What Is Time to Delamination in PCB?
Time to Delamination (TMA Method, IPC-TM-650 2.4.24.1) describes the method for determining the time to delamination of laminates and printed boards through the use of thermomechanical analyzer (TMA). Delamination refers to the separation of layers from one another – e.g., of a resin from a laminate or of fibers from a resin. Such processes cause defects in printed circuit boards.
- IPC-TM-650 No. 2.4.24.1 describes the method of determining the time to delamination for laminates and printed boards through the use of a thermomechanical analyzer (TMA).
- The sample is heated to a specified isothermal temperature at 10 K/min and is then held at this temperature for 10 minutes or until failure
The time to delamination is determined as the time from the onset of the isotherm to failure. Failure is any event or deviation of the date plot where the thickness is shown to have irreversibly changed. The scan is typical of an epoxy material at 260°C isothermal temperature. On occasion, some materials will determinate before the isotherm is reached. In this case, the temperature at the time of failure shall be recorded.
For epoxy laminates and similar materials, the recommended isothermal temperature is 260°C (T260). For polyimides and other high temperature materials, the isothermal temperature may be increased to 288°C (T288). For other material types, consult with the material manufacturer.
Time to delamination is a common measurement used to assess base material performance. It is a measure of the time it takes for the resin and copper, or resin and reinforcement, to separate or delaminate. This test utilizes TMA equipment to bring a sample to a specified temperature and then measures the time it takes for failure to occur. Temperatures of 260℃ (T260) and 288℃ (T288) are commonly used for this testing. Many high-Tg FR-4 materials will exhibit lower times to delamination than low-Tg FR-4 materials. With Pb-free assembly temperatures reaching 260℃, the T260 test has become a much more relevant measure of performance.
What Cause Delamination?
- Thermal shock: including wave soldering process, manual soldering, and reflow & repair process.
- Moisture in the board
- Poor lamination process
- Wrong Tg for FR-4 material
What Can Help Prevent Delamination?
- Oxide layer on inner layers
- Baking of board prior to thermal processing
- Keeping them dry in storage
- Qualification of supplier to provide boards that are acceptable to the process
Some Typical Stress Testing Parameters
- Solder float test 6X @288℃
- Interconnect stress test 6X @230℃
- N passes in reflow simulation @260℃
- Time at 260℃ must be greater than 10 minutes
Types of Tests to Measure Delamination
- Time to delamination is a common measurement used to assess base material performance
- Time to delamination is a measure of the time it takes for the resin and copper, or resin and reinforcement, to separate or delamination.
- This test utilizes TMA equipment to bring a sample to a specified temperature and then measure the time it takes for failure to occur.
- Temperatures of 260℃ (T260) and 288℃ (T288) are commonly used for this testing.
- Many high-Tg FR-4 materials will exhibit lower times to delamination than low-Tg FR-4 materials.
- With lead free assembly temperatures reaching 260℃, the T260 test has become a much more relevant measure of performance.