Features of resistors for aerospace applications
Use of lead-containing solder terminals
In general electronic parts, lead-free terminals are the mainstream, but resistors for space applications use lead-containing solder terminals for the following reasons.
Improvement of the reliability by suppressing whisker*
It is known that for Sn and Zn, whiskers grow more prominently in the zero-gravity environment such as outer space than on the ground.
Whiskers have been observed to grow faster in lead-free solders such as Sn for the external electrodes of electronic components and Sn-Ag-Cu used as a joining material. On the other hand, they have been observed to grow slower in Sn-Pb-based lead-containing solders.
Since whiskers can cause short circuits between circuits and poor continuity, it is necessary to use materials that do not easily generate whiskers.
* What is a whisker?
A needle-like metal crystal grown over time from lead-free tin (Sn) or zinc (Zn) plating layer. Because whiskers grow thin and long under zero gravity, they are more likely to cause problems, such as short circuits, than they do on the ground.
Improvement of mechanical durability
Compared to Sn-plated products, lead-containing solder-plated products have the stress relaxation effect due to the creep deformation, improving reliability against the heat shock (thermal shock) and mechanical shock after mounting.