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Arduino Goes Hybrid, Flexible

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WBair
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Re: Flexible chips on flexible boards
WBair   8/14/2017 2:38:50 PM
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Stiffeners are common with conventional Flexible Copper substrates.

American Semiconductor uses a Flexible Hybrid Electronics approach and as with the NextFlex Arduino project is not using any stiffeners. The goal is optimize the flexible assembly process to accomodate flexing instead of reducing the area of flex. 

American Semiconductor is a member of NextFlex.

 

WBair
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Re: Footprint
WBair   8/14/2017 2:31:42 PM
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The Arduino rigid boards have standard footprints and IO locations. a flexible board opens new interface options and new connection methods (eg. ZIF connector) while still having all IOs available. Flexible Hybrid versions applied to a wireless Arduiono would definitely benefit from smaller footprint and reduced size for conformal attachment.

WfrMkr
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Flexible chips on flexible boards
WfrMkr   8/14/2017 11:35:13 AM
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American Semiconductor just did a demonstration of this type of system. Flexible SoP ICs on flexible substrates appear to provide the necessary performance and meet reliability requirements with no stiffeners.  Wouldn't a stiffener kinda defeat the purpose of a flexible device??

nick_rb
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Footprint
nick_rb   8/9/2017 3:10:23 AM
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The Arduino footprint is optimised to enable easy access to all the IOs. Why is footprint reduction a comparison factor in the project?

WBair
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Re: Reliability?
WBair   8/7/2017 11:04:47 AM
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Adding stiffeners is the most common way to increase reliability for flex boards. It does this by intentionally limiting the bend and flex ability of the flex circuit. it also adds cost to the system. for IC's we will be using direct die attach and ultimately thinning the die to provide flexibility with conductive adhesives. we will use mandrel bend tests to determine the achievable bend radii with different design approaches.

Reliability and yield are key concerns to move this technology to a production readiness level.

WBair
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Re: Reliability?
WBair   8/7/2017 10:57:46 AM
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Your concern is very valid. attaching rigid components to flexible substrates will create reiliability concerns. we are not using raditional copper clad flexible substrates but printing conductors with silver ink on PET substrates and using conductive adhesives to attach components. selecting the smallest components for SMT mount will reduce strain levels as well. for test and compatibility reasons our first Arduino Flex design will use the same components (size and count) as the rigit board. This will limit the bend radius this specific design will be able to accomodate. Future design revisions will optimize component placement and possibly replace some components with printed structures.

elizabethsimon
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Re: Reliability?
elizabethsimon   8/4/2017 11:04:50 AM
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@relaxe

I don't have much experience with populated flex pcbs either but most of the ones I've seen have stiffeners in the areas where components are soldered. Even adding a stiff area just a bit bigger than the IC with leads would help a lot.

I still want to see the reliability specs on this though...

relaxe
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Reliability?
relaxe   8/4/2017 8:40:47 AM
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I'm all for that, but is it just me or the flexing of a pcb with non-flexible parts on it will lead to reliability issues?

I mean, that C7 1210 Capacitor will sure have a lot of strain either on the cap, or on the PCB traces near it.

I'm worried for the solder on the higher pin-count device, where each solder pad is subject to force at each flex...

Am I wrong on this? I don't have much experience with populated flex pcbs.

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