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I. PCB stress: After precision resistors mounted on a PCB are soldered to it, they are subjected to compression or tension caused by the thermal expansion and contraction of the PCB, which in turn transfers stress to the resistor layer and affects its resistance value and long-term stability. In situations with very rapid temperature changes, breakage can even occur. The resistance of the pins relieves the stress transmitted by the PCB through the slender solder legs, so there is no issue with surface-mounted resistors. II. Environmental stresses: Humidity, sulfur, salt spray, etc., can all affect the resistance value. The protective layer of precision resistors in surface-mount form is generally much weaker than that of through-hole resistors; therefore, their ability to shield against external environmental stresses is inferior to that of through-hole resistors. Typical pin-type precision resistors are encased in epoxy or plastic; some fully sealed pin resistors have oil filled inside them, which completely shields them from external factors that could affect their resistance value. Such resistors can be used as secondary measurement standards. III. Welding stress: After the impact of welding heat, the change in resistance value of pin resistors is significantly smaller than that of surface-mounted resistors. For precision SMD resistors, we generally recommend that the solder height be at least 30% lower than the height of the resistor leads. When installing precision through-hole resistors, it is also advisable to leave at least 1 mm of space between them and the PCB, in order to avoid stress caused by the thermal expansion and contraction of the PCB. Precision surface-mounted resistors are used in many applications; sometimes this is due to cost considerations, and other times it is because of space constraints or the requirements of automated manufacturing processes. Flexible soldered surface-mounted precision resistors can combine the advantages of both surface-mounted and through-hole resistors, enabling them to effectively withstand various types of stress.