Solder Joint Reliability with Surface Finishes

This project serves to evaluate the toughness of solder joints on boards, coated with various surface finishes, and assembled with large components and fine-pitch components using different solder alloys used in harsh-use environment. The assembled boards will go through thermal cycling and vibration tests (latter for thick boards only), and the results analysed to find the effects the various surface finishes, in both thin and thick coating, have on solder joints.

Project stage: 
Lead company: 
RBP Chemical Technology

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Idea Information

Background: 

The initial intent of this project was to study the solder joint toughness against handling, assembly, thermal cycling and operational mechanical stresses, then gather, analyze and compare solder joint performance data of various surface finishes.

As numerous articles on PWB surface finishes have been written, the team decided to differentiate from earlier work by using and testing alloys in a harsh use environment, leveraging on the test vehicle from the Harsh Use Environment (HUE) Alloy Evaluation.

This project also intends to use a comprehensive approach to compare the pros and cons of the different types of surface finishes, and provide an up-to-date test data on the solder joint strength as most previous test reports were done years ago.

In addition to surface finishes, the effects of board and coating thicknesses have on the solder joint reliability will also be studied.

Problem: 

Is BGA solder joint soldered on gold surface finishes and OSP robust against thermal cycling and mechanical bending tests? How about other type of components including IMD (Insert Mounted Device)?

How will the solder joint strength change with package size, board thickness and even a change of solder paste?

It is hoped that this new project will fill the gap on the lack of practical solder joint performance data of the newer surface finishes.

Definition Information

Goals / Benefits: 

We want to achieve the following benefits in this project.

  • Present the comparative advantages and disadvantages (or risks) of the PCB surface finishes under study.
  • Identify what components and what sizes are suitable for which type of surface finishes, and the impact of board thickness.
  • Ascertain suitable thickness of surface finishes (such as Pd).

 

Approach: 

To manage the numerous test vehicles required, the project will be conducted in two phases.

1)The first phase is to assemble and test large components (such as BGA) on thick board (24L).
2)The second phase is to assemble and test fine-pitch components (such as CSP or QFN) on thin board (6L). With the test data collected from phase 1, test vehicle modifications may be implemented at this phase to accomplish better results.

 

The phase 1 project flow chart is as below:

Key Participants: 
Cisco
FCI / Amphenol
Flex
Fujitsu
i3 Electronics
Juniper
Keysight Technologies
MacDermid Enthone
Nihon Superior
Oracle
RBP Chemical Technology
Sanmina
Shikoku Chemicals Corporation
TTM Technologies
Public