Low Temperature Solid State Gold Bonding of Si Chips to Alumina Substrates

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Chu-Hsuan Sha ◽  
Chin C. Lee
Keyword(s):  
Solid State ◽  
Static Pressure ◽  
Coefficient Of Thermal Expansion ◽  
Bonding Temperature ◽  
Bond Line ◽  
Bonding Process ◽  
Pure Gold ◽  
Solid State Bonding ◽  
Reflow Temperature ◽  
Atomic Distance

Pure gold (Au) is used as a bonding medium to bond silicon (Si) chips to alumina substrates. The bonding process is performed at 260 °C with only 150 psi (1.0 MPa) static pressure applied. This is a solid-state bonding without any molten phase involved. The Au layer plated on alumina is ductile enough to deform for its surface to mate with the thin Au layer coated on Si. Au atoms on both sides of the bond line are brought within atomic distance and bonding is achieved. The ductile Au joint also accommodates the significant mismatch in coefficient of thermal expansion (CTE) between Si and alumina. Scanning electron microscope (SEM) evaluations show that nearly perfect joints are achieved and no voids are observed. Five samples are shear tested. They all pass the MIL-STD-883G standard. This bonding technique can be applied to bonding any two objects that can be coated with smooth Au layers. The 260 °C bonding temperature is compatible with typical reflow temperature of Sn3.5Ag solders used in electronic industries.

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

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Chu-Hsuan Sha ◽  
Pin J. Wang ◽  
Wen P. Lin ◽  
Chin C. Lee
Keyword(s):  
Shear Strength ◽  
Solid State ◽  
Shear Test ◽  
Static Pressure ◽  
Bonding Temperature ◽  
Bonding Process ◽  
Sem Images ◽  
Solid State Bonding ◽  
Reflow Temperature ◽  
Atomic Distance

Silver (Ag) foils are bonded to alumina substrates by a low temperature solid state bonding process. The alumina substrate is premetalized with 40 nm titanium tungsten (TiW) and 2.54 μm gold (Au). The bonding temperature is just 260 °C, compatible with the peak reflow temperature of lead-free (Pb-free) solders used in electronic industries. The Ag foil is quite soft and ductile. It can deform to mate with the Au surface on alumina. Thus, only 1000 psi of static pressure is needed to bring Ag atoms and Au atoms within atomic distance on the interface. Ag has superior physical properties. It has the highest electrical and thermal conductivities among the metals. Scanning electron microscope (SEM) images show that the Ag foil is well bonded to the Au layer on alumina. A standard shear test is performed to determine the shear strength of the bonding. The shear strength of five samples tested far exceeds the strength requirement of MIL-STD-883 G standard.

Fe/Ni diffusion behavior in the shear-extrusion solid state bonding process

2021 ◽  
Vol 67 ◽  
pp. 35-45
Author(s):  
Shuangjie Zhang ◽  
Wei Wang ◽  
Shibo Ma ◽  
Qiang Li
Keyword(s):  
Solid State ◽  
Bonding Process ◽  
Diffusion Behavior ◽  
Solid State Bonding

40 μm Copper–Silver Composite Flip-Chip Interconnect Technology Using Solid-State Bonding

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Chu-Hsuan Sha ◽  
Wen P. Lin ◽  
Chin C. Lee
Keyword(s):  
Solid State ◽  
Flip Chip ◽  
Thermal Expansion Mismatch ◽  
Conduction Electrons ◽  
Solid State Bonding ◽  
Cu Substrates ◽  
Atomic Distance ◽  
Free Solder ◽  
Interconnect Technology ◽  
Silver Composite

Copper–silver (Cu–Ag) composite flip-chip interconnect between silicon (Si) chips and Cu substrates is demonstrated. Array of Cu–Ag columns, each 28 μm in height and 40 μm in diameter, is electroplated on 2-in. Si wafers coated with chromium (Cr)/gold (Au) dual layer. The Si wafers are diced into 6 mm × 6 mm chips, each containing 50 × 50 Cu–Ag columns. The Si chip with Cu–Ag columns is bonded to Cu substrates at 260 °C in 80 mTorr vacuum. A bonding force of only 1.8 kg is applied, corresponding to 0.71 g per Cu–Ag column. During bonding, Ag atoms in Cu–Ag columns deform and their surfaces conform to and mate with the surface of Cu substrate. Solid-state bonding incurs when Ag atoms in Cu–Ag columns and Cu atoms in Cu substrates are brought within atomic distance so that they share conduction electrons. The Cu–Ag columns are indeed bonded to the Cu. No molten phase is involved in the bonding. The joint consists of 60% Cu section and 40% Ag section. The ductile Ag is able to accommodate the thermal expansion mismatch between Si and Cu. The Cu–Ag joints do not contain any intermetallic compound (IMC). This interconnect technology avoids all reliability issues associated with IMC growth in conventional soldering processes. Compared to tin-based lead-free solder joints, Cu–Ag composite joints have superior electrical and thermal properties.

