Transient Liquid Phase Sintering Pastes as Solder Alternatives in High Temperature Applications

2015 ◽  
Vol 2015 (1) ◽  
pp. 000453-000458 ◽  
Author(s):  
Catherine Shearer ◽  
Ken Holcomb
Keyword(s):  
High Temperature ◽  
Liquid Phase ◽  
Mechanical Performance ◽  
Operating Temperature ◽  
Transient Liquid Phase ◽  
Liquid Phase Sintering ◽  
Solder Paste ◽  
Reactive Metal ◽  
High Operating Temperature ◽  
Temperature Applications

High operating temperature electronics are a growing market in the electronics industry. Most of the components and substrates necessary to support the production of these harsh environment devices are now available, but the interconnect materials for component, module and board level assembly are lagging in development. Currently the high operating temperature markets are being served by lead-bearing solders and expensive alloys such as gold-tin or gold-germanium. Lead has been banned from the majority of electronics applications in many areas of the world, but so far has been exempted in the high temperature solder applications due to the lack of an adequate replacement. Even without the impending regulatory restrictions, the melting temperature of the lead containing solders is marginal for the next generation of high operating temperature electronics. Transient liquid phase (TLPS) sintering paste compositions are a new class of solder replacement materials that can be processed at typical reflow temperatures, but which do not remelt when subjected to subsequent thermal excursions. TLPS pastes combine solder alloy particles and reactive metal particles in proportions such that the solder ‘thermosets’ during a typical solder reflow cycle. This ‘thermosetting’ behavior results in a joint that does not remelt at the original reflow temperature, and thus enables the highly reliable electrical interconnect essential for high operating temperature applications. TLPS pastes are similar to solders in many respects. The electrical, thermal and mechanical performance is similar to conventionally used tin-based solders. The TLPS pastes are stored and applied like solder pastes. The reflow cycles used to form the TLPS paste joints are also similar to those for forming solder joints. However, unlike solder, TLPS materials do not change shape during reflow or wet substrates beyond the deposition footprint. Also unlike solder, the metals within the bulk of the TLPS interconnect react with one another resulting in a stable interconnect with a thermally robust bonding structure to joining surfaces, even after subsequent thermal cycles. Though not a practical replacement for solder in common assembly operations, TLPS technology is an attractive solder alternative for specialty interconnect applications. In this paper, the nature and characteristics of TLPS pastes will be will be explored in comparison to solder paste materials commonly used in high operating temperature applications.

Silver-Indium Transient Liquid Phase Sintering for High Temperature Die Attachment

2009 ◽  
Vol 6 (1) ◽  
pp. 66-74 ◽  
Author(s):  
Pedro O. Quintero ◽  
F. Patrick McCluskey
Keyword(s):  
High Temperature ◽  
Liquid Phase ◽  
Transient Liquid Phase ◽  
Wide Band ◽  
Liquid Phase Sintering ◽  
Processing Temperature ◽  
Solder Paste ◽  
Scanning Calorimetry ◽  
Die Attach ◽  
Transient Liquid Phase Sintering

The demand for electronics capable of operating at temperatures above the traditional 125°C limit continues to increase. Devices based on wide band gap semiconductors have been demonstrated to operate at temperatures up to 500°C, but packaging remains a major hurdle to product development. Recent regulations, such as RoHS and WEEE, increase the complexity of the packaging task as they prohibit the use of certain materials in electronic products such as lead (Pb), which has traditionally been used in high temperature solder die attach. In this investigation, an Ag-In solder paste is presented as a die attach alternative for high temperature applications. The proposed material has been processed by a transient liquid phase sintering method resulting in an in situ alloying of its main constituents. A shift of the melting point of the system, confirmed by differential scanning calorimetry, provided the basis for a breakthrough in the typical processing temperature rule. The mechanical integrity and reliability of this novel attachment material is discussed.

Microstructure stability of TLPS interconnects in high operating temperature applications

2017 ◽  
Vol 2017 (HiTEN) ◽  
pp. 000226-000233
Author(s):  
Catherine Shearer
Keyword(s):  
Operating Temperature ◽  
Failure Mechanisms ◽  
Intermetallic Phases ◽  
Liquid Phase Sintering ◽  
Interfacial Structure ◽  
High Operating Temperature ◽  
Thermal Work ◽  
Operating Temperatures ◽  
High Lead ◽  
Temperature Applications

