Mobile Packaging and Interconnect Trends

2014 ◽  
Vol 2014 (DPC) ◽  
pp. 1-21
Author(s):  
Brandon Prior
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Thick Film ◽  
Cross Sections ◽  
Shear Test ◽  
Short Review ◽  
Test Machine ◽  
Die Attach ◽  
Shear Failures ◽  
Film Substrate

This paper will focus on emerging and fast growth package solutions to meet mobile products' density and cost requirements. A short review of where package miniaturization and modularization has taken us so far, and where it will lead in the next 5 years. Teardowns of high density systems and packages will be used to illustrate key points. Low temperature Ag sintering technology provides a lead-free die attachment compatible with high temperature (300°C) applications. Previous work with Ag sintering has required some pressure during the sintering process or been limited to small area die. In this paper, a pressureless sintering of micro-scale silver paste procedure is presented for large (8mm x 8mm) area die. Experimental combinations included: Ag metallized Si die, Au metallized Si die, Ag thick film substrate metallization, Au thick film substrate metallization, PdAg thick film metallization and sintering temperature. For Au metallization (die and/or substrate), the initial shear strength results were good with 8mm x 8mm die sintered at lower temperatures (200°C). The shear strength was out range of our shear test machine (100 kg), corresponding to >15.3 MPa. However, after aging for 24 hours at 300°C, the shear strength dropped significantly to 40.38 Kg (6.183 MPa). An SEM was used to characterize cross sections of as-built and aged sample. The decrease in die shear strength with high temperature sintering (250°C and 300°C) or high temperature aging is attributed to surface diffusion of Ag along the Au surface resulting in a dense Ag layer adjacent to the Au surface and a depletion layer within the die attach on the opposite side of the the dense Ag layer. Shear failures occurred through the depleted region. For Ag metallization, no decrease in shear strength was observed with 300°C aging. Shear strength of 8x8cm2 dies was out range of our shear test machine (>100 kg, >15.3 MPa) as-built. The shear strength remained out of range (>15.3MPa) after more than 2000 hours of 300C aging.

Pressureless, Low Temperature Sintering of Micro-scale Silver Paste for Die Attach for 300°C Applications

2014 ◽  
Vol 2014 (HITEC) ◽  
pp. 000165-000171 ◽  
Author(s):  
Fang Yu ◽  
R. Wayne Johnson ◽  
Michael Hamilton
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Low Temperature ◽  
Cross Sections ◽  
Test Machine ◽  
Silver Paste ◽  
Micro Scale ◽  
Die Attach ◽  
Shear Failures ◽  
Film Substrate

Low temperature Ag sintering technology provides a lead-free die attachment compatible with high temperature (300°C) applications. Previous work with Ag sintering has required pressure during the sintering process or been limited to small area die. In this paper, the pressureless sintering of micro-scale silver paste is examined for larger (8mm × 8mm) area die. Experimental combinations included: Si die metallization (Ag and Au); thick film substrate metallization (Au, Ag and PdAg); and sintering temperature. For Au metallization (die and/or substrate), the initial shear strength results were good with 8mm × 8mm die sintered at lower temperatures (200°C). The shear strength was beyond the limit of the shear test machine (100 kg), corresponding to >15.3 MPa. However, after aging for 24 hours at 300°C, the shear strength dropped significantly. An SEM was used to characterize cross sections of as-built and aged sample. The decrease in die shear strength with high temperature sintering (250°C and 300°C) or high temperature aging is attributed to surface diffusion of Ag along the Au surface resulting in a dense Ag layer adjacent to the Au surface and a depletion layer within the die attach adjacent to the dense Ag layer. Shear failures occurred through the depleted region. For Ag metallization (die and substrate), no decrease in shear strength was observed with 300°C aging. Shear strength of 8 mm × 8 mm dies was >100 kg ( >15.3 MPa) as-built. The shear strength remained >15.3MPa after 3000 hours of 300°C aging.

