Indium(In)has been used as a thermal interface material(TIM1)in high-performance central processing unit(CPU)for better heat dissipation.However,leakage or pump-out of liquid indium during the multiple reflow cycles l...Indium(In)has been used as a thermal interface material(TIM1)in high-performance central processing unit(CPU)for better heat dissipation.However,leakage or pump-out of liquid indium during the multiple reflow cycles limits its application in advanced flip chip ball gray array(FCBGA)packaging.Former researchers place a seal or dam structure to prevent In leakage,leading to the risk of In explosion,thermal degradation,or require additional keep-out zones.In this work,a copper foam(CF)matrix was embedded in In to absorb the liquid In and eliminate the leakage of In TIM1 during the multiple reflow cycles,as the CF capillary force.Au/Ni/Cu-Au/Ni/Cu joint was fabricated by soldering with the composite solder at 190℃for 2 min.After reflow cycles,good metallurgical bonding was formed at interfaces of joint.Rod-like Cu_(11)In_(9) formed at the CF and In interface,due to the re-dissolved of Cu_(11)In_(9) crystal.Small amount of Cu atoms from CF can reduce the activity of In,which inhibits the growth of Ni_(3)In_(7) intermetallic compound(IMC)at the interface of In and Au/Ni/Cu substrate.The CF matrix also improved the shear strength(22.9%)and thermal conductivity of the solder joints.Besides,the fracture behavior of solder joints without CF matrix was classified to be ductile type while that with CF matrix was changed to be ductile-brittle mixed type.展开更多
Using thermal models to describe the heat dissipation process of FCBGA is a significant topic in the field of packaging.However,the thermal resistance model considering the structure of each part of the chip is still ...Using thermal models to describe the heat dissipation process of FCBGA is a significant topic in the field of packaging.However,the thermal resistance model considering the structure of each part of the chip is still ambiguous and rare,but it is quite desirable in engineering.In this work,we propose a detailed thermal resistance network model,and describe it by using thermal conduction resistance and thermal spreading resistance.For a striking FCBGA case,we calculated the thermal resistance of each part of the structure according to the temperature field simulated by COMSOL.The thermal resistance network can be used to predict the temperatures in the chip under different conditions.For example,when the power changes by 40%,the relative error of junction temperature prediction is only 0.24%.The function of the detailed thermal resistance network in evaluating the optimization space and determining the optimization direction is clarified.This work illustrates a potential thermal resistance analysis method for electronic devices such as FCBGA.展开更多
This paper studies the typical failure modes and failure mechanisms of non-wetting in an FCBGA（flip chip ball grid array） assembly.We have identified that the residual lead and tin oxide layer on the surface of the ...This paper studies the typical failure modes and failure mechanisms of non-wetting in an FCBGA（flip chip ball grid array） assembly.We have identified that the residual lead and tin oxide layer on the surface of the die bumps as the primary contributor to non-wetting between die bumps and substrate bumps during the chipattach reflow process.Experiments with bump reflow parameters revealed that an optimized reflow dwell time and H_2 flow rate in the reflow oven can significantly reduce the amount of lead and tin oxides on the surface of the die bumps,thereby reducing the non-wetting failure rate by about 90%.Both failure analysis results and mass production data validate the non-wetting failure mechanisms identified by this study.As a result of the reflow process optimization,the failure rate associated with non-wetting is significantly reduced,which further saves manufacturing cost and increases capacity utilization.展开更多
基金Project(2023GK2063)supported by the Key R&D Program of Hunan Province,ChinaProject(2023GXGG006)supported by the Key Products in Manufacturing Industry of Hunan Province,ChinaProject(kq2102005)supported by Key Project of Science and Technology of Changsha,China。
文摘Indium(In)has been used as a thermal interface material(TIM1)in high-performance central processing unit(CPU)for better heat dissipation.However,leakage or pump-out of liquid indium during the multiple reflow cycles limits its application in advanced flip chip ball gray array(FCBGA)packaging.Former researchers place a seal or dam structure to prevent In leakage,leading to the risk of In explosion,thermal degradation,or require additional keep-out zones.In this work,a copper foam(CF)matrix was embedded in In to absorb the liquid In and eliminate the leakage of In TIM1 during the multiple reflow cycles,as the CF capillary force.Au/Ni/Cu-Au/Ni/Cu joint was fabricated by soldering with the composite solder at 190℃for 2 min.After reflow cycles,good metallurgical bonding was formed at interfaces of joint.Rod-like Cu_(11)In_(9) formed at the CF and In interface,due to the re-dissolved of Cu_(11)In_(9) crystal.Small amount of Cu atoms from CF can reduce the activity of In,which inhibits the growth of Ni_(3)In_(7) intermetallic compound(IMC)at the interface of In and Au/Ni/Cu substrate.The CF matrix also improved the shear strength(22.9%)and thermal conductivity of the solder joints.Besides,the fracture behavior of solder joints without CF matrix was classified to be ductile type while that with CF matrix was changed to be ductile-brittle mixed type.
基金supported by the National Natural Science Foundation of China (NSFC) (Grants.52176078, and 51827807)the Research Foundation of Zhongxing Telecom Equipment Corporation (Analysis and optimization of internal thermal resistance of FCBGA chip)the Tsinghua University Initiative Scientific Research Program。
文摘Using thermal models to describe the heat dissipation process of FCBGA is a significant topic in the field of packaging.However,the thermal resistance model considering the structure of each part of the chip is still ambiguous and rare,but it is quite desirable in engineering.In this work,we propose a detailed thermal resistance network model,and describe it by using thermal conduction resistance and thermal spreading resistance.For a striking FCBGA case,we calculated the thermal resistance of each part of the structure according to the temperature field simulated by COMSOL.The thermal resistance network can be used to predict the temperatures in the chip under different conditions.For example,when the power changes by 40%,the relative error of junction temperature prediction is only 0.24%.The function of the detailed thermal resistance network in evaluating the optimization space and determining the optimization direction is clarified.This work illustrates a potential thermal resistance analysis method for electronic devices such as FCBGA.
基金Project supported by the National Natural Science Foundation of China(Nos.70871091,61075064,61034004,61005090)the PhD Program Foundation of Ministry of Education of China(No.20100072110038)the Program for New Century Excellent Talents in University of Ministry of Education of China
文摘This paper studies the typical failure modes and failure mechanisms of non-wetting in an FCBGA（flip chip ball grid array） assembly.We have identified that the residual lead and tin oxide layer on the surface of the die bumps as the primary contributor to non-wetting between die bumps and substrate bumps during the chipattach reflow process.Experiments with bump reflow parameters revealed that an optimized reflow dwell time and H_2 flow rate in the reflow oven can significantly reduce the amount of lead and tin oxides on the surface of the die bumps,thereby reducing the non-wetting failure rate by about 90%.Both failure analysis results and mass production data validate the non-wetting failure mechanisms identified by this study.As a result of the reflow process optimization,the failure rate associated with non-wetting is significantly reduced,which further saves manufacturing cost and increases capacity utilization.
