How to install FBGA ICs on both sides of Flex boards with no stiffeners ? | 10 August, 2018

I am sorry to hear that they are unable to help you out too. If you do came up with the doable solution later, be sure to let me know about it too. I would like to learn new trick or knowing which house that can handle such task.

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#80876

How to install FBGA ICs on both sides of Flex boards with no stiffeners ? | 10 August, 2018

Absolutely I will share the solution with you if I find something.

Thomas, thank you for your help. Have a great weekend!

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