A review of phase change materials for vehicle component thermal buffering

A chip scale ball grid array for integrated circuit packaging having a nonpolymer layer or support structure positioned between a semiconductor die and a substrate. The nonpolymer support structure acts to increase circuit reliability by reducing thermal stress effects and/or by reducing or eliminating formation of voids in an integrated circuit package. A nonpolymer support structure may be a material, such as copper foil, having sufficient rigidity to allow processing of chip scale package in strip format.

Chip scale ball grid array for integrated circuit package

The electrical applications of carbons and their composites are reviewed, with emphasis on applications that are relevant to industrial needs. The applications include electrical conduction, electrical contacts, electrodes, electromagnetic interference shielding, resistance heating, thermoelectricity, sensing, electrical switching, electronic devices and thermal pastes. The carbons include graphite, coke, carbon fibers, carbon filaments, carbon black and flexible graphite.

Electrical applications of carbon materials

Tests have been conducted in a wind tunnel with seven types of heat sinks including plate fin, strip fin, and pin fin heat sinks. In the case of strip fin, and pin fin heat sinks, both in-line and staggered arrays have been studied. The pin fin heat sinks had circular and square cross-sections. For each type, tests were run with fin heights (H) of 10, 15, and 20 mm while the heat sink width (B) was kept constant and equal to 52.8 mm. In total, 42 different heat sinks were tested. The width of the wind tunnel duct (CB) was varied in such a way that results were obtained for B/CB=0.84, 0.53, and 0.33. The wind tunnel height (CH) was varied similarly, and data were recorded for H/CH=1, 0.67, and 0.33 while the duct Reynolds number was varied between 2000 through 16500. An empirical bypass correlation has been developed for the different fin designs. The correlation predicts the Nusselt number and the dimensionless pressure drop and takes into account the influence of duct height, duct width, fin height, fin thickness, and fin-to-fin distance. The correlation parameters are individual for each fin design. Further, a physical bypass model for plate fin heat sinks has been developed to describe the bypass effect.

Modeling of the thermal and hydraulic performance of plate fin, strip fin, and pin fin heat sinks-influence of flow bypass

Carbon black dispersions as thermal pastes that surpass solder in providing high thermal contact conductance

Numerical and experimental studies were carried out to evaluate the air cooling characteristics of plate fins for MCMs (multichip modules) with and without some spanwise space around the plate fins. The flow field in-between the plate fins can be assumed to be similar to that of a parallel plate duct, and hence two dimensional laminar flow analyses using the finite volume method were performed. Calculations were carried out for Res (S/L)=1 to 200 and S/t (plate spacing to plate thickness ratio)=3, 4 and 7. Some empirical equations for the Nusselt number and friction factor based on the numerical results are proposed. Considering the fin efficiency calculated from the conventional conduction fin model, the thermal resistance of the plate fins with no space around the fins could be estimated easily on the basis of the above-mentioned equations. Comparisons with experimental results show that this method is valid for H/S (fin height to plate spacing ratio)/spl ges/7. In the case of H/S=4, the thermal resistance is overestimated by this method. Furthermore, nodal network analyses were carried out to estimate the thermal resistance of the plate fin including some spanwise space by specifying the cooling characteristics of the plate fin with no space around the fin. The good agreement between the predicted results and corresponding experimental data shows that this relatively simple nodal network method is quite useful to estimate the thermal resistance of plate fills including some spanwise space. >

Cooling performance of plate fins for multichip modules

Numerical simulation was carried out on the flow and the temperature fields around a plate fin array subjected to a uniform flow, varying the ratio of fin length L to the half-pitch of fins s. As Re/sub 0/s/L decreased, the flow approaching the fin array had a tendency to bypass it and thus the average flow velocity through fins U/sub f/ became lower, where Re/sub 0/ is the Reynolds number defined by uniform flow velocity and s. It was also found that frictional resistance and heat transfer of the fins showed excellent agreement with those for the developing flow between parallel plates with uniform inlet flow velocity equal to U/sub f/. A prediction technique for the cooling performance of the array was developed in which U/sub f/ was estimated under the condition of constant pressure distribution at its downstream edge. The present technique can predict the heat transfer of the fin array with an error level below 30% under practical conditions of electronics design, although it underestimates U/sub f/ in the region of small Re/sub 0/s/L.

Development of prediction technique for cooling performance of finned heat sink in uniform flow

Three-dimensional laminar flow simulation was carried out in order to investigate forced convection air cooling characteristics of compact plate fin arrays expected to be used for cooling notebook personal computers under the condition for which the fin tips were shrouded and no spanwise space around the fins was provided. The numerical simulation was performed by considering a conjugate problem which solved both flow and heat transfer in air stream and heat conduction in the fins and fin bases. Numerical results showed that the average heat transfer coefficient of the fin base was approximately one half of that of the fin. Based on the results of computation, some empirical equations for average Nusselt number of the fins and the fin bases and the friction factor were proposed as a function of Reynolds number. Using the fin efficiency calculated on the basis of the conventional conduction fin model, the thermal resistance of the plate fins could be estimated easily on the basis of the above-mentioned equations within an error level of 5% compared with the numerical results. The results also led to an important finding that there existed an optimum fin spacing fora given heat flux which could minimize blowing power.

Forced convection air cooling characteristics of plate fins for notebook personal computers

Air Flow Resistance of Wire Nettings in Natural Convection

A semiconductor switching apparatus includes a member for radiating heat generated from semiconductor switching element chips and for reducing a thermal stress. The lengths of gate electrode wires are equally set. The semiconductor switching apparatus has a large capacity and good switching characteristics.

Masaru Ishizuka

Papers

Cooling performance of plate fins for multichip modules

Development of prediction technique for cooling performance of finned heat sink in uniform flow

Forced convection air cooling characteristics of plate fins for notebook personal computers

Air Flow Resistance of Wire Nettings in Natural Convection

Power semiconductor switching apparatus with heat sinks