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no longer a concern for the LAB process. The evolution of various
chip attach technologies from MR to LAB is shown in Figure 2.
© 2017 Brewer Science, Inc.

Creating Safe

Environments

Laser Release System

In the laser release system, the device wafer
Table 1: Pros and cons among MR, TCB, and LAB.
is bonded to a transparent glass carrier using
a bonding material and a release material.
Once processing is completed, the pair is
separated by exposing the release material
with an excimer laser or solid-state laser. Low-
stress separation coupled with high throughput
make the laser release system suitable for all
production environments.

Laser
Transparent
Carrier
Thin Device Wafer
Release Layer Bonding Material

Laser Release System Benefits:
•Highest-throughput system available with a Figure 2: Evolution of various chip joining technologies from traditional mass reflow
release time of less than 30 seconds (MR) to thermal compression bonding.

•Ultraviolet laser does not heat or penetrate Thermomechanical simulation results
the bulk bonded structure As stated earlier, the thermal mismatch in LAB is lower compared
to that of MR because of the substrate staging temperature in LAB.
•Low-stress processing through use of CTE- Typically, in LAB, substrates are held at 145ºC and die at 250ºC,
matched carrier and room temperature respectively. The effective temperature difference between die and
substrate, which causes higher warpage and stress, is significantly
separation smaller in LAB. A few simulations were conducted to verify the
results. One simulation was done on a 35X35mm package with a
Compatible with: 308 nm 343 nm 355 nm 20X14mm die size using Cu pillar bump at 130µm pitch. Results
found an approximately 60% lower die stress with the LAB process
than with MR as shown in Figure 3. A similar study was conducted
for other test vehicles (TVs), which found a similar trend.
www.brewerscience.com Tensile stress, S1, is typically used to identify the severity of die
stress in the package. An infra-red (IR) laser is used to heat up the

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