Lead-free Solder Attach for 200°C Applications

2013 ◽  
Vol 2013 (HITEN) ◽  
pp. 000260-000267 ◽  
Author(s):  
Zhenzhen Shen ◽  
Kun Fang ◽  
Mike Hamilton ◽  
R. Wayne Johnson ◽  
Erica Snipes ◽  
...  
Keyword(s):  
Shear Strength ◽  
Thick Film ◽  
Solidus Temperature ◽  
Lead Free ◽  
Thermal Testing ◽  
Ceramic Substrates ◽  
Shear Strength Test ◽  
C Storage ◽  
Free Solder ◽  
Lead Free Solders

Conventional SAC lead-free solders have a melting point of 217°C to 227°C, limiting their suitability for applications at 200°C. AgBiXTM solder has potential for 200°C applications because of its ~260°C solidus temperature. BiAgX paste has been used to assemble SiC test die to ceramic substrates with direct bond copper (DBC), reactive brazed CuMo, thick film Au, thick film PtAu, thick film PdAg and thick film Ag. Surface mount chip resistors have also been attached to thick film metallized substrates. The assembly process and initial shear strength test results are presented. Assemblies have also been subjected to thermal testing: thermal cycling (−55°C to +195°C) and high temperature (200°C) storage. The shear strength of these assemblies after thermal testing are presented and compared to initial results.

How Silver Powder Metallurgy Affects the Physical Properties of Low Temperature Firing Silver Conductor

2011 ◽  
Vol 2011 (1) ◽  
pp. 000099-000106 ◽  
Author(s):  
Samson Shahbazi ◽  
Mark Challingsworth
Keyword(s):  
Powder Metallurgy ◽  
Thick Film ◽  
Silver Powder ◽  
Lead Free ◽  
Lead Free Solder ◽  
Pure Silver ◽  
Solder Alloys ◽  
Film Conductor ◽  
Free Solder ◽  
Lead Free Solders

With the implementation of RoHS (the Restriction of Hazardous Substance) Directive banning the use of Lead, Cadmium, Mercury and Hexavalent Chromium, hybrid microelectronic manufacturers are globally embracing the lead free movement. These manufacturers must not only understand the implications of their material choice but must be aware of the interaction between lead free solder alloys and their RoHS compliant thick film materials. It is commonly known that lead free solder alloys process at much higher reflow temperatures than lead containing solder which can directly impact the fired film leach resistance and the loss of adhesion. There are also other concerns; lead free solders alloys generally require a different organic flux system to promote wetting and reflow, but this change may cause a fired film conductor to leach more easily than the flux used in the lead containing solders. The use of lead free solders such as SAC305, SAC405 or 95/5 on a low firing (550–570 °C) pure silver conductor has the tendency of leaching the fired film more readily than conductors containing small amounts of palladium or platinum. Many of these situations provide new challenges for the hybrid circuit manufacturer. There is little information available regarding the effects of the lead free solders on low firing silver thick film conductors. This paper discusses the results of a newly developed Pb and Cd free silver thick film conductor paste with a modified silver powder metallurgy to improve the leach resistance, solder acceptance and adhesion using lead free solder. In addition, the pure silver conductor was fired on top of a low temperature dielectric paste. This conductor was evaluated by comparing lead free solder alloys to traditional tin-lead-silver solder alloys. This study included evaluations based on SEM photos, solderability, leach resistance, and initial and long term adhesions. Results are published describing the difference in behavior between the different solder alloys in conjunction with the different silver powder metallurgy.

Influence of thermal ageing on void content and shear strength for selected lead free solder die-attach

2012 ◽  
Vol 2012 (1) ◽  
pp. 000882-000890
Author(s):  
K. C. Otiaba ◽  
N. Raju ◽  
R. S. Bhatti ◽  
S. Mallik ◽  
P.K. Bernasko
Keyword(s):  
Shear Strength ◽  
Thermal Ageing ◽  
Thermal Interface Material ◽  
Lead Free ◽  
Void Content ◽  
Lead Free Solder ◽  
Heat Spreader ◽  
Thermal Interface ◽  
Free Solder ◽  
Lead Free Solders

