Did you know that a multi-layer ceramic capacitor (MLCC) stored at room temperature in a warehouse or other facility can lose capacitance, causing it to test out of tolerance? This is sometimes seen in medium to large chip caps, such as 1005 through 1812, but it is most common in smaller package capacitors such as 0201 and 0402 through 0805. Fortunately, heat treatment, and “burn-in,” can frequently solve this common issue. In fact, many manufacturers suggest heat treatment before capacitance pre-testing.
What Is Heat Treatment?
Capacitors tend to lose capacitance due to aging, and multi-layer ceramic capacitors are especially prone to this problem. Heat treatment resets the aging process, returning the structure to its optimal unaligned configuration and, thus, its maximum capacitance. This is done by heating the capacitor above its Curie temperature (approximately 125 C), which is defined as the point at which the crystalline structure is altered.
Burn-in, or the exercising of components, before being completely assembled or even pre-assembly, for the purpose of stress testing before putting into service, has long been used by manufacturers. They found that when capacitance was degraded by aging, applying heat above the Curie temperature, such as during soldering, recovered it. Of course, the aging process begins again when the capacitor cools below its Curie temperature.
Heat Treating Instructions for MLCC
Capacitor manufacturers have recommended that MLCC be heat treated before use, especially after prolonged storage, in order to provide the necessary burn in. This simple procedure will ensure that the capacitors fall within the stated tolerance. Heat treatment can be done either before or after installation into circuitry. However, if done after installation, the temperature specifications of other components must be taken into consideration to avoid damaging them.
The heat treatment procedure requires:
- Step 1 – The capacitors be brought to a temperature of 150 degrees C (300°F) +0°C/-10°C for 1 hour.
- Step 2 – The capacitors should be left in normal ambient air temperature for 24 hours ±2 hours to cool.
Please note that it is not necessary to follow this procedure with all MLCCs, but only those which test out of tolerance. Once this procedure has been completed the capacitors will have returned to their normal rating and be ready for testing and use.
In an effort to provide our customers with the best possible service, we have conducted our own testing of this procedure here at Quest Components and have determined that it is effective at restoring these components to their correct capacitance, within normal tolerances.
Here at Quest Components, we are committed to providing you with the information you need to help your business continue to run smoothly. An ISO 9001:2015 Certified Company headquartered in Industry, CA, Quest Components specializes in passive and active board level components. We also provide a variety of services to OEMs (original equipment manufacturers) and CEMs (contract electronics manufacturers) across the globe.