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July 2018

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From:
"MacFadden, Todd" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, MacFadden, Todd
Date:
Thu, 5 Jul 2018 13:09:18 +0000
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Hi Daragh, 



We have had good success with the magnetic hold down approach you mention. We use aluminum sheets that cover the entire circuit array with cutouts only at the SMT areas (we epoxy magnets on the underside of the Al sheets that align with opposite-polarity magnets embedded in corresponding holes in the fiberglass carriers). This works really well to keep the flex circuits flat during stenciling and pick-and-place. 





Todd MacFadden

Component Reliability Engineer 



BOSE

Technology Centers of Excellence

Materials Engineering and Analysis



Office: +1 508.766.6259





-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Daragh OLoughlin

Sent: Thursday, July 5, 2018 7:06 AM

To: [log in to unmask]

Subject: [TN] Screen Printing on 0.4 mm +/-0.1 thick PCB's



Hi All,



I'm looking for advice from anyone with experience printing to thin Flex-Rigid Polyimide-based PCB's. I'm interested in suggestions/tips for carrier retention mechanisms/designs and/or Screen Print tooling support of PCB's of 0.4 mm +/-0.1 thickness. 



As far as carrier design concepts, with a 0.4mm thin board, using low height tooling pins to date do not provide adequate retention/support. We have also tried various spring systems in the carrier to provide tension through the tooling pins to the board in X/Y directions to assist the retention, but to date no concept was worked well. Additionally, our carrier supplier recommended a high friction coating applied to carriers, however this coating degrades with use and has a limited life, and it's not a preferred option. I have personally visited a large manufacturing site in China, and saw them use magnets inserted into holes bored in the underside of the carrier, epoxy sealed in place, and use a thin metal foil overlay (with a large window with ~5mm clamping area on each side of the panel) to provide X, Y and Z retention.   



Does anyone have any suggestions for a robust carrier design suitable? Or perhaps can recommend a supplier to contact?



Product Info:

Flex-Rigid Polyimide-based PCB is panelised – width 69mm, length 128 mm Finished PCB thickness: 0.4 mm +/-0.1 mm There are two fine pitch BGA components located 3mm from the panel edges (both clamping sides)

Pitch: 0.4 mm and 0.35 mm

Bump diameter: nominal 0.130 mm

Pad Diameter: 0.2 mm



Manufacturing equipment

DEK Horizon 03iX Screen printer

DEK Horizon 02i Screen Printer



Stencil Info:

0.0762mm (~0.003”) Laser Cut Electro-polished Stencil 



Daragh OLoughlin

Lead NPI Engineer



Cochlear Limited

12 Helen Street

Newstead QLD 4006

AUSTRALIA



Phone: +61736346775

Email: [log in to unmask]

www.cochlear.com





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