Heat Treating a Multi-Layer Ceramic Capacitors

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?

تميل المكثفات إلى فقد السعة بسبب التقادم ، والمكثفات الخزفية متعددة الطبقات معرضة بشكل خاص لهذه المشكلة. تعيد المعالجة الحرارية ضبط عملية الشيخوخة ، وتعيد الهيكل إلى التكوين الأمثل غير المحاذي ، وبالتالي ، السعة القصوى. يتم ذلك عن طريق تسخين المكثف فوق درجة حرارة كوري (حوالي 125 درجة مئوية) ، والتي يتم تعريفها على أنها النقطة التي يتم فيها تغيير الهيكل البلوري.

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:

l Step 1 - The capacitors be brought to a temperature of 150 degrees C (300°F) +0°C/-10°C for 1 hour.

l 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.

Source:Quest