| 1. |
- Chen, Xingrui, et al.
(författare)
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Enhancing the mechanical reliability of miniaturized thermoelectric cooler using nanotechnology underfill
- 2010
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Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. - 9781424481422 ; :Article number 5582779, s. 1250-1254
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Konferensbidrag (refereegranskat)abstract
- Miniaturized thermoelectric coolers is one of the most promising active heat dissipating methods in hot spot cooling, laser cooling and other applications. Improving mechanical strength can potentially boost the reliability of this technology. In this paper, simulations and mechanical compression experiments were carried out on miniaturized thermoelectric coolers both with and without underfiller. The results of the simulations and experiments indicate that the underfill process technology is highly effective means to improve the mechanical strength of miniaturized thermoelectric coolers.
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| 2. |
- Du, Wenhui, et al.
(författare)
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New fast curing isotropic conductive adhesive for electronic packaging application
- 2010
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Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. - 9781424481422 ; :Article number 5582446, s. 199-201
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Konferensbidrag (refereegranskat)abstract
- With the rapid development of technologies on high density assembly and packaging in electronic industry, isotropic conductive adhesive (ICA) has been paid more and more attention as a potential substitute of solder, due to its advantages of low processing temperature, simple processing conditions and good manufacturability. However, the curing time of most traditional ICA is more than half an hour. The process duration of ICA is 2 or 3 times longer than that of solder. Thus, low efficiencies of energy using and product manufacturing has been one of factors which limits widely application of ICA. Generally, the curing speed of ICA depends on types and amount of curing agent as well as curing temperature. In our previous experiments, the effects of curing temperature and amount of curing agent have been investigated. So, the present work attempts to choose a new kind of curing agent to shorten process duration of ICA. By using new curing agent, the curing duration of ICA could be shortened in 5 minutes with a high curing rate compared with the previous version. In addition, the basic performance including bulk resistivity and viscosity are also investigated in this work. Finally, we present some discussions about the further optimization of performance, for example regarding the ways of achieving better electrical conductivity with lower filler content and improvement of viscosity etc. © 2010 IEEE.
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| 3. |
- Hu, Zhili, 1983, et al.
(författare)
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The effect of modulus on the performance of thermal conductive adhesives
- 2010
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Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. - 9781424481422 ; :Article number 5582884, s. 648-651
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Konferensbidrag (refereegranskat)abstract
- By analyzing the effect of modulus of epoxy and modulus of filler particles on the thermal conductivity of thermal conductive adhesives (TCA), this paper concludes, in contrast to intuition, that the stiffer epoxy will generate a larger contact area, and the "soft" epoxy with modulus of 0.5GPa will create the largest contact area, hence the highest thermal conductivity. Therefore, it is advisable to adopt softer epoxy in TCA. On the other hand, this paper finds that if the shrinkage of epoxy is low, i.e. 1% linear shrinkage, fillers composed of a mixture of Ag flakes and certain high stiffness material will cause a higher thermal conductivity, i.e. 7% larger than that of pure Ag fillers. This suggests that with low shrinkage epoxy, it is advisable to mix Ag flakes with high stiffness particles, e.g. Diamond or SiC. However, when linear shrinkage of epoxy is high, i.e. 3%, the highest thermal conductivity is achieved by using pure Ag fillers. Therefore, in such cases it is not advisable to use Bi-model. © 2010 IEEE.
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| 4. |
- Lai, Huaxiang, et al.
(författare)
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Effects of BN and SiC nanoparticles on properties of conductive adhesive
- 2010
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Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. - 9781424481422 ; :Article number 5582434, s. 235-239
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Konferensbidrag (refereegranskat)abstract
- Isotropic conductive adhesives (ICAs) are a type of interconnect material used more and more widely in computer, robot, mobile phone, LED and so on. Compared with traditional solders, isotropic conductive adhesives have better working plasticity, creep resistance and heat resistance. In particular, isotropic conductive adhesives are more responsive in high density packaging than solder, which determines the dominance of ICAs in high density packaging in the future. In order to improve the thermal conductivity of ICA with acceptable electrical conductivity, Ag flakers, BN and SiC nanoparticles were added into the matrix. The content of silver flakes was 75wt%, and the content of nanoparticles (BN or SiC) in the isotropic conductive adhesives were 0wt%, 0.5wt%, 1.5wt%, 2.5wt%, 3wt%, 5wt% in weight. The conductive adhesives were coated on the PCBs with stencil printing and fifty SR1206 chip components were mounted on a PCB using conductive adhesive. All samples were cured at 150°for 1h. Further research into the reliability of the above isotropic conductive adhesives after temperature & humidity and thermal-cycling was carried out to analyze the effects of BN and SiC nanoparticals on the properties of ICA. The condition of the temperature & humidity test was 85 ° /85%RH, 500h. The thermal-cycling test was -40 °∼125°, 500 cycles and the soaking time and ramping rate were 19min and ±15°/min. Changes to electrical resistance were used to estimate the reliability of the isotropic conductive adhesives in this study. The microstructure of the failure samples was observed using a Scanning Electron Microscope (SEM). The water absorption of all ICAs is the same after 94h temperature and humidity aging and the rate of water absorption is also the same during the aging. The ICA with 3% boron nitride nanoparticles and 75% micron silver flakes shows the best temperature and humidity reliability, with the fewest cracks on the interface between ICA and component. After 500h thermal cycling aging, the resistance reduces in the first 100h and maintains in a certain value after 332h cycled thermal. The samples have no wide cracks but a few small ones on the interface. © 2010 IEEE.
