Heat cycle resistant

What are solder cracks caused by heat cycle?

In applications where temperature changes are remarkable, such as in automobiles, when temperature change (= heat cycle) occurs, the difference in the linear expansion coefficient between the printed wiring board and the electronic component may cause cracks in the solder joint, leading to connection failure.

In the case of chip resistors, large size chip resistors are generally used when large rated power is required. However, the larger the chip resistor, the greater the absolute value of expansion/contraction and the higher the rate of failure.

In order to achieve both the high rated power and measures against solder cracks, multiple small-sized resistors are used in some cases to secure the required rated power, but it increases the number of parts and mounting area.

In such cases, we recommend the wide terminal type WK73R, WG73, WK73S and WU73, and the mold sealed type TSL, SL, SLN and SLZ, which are large rated power and resistant to the heat cycles.

Improved heat cycle resistance

As mentioned above, when using in an environment where the temperature changes drastically, there is a concern about cracks and poor connection in general chip resistors. Therefore, by reviewing the electrode structure and improving the electrode strength, the occurrence of cracks can be reduced. It is possible to improve the heat cycle resistance.

Advantages of wide terminal type

Compared to general resistors, the wide terminal type has a shape in which the electrodes are vertically and horizontally swapped and the distance between the electrodes is shorter. That allows it to have the higher heat cycle resistance compared to the general resistors of the same size. In addition, since the large electrode area achieves the better heat dissipation, the rated power per size is higher than that of general products.

Advantages of metal plate terminal

The resin mold type, in which the external electrodes are composed of metal plates, has a structure that is resistant to heat cycles and mechanical stress because the metal plate has a stress relaxation structure against the contraction of printed wiring board.