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High-throughput, high-accuracy flip-chip bonding

By Horst Clauberg [Kulicke & Soffa Industries Inc.]
T he two main driving forces in features that ensure high yield because any diagrammatically in Figure 1 and its

the electronics industry are
equipment would quickly erode any benefits
increasing performance and larger yield loss compared to an alternative specifications in Table 1. The bonder
architecture has the following key
lowering cost. From a device packaging gained by paying less for the equipment. features to enhance throughput, each of
perspective, the high-performance portion which we will then discuss in more detail:
of the market is driving a number of Bonder architecture
advanced technologies, such as 2.5 and There are three basic contributions to
3D technologies, that require new bonding throughput of a FC bonder:
equipment such as thermocompression
bonding and Cu-SiOx hybrid bonding. 1. Die handling time: the time needed
However, the vast majority of devices in to get the die from the source wafer
consumer products are bonded by standard to the target location;
flip-chip (FC) bonding, growing at a rate 2. Alignment time: the time spent
of about 9% over the next several years finding fiducials on the substrate and
[1]. Flip-chip bonding allows for a high die; and
number of I/Os with very low assembly 3. Process time: the pick time, time for
costs. In this market space, the driver is flux dipping, and placement time.
mainly for lower cost by increasing the
throughput of the FC bonder with an The design considerations for a bonder
additional need for higher accuracy. The are then: 1) to increase the number of Figure 1: Schematic representation of the high-
throughput, high-accuracy flip-chip bonder (BH =
latter is driven by a desire to keep using processes that can be performed in bond head).
low-cost mass-reflow flip-chip bonding parallel, and 2) reduce the speed of any
technology for next-generation devices, individual process steps.
instead of moving them to more costly 1. 12 die place heads in the form of two
advanced packaging methods, such as T he bonder t hat we developed bond heads on independent gantries
thermocompression bonding. Many to meet these challenges is shown with 6 place heads (nozzles) each.
assembly houses are now asking for flip-
chip accuracy capability below 5μm.
In this paper, we will describe the
guiding principles for developing a FC
bonder at the leading edge of throughput
and accuracy. The design goals that we
set for the Katalyst™ FC bonder were:
a throughput of 15,000 units/hour at an
accuracy of <5μm @ 3 sigma, and the
ability to achieve accuracy of <3μm (3s)
at a nominally reduced throughput.

Cost of ownership
The decision of an end user to purchase
a specific piece of equipment is generally
based on the ability of the equipment to
run the expected mix of applications and
minimizing the cost of ownership (CoO).
The most fundamental aspect of CoO is, of
course, cost of the machine per achievable
throughput in terms of units per hour
($/UPH). But many additional factors
are considered: floor space, application
conversion time, tooling cost, and uptime.
Also important are capabilities and
Table 1: Katalyst™ specifications.

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