Solid State Bonding of Silver Foils to Metalized Alumina Substrates at 260°C

Sha, Chu-Hsuan; Wang, Pin J.; Lin, Weitao; Lee, Chin C.

doi:10.1115/1.4005295

Cited by 7 publications

(5 citation statements)

References 9 publications

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“…It is worth mentioning that the bonding is between Ag and Au in our design. Based on previous study [27], pure Ag can be easily bonded to pure Au since both of them are very soft and thus easy to deform during bonding and they are free of oxidation issues. No IMCs form between Ag and Au, which is an indication of high long-term reliability.…”

Section: Experimental Design and Proceduresmentioning

confidence: 99%

Solid-state bonding of silicon chips to copper substrates with graded circular micro-trenches

Lee

2018

J Mater Sci: Mater Electron

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Silicon (Si) chips of 5 mm × 5 mm were bonded directly to copper (Cu) substrates using solid-state process at 300 °C without using any die-attach materials. A static pressure of 6.9 MPa was applied. To deal with the large mismatch in coefficient of thermal expansion (CTE) between Si and Cu, graded circular micro-trenches were fabricated on the Cu substrates. The micro-trenches provide space for Cu material to move into during the bonding process where the Cu surface incurs plastic deformation to conform to Si bottom surface for intimate contact. The micro-trenches also help relax stresses on the bonding interface caused by the fact that Cu contracts significantly more than Si during cooling down. The results obtained are encouraging, implying that the concept of using micro-trenches work. Scanning electron microscopy (SEM) images on cross sections of bonded structures show that Si chips were well bonded to Cu substrates without voids or defects on the interface and without any cracks on Si chip. Shear test were performed on six samples. It turned out that, of all six samples, the Si chip fractured first and the entire Si bottom surface was stilled well bonded to the Cu substrate. The average breakage force of Si chips on six samples is 13.5 Kgf. The breakage force of the joint cannot be determined but is certainly higher than 13.5 Kgf, which is more than twice of the specification American Military Standard. The new chip bonding structure with solid-state process reported in this paper eliminates the use of die-attach materials and the thermal resistance associated with the dieattach. It also removes the operating temperature limit constrained by the melting temperature of die-attach materials. We except this new bonding structure design to be a valuable alternative to high power and high temperature devices.

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Section: Experimental Design and Proceduresmentioning

confidence: 99%

Solid-state bonding of silicon chips to copper substrates with graded circular micro-trenches

Lee

2018

J Mater Sci: Mater Electron

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“…Due to the film hypothesis by S. B. Ainbinder et al, all metals and alloys possess an equal property to seize when clean surfaces are brought together within the range of interatomic forces [29]. C. H. Sha et al explain the bonding of Ag foils with precoated Au by the solid-state bonding theory where Ag atoms and Au atoms are brought within atomic distance so that they can share electrons [30]. Accordingly, metallic bonds potentially formed between Mo and Cu atoms with the electrostatic attraction of free electron and metal ion lattice.…”

Section: Microstructure Of Mo/cu Interfacementioning

confidence: 99%

Interface of Mo–Cu laminated composites by solid-state bonding

Wang

Chen

Yang

et al. 2015

International Journal of Refractory Metals and Hard Materials

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“…The applied force includes the weight of MACRO core. The 6.89 MPa pressure is 10 times lower than what has been used in industrial thermo-compression bonding processes [26,27]. The assembly is taken out of the bonding chamber after natural cooling in 1.33 9 10 -5 MPa vacuum.…”

Section: Experimental Designs and Proceduresmentioning

confidence: 99%

A solid-state bonding technique of large copper wires for high power devices operating at high temperature

Lee

2015

J Mater Sci: Mater Electron

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Solid-state processes of bonding 1 mm copper (Cu) wires on Cu substrates and silicon (Si) chips, respectively, were developed. To overcome Cu oxidation issue, the bonding surface on the wire was plated a silver (Ag) layer. An annealing step followed to make the Ag layer much easier to deform and conform to the Cu or Si bonding surfaces. The bonding process was performed at 300°C with 6.89 MPa. Wire-bond cross sections were studied using optical and electron microscopy, respectively. The images obtained exhibit nearly perfect Ag-Cu bonding interface. For wire-bonds made on Cu substrate, in-plane (shear) pull test measured a breaking of force 20.7-23.7 kg, comparable to the 22.5 kg breaking force of the Cu wire itself. Breaking forces on vertical (peel) pull test are about one-half of in-plane pull test results. For wire-bonds made on Si chip, breaking forces are about 80 % of those made on Cu substrate. Fracture modes were evaluated in details. 90 % of the wire-bonds broke with three modes mixed together: near Cu-Ag plating interface, inside Ag layer, and Ag-Cu bonding interface. Thus, the bonding interface is as strong as other regions of the wirebond. This solid-state wire bonding process is expected to have valuable applications in high power and high temperature devices and modules where the wire-bonds have to stand alone without protection due to lack of high temperature molding compound and reinforcing materials.

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Solid State Bonding of Silver Foils to Metalized Alumina Substrates at 260°C

Cited by 7 publications

References 9 publications

Solid-state bonding of silicon chips to copper substrates with graded circular micro-trenches

Solid-state bonding of silicon chips to copper substrates with graded circular micro-trenches

Interface of Mo–Cu laminated composites by solid-state bonding

A solid-state bonding technique of large copper wires for high power devices operating at high temperature

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