Component Attachment with Pressureless Sintering for 300°C Applications

2016 ◽  
Vol 2016 (HiTEC) ◽  
pp. 000226-000233
Author(s):  
Fang Yu ◽  
Jinzi Cui ◽  
Zhangming Zhou ◽  
R. Wayne Johnson ◽  
Michael C. Hamilton
Keyword(s):  
High Temperature ◽  
Thick Film ◽  
Cross Sections ◽  
High Power ◽  
Shear Force ◽  
Passive Component ◽  
Pressureless Sintering ◽  
High Temperature Electronics ◽  
Die Attach ◽  
The Mean

Abstract With an increased demand for high power and high temperature electronics, Ag sintering paste has been considered a promising Pb-free die attach material candidate for these applications. A large amount of research has been performed investigating pressure and pressureless Ag sintering for die attach. In this work, passive component (chip resistor) attachment with Ag sintering was explored. Due to termination geometry differences between resistors and die, different processing procedures and parameters were developed. For PtAu terminated resistors, the mean shear force of as-built samples on thick film Ag metallized substrates was 90 N, but dropped to 18.6 N after 1500 hours at 300°C. Formation of a dense Ag layer near the PtAu resistor termination and a void region near the thick film metallization was observed in cross-sections after 1000 hours at 300°C. For PdAg terminated resistors with a plated Ni/Au finish, the initial shear force results were low due to Ag diffusion along Au metallization surface. For PdAg terminated resistors with Ag thick film substrates, the initial shear force was approximately 60 N and remained in the range of 50–70 N during aging at 300°C for 1500 hours. A new thick film metallization (Au+Ag) was developed to enable the use of thick film Au interconnect metallization.

Component Attachment with Pressureless Ag Sintering for 300°C Applications

2016 ◽  
Vol 13 (4) ◽  
pp. 155-162
Author(s):  
Fang Yu ◽  
Jinzi Cui ◽  
Zhangming Zhou ◽  
R. Wayne Johnson ◽  
Michael C. Hamilton
Keyword(s):  
High Temperature ◽  
Thick Film ◽  
Cross Sections ◽  
High Power ◽  
Shear Force ◽  
Passive Component ◽  
High Temperature Electronics ◽  
Die Attach ◽  
The Mean

With an increased demand for high-power and high-temperature electronics, Ag sintering paste has been considered a promising Pb-free die-attach material candidate for these applications. Extensive research has been carried out investigating pressure and pressureless Ag sintering for die attach. In this work, passive component (chip resistor) attachment with Ag sintering was explored. Due to termination geometry differences between resistors and dies, different processing procedures and parameters were developed. For PtAu terminated resistors, the mean shear force of as-built samples on thick-film Ag metallized substrates was 90 N, but dropped to 18.6 N after 1,500 h at 300°C. Formation of a dense Ag layer near the PtAu resistor termination and a void region near the thick-film metallization was observed in cross sections after 1,000 h at 300°C. For PdAg terminated resistors with a plated Ni/Au finish, the initial shear force results were low due to Ag diffusion along Au metallization surface. For PdAg terminated resistors with Ag thick-film substrates, the initial shear force was ~60 N and remained in the range of 50–70 N during aging at 300°C for 1,500 h. A new thick-film metallization (Au + Ag) was developed to enable the use of thick-film Au interconnect metallization.

scholarly journals Test Vehicle for Studying Thermal Conductivity of Die Attach Adhesives for High Temperature Electronics

2012 ◽  
Vol 188 ◽  
pp. 238-243
Author(s):  
Conor Slater ◽  
Fabrizio Vecchio ◽  
Thomas Maeder ◽  
Peter Ryser
Keyword(s):  
Thermal Conductivity ◽  
Shear Strength ◽  
High Temperature ◽  
Thick Film ◽  
Test Vehicle ◽  
High Temperature Electronics ◽  
Temperature Decay ◽  
Die Attach ◽  
Viable Method ◽  
Degree Of Degradation

Polymer adhesives offer a viable method for mounting silicon dies for high temperature applications. Here a test vehicle for comparing the thermal conductivity of different die attach materials is presented. The setup can be used to determine the degree of degradation of polymers. It consists of a mock die that has an integrated thick film heater, which is mounted onto a substrate. In operation, the substrate is placed on a heatsink and the die is heated. When the temperature reaches equilibrium the heater is switched off and the temperature of the die is measured as it cools. The time constant of the temperature decay is calculated to give the thermal conductivity. In this paper the thermal conductivity of an epoxy die attach adhesive is compared to its shear strength.

