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What’s black and stuck on a PCB?

Hmmm…

If you’re guessing it’s a chip package, you’re right – got it in one. Well done!

OK, so what type of package is it?

If you’re thinking it’s a silly question as you don’t know anything about the package, other than I’ve told you its black – that was a hint that it’s an encapsulated plastic part by the way – you’d be right.

You’d need me to tell you if it had leads, and if so on how many sides – one, two or four, and if so whether it has a metal tab. If not, you’d need me to tell you if there are solder balls underneath it, etc. This is like a parody of the ‘guess the animal’ games that operators, bored of writing JCL to run payroll jobs, wrote for the early mainframe computers of the 1960s. Knowing the package is rectangular and has leads on the two longest sides doesn’t exactly nail it down – so it’s not like knowing the animal has a trunk! More importantly it doesn’t tell you anything about its internals, like whether it has a drop-in heat slug.

Unfortunately there’s quite a bit of subtle variation in IC packaging. Wikipedia has quite a long list of these.

We encountered this issue many years back, when customers first started performing detailed thermal simulations on PCBs and wanted to model the packages explicitly in order to predict case or junction temperature. We realized pretty quickly that we needed to help customers to build package thermal models or risk this limiting the use of our tools.

To address this we started an internal research project, titled (rather unimaginatively) our Package-Level Thermal Initiative. A number of customers got involved and the effort evolved into in a 3-year EU-funded collaborative research project called DELPHI, that went on to develop a new approach to modeling chip packages – compact thermal models, or CTMs. These modeling methodologies are now standardized by JEDEC, and the 2 Resistor and DELPHI guidelines are available to all:

JEDEC Standard: Two-Resistor Compact Thermal Model Guideline, JESD15-3, July 2008

JEDEC Standard: DELPHI Compact Thermal Model Guideline, JESD15-4, October 2008

Next time I’ll tell you how FloTHERM.PACK, which evolved as a product from the DELPHI project, can really help your thermal modelling by helping you build accurate thermal models of chip packages.

Dr. J, Hampton Court

Thermal Guideline, CFD, Chip Package, Thermal Standard, FloTHERM.PACK, IC Packaging

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About John Parry

John ParryI started my career in the consultancy group at CHAM Ltd., using PHOENICS for a variety of CFD applications. From the consultancy group I moved into support, helping customers debug models, and figuring out how to model new applications. That broadened into delivering training courses and creating training material. I was invited to join Flomerics when it started in 1989 to head up Customer Services, and I jumped at the chance to work for a startup. After a few years supporting customers using FloTHERM I moved across into research, developing thermofluid models of common electronic parts, like fans and IC packages, later managing the DELPHI and SEED projects. More recently I worked with Flomerics’ Finance Director on the acquisition of MicReD, helping to integrate MicReD’s business into Flomerics Group which was great fun. Since Flomerics acquired Nika, I’ve been responsible for promoting the FloEFD suite in education, and moved into marketing. I now work as part of the Mechanical Analysis Division’s Corporate Marketing group, responsible for ElectronicsCooling Magazine and the division’s Higher Education Program. Expertise: I’m a chemical engineer by training and did a PhD in reactor design before getting involved with CFD more than 25 years ago. Visit John Parry’s Blog

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