Novel cooling strategy for electronic packages: Directly injected cooling

TLDR: In this article, the authors describe the development of a novel cooling strategy for electronic packages, which increases design flexibility and results in electronic products with advantages in terms of performance, compactness, weight and production efficiency.

Abstract: This publication describes the development of a novel cooling strategy for electronic packages. During the conceptual design phase, the engineering disciplines involved are considered simultaneously. Through a case study, it is demonstrated that this integrative approach is an effective methodology leading to an innovative design. A novel, improved and highly integrated cooling strategy for electronic packages is presented. Standardized package types, as for instance ball grid array packages, are equipped with a directly injected cooling support. The developed concept is a new and very cost effective concept, as fewer productions steps and fewer procured parts are required compared to traditional cooling concepts. The new concept is also easily scalable, as multiple components on an electronic product can be cooled both uniformly across the product and simultaneously. This increases design flexibility and results in electronic products with advantages in terms of performance, compactness, weight and production efficiency.

Figures

Figure 5: Conduction concepts.

Figure 6: Novel concepts.

Figure 4: Integrated design process.

Figure 2: Traditional design process.

Figure 3: Increasing heat sink sizes.

Figure 8: Temperature vs. power measurements.

Frequently asked questions

Q1. What have the authors contributed in "Novel cooling strategy for electronic packages: directly injected cooling" ?

A case study illustrates how this approach is applied to the design process of a high performance electronic product. A novel and improved method for the cooling of electronic packages is presented. 

Q2. What is the basic strategy of the design process?

The basic strategy is to bring the coolant closer to the heat source and reduce thermal resistance between the heatsource and its heat exchanger. 

Q3. What are some other common types of grid arrays?

Other standardizedpackaging types as land grid arrays (LGA), pin grid arrays (PGA), stud bump arrays and quad flat-no leads (QFN) are also often seen. 

Q4. What is the main purpose of the BGA?

In this novel cooling concept the BGA is not only used for the transmission of electronic signals and mechanical fixation, but also acts as an integrated heat exchanger. 

Q5. How does air flow through a BGA?

By injecting air directly into the BGA, it is brought very close to the hot underside of the rigid laminate, thus bypassing several thermal resistances. 

Q6. What is the only dedicated feature in the PCB?

The only dedicated feature is a (non-plated through) hole in the PCB, which can be produced using standard PCB production techniques. 

Q7. How can an electronic package be cooled efficiently?

Without additional heat sinks and by adding just one (non-plated through) hole in the PCB an electronic package can be cooled efficiently. 

Q8. What is the new design of the BGA?

The new design is also easily scalable, electronic products with multiple components can be cooled both uniformly and simultaneously. 

Q9. What is the definition of thermal management?

In other words: the generated heat has to travel from the die through a series of thermal resistances before it finally is disposed to the ambient. 

Q10. What are the thermal resistances of electronic products?

These thermal resistances consist, for instance, of adhesive layers, encapsulation resins, solder connections, pockets or layers of stationary air and others. 

Q11. Why is a new cooling strategy needed?

As indicated in the previous section, due to thermal management issues, a new cooling strategy is required to manage heat dissipations of electronic packages. 

Q12. How much air flow is required to achieve the optimal heat transfer?

For optimal heat transfer, this ratio should be low, close to unity:1≈ dh (1)The jet-to-target spacing (h) is determined by the standoff distance of the rigid laminate. 

Q13. What is the common way of dissipating heat from electronic packages?

Many electronic packages dissipate most heat through their top surface to either a heat sink or a more sophisticated (active) cooling device. 

Q14. How low is the thermal resistance of a typical BGA package?

Combining this value with the thermal conduction properties of a typical BGA package, with 1cm 2 die, an overall thermal resistance of junction to ambient as low as 8 K/W can be obtained. 

Q15. What is the standoff distance for a BGA package?

For BGA packages the standoff distance is determined by the size of the solder balls and the amount of solder required to make a reliable electrical and mechanical connection. 

Q16. What is the main point of the article?

As a result, the continuous product improvement cycle threatens to stall, if no appropriate action is taken towards thermal innovation in the design and manufacturing process.