Defining the Appropriate Reflow Profiling Set-up for Molded Air Cavity Package

Abstract

This study aims to assess and define the appropriate reflow profiling set-up on molded air cavity packages in reference to molded packages during its qualification. The reflow evaluation was done using two reflow profile set-ups: 1) thermocouple on top of the molded package (adapted from JEDEC 020-E industry standard); 2) modified reflow profile set-up where the thermocouple was located on leads (target area during qualification) and in two reflow temperature settings at 245°C and 260°C. Additional reliability tests like moisture resistance test and temperature cycle were also done on the units to check response to package reliability. Results showed that if the reflow profile set-up adapted is putting the thermocouple on top of the designed molded air cavity package with a package thickness of 4.97 mm and top height of 3.15 mm (height with respect to the leads), a delta temperature of around +10°C will be experienced on the lead area. This had led to bubble leak test failure due to mold-lead delamination during reflow process. Taking into consideration the JEP140 guideline for the beaded thermocouple temperature measurement of semiconductor packages, package type and dimension, the package interface or area of interest on a molded air cavity package must have a thermocouple attached to it (i.e., lead interface) and be the basis for the reflow profiling to have an accurate assessment and qualification of the package.