Hitachi bond force leveling for Thermocompression Bonding (TCB): a closer look
At the recent Semicon Taiwan Conference Toshihisa Nonaka from Hitachi Chemical described their materials solution to improve the speed of thermos-compression bonding. i-Micronews thought it was worth… a closer look.
Hitachi Chemical offers a wide variety of products for the advanced packaging community as shown in the figure below.
Advanced packaging offerings of Hitachi Chemical (Source: Hitachi Chemical)
Thermo-compression bonding (TCB) has many advantages for flip chip bonding in advanced packaging such as better fine pitch connection and warped de assembly, but suffers from low productivity.
Comparison of mass reflow to Thermo-compression Bonding (ref: T. Nonaka, Semicon Taiwan, 2016)
While several groups have suggested the use of pre-bonding (or tacking) followed by “in plane collective TCB” ,as shown in the figure below, unevenness of bump height and pad thickness, non flatness of
substrate surface and non parallelism between the bonding head and the stage can lead to die shifting and uneven bonding force.
Issues with in plane collective bonding (ref: T. Nonaka, Semicon Taiwan, 2016)
Hitachi Chemical has developed a Bond Force Leveling (BFL) film which is inserted between the head and the dies to level (even out) the applied bonding force among the pre-placed dies as shown below. The film melts, flows and is cured. Next the multi-die bonding force is applied evenly through the cured resin layer.
The use of Bond Force Leveling (BFL) film (Source: Hitachi Chemical)
Below we see a simulation of no film, a thermoplastic film and a thermoset film. The thermoset film was most effective in leveling the bonding force as shown by the height of the gold bumps ( in this example) after TCB.
Simulation results of the leveling performance of film and no film solutions (ref: T. Nonaka, Semicon Taiwan, 2016)
The thermoset BFL also shows significantly better die shift control.
Die Shift results with and without BFL film (ref: T. Nonaka, Semicon Taiwan, 2016)
Dr. Phil Garrou for Yole Développement
Source: www.yole.fr