Die size estimation for STM32F378 at wafer level only, without package

[Nickname16368_O]

Posted on February 10, 2017 at 14:47

I would like to understand how to assess the size of a ST product (STM32F378CC

https://community.st.com/external-link.jspa?url=http%3A%2F%2Fwww.st.com%2Fcontent%2Fst_com%2Fen%2Fproducts%2Fmicrocontrollers%2Fstm32-32-bit-arm-cortex-mcus%2Fstm32f3-

series / stm32f3x8 / stm32f378cc.html) in a WLCSP package (WLCSP66 - 66-pin, 3.767 x 4.229 mm, 0.4 mm of step of wafer level chip scale).

On Wikipedia I find that 'the package must not have an area greater than 1.2 times that of the die and must be a single-die mountable package, the direct area.'So it means that the die size should be estimated equal to area_package / 1.2?

Also the same product may have different die size in different packages?

In the sense that STM32F378CC could be sold in LQFP with different dimensions and UFBGA. For EVERY type of package there are Different designs of the same product and thus Different die sizes?The WLCSP Technology should not be sinónimo of minimum die size?

[Tesla DeLorean]

Posted on February 10, 2017 at 17:04

May be you should talk to someone in the IC packaging group? Some of this is farmed out to third-parties.

A singular small die can be placed in very large packages/lead frames. The LQFP176 can hold the same die as the UFBGA176, and one can safely assume the die isn't bigger than 10x10mm. I'd assume there are far fewer die than package combinations. 

Got an XRAY machine or some fuming nitric acid?

I think there are STM32 parts that ST has build where functionality has been removed to get the die small enough for the 36 pin packages etc. ie much smaller FLASH and RAM arrays.

[Jan Waclawek]

Posted on February 10, 2017 at 18:46

So it means that the die size should be estimated equal to area_package / 1.2?

I am not sure wikipedia is an authoritative source of this sort of information. One thing is sure, though - the chip is not bigger than the smallest package.

Also the sameproduct may have different die size in different packages?

The manufacturer is obsolutely free to do anything, as long as the resulting product conforms to the written specifications (datasheet et al.), even if the above sounds unlikely given the fixed costs mainly mask costs.

But the most important question here is: Why do you need to ask this?

JW

[Nickname16368_O]

Posted on February 13, 2017 at 10:07

Ciao Jan, first of all thanks for the answer.

I need to know the minimum size of this die because I am doing a design in which I have little space and I would understand if I can use the die without package and what are the dimensions.

My question is: which may be its minimum size knowing that of STM32 product I need especially its 16bit SDADC ?

Thanks again

Giuditta

[Nickname16368_O]

Posted on February 13, 2017 at 11:38

Thanks to all for the answers.

In any case I got the information that the STM32F378 at WLCSP package is the smallest PCB real estate I can get for an STM32 with a Sigma Delta ADC.

I have so solved my problem!

Best Regards

Giuditta