The Global deployment of 5G and the exponential growth of data centers is driving the demand for high-performance optical devices. These new high-performance optical devices generate many new requirements including much smaller packaging design, and smaller chips/dies with higher density in the package. These new high-performance photonic device requirements are not limited to 5G and Data Center applications. The new requirements are also needed in LiDAR, AR/VR, advanced photonic sensors, as well as in highly integrated silicon photonics devices.
These requirements present significant challenges to the die bonding process. The eutectic die bonding process for the higher density components within these optical devices requires the machine to provide special high-precision top pulsed heating tools in case the neighbor chips/dies double reflow during the eutectic process. This high-precision pulsed heating is very useful for high-density optical devices.
MRSI specifically designed the heated head to address this issue, which can be installed in MRSI-H and MRSI-HVM machines. The objective is to provide a eutectic process solution for customers manufacturing these high-density photonics devices. In the case of our MRSI-HVM, the right-side bonding head can be configured to a heated head (see Figure 1). The tips on the heated head can do localized eutectic bonding of multiple dies onto a common submount without reflowing the neighboring solder pads with spacing >0.20mm. The top heated head/tip can be used with the eutectic stage for bottom heating at the same time. The heated head can also be configured alongside an automatic tools change functionality with a 9-position tool bank located nearby the heated head for fast tool change.
The dual head step in the MRSI-HVM with heated head can improve the total throughput. The left side head is standard cool head that handle materials including picking up dies from wafer tape or Gel-Pak® without worry about the need to waiting for a heated head to cool down. The dies will be put on a metal/ceramic intermediate stage (I-stage). The I-stage will transfer the die to the right side. The right side heated head can pick up die from the I-stage at any desirable temperatures.
Figure 1. Heated Head on MRSI-HVM
The heated head has good pulsed heating performance for fast temperature ramp up/down. The temperature ramp up speed can be >40 ℃/sec and the ramp down speed can be >25℃/sec without undesirable over or undershoots. An experiment was completed for a high-density photonics device, which used a heated head to do eutectic bonding for three dies. The heated head temperature profile control is the same as the bottom heated standalone eutectic station. The heated head pick and place test results, using glass dies, shows the accuracy is <±1 µm @3σ; and the heated head eutectic bonding actual sample dies results show the accuracy is <±3 µm @3σ.
The results show MRSI’s heated head meets the objectives we set out to achieve to satisfy our customers’ needs concerning the high-density photonics device eutectic process. They demonstrate that our heated head can achieve post bonding <±3 µm @3σ high-precision using high-speed eutectic bonding. This newly released configurable option expands MRSI’s ability to deliver flexible solutions for our customers supplying high-density photonic devices.