Several methods of PCB thermal stress test
Printed Circuit Board：How many ways of PCB thermal stress test? What are the main conditions and inspection items? What information can be obtained from the test?
The thermal stress test used in PCB mainly includes thermal shock and thermal cycle. There are some differences in the presentation and definition of this kind of practice, but these two are the main types to compare. The main purpose of thermal shock experiment is to simulate the rapid rise and drop condition of circuit board assembly and to detect the stress effect of rapid temperature change on circuit board. Common test methods include: soldering tin (floating the circuit board on the tin furnace, simulating the condition of wave soldering), immersion hot oil (also simulating the condition of wave soldering, but with no amount of tin remaining on the surface, it is easier to observe and analyze the defects), soldering tin (simulating the condition of SMT assembly back soldering).
The main purpose of thermal cycling experiment is to simulate the changes of thermal stress that may occur in the life cycle of electronic products. In this way, it can test whether the circuit board can meet the product's long-term reliability demand, so as to guarantee its long-term reliability. This type of test, which can be tested at different levels for different products, has been defined by organizations such as IPC and JDEC. There are many kinds of test simulation methods, typical of which are: pressure cooker test (PCT), heat circulation test (TCT), high-speed stress test (applicable), etc. This type of testing takes a long time due to the large and time consuming standard testing cycles required for most product reliability tests. Some manufacturers have begun to develop faster simulation tests to cope with the rapidly changing world of electronics, and the current typical method, such as high current stress test (IST), is one of them.
In addition to common standards, some large manufacturers also adjust their test cycle number according to product requirements, which should be clearly followed by both parties. However, in the early stage of product development, most manufacturers will adopt stricter methods to verify materials and products, and only in the period of mass production monitoring will they begin to relax to monitoring standards.