-
- News
- Books
Featured Books
- smt007 Magazine
Latest Issues
Current IssueCounterfeit Concerns
The distribution of counterfeit parts has become much more sophisticated in the past decade, and there's no reason to believe that trend is going to be stopping any time soon. What might crop up in the near future?
Solder Printing
In this issue, we turn a discerning eye to solder paste printing. As apertures shrink, and the requirement for multiple thicknesses of paste on the same board becomes more commonplace, consistently and accurately applying paste becomes ever more challenging.
A Culture of Thriving
One cannot simply command thriving; it must be nurtured, developed, and encouraged. In this issue, we explore strategies to improve your working relationship model—both internally and externally. In this culture of thriving, your business will grow in the process.
- Articles
- Columns
Search Console
- Links
- Media kit
||| MENU - smt007 Magazine
Gold Embrittlement Mitigation: Understanding the New J-STD-001 Requirements
October 20, 2015 | Bob Wettermann, BEST Inc.Estimated reading time: 2 minutes
A significant change to the soldering assembly specifications is outlined in the recently released "F" version of the J-STD-001, Requirements for Soldered Electrical and Electronic Assemblies (July 2014) for gold-plated components. With the advent of more information from studies on the behavior of how much gold can impact the mechanical structure of the solder joint, the "washing away" of gold has become more important.
Gold is widely used in electronic package finish designs in order to enhance solderability and wire bondability. A thick, pure gold finish can be used to enhance wire bondability, but can be too thick for soldering, causing solder joint embrittlement. It does not oxidize very readily, melts at relatively low temperature, and dissolves rapidly in the soldering process. However, too much remnant gold in the solder joint can weaken the integrity of the interconnection.
If the gold dissolution is excessive during the solder alloy’s liquid phase formation, then the composition, mechanical properties and durability of the resulting joint alloy can change, compared with the original solder alloy. As the finished electronic assemblies heat up and cool down, or when exposed to stresses, the gold in the solder joint can weaken or embrittle it and fail. Given the above understandings, solder joint embrittlement is defined as a change of solder joint durability due to dissolution and/or reaction with a finish such as gold and/or palladium.
The changes are expressed in tin-based solders by the appearance of AuSn4 intermetallic compounds from gold finishes. The compounds can occur in the bulk of the solder joint, at the finish interface or in both locations. The compounds are brittle in comparison with the soft solder alloy. As a result, the ability of the joint to be robust when subjected to mechanical strains is reduced.
Limiting these localized weaknesses and maintaining a reliable solder joint is the reason, along with the corresponding testing to verify this, behind the J-STD specification change.
Changes in the J-STD-001 Specification
With the advent of the new version of IPC JSTD-001, the governing the assembly of printed circuit boards, changes to the procurement and preparation of gold plated parts for the military and aerospace markets has taken a new turn.
The following significant changes were made to the specification:
1. Gold embrittlement mitigation (gold washing), which when not done, was a process indicator for class 2 assemblies in "E" is now a defect if NOT done in "F"
2. All through-hole leads required to be hand-soldered regardless of gold thickness need to be "washed" (and hence are a reliability concern
3. A new warning that gold embrittled solder terminations can be present when the solder volume is low (i.e., very small components) or when the dwell time is not sufficient in the soldering process
Editor's Note: This article originally appeared in the October 2015 issue of SMT Magazine.
Suggested Items
AIM to Highlight NC259FPA Ultrafine No Clean Solder Paste at SMTA Space Coast Expo & Tech Forum
10/22/2024 | AIMAIM Solder, a leading global manufacturer of solder assembly materials for the electronics industry, is pleased to announce its participation in the upcoming SMTA Space Coast Expo & Tech Forum taking place on November 14 at the Melbourne Auditorium in Melbourne, Florida.
AIM to Present on High Reliability and Highlight NC259FPA Ultrafine No Clean Solder Paste at SMTA South China Expo & Tech Forum
10/18/2024 | AIMAIM Solder, a leading global manufacturer of solder assembly materials for the electronics industry, is pleased to announce its participation in the upcoming SMTA South China Expo & Tech Forum taking place November 6-7 at the Shenzhen World Exhibition & Convention Center in Shenzhen, China.
All Flex Solutions Invests in Assembly Inspection Automation
10/17/2024 | All Flex SolutionsAll Flex has acquired an Omron VP9000 3D Solder Paste Inspection System and an Omron VT-S1080 3D Automatic Optical Inspection System for their flexible circuit assembly facility in Bloomington, Minnesota. These acquisitions are one part of All Flex Solutions’ four-year SMT Roadmap to expand the scale and capability of their assembly operations.
TopLine to Exhibit 'Drop-in Replacement' for BGA at Electronica
10/16/2024 | TopLineTopLine Corporation will exhibit its latest technology solutions at Electronica in Munich, Germany, November 12 – 15, 2024, in stand B4.428.
Indium Experts to Present at International Electronics Manufacturing Technology Conference
10/15/2024 | Indium CorporationIndium Corporation is proud to announce its participation in the upcoming International Electronics Manufacturing Technology Conference (IEMT), taking place October 16-18 in Penang, Malaysia.