LT-TLPS Die Attach for High Temperature Electronic Packaging

2014 ◽  
Vol 11 (1) ◽  
pp. 7-15
Author(s):  
Hannes Greve ◽  
F. Patrick McCluskey
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Melting Point ◽  
Low Temperature ◽  
Transient Liquid Phase ◽  
Liquid Phase Sintering ◽  
Die Attach ◽  
Metallic Interfaces ◽  
Dsc Analyses ◽  
Transient Liquid Phase Sintering

Low temperature transient liquid phase sintering (LT-TLPS) can be used to form high-temperature joints between metallic interfaces at low process temperatures. In this paper, process analyses and shear strength studies of paste-based approaches to LT-TLPS are presented. The process progression studies include DSC analyses and observations of intermetallic compound (IMC) formation by cross-sectioning. It was found that the sintering process reaches completion after sintering times of 15 min for process temperatures approximately 50°C above the melting point of the low temperature constituent. For the shear studies, test samples consisting of copper dice and copper substrates joined by sintering with a variety of sinter pastes with different ratios of copper and tin have been assessed. A fixture was designed for high temperature enabled shear tests at 25°C, 125°C, 250°C, 400°C, and 600°C. The influence of the ratio of the amount of high melting-point constituent to the amount of low melting-point constituent on the maximum application temperature of the sinter paste was analyzed. Ag20Sn and Cu50Sn pastes showed no reduction in shear strength up to 400°C, and Cu40Sn pastes showed high shear strengths up to 600°C. It was shown that LT-TLPS can be used to form high temperature stable joints at low temperatures without the need to apply pressure during processing.

Metallurgy for SiC Die Attach for Operation at 500°C

2010 ◽  
Vol 2010 (HITEC) ◽  
pp. 000008-000017 ◽  
Author(s):  
Ping Zheng ◽  
Phillip Henson ◽  
R. Wayne Johnson ◽  
Liangyu Chen
Keyword(s):  
High Temperature ◽  
Thick Film ◽  
Failure Surface ◽  
Nano Particle ◽  
Test Results ◽  
Shear Tests ◽  
Die Attach ◽  
Film Layer ◽  
Potential Failure ◽  
Dc Bias

Metallurgy for high temperature SiC die attach involves the substrate metallization, die metallization, and die attach material. This paper examines off-eutectic Au-Sn as the die attach alloy with a PtAu thick film metallization on AlN substrates. A pure Au thick film layer was printed over the PtAu thick film layer. The SiC backside metallizations evaluated were Ti/TaSi/Pt/Au and Cr/NiCr/Au. Die shear tests were performed after aging at 500°C and after thermal cycling. The shear test results and failure surface analysis are discussed. Nanoparticle Ag and liquid transient phase bonding with Ag based metallurgies have been proposed for high temperature die attach. Data on the migration of sintered nano-particle Ag and thin film Ag dc bias during storage in air at 300°C and 375°C are presented. Migration of Ag is a potential failure mechanism for Ag based high temperature metallurgies.

Reliability and Corrosion Resistance of High Temperature Lead-Free BiAgX™ Paste

2014 ◽  
Vol 2014 (HITEC) ◽  
pp. 000347-000354 ◽  
Author(s):  
HongWen Zhang ◽  
RunSheng Mao ◽  
Ning-Cheng Lee ◽  
Satoshi Tanimoto
Keyword(s):  
Corrosion Resistance ◽  
Shear Strength ◽  
High Temperature ◽  
Salt Water ◽  
Lead Free ◽  
Water Spray ◽  
Bond Shear Strength ◽  
Die Attach ◽  
Increasing Temperature ◽  
Average Bond

The BiAgX™ paste, designed for die attach application, composed of the majority of BiAg powders (melting point >260°C) and the minority of additive powders. The additive powders are dominating the interfacial reaction to improve the wetting of the paste on various commonly-used surface finish materials. After reflow, the joint shows the above 260°C remelting temperature. The average bond shear strength of BiAgX joint between SiC die and AMBC-SiN substrate (Package A) decreases from 54MPa to 16MPa with increasing temperature from RT to 250°C. Upon thermal storage at 200°C or 230°C for 3000hrs, the bond shear strength decreases from 54MPa to 38MPa and 21MPa, respectively. Upon thermal cycling from −55°C to 125°C for 2000cycles and thermal shock from −55°C to 150°C for 2000cycles, BiAgX outperforms Pb5Sn2.5Sn (Package B). BiAgX also show the better corrosion resistance than SAC305 and Pb5Sn2.5Ag under 96hrs salt water spray (SWS) tests.

