Low/No Silver Alloy Solder Paste Phase 1 Process Characterization

 

The price of metals and particularly silver (Ag) has been increasing in recent years. This has created an increased interest in the use of low/no silver alloy in the manufacturing process. Low silver alloy BGA solder balls (such as SAC105) are being used in products, but there is very little information about the alternative (low/no) silver alloy solder pastes, it’s process feasibility and reliability. Within the past couple of years, many alternative low/no silver alloy solder pastes have been developed and are available in the market.

 This is a multi-phased project, the first phase was designed to characterize the candidate solderpaste to verify that they could be used to assemble the Phase 2 reliability components. Phase 2 will evaluate the reliability of some of the candidate solderpaste.

 The Phase 1 project studied and documented the process feasibility/characterization of low/no silver alloy solder pastes compared to the standard SAC 305 paste for integration into a development assembly line.

 Phase 1 studied the process feasibility and reliability of low/no silver alloy solder pastes including

 ·         Low/no silver high temperature alloy solder pastes (liquidus temperature >217°C)

 ·         Low/no silver low temperature alloy solder pastes. (liquidus temperature <217°C)

 

Project stage: 
Lead company: 
Flex

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Idea Information

Background: 

The price of metals and particularly silver (Ag) has been increasing in recent years. This has created an increased interest in the use of low/no silver alloy in the manufacturing processes.

Low silver alloy (such as SAC105) for the BGA solder balls are being used in product.  Within the past couple years, many alternative low/no silver alloy solder pastes have been developed and are available in the market.

Problem: 

Reliability studies have been done for the solder joint assembled using the alternative low/no silver alloys solder balls (iNEMI/HDPUG alternative alloy projects). But, there is very little information about the alternative (low/no) alloy solder paste, its process feasibility and reliability.

There are no HDPUG consortia projects on low/no silver alloy solder paste.

Definition Information

Goals / Benefits: 

Scope:

•This project will study the process feasibility of low/no silver alloy solder pastes including
–Low/no silver high temperature alloy solder pastes (liquidus temperature >217°C)
–Low/no silver low temperature alloy solder pastes. (liquidus temperature <217°C)
•This project will not focus on low/no silver alloy composition or material evaluation nor recommend a low/no silver alloy solder paste.
 
Goals:
•Characterize the process window of low/no silver alloy solder paste.
•Study the microstructure and morphology of solder joint reflowed with low/no silver alloy solder paste  at different temperature/ process condition.
•Study the reliability of solder joint assembled with low/no silver solder pastes and compare the data with SAC305 and possibly other alternatives alloys (SAC105 etc.)
•Publish the results to encourage the wider acceptance of Low Ag Alloy Solderpaste

 

High level objectives: 

Process Feasibility Phase 1:  Objectives

•Publish the Process Window for Low Ag Alloys Solderpaste
•Publish the results of Low Ag Alloys Solderpaste evaluation, including :
–*Printability  *Wettability
–*Voiding Behavior  *Bridging  *Common Defects
.
•The team will publish a paper/presentation at several major conferences (SMTA/IPC) to help encourage the industry to accept alternative alloys solderpaste once the follow on Reliability Phase is completed.
 
 


Benefits of Project:

·         Low Ag / Low Temperature Alloys are more Environmentally Friendly. They lower ground pollution, lower energy consumption by lower processing temperature.

·         Low Ag / Low Temperature Alloys can extend the temperature headroom for assembly. The industry is running out of temperature headroom with Pb Free alloys, especially for large components.

·         Low Ag / Low Temperature Alloys can improve reliability of the final OEM product by lowering thermal stress and potential warpage on the components/PBCA.

 

Key Participants: 
Celestica
Cisco
Flex
Fujitsu
IBM
Indium
Juniper
Keysight Technologies
Nihon Superior
Plexus
Sanmina
Senju Comtek
TTM Technologies
WUS
Public