Humidity sensitivity in the SMT patch processing process harms product reliability
When the MSD is exposed to the atmosphere, the moisture in the atmosphere will penetrate into the packaging material of the humidity sensitive device through diffusion. After the device is mounted on the PCB through the patch, it must flow into the reflow oven for reflow soldering. In the reflow zone, the entire device needs to be above 183 degrees for about 30-90s, the highest temperature may be 210-235 degrees (SnPb eutectic), and the peak value of lead-free soldering will be higher, at about 245 degrees. Under the action of high temperature in the reflow zone, the moisture inside the device will expand rapidly, the fit between the different materials of the device will lose adjustment, and various connections will have undesirable changes, which will cause the device to peel off and delaminate or burst. Performance is affected or destroyed. If the damage is severe, the appearance of the device is deformed, cracks, etc. (usually called “popcorn”). Like ESD damage, in most cases, these changes are not visible to the naked eye, and the MSD will not show a complete failure during the test.
