Page 49 - Chip Scale Review_May June_2022-digital

a flip-chip device. One option to improve technology [5]. This embedded chip using laser-based photolithography. A
topside cooling of a FIWLP device is to technology mounted chips face up in similar technique has been implemented by
form a thermal pad under each array solder cavities using liquid-dispensed chip Deca on its FOPLP processing line. It uses
pad. This could be done by opening vias attach adhesive. The combination of chip an automated imaging system to measure
in the first dielectric layer directly under placement tolerances and excessive chip each chip’s exact location based upon
each array pad to the chip passivation layer. movement resulted in die location errors its corner I/O pads. It then recomputes
During the first RDL metal processing of 25 to 100µm. This technique measured the laser drill data base and RDL laser
step, the thermal vias could be metallized, the exact position of each chip corner pad patterning data and forms the microvias in
forming thermally-conductive posts that using an automated vision system and the correct locations and correctly routes
provide each solder bump with a direct adjusted microvia locations and RDL the RDL lines and pads [6]. This technique
thermal path to the chip. routing. This is only applicable to FIWLP would be needed to extend molded-wafer
Higher device switching frequencies.
Higher device switching frequencies can
create additional RDL line cross talk
that can affect switching margins. Faster
switching may require isolating ground
planes within the RDL layers to either
provide a controlled impedance transmission
line, or to minimize cross talk between
adjacent lines. Lower supply voltages
generate higher power and ground currents LEADERS IN
that will increase resistive line losses and
a higher device sensitivity to power rail MICRO DISPENSING
droop and surges, thereby lowering device
operating margins. TECHNOLOGY
Chip misplacement and movement.
A unique problem for all molded-wafer SMALL REPEATABLE VOLUMES
FIWLP devices, are lateral and rotational ARE A CHALLENGE, BUT NOT
chip placement tolerances and chip IMPOSSIBLE IF YOU HAVE BEEN
movement after placement. Whereas chip CREATING THEM AS LONG AS WE HAVE.
locations for on-wafer FIWLP processes
are precise down to fractions of microns, all
molded carrier processes use pick and place
machines that inherently have placement TO DO IT WELL,
tolerances more than an order of magnitude
higher, i.e., multiple microns. Depending WE PROVIDE THREE THINGS:
on the processes and the organic materials
used to bond the chip to the carrier before
molding, there can be chip movement after
placement included during adhesive curing, Dispensing Expertise in a variety of microelectronic
molding and molding material curing. The packaging applications.
molded carrier shrinks during the molding
process, thereby adding a varying global Feasibility Testing & Process Verification based
offset. Finally, the molded-wafer has a on years of product engineering, material flow testing
higher composite CTE than a wafer does and software control.
resulting in a varying chip position caused
by temperature changes from the elevated Product Development for patented valves,
temperature during adhesive and molding dispensing cartridges, needles, and accessories.
material curing and the lower temperature
during photolithography steps. These chip
position tolerances will limit the ability of
molded-wafer FIWLP processes to shrink
RDL line widths and solder bump pitches.
RDL adaption. One approach to Our Micro Dispensing product line is proven and trusted by
overcoming chip misplacement and chip manufacturers in semiconductor, electronics assembly, medical
movement issues is adapting the locations device and electro-mechanical assembly the world over.
of microvias and RDL routing for each www.dltechnology.com.
device based on its precise position. This
was first done using the GE high-density
interconnect (HDI) multi-chip interconnect 216 River Street, Haverhill, MA 01832 • P: 978.374.6451 • F: 978.372.4889 • info@dltechnology.com

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