Abstract Interconnect materials for high operating temperature applications are becoming a limiting factor within the chain of materials. While materials such as capacitor dielectrics, semiconductor platforms (e.g. SiC), and baseplate materials (e.g. SiN composites) have paved a pathway to deploying electronics in high operating temperature applications, interconnect materials are a clearly identified weak link. As is often the case in advancements in technology, the materials technologies that were the bottlenecks to advancement give way to new solutions that create new bottlenecks in the material supply chain. Rather than a fluid march towards advancements in new frontiers in electronics, the high operating temperature sphere, like much of advanced electronic, suffers from a ‘slip-fault’ mode of development where advances occur in one segment while others lag behind creating drag on implementation. For high operating temperature applications the available interconnect solutions are becoming the jarring stop to the smooth tectonic shift. Current solutions are diverse: high-lead, gold-based, and nano-sintering and its hybrids, but none are ideal. Even disregarding he toxicity of lead and the ongoing limbo of its regulatory status, the operating temperatures of the high-lead solders are on the low end of the requirements for future harsh environment electronics applications; whereas, the gold and nano-based alternatives have significant cost barriers - either at from the constituent materials perspective or the required investment in new processes. There is also the concern about the assessment of the action of nanomaterials in the waste stream due to their fundamentally different surface reactivity in a variety of situations. Reliance on conventional, solder-type interconnection structures, regardless of composition, introduces the perennial problem of the growth of the interfacial phases due to the essentially unlimited volume of the bulk solder material. The changes in the interfacial structure with additional thermal work - as is provided by high operating temperature applications - creates an environment that is ripe for growth of a variety of failure mechanisms. These failure mechanisms are often related to the uncontrolled laminar growth of intermetallic phases at the interfaces and the mechanical characteristics of these intermetallic phases in comparison with the materials joined and the bulk constituent material of the solder. An alternative class of interconnect materials, transient liquid phase sintering (TLPS) pastes, introduce a joint microstructure that is homogeneous throughout. The interfacial metallurgical reactions with the solderable surfaces are fundamentally similar to those that occur throughout the bulk of the joint. A reactant metal is included in the composition. This reactant metal, most often copper, reacts with and converts the bulk tin in the bulk of the solder interconnect to alloy structures with melting points well above the operating temperatures currently contemplated. At the conclusion of the joining process, which is generally a near drop-in for existing solder reflow processes, there is no large source of unreacted metal (e.g. Sn) that can continue to drive major microstructural changes with the continued thermal work provided by the application environment. For this reason the joints are homogeneous and do not have the free reactants necessary to drive substantial changes in joint morphology during cycling and use conditions. In this paper, we will explore the differences between TLPS joints and solder-type joints with the anticipated thermal work that would be introduced in a high operating temperature environment.

Microstructure of Transient Liquid Phase Sintering Joint by Sn-Coated Cu Particles for High Temperature Packaging

2015 ◽  
Vol 2015 (1) ◽  
pp. 000449-000452 ◽  
Author(s):  
Xiangdong Liu ◽  
Hiroshi Nishikawa
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Liquid Phase ◽  
Applied Pressure ◽  
Transient Liquid Phase ◽  
Liquid Phase Sintering ◽  
Thermally Stable ◽  
Bonding System ◽  
Cu Substrates ◽  
Transient Liquid Phase Sintering

We develop a transient liquid phase sinter (TLPS) bonding using Sn-coated Cu micro-sized particles. With this bonding process, a thermally stable joint comprising Cu3Sn phase and a dispersion of ductile Cu particles can be obtained. The particle paste, which contained Cu particles with a thin Sn coating and terpineol, was used to join Cu substrates. The setup was bonded at 300 °C for 30s under an applied pressure of 10 MPa using a thermo-compression bonding system under a formic acid gas atmosphere for reducing the oxide layer on the Sn coating and the Cu substrate. After bonding, the TLPS joint showed a thermally stable microstructure with a good shear strength, which was fully consisted of Cu3Sn intermetallic compounds matrix and embedded ductile Cu particles. The kinetics of the microstructure transformation and high temperature reliability of the TLPS joint were investigated. After 300 °C isothermal aging for 200h, the shear strength and microstructure of the TLPS joints showed almost unchanged. The results demonstrate that joint with high-melting-point obtained by the TLPS bonding using Sn-coated Cu particle paste has the potential to fulfill the requirement of high temperature electronic packaging.

Microstructure and growth kinetic study in Sn–Cu transient liquid phase sintering solder paste

2020 ◽  
Vol 31 (14) ◽  
pp. 11077-11094
Author(s):  
R. Mohd Said ◽  
M. A. A. Mohd Salleh ◽  
N. Saud ◽  
M. I. I. Ramli ◽  
H. Yasuda ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Kinetic Study ◽  
Growth Kinetic ◽  
Transient Liquid Phase ◽  
Liquid Phase Sintering ◽  
Solder Paste ◽  
Transient Liquid Phase Sintering

Transient Liquid Phase Soldering for lead-free joining of power electronic modules in high temperature applications

2012 ◽  
Vol 2012 (HITEC) ◽  
pp. 000025-000033 ◽  
Author(s):  
Christian Ehrhardt ◽  
Matthias Hutter ◽  
Hermann Oppermann ◽  
Klaus-Dieter Lang
Keyword(s):  
High Temperature ◽  
Liquid Phase ◽  
Copper Powder ◽  
Transient Liquid Phase ◽  
Intermetallic Phases ◽  
Lead Free ◽  
Power Electronic ◽  
Soldering Process ◽  
New Variant ◽  
Temperature Applications

The study focuses on a new variant of transient liquid phase soldering (TLPS) using tin based solder with copper powder. This technology may act as an alternative for lead free joining of semiconductor dies in power electronic applications at high operating temperature. Lead-free joining technologies currently used like gold-rich solders and silver sintering are well suited for high temperature applications. However, due to the high metal price they have a limited acceptance. Using a special soldering process it is feasible to produce an almost void-less solder joint, using a paste of tin-based solder powder (e.g. SAC305), copper powder and a solvent which is hardly activated. The resulting interconnection is characterized by an almost complete transformation into intermetallic phases of Cu6Sn5 and Cu3Sn. Thus the melting point of the transformed interconnect can be increased up to the decomposition temperature of the Cu6Sn5 intermetallic phase which is 415 °C. A two-step soldering process allows to eliminating the typical skeleton structure that forms as a result of the immediate reaction of the liquid tin-based solder with the higher melted copper powder to form the Cu6Sn5 and Cu3Sn intermetallic phases. An alternative way compared to the two-step-process is also explained in this study: Capillary forces let the solder flow into the gap filled with Cu spheres.

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