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Design >> RF Design >> QFN48: maximum die size
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Message started by Faisal on Nov 9^th, 2009, 3:06am

Title: QFN48: maximum die size
Post by Faisal on Nov 9^th, 2009, 3:06am

Dear Packaging Gurus :)

I have a question related to QFN48: What is the maximum die size that can be placed inside this package?

There are also down bonds to the paddle and I am not not sure how much margin should be allocated for them.

have fun,
Faisal

Title: Re: QFN48: maximum die size
Post by loose-electron on Nov 9^th, 2009, 5:09pm

Put the inquiry to the packaging manufacturer. As well, ask the assembly shop what space they need to hit the ground slug with the downbonds.

Title: Re: QFN48: maximum die size
Post by pauloau on Nov 11^th, 2009, 12:06pm

Hi,

From the site of a manufacturer (ASE) I could find the value for the die size to be 3.8 x 3.8.

http://www.asetwn.com.tw/content/2-4-4-1.html

Regards,
Paulo

Title: Re: QFN48: maximum die size
Post by loose-electron on Nov 11^th, 2009, 2:14pm

yes but frequently each package manufacturer is slightly different inside, and certain shops want different space allocations for the downbond area.

Bottom line: Talk to both you package manufacturing shop, and your assembly people (die mount and bonding) and make sure everyone agrees before the layout and tape-out.

Title: Re: QFN48: maximum die size
Post by ACWWong on Nov 11^th, 2009, 3:25pm

As loose has said, QFN48 encompasses alot of packages, each with slightly different dimensions, construction, diepad/paddle size etc....

and then there are different bonding houses with again different rules for downbonds clearance, max die size, max bond angles etc.

but having said that, a safe rule of thumb is 0.5mm for a down bond is something most bonding houses would easily be able to make.

Title: Re: QFN48: maximum die size
Post by loose-electron on Nov 12^th, 2009, 5:51pm

Rule one of successful design: Assume Nothing.

A trip to the foundry costs between $100k and $2.5E6

If you have to re-layout the chip and take it to the foundry again, you just spent somebody's lunch money for the rest of their life.

Please see rule 1.

Check with both your package supplier and the group doing the assembly & bonding. Get the die size definition and bonding placements approved and checked before the chip goes together.

Jerry