-
- News
- Books
Featured Books
- smt007 Magazine
Latest Issues
Current IssueBox Build
One trend is to add box build and final assembly to your product offering. In this issue, we explore the opportunities and risks of adding system assembly to your service portfolio.
IPC APEX EXPO 2024 Pre-show
This month’s issue devotes its pages to a comprehensive preview of the IPC APEX EXPO 2024 event. Whether your role is technical or business, if you're new-to-the-industry or seasoned veteran, you'll find value throughout this program.
Boost Your Sales
Every part of your business can be evaluated as a process, including your sales funnel. Optimizing your selling process requires a coordinated effort between marketing and sales. In this issue, industry experts in marketing and sales offer their best advice on how to boost your sales efforts.
- Articles
- Columns
Search Console
- Links
- Events
||| MENU - smt007 Magazine
IPC Sets Standards on Strain Gauge Tests
May 14, 2012 |Estimated reading time: 2 minutes
Any time that the bond between printed boards and electronic components undergoes a fair amount of stress, there’s a chance that problems will arise. Product developers and manufacturers have to know how to measure this strain so they can determine whether parts are undergoing enough stress to raise concerns about reliability.
However, it’s a challenge to measure stress using uniform practices, for example when EMS companies and OEMs are attempting to set maximum strain levels. IPC, together with JEDEC, recently updated its offering in this arena, IPC/JEDEC-9704A, Printed Circuit Assembly Strain Gage Test Guideline. The new version aims to make it simpler for users to run tests that can be administered at any point during manufacturing.
“The revision is about making sure there’s a common, accepted practice for measuring manufacturing strain on printed board assemblies due to board flexure,” said Intel Corporation’s Jagadeesh Radhakrishnan, a co-chair of the task group that developed IPC/JEDEC-9704A. “This document changes the focus to providing a methodology. It doesn’t give you targets; it explains how to measure strain.”
One of the biggest changes was the decision to eliminate pass/fail points that were in the first-generation document. IPC and JEDEC task group members found that many companies felt they could set their own levels for specific products. What they really wanted was an approach that would yield good results every time.
“The revised guideline better defines the problems that excessive strain can cause,” said John Perry, IPC technical project manager.
There are many types of failures, he explained. Solder ball cracking, conductor damage and cracking of packages are among them. Another is pad cratering, where a BGA strains the connection to the board and rips up the laminate at the solder ball/board interface.
The standard also has an expanded scope. “IPC/JEDEC-9704A now has recommendations for sockets and ceramic capacitors. In the past, it just addressed BGAs,” Radhakrishnan said. “It also changes some parameters for in-circuit test fixtures, providing best design practices so users will have fewer issues.”
This expanded scope includes techniques for measuring strain for array packages that are larger than 27 mm per side. This description makes it fairly straightforward to set up tests for these BGAs as well as for sockets and a number of passives. IPC/JEDEC-9704A describes best practices for strain gauge placement and other parameters, as well as techniques for understanding these results.
“The document provides formulas for calculating strain, for example they can use this equation for measuring strain in a given type of product,” Radhakrishnan said. “We also wanted to set a common strain metric and establish common terminology.”
The document also describes techniques for analyzing the data derived from these tests. For example, there is a section describing the manufacturing processes that causes board flexure, such as a package with a heat sink installation, functional testing and final system assembly.
The tests can be performed at many stages during manufacturing of printed board assemblies. Components can be tested during assembly and during test processes in the factory, or just before they’re packaged to go out the door.
The latest version of the standard can be purchased through the IPC Online Store.