In flip-chip packaging technology, thermal performance can be improved by attaching heat spreader to the backside of the heat generating silicon die via thermal interface material. Solder thermal interface materials (STIMs) are preferred to their polymer-based counterparts because they relatively offer higher thermal conductivities. Unlike lead-based solders which have had a longer application history, lead-free solders are relatively new; thus, the reliability of these lead-free solders are subject of research interest. In this study, lead-free solder preforms with compositions of 96.5Sn3Ag0.5Cu, 99.99In, 97In3Ag and 58Bi42Sn were used for silicon die attachment on copper heat spreader. The void content and shear strength of the soldered joints after thermal ageing at 125°C for 50 hours, 100 hours, 200 hours and 300 hours were evaluated. Generally, the four studied solder joints show decrease in voids with thermal ageing though 96.5Sn3Ag0.5Cu and 58Bi42Sn comparatively manifested more reduction in voids. The shear strengths of 96.5Sn3Ag0.5Cu alloy and 99.99In are shown to be relatively more stable throughout the ageing time. The results also indicate that samples with lower void content comparatively result in higher shear strength and vice versa. These results are especially important for high temperature application environments of Pb-free STIMs like in automotive systems.

scholarly journals Experimental Investigations on Impact Toughness and Shear Strength of Novel Lead Free Solder Alloy Sn-1Cu-1Ni-XAg

2019 ◽  
Vol 19 (2) ◽  
pp. 90-96
Author(s):  
S Jayesh ◽  
Jacob Elias
Keyword(s):  
Shear Strength ◽  
Impact Toughness ◽  
Charpy Impact ◽  
Energy Difference ◽  
Test System ◽  
Lead Free ◽  
Experimental Investigations ◽  
Lead Free Solder ◽  
Shear Strength Test ◽  
Free Solder

AbstractLead is known to be banned in alloy making, highlighting toxicity concerns and environmental legislations. Researchers and scholars around the globe were in immediate search of new lead free solder alloys which could potentially replace the old Sn-Pb alloy. In this comprehensive study, shear strength and impact toughness tests were conducted on Sn-1Cu-1Ni when different amounts of Ag (0.25, 0.5, 0.75 1 % by wt.) is added. Shear strength test is tested using micro force test system. Impact toughness test is analyzed using Charpy impact test set up by calculating the energy difference before and after impact. The study reveals that, Ultimate shear stress increased from 19 MPa to 21.3 MPa. Yield strength increased from 27.4 MPa to 29.7 Mpa. Impact toughness of the alloys increased from 9.4 J to 10.1 J. Thus, Sn-1Cu-1Ni-1Ag is found to have improved shear strength and impact toughness than Sn-1Cu-1Ni.

Effect of aluminum content on structure, transport and mechanical properties of Sn-Zn eutectic lead free solder alloy rapidly solidified from melt.

2015 ◽  
Vol 10 (1) ◽  
pp. 2641-2648
Author(s):  
Rizk Mostafa Shalaby ◽  
Mohamed Munther ◽  
Abu-Bakr Al-Bidawi ◽  
Mustafa Kamal
Keyword(s):  
Mechanical Properties ◽  
Melting Point ◽  
Lead Free ◽  
Al Alloy ◽  
Lead Free Solder ◽  
Pronounced Increase ◽  
Mass Unit ◽  
Size Refinement ◽  
Free Solder ◽  
Lead Free Solders

The greatest advantage of Sn-Zn eutectic is its low melting point (198 oC) which is close to the melting point. of Sn-Pb eutectic solder (183 oC), as well as its low price per mass unit compared with Sn-Ag and Sn-Ag-Cu solders. In this paper, the effect of 0.0, 1.0, 2.0, 3.0, 4.0, and 5.0 wt. % Al as ternary additions on melting temperature, microstructure, microhardness and mechanical properties of the Sn-9Zn lead-free solders were investigated. It is shown that the alloying additions of Al at 4 wt. % to the Sn-Zn binary system lead to lower of the melting point to 195.72 ˚C.  From x-ray diffraction analysis, an aluminium phase, designated α-Al is detected for 4 and 5 wt. % Al compositions. The formation of an aluminium phase causes a pronounced increase in the electrical resistivity and microhardness. The ternary Sn-9Zn-2 wt.%Al exhibits micro hardness superior to Sn-9Zn binary alloy. The better Vickers hardness and melting points of the ternary alloy is attributed to solid solution effect, grain size refinement and precipitation of Al and Zn in the Sn matrix.  The Sn-9%Zn-4%Al alloy is a lead-free solder designed for possible drop-in replacement of Pb-Sn solders.  

