How to properly select chip package?

[AndyJing]

how to select package

power?
pin num?

 

[falling_stone]

Re: how to select package

Hi,
There are folowing considerations:
1.Environmental (Thermal, Mechanical)
2.Electrical

Mechanical conditions may be dictated by the type of the chip You create: for example, if You create military spec chip, You may have to use ceramic package because of the vibration and temperature cycling requirements,
Thermal - As far as I understand there are two approaches:
First:
1. Carefully calculate Your chip maximum power consumption.
2. Select the package which may dissipate the corresponding amount of power.
3. Simulate steady state thermal conditions with Your actual die size. (different die size may significantly change the ThetaJ-A and ThetaJ-B parameters from thise listed in the package spec). It can be done with tools like Paksi-TM, IcePack, etc.
Second:
The second approach is usefull if Your chip uses advanced power management (clock frequency adjustment, clock enables on parts of the chip, etc). In this case average power may be relatively low, but carefull thermal TRANSIENT simulation shoud be done in order to ensure that the chip will not go out of temperature limit.
Electrical design today may be more than a challenge for an engineer:
If You speak about digital chip the methodology I use is like this:
1. After the package type was chosen take equivalent inductance of the IO power/ground (worst value of two) and according to this and the type of IO cells used determine power/ground cell quantity and design chip pad ring accordingly.
2. Run a simulation and extract real RLC parasitic parameters from package connections. Ansoft (HFSS, SpiceLink), Optimal(Paksi), Microwave Office may be used for this task.
3. Go to step 1 and optimize the padring design using real power distribution system L parameters.
Best Regards,
F.S.

 

[gold_kiss]

Re: how to select package

can anyone give me material on this topic. Is it by mere experience one chooses the package? or ther some thump rules that you mentioned...any additional good document is appreciated.

Cheers,
Gold_kiss

 

[delay]

Re: how to select package

Biggest factor is cost both for engineering prototyping and manufacturing. Always need to justify $'s.

 

[hcet]

Re: how to select package

you can find the table of content file also here:
http://smithsonianchips.si.edu/ice/cd/PKG_BK/tofc.pdf
i guess also the rest of the book.

 

[tochaHCM]

Re: how to select package

The package and footprint are usually select by your customer. The first chip package is very much determined by its pin count

 

[riz_aj]

Re: how to select package

it depends on floorplan, interface speed, cost, process technology, thermal requirement and most important of customer requirement. Flip chip is preferred for higher performance application compared to wirebond but wirebond is slightly cheaper