Evaluation of Pressure Free Nanoparticle Sintered Silver Die Attach on Silver and Gold Surfaces

2013 ◽  
Vol 2013 (HITEN) ◽  
pp. 000237-000245 ◽  
Author(s):  
G. Lewis ◽  
G. Dumas ◽  
S. H. Mannan
Keyword(s):  
Shear Strength ◽  
Cross Sections ◽  
Storage Time ◽  
Sintering Process ◽  
Die Attach ◽  
Free Process ◽  
Sintered Ag ◽  
Bondline Thickness ◽  
Ag Substrate ◽  
Thickness Measurements

A commercially available silver nanoparticle based die attach material was used in a pressure free process to bond 2.5 mm square Ag plated Si die to Ag and Au plated substrates. The two substrate types were 5mm square Ni/Ag plated silicon substrate and a W/Ni/Au metallised cofired alumina package. The assemblies were stored at 300 °C for up to 500 h and the morphology of the sintered Ag and the shear strength was monitored as a function of time. Bondline thickness measurements were carried out after following the paste manufacturer's drying and sintering temperature profile. On Ag substrate it was found that die shear strength increased with storage time. The fracture surfaces of the sheared die and substrate as well as cross sections of untested die were examined using electron microscopy. It was found that the Ag grains grew in size and porosity decreased over time. There was also a clear difference in morphology between sintered Ag at the die edge and centre. During shearing the Ni layer was found to separate from the chip at the edges of the die after ageing. On Au substrate, it was found that die shear strength decreased with storage time. It was found that the Au diffused into the Ag, creating a low porosity Au-Ag layer. Ag also migrated towards the Au surface, leaving behind a layer of voids which contributed to weakening of the joint. Rapid Au diffusion was associated with the high density of grain boundaries arising from the sintering process.

Investigation into the Role of Different Substrate Ni Compositions and Plating Methods on Die Attach Reliability

2015 ◽  
Vol 2015 (HiTEN) ◽  
pp. 000073-000082
Author(s):  
Jinzi Cui ◽  
R. Wayne Johnson ◽  
Michael C. Hamilton
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
High Power ◽  
Diffusion Barrier ◽  
Die Attach ◽  
High Temperature Storage ◽  
The Impact ◽  
Direct Bond Copper ◽  
Temperature Storage

Nickel is a commonly used diffusion barrier for direct bond copper (DBC) substrates used in high temperature, high power applications. The Ni can be deposited by electroless or electrolytic plating and may be pure Ni, Ni:P, Ni:B or Ni:Co. The reactivity of these different Ni layers with AuGe and BiAgX® solder is explored. Specifically the reaction to form Ni-Ge intermetallics and NiBi3 during high temperature storage and the impact on die shear strength and failure mode are discussed.

Lead-Free Alternatives for Interconnects in High-Temperature Electronics

2017 ◽  
Author(s):  
Sandeep Mallampati ◽  
Liang Yin ◽  
David Shaddock ◽  
Harry Schoeller ◽  
Junghyun Cho
Keyword(s):  
Thermal Conductivity ◽  
Plastic Deformation ◽  
Shear Strength ◽  
High Temperature ◽  
Heat Dissipation ◽  
Volume Fraction ◽  
High Volume ◽  
Die Attach ◽  
Average Shear Strength ◽  
Average Shear

Predominant high melting point solders for high temperature and harsh environment electronics (operating temperatures from 200 to 250°C) are Pb-based systems, which are being subjected to RoHS regulations because of their toxic nature. In this study, high bismuth (Bi) alloy compositions with Bi-XSb-10Cu (X from 10 wt.% to 20 wt.%) were designed and developed to evaluate their potential as high-temperature, Pb-free replacements. Reflow processes were developed to make die-attach samples made out of the cast Bi alloys. In particular, die-attach joints made out of Bi-15Sb-10Cu alloy exhibited an average shear strength of 24 MPa, which is comparable to that of commercially available high Pb solders. These alloy compositions also retained original shear strength even after thermal shock between −55°C and +200°C and high temperature storage at 200°C. Brittle interfacial fracture sometimes occurred along the interfacial NiSb layer formed between Bi(Sb) matrix and Ni metallized surface. In addition, heat dissipation capabilities, using flash diffusivity, were measured on the die-attach assembly, compared to the corresponding bulk alloys. The thermal conductivity of all the Bi-Sb alloys was higher than that of pure Bi. By creating high volume fraction of precipitates in a die-attach joint microstructure, it was feasible to further increase thermal conductivity of this joint to 24 W/m·K, which is three times higher than that of pure Bi (8 W/m·K). Bi-15Sb-10Cu alloy has so far shown the most promising performance as a die-attach material for high temperature applications (operated over 200°C). Hence, this alloy was further studied to evaluate its potential for plastic deformation. Bi-15Sb-10Cu alloy has shown limited plastic deformation in room temperature tensile testing, in which premature fracture occurred via the cracks propagated on the (111) cleavage planes of rhombohedral crystal structure of the Bi(Sb) matrix. The same alloy has, however, shown up to 7% plastic strain under tension when tested at 175°C. The cleavage planes, which became oriented at smaller angles to the tensile stress, contributed to improved plasticity in the high temperature test.

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