AgIn2 thickness on void rate, microstructure, IMC growth, thermal and mechanical properties of fluxless In@AgIn2 joint
Indium (In) has been extensively used as a thermal interface material (TIM1) between the die and lid in high-power central processing units (CPUs) to enhance heat dissipation. However, organic flux residues trapped within the In solder during indium reflow process can outgas during subsequent solder...
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Elsevier
2025-03-01
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| Series: | Journal of Materials Research and Technology |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2238785425000985 |
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| author | Jing Wen Guoliao Sun Jinyang Su Yi Fan Linzheng Fu Zhuo Chen Wenhui Zhu |
| author_facet | Jing Wen Guoliao Sun Jinyang Su Yi Fan Linzheng Fu Zhuo Chen Wenhui Zhu |
| author_sort | Jing Wen |
| collection | DOAJ |
| description | Indium (In) has been extensively used as a thermal interface material (TIM1) between the die and lid in high-power central processing units (CPUs) to enhance heat dissipation. However, organic flux residues trapped within the In solder during indium reflow process can outgas during subsequent solder ball reflow cycles, leading to the formation of significant voids (up to 35% void fraction) in the In TIM1. This issue limits the application of In in advanced ball grid array (BGA) packages. In this study, for the first time, varying thicknesses Ag coatings were electroplated onto the surfaces of thick In TIM1 to form a non-oxidizing AgIn2 layer (In@xAgIn2, where x = 0.4, 1, 3, 6 μm) to protects the inner In from oxidation and enables fluxless reflow. Joints prepared with In or In@xAgIn2 underwent indium reflow and three solder ball reflow cycles to simulate the reflow processes typical of BGA packages. A clear AgIn2 thickness effect on solder wettability, microstructure, intermetallic compound (IMC) growth, joint thermal and mechanical properties were found. The results showed that In@0.4AgIn₂; had a contact angle of 26.2°, which was 2.6° lower than that of pure In solder. Joints prepared with In@0.4AgIn₂; also exhibited the lowest void fraction (≤2%), which contributed to better heat dissipation. During reflow, the Ag atoms from the AgIn2 protective layer altered the morphology and reduced the thickness of the Ni3In7 IMC layer. After reflow, the Ag atoms either solubilized in In or formed AgIn2 IMC with distinct distribution characteristics in the solder layer, which increased the shear strength of the joints by 81.5%. The fracture mode of the joints also changed from ductile to ductile-brittle, and ultimately to brittle. |
| format | Article |
| id | doaj-art-36b17d1301ef4caf81bfbcfceee07a00 |
| institution | Kabale University |
| issn | 2238-7854 |
| language | English |
| publishDate | 2025-03-01 |
| publisher | Elsevier |
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| series | Journal of Materials Research and Technology |
| spelling | doaj-art-36b17d1301ef4caf81bfbcfceee07a002025-01-18T05:04:45ZengElsevierJournal of Materials Research and Technology2238-78542025-03-013510721089AgIn2 thickness on void rate, microstructure, IMC growth, thermal and mechanical properties of fluxless In@AgIn2 jointJing Wen0Guoliao Sun1Jinyang Su2Yi Fan3Linzheng Fu4Zhuo Chen5Wenhui Zhu6The State Key Laboratory of High-Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha, 410083, ChinaThe State Key Laboratory of High-Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha, 410083, ChinaThe State Key Laboratory of High-Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha, 410083, ChinaThe State Key Laboratory of High-Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha, 410083, ChinaThe State Key Laboratory of High-Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha, 410083, ChinaCorresponding author.; The State Key Laboratory of High-Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha, 410083, ChinaCorresponding author.; The State Key Laboratory of High-Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha, 410083, ChinaIndium (In) has been extensively used as a thermal interface material (TIM1) between the die and lid in high-power central processing units (CPUs) to enhance heat dissipation. However, organic flux residues trapped within the In solder during indium reflow process can outgas during subsequent solder ball reflow cycles, leading to the formation of significant voids (up to 35% void fraction) in the In TIM1. This issue limits the application of In in advanced ball grid array (BGA) packages. In this study, for the first time, varying thicknesses Ag coatings were electroplated onto the surfaces of thick In TIM1 to form a non-oxidizing AgIn2 layer (In@xAgIn2, where x = 0.4, 1, 3, 6 μm) to protects the inner In from oxidation and enables fluxless reflow. Joints prepared with In or In@xAgIn2 underwent indium reflow and three solder ball reflow cycles to simulate the reflow processes typical of BGA packages. A clear AgIn2 thickness effect on solder wettability, microstructure, intermetallic compound (IMC) growth, joint thermal and mechanical properties were found. The results showed that In@0.4AgIn₂; had a contact angle of 26.2°, which was 2.6° lower than that of pure In solder. Joints prepared with In@0.4AgIn₂; also exhibited the lowest void fraction (≤2%), which contributed to better heat dissipation. During reflow, the Ag atoms from the AgIn2 protective layer altered the morphology and reduced the thickness of the Ni3In7 IMC layer. After reflow, the Ag atoms either solubilized in In or formed AgIn2 IMC with distinct distribution characteristics in the solder layer, which increased the shear strength of the joints by 81.5%. The fracture mode of the joints also changed from ductile to ductile-brittle, and ultimately to brittle.http://www.sciencedirect.com/science/article/pii/S2238785425000985Indium thermal interface materialsAgIn2 thicknessFluxlessLow void rateHeat dissipationBGA |
| spellingShingle | Jing Wen Guoliao Sun Jinyang Su Yi Fan Linzheng Fu Zhuo Chen Wenhui Zhu AgIn2 thickness on void rate, microstructure, IMC growth, thermal and mechanical properties of fluxless In@AgIn2 joint Journal of Materials Research and Technology Indium thermal interface materials AgIn2 thickness Fluxless Low void rate Heat dissipation BGA |
| title | AgIn2 thickness on void rate, microstructure, IMC growth, thermal and mechanical properties of fluxless In@AgIn2 joint |
| title_full | AgIn2 thickness on void rate, microstructure, IMC growth, thermal and mechanical properties of fluxless In@AgIn2 joint |
| title_fullStr | AgIn2 thickness on void rate, microstructure, IMC growth, thermal and mechanical properties of fluxless In@AgIn2 joint |
| title_full_unstemmed | AgIn2 thickness on void rate, microstructure, IMC growth, thermal and mechanical properties of fluxless In@AgIn2 joint |
| title_short | AgIn2 thickness on void rate, microstructure, IMC growth, thermal and mechanical properties of fluxless In@AgIn2 joint |
| title_sort | agin2 thickness on void rate microstructure imc growth thermal and mechanical properties of fluxless in agin2 joint |
| topic | Indium thermal interface materials AgIn2 thickness Fluxless Low void rate Heat dissipation BGA |
| url | http://www.sciencedirect.com/science/article/pii/S2238785425000985 |
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