Shear Strength and Dsc Analysis of High-Temperature Solders

2013 ◽  
Vol 58 (2) ◽  
pp. 529-533 ◽  
Author(s):  
R. Koleňák ◽  
M. Martinkovič ◽  
M. Koleňáková
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Lead Free ◽  
Dsc Analysis ◽  
Ultrasonic Activation ◽  
Metallic Substrates ◽  
Cu Substrate ◽  
Lead Free Solders

The work is devoted to the study of shear strength of soldered joints fabricated by use of high-temperature solders of types Bi-11Ag, Au-20Sn, Sn-5Sb, Zn-4Al, Pb-5Sn, and Pb-10Sn. The shear strength was determined on metallic substrates made of Cu, Ni, and Ag. The strength of joints fabricated by use of flux and that of joints fabricated by use of ultrasonic activation without flux was compared. The obtained results have shown that in case of soldering by use of ultrasound (UT), higher shear strength of soldered joints was achieved with most solders. The highest shear strength by use of UT was achieved with an Au-20Sn joint fabricated on copper, namely up to 195 MPa. The lowest average values were achieved with Pb-based solders (Pb-5Sn and Pb-10Sn). The shear strength values of these solders used on Cu substrate varied from 24 to 27 MPa. DSC analysis was performed to determine the melting interval of lead-free solders.

Solder Joint Reliability of Sn-Cu and Sn-Ag-Cu Lead-Free Solder Alloys Solidified on Copper Substrates with Different Surface Roughnesses

2015 ◽  
Vol 830-831 ◽  
pp. 265-269
Author(s):  
Satyanarayan ◽  
K.N. Prabhu
Keyword(s):  
Solder Joint ◽  
Solder Matrix ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Alloys ◽  
Cu Substrate ◽  
Cu Substrates ◽  
Free Solder ◽  
Substrate Surfaces ◽  
Lead Free Solders

In the present work, the bond strength of Sn-0.7Cu, Sn-0.3Ag-0.7Cu, Sn-2.5Ag-0.5Cu and Sn-3Ag-0.5Cu lead free solders solidified on Cu substrates was experimentally determined. The bond shear test was used to assess the integrity of Sn–Cu and Sn–Ag–Cu lead-free solder alloy drops solidified on smooth and rough Cu substrate surfaces. The increase in the surface roughness of Cu substrates improved the wettability of solders. The wettability was not affected by the Ag content of solders. Solder bonds on smooth surfaces yielded higher shear strength compared to rough surfaces. Fractured surfaces revealed the occurrence of ductile mode of failure on smooth Cu surfaces and a transition ridge on rough Cu surfaces. Though rough Cu substrate improved the wettability of solder alloys, solder bonds were sheared at a lower force leading to decreased shear energy density compared to the smooth Cu surface. A smooth surface finish and the presence of minor amounts of Ag in the alloy improved the integrity of the solder joint. Smoother surface is preferable as it favors failure in the solder matrix.

Effect of Aging on the Properties of Intermetallic Layers in SAC+Bi Solder Joints

2021 ◽  
Author(s):  
Mohammad Ashraful Haq ◽  
Mohd Aminul Hoque ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Solder Joints ◽  
Lead Free ◽  
Lead Free Solder ◽  
Aging Condition ◽  
Sac305 Solder ◽  
The Poor ◽  
Free Solder ◽  
Lead Free Solders ◽  
Overall Reliability ◽  
Intermetallic Layers

