Radiant substrate heating for thermocompressive bonding and apparatus for implementing the same

A method of forming a bonded assembly, the method comprising:

• disposing a packaging substrate having substrate-side bonding structures over a transparent plate;
• attaching a semiconductor die having die-side bonding structures to a bottom of a thermocompressive bonding head, wherein an array of solder material portions is attached to the substrate-side bonding structures or to the die-side bonding structures;
• holding a top surface of the transparent plate at a pre-bonding plate temperature that is lower than a reflow temperature of the solder material portions;
• heating the bottom of the thermocompressive bonding head to a first temperature which is lower than the reflow temperature;
• heating the top surface of the transparent plate to a second temperature, wherein the second temperature is higher than the reflow temperature;
• bringing the semiconductor die and the packaging substrate to indirect contact with each other with the array of solder material portions therebetween while maintaining the top surface of the semiconductor die at the first temperature and while maintaining a bottom surface of the packaging substrate at the second temperature, thereby producing a net heat flow from the packaging substrate through the solder material portions into the semiconductor die;
• and
• bonding the semiconductor die to the packaging substrate by reflowing and solidifying the solder material portions.

An apparatus comprising:

• a transparent plate having an average optical transmission coefficient greater than 80% in a wavelength range from 400 nm to 2 microns and configured to hold a substrate thereupon;
• a radiative heating source configured to heat a bottom surface of the substrate by providing radiation through the transparent plate;
• a thermocompressive bonding head configured to hold a semiconductor die over the substrate;
• a process controller comprising a processor and a memory in communication with the processor and configured to run an automated bonding process control program that comprises:
• heating a bottom surface of the thermocompressive bonding head to a first temperature;
• heating a top surface of the transparent plate to a second temperature that is higher than the first temperature;
• reflowing solder material portions, wherein the top surface of the transparent plate is heated to a third temperature not lower than the second temperature;
• and
• heating the top surface of the transparent plate to a fourth temperature not higher than the third temperature,
• wherein the radiative heating source comprises at least one laser source that scans a laser beam within an area of the transparent plate in a raster pattern.