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| 5. |
- Liu, Yangming, et al.
(författare)
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Numerical investigation on the thermal properties of the micro-cooler
- 2010
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Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. - 9781424481422 ; :Article number 5583917, s. 634-638
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Konferensbidrag (refereegranskat)abstract
- The micro-pin-fins prepared on the back side of the power chip enable heat removal on the level of modern microsystem demands. Carbon nanotube (CNT) has been proven to be a potential material for micro-cooler because of its superior advantages including high thermal conductivity, good mechanical property and so forth. And there emerges various applications of CNT in the micro-cooler system. In the present paper, micro-pin-fin heat sink with gas impinging jet as the cooling medium is analyzed. The heat dissipation of forced air convection cooling with micro-pin-fin structures made of aligned carbon nanotube arrays has been taken into consideration. The three-dimensional computational fluid dynamics (CFD) simulation was carried out. The temperature distribution and the pressure drop are studied in the cases of various geometrical parameters of the micro-pin-fin heat sinks at the same heating power prescribed. The fluid flow and the heat transfer phenomena in the micro-pin-fins heat sinks are investigated. The heat removal efficiency of the air microcooler is evaluated. An array of 8×8 fins with the optimized fin-to-base length ratio achieves the best cooling effect © 2010 IEEE.
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| 6. |
- Tao, W., et al.
(författare)
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Reliability characterisation of bi-modal high temperature stable Isotropic Conductive Adhesives
- 2010
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Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010, Xian, 16-19 August 2010. - 9781424481422 ; :Article number 5582437, s. 225-228
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Konferensbidrag (refereegranskat)abstract
- Conductive adhesives are generally considered to be one of the strongest candidates for replacement of solder in electronics industry. However, some problems related to the performance have so far limited wider applications of conductive adhesives. One of the major problems is tendency to degrade during temperature and humidity aging. In this paper, two kinds of Isotropic Conductive Adhesives (ICA) with high temperature stable matrix and different fillers were fabricated. The first one was fabricated by simply adding silver flakes into matrix as filler using this high temperature stable matrix based on highly cross-linked aromatic functional groups. For the second one, in addition to silver flakes, nanosilver particles with different weight percentages were also added as filler into matrix to form a bi-modal ICA. The weight percentages of nano-silver particles in filler are 1wt%, 2wt% and 3wt% respectively. The filler content of these two ICAs are both 75wt% in total. All test samples were cured at 150°for 1 hour. The random distribution of the silver flakes in the adhesive was observed by SEM. The bulk resistivity of the ICAs with different fillers was investigated to characterize the electrical conductivity of the ICA. The results show that addition of small amount of nano-silver particles improve the electric conductivity of the ICA but the excessive amount of nano-silver particles led to the increase of the ICA's bulk resistivity. The humidity (85°/85RH) test was carried out and the resistances of the samples were measured. It was shown that some electrical resistance increase was observed during the humidity testing with time. The addition of the nano-particles has also some negative effect of the electrical resistance change. But the effect is limited in a few percentage range of the nano-particle addition.
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| 7. |
- Wang, Shun, et al.
(författare)
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MDS study on the adhesive heat transfer in micro-channel cooler
- 2010
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Ingår i: Proceedings - 2010 11th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2010; Xi'an; 16 August 2010 through 19 August 2010. - 9781424481422 ; :Article number 5583859, s. 630-633
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Konferensbidrag (refereegranskat)abstract
- Carbon nanotube (CNT) can be used in micro-channel cooler construction due to its excellent thermal conductivity. When fabricating CNTs directly onto the chip, the chip could be damaged because of the high temperature required for CNT growth (about 750°C). As a solution, a transfer technique is developed where the desired carbon nanotube pattern can be obtained by taking off a pre-fabricated CNT forest with a designed adhesive, and the transfer process could make the chip or other components immune from the high temperature required for the CNT growth process. This process can also improve the bonding/adhesive strength. Nevertheless, the use of adhesive in the CNT-based micro-channel structure might affect the thermal conduction of the cooling system. In particular, the heat transfer between the heat generator and the CNT fin in the micro-channel cooler shall be evaluated. In this paper the thermal conductivity of the adhesive is studied by molecular dynamics simulation (MDS). The adhesive considered in the present MDS model consists of the epoxy and the curing agent. After the curing process, the epoxy molecules construct a network, which is established in the epoxy matrix generation before the simulation. Nonequilibrium Molecular Dynamics Method (NEMD) is adopted in the modeling and periodic boundary conditions are applied. Furthermore, the heat transfer through CNT and adhesive interface is simulated in this work based on the adhesive results, which can provide information for future macro-analysis of the thermal performance of the CNT microchannel cooler. © 2010 IEEE.
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