A Study of Solid State Bonding Strength of Nonferrous Metals by Using Metal Salt Generation Bonding Method

2014 ◽  
Vol 783-786 ◽  
pp. 2450-2455
Author(s):  
Shinji Koyama
Keyword(s):  
Solid State ◽  
Formic Acid ◽  
Metal Salt ◽  
Bonding Temperature ◽  
Copper Surface ◽  
Solid State Bonding ◽  
Bonded Joint ◽  
Set Up ◽  
Bonding Method ◽  
Aluminum Surfaces

In recent years, an enormous pressure was put on the need to design and develop products that are compliant with the stringent environmental regulations set up various countries. Among the problems that need to be addressed is the need to design and develop environmentally friendly products that are energy efficient and easy to recycle. In this study, the effect of metal salt generation processing on the tensile strength of the bonded interface of Al/Al and Al/Cu was investigated by SEM observations of interfacial microstructures and fractured surfaces. Aluminum surfaces were modified by boiling in 5% aqueous solution of NaOH for 30 s and 98% formic acid for 60 s. Copper surface were modified by boiling 98% formic acid for 60 s. Solid-state bonding was performed at bonding temperature of 673 ~ 813 K and under a pressure of 6 MPa ( bonding time of 1.8 ks). Using metal salt generation bonding technique, the bonded joint is able to reach 0.2% proof stress at lower bonding temperature and with less deformation.

Solid-State Diffusion Bonding of Titanium by Using Metal Salt Coated Aluminum Sheet

2017 ◽  
Vol 741 ◽  
pp. 31-35
Author(s):  
Shinji Koyama ◽  
Van Phu Nguyen
Keyword(s):  
Solid State ◽  
Metal Salt ◽  
Bonding Temperature ◽  
High Strength ◽  
Bonding Process ◽  
Aluminum Surface ◽  
Solid State Diffusion ◽  
State Diffusion ◽  
Aluminum Surfaces ◽  
Salt Coating

In this study, the effect of metal salt coating processing of aluminum surface on the bond strength of the solid-state diffusion bonded interface of titanium and aluminum has been investigated by SEM observation of the interfacial microstructures and fractured surfaces after tensile test. Aluminum surfaces were coated by boiling in 5% aqueous solution of NaOH for 90 s and 98% formic acid for 60 s. Bonding process was performed at a bonding temperature of 713 ~ 773 K under a load of 12 MPa (for a bonding time of 900 s). As a result of the metal salt coating processing, high strength joint can be achieved with lower bonding temperature compared with unmodified joints. From this study, it is found out that metal salt coating processing is effective at removing oxide film and substitution to metal salt on the aluminum bonding surface.

A Study on High Temperature Oxidation of Titanium Alloys in Solid State Bonding Process

2007 ◽  
Vol 544-545 ◽  
pp. 183-186 ◽  
Author(s):  
Ho Sung Lee ◽  
Jong Hoon Yoon ◽  
Yeong Moo Yi
Keyword(s):  
Solid State ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Surface Oxidation ◽  
Bonding Process ◽  
Bonding Interface ◽  
Temperature Oxidation ◽  
Solid State Bonding ◽  
Bonding Condition ◽  
State Diffusion

The surface oxidation behavior was investigated over a range of solid state bonding condition of the Ti-6Al-4V ELI alloy. Since the oxides at the bonding interface may prevent the materials from complete bonding, it is important to understand the oxidation behavior at solid state bonding condition. The activation energy of oxidation of Ti-6Al-4V ELI is estimated to be 318 KJ/mol in an environment of solid state bonding process. For Ti-6Al-4V ELI alloy, strucutral integrity of bonding interface without oxides have been obtained at 850°C applying pressure of 3MPa for 1 hour. Solid state diffusion bonding of Ti-15V-3Cr-3Sn-3Al alloy was also obtained under a pressure of 6MPa for 3 hours at 925°C.

Studies on Shielded Active Gas Forge Welded API 5CT L80 Material at Different Cooling Rates

2011 ◽  
Vol 409 ◽  
pp. 871-876 ◽  
Author(s):  
P. Vinothkumar ◽  
S.M. Ganesan ◽  
Jan K. Solberg ◽  
B. Salberg ◽  
P.T. Moe
Keyword(s):  
Mechanical Properties ◽  
Solid State ◽  
Processing Parameters ◽  
Bonding Process ◽  
Small Scale ◽  
Controlled Cooling ◽  
Cooling Rates ◽  
Solid State Bonding ◽  
Pipe Line ◽  
Grade Material

Shielded Active Gas Forge Welding (SAG-FW) is a solid state bonding process in which two mating surfaces are locally heated and forged together to form a bond. SAG-FW has so far mainly been used to join materials for pipe-line and casing applications. The present study has been conducted on an API 5CT L80 grade material in a prototype forge welding machine. Small-scale pipe specimens have been extracted from the wall of the production casing. The SAG-FW process is completed within a few seconds of heating and forging followed by controlled cooling. The microstructure of the weld is determined by the processing parameters. In this paper, microstructure results for SAG-FW processed L80 material have been obtained for a range of cooling rates and systematically compared with microhardness values. Microstructure observations at different regions of the weld have been made. Faster heating rate and controlled cooling resulted in a mixture of non equilibrium microstructures, but satisfactory mechanical properties have been obtained for optimized processing parameters.

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