Abstract A major problem faced by electronic packaging industries is the poor reliability of lead free solder joints. One of the most common methods utilized to tackle this problem is by doping the alloy with other elements, especially bismuth. Researches have shown Bismuth doped solder joints to mostly fail near the Intermetallic (IMC) layer rather than the bulk of the solder joint as commonly observed in traditional SAC305 solder joints. An understanding of the properties of this IMC layer would thus provide better solutions on improving the reliability of bismuth doped solder joints. In this study, the authors have used three different lead free solders doped with 1%, 2% and 3% bismuth. Joints of these alloys were created on copper substrates. The joints were then polished to clearly expose the IMC layers. These joints were then aged at 125 °C for 0, 1, 2, 5 and 10 days. For each aging condition, the elastic modulus and the hardness of the IMC layers were evaluated using a nanoindenter. The IMC layer thickness and the chemical composition of the IMC layers were also determined for each alloy at every aging condition using Scanning Electron Microscopy (SEM) and EDS. The results from this study will give a better idea on how the percentage of bismuth content in lead free solder affects the IMC layer properties and the overall reliability of the solder joints.

Evaluation of Emerging High Melting Point Lead-free Solder and Hybrid Sinter Paste as Attaching Material for Clip Bond Package

2020 ◽  
Vol 2020 (1) ◽  
pp. 000235-000241
Author(s):  
Fred Fuliang Le ◽  
Rinse van der Meulen ◽  
Yoon Kheong Leong ◽  
Manoj Balakrishnan ◽  
Zunyu Guan
Keyword(s):  
Melting Point ◽  
Lead Free ◽  
Lead Free Solder ◽  
Reliability Testing ◽  
High Melting ◽  
High Melting Point ◽  
Basic Scheme ◽  
Free Solder ◽  
Lead Free Solders ◽  
High Lead

Abstract High melting point (HMP) lead-free solder, hybrid sinter and transient liquidus phase sinter (TLPS) are the emerging lead-free alternatives for the potential replacement of high-lead solder. Lead-free solder is perfectly compatible with existing high-lead soldering processes for clip bond packages. The benefit of hybrid sinter is that it has much higher thermal and electrical conductivity than lead-free or high-lead solder. In this study, ten materials (including lead-free solders, hybrid sinter paste and TLPS) were first evaluated via die shear test. With the initial material screening, two lead-free solders (solder 1 and 2), two hybrid Ag sinter pastes (sinter i and ii) and one TLPS proceeded to internal sample assembly. For the lead-free solders, a process optimization with the aid of vacuum reflow was made to reduce void rate. Due to the slow and unbalanced inter-diffusion of Ag-Cu sintering than Ag-Ag sintering, optimizations to enhance the hybrid Ag sintering include Ag finishing for the die metallization and Ag plating for the clip and bond area of the leadframe. In 0-hour package electrical test, solder 1 and sinter i passed and were sent for reliability testing while solder 2, sinter ii and TLPS failed due to intermetallic compound (IMC) cracking, material bleeding and die cracking, respectively. In the reliability testing, a basic scheme of thermal cycling (TC) 1000 cycles, intermittent operating life (IOL) 750 hrs and highly accelerated temperature and humidity stress test (HAST) 96 hrs was defined for the early feasibility study. 1 of 75 sinter i units failed by TC 1000 cycles due to separation between silver sinter structure and die bottom metallization. Solder 1 passed the basic scheme without defects, and next the material workability and clip bond strength need to be improved to the equivalent level of high-lead solders.

High Melting Temperature Lead Free Solder for Die Attach Application

2011 ◽  
Vol 2011 (1) ◽  
pp. 000322-000326
Author(s):  
Jianxing Li ◽  
Daniel Lau ◽  
Pingliang Tu ◽  
Andrew Delano ◽  
Brian Knight
Keyword(s):  
Thermal Conductivity ◽  
Copper Substrate ◽  
Process Condition ◽  
Lead Free ◽  
Test Results ◽  
Melt Temperature ◽  
Die Attach ◽  
Free Solder ◽  
Lead Free Solders ◽  
Board Level

Two lead free solders were developed for die attach application. The bismuth based solder has a melt temperature of 271C and thermal conductivity of 18W/mK. The zinc based solder has a melt temperature of 337C and thermal conductivity of 85W/mK. Both solders have acceptable wetting on bare copper and nickel plated copper substrate, could be processed using modified high lead solder process condition and survived 260C board level reflow simulation. This paper discusses the solder material properties, and presents the die attach process and reliability test results in a manufacturing environment.

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