While completing some paperwork at the DMV one day, I watched as a car returned from a driving test. I knew that it hadn’t gone well when I saw that it was the tester who was driving instead of the student. Once parked, the tester explained very emphatically to the parents exactly why their student had no business driving a car. Although it was an uncomfortable moment, it was far better to be embarrassed now than to let someone behind the wheel that wasn’t prepared for it.
This is what testing is all about—to make sure that whatever it is being tested is prepared for what it is intended to do. In the case of printed circuit boards used in the telecom industry, they must pass important testing to ensure they will function as expected in their intended operational environments. This testing is known as Highly Accelerated Life Tests (HALT) and Highly Accelerated Stress Screens (HASS). Let’s look a little closer at what the HALT and HASS test methodologies are, and how your PCB contract manufacturer should implement them.
What HALT and Hass Test Methodologies Are and Why They are Important
Electronic equipment in the telecom industry is often subject to some very harsh environments. To fully test this equipment, it is important to mimic the environments they will operate in. Standard environmental testing, however, takes a long time and may not reveal all the possible failures that may occur.
To get the job of testing done faster, more efficiently, and with more reliable results, telecom equipment is often tested using HALT and HASS methodologies. Together, these tests are referred to as Accelerated Stress Testing, or AST, and they will reveal problems in a matter of days or even hours instead of the weeks or months that traditional testing would take.
HALT testing is designed to detect problems in product design, component selection, and manufacturing. The product sample being tested will be subject to levels of stress that are progressively increased throughout the test. These stresses can include rapid changes in temperatures as well as vibration, and will continue until a failure is achieved to determine how far above its specified level of stress that the product will operate in. When completed, the HALT testing will provide data on the different stress characteristics of the product, allowing the design and manufacturing processes to be altered as needed.
HASS testing will take the operating limits determined by the HALT testing and develop a screen for testing products that are in regular production. With the results of the HASS testing, the production testing can be set up to find manufacturing flaws without jeopardizing the life of the product. The goal of HASS testing is to leverage the same stress testing parameters used in the HALT testing but only for a predetermined number of test runs to check for manufacturing defects before product failure occurs.
How Your CM Should Environmentally Test Your Circuit Boards
To conduct HALT and HASS testing on your circuit board, your PCB contract manufacturer should first start by developing a detailed testing plan with your engineering and reliability teams. This testing plan should include:
- Product and testing specifications.
- Testing procedures, instructions, and recording processes.
- Incorporation of testing into the master work and process flow.
Once this testing plan is approved by all parties, it should be released through a document change order to become part of the overall PCB build documentation.
Your CM should use what is essentially an environmental chamber to conduct the tests in. This chamber allows them to control different stress parameters, such as temperature and humidity, while the unit under test (UUT) is powered up. The chamber itself has access ports for PCB inputs and outputs as well as power for the board to be operational while being tested.
Depending on the needs of the boards being tested, your CM may also choose to use the services of a third-party tester. This can allow for higher volumes of boards to be tested as well provides more strenuous testing or accommodates larger board sizes.
What You Gain Working with a CM Experienced in the Telecom Industry
HALT and HASS testing are just the beginning of the benefits you can realize by working with a contract manufacturer that is an experienced telecom equipment builder. In addition to understanding the testing that is needed and having the resources to accomplish that testing, a CM with telecom experience will have the manufacturing and documentation process that you need already in place.
At VSE, we have spent years providing service to our partners in the telecom industry. We understand your particular manufacturing requirements that you have, and our processes already include the key inspection points you require. Our copy exactly process ensures that once the build configuration for your telecom product is locked in, it will remain that way during the course of its production run without any modifications. And when you do decide to make modifications at some point, you will benefit from the clear and concise communication with us through our documentation and tracking systems.
