Page 45 - ChipScale_Nov-Dec_2020-digital

Functionalized materials enable yield improvement in

package test

By Jerry Broz, Bret Humphrey [International Test Solutions, Inc.]
A pplication demands are

bei ng d r iven by major
technological megatrends in
personal devices, data cloud, connectivity,
and automotive content. Additionally,
Moore’s Law is slowing, so semiconductor
manufacturers are pursuing heterogeneous
integration strategies that combine the
benefits of multiple processors, memory
modules, and other intellectual property
(IP) from different nodes and various
integrated device manufacturers (IDMs) Figure 1: Technological trending challenges for contactor pins and sockets to meet the test frequency
and outsourced semiconductor assembly requirements for processors, communication, and radar devices.
and test suppliers (OSATS). Heterogeneous technology trends for going from when performance specification limits are
integration refers to the integration of typical spring pins and sockets to higher exceeded, the testing operations must be
separately manufactured components into performance small-pin designs and paused to facilitate some level of cleaning
a higher-level assembly, such as system innovative, advanced sockets and materials. execution [3]. Contactor cleanliness,
in package (SiP) that, in the aggregate, These, combined with wafer-level test, especially at the temperature extremes
provides enhanced functionality and address the broad industry demands for often used for automotive devices, will
improved operating characteristics. testing complexity and KGD strategies. adversely affect socket performance, and
Before integration into the highest value Accurate testing using sockets detrimentally impact the device first-pass
modules, each of the various parts must be with high-volume device handlers is yields such that one or more recovery
individually verified to provide a high level the primary method of verifying that passes are needed. Unscheduled downtime
of confidence that they are “probably” good the final assembled devices meet the and inefficient procedures will result in
die (often called known good die, or KGD). necessary performance and reliability increasing the overall test costs [4].
During the device test flow, the passing criteria. Repeated test insertions demand
parts may or may not be 100% “known efficient, controlled physical and electrical Automated contactor cleaning
good” and could be better categorized at contact. The performance requirements In legacy handlers, socket cleaning
each step as “known not bad,” or what can for bandwidth frequencies greater than must be performed with the handler in an
be called KNB die [1]. With the added test 40GHz, high power, and reduced pitch idle state at room temperature to prevent
complexity requirements for the high-value require shorter pins and precise ball-to- risk of injury to operators and technicians.
devices, a paradigm shift is needed away pin alignment. Over time, contamination Manual offline cleaning is executed
from assuming just because the die was from the package, pads, and solder balls reactively (i.e., cleaning is performed after
good enough to pass-on, that it will also be will accumulate within the socket and yield drops below the specification limit)
good enough to meet the requirements of onto the contactor surfaces. During high- or proactively (i.e., cleaning is performed
each subsequent test insertion [2]. A single volume package testing, yield metrics and at some predetermined interval before
failure within these assembled systems binout trending are closely monitored and
creates new requirements for earlier testing
and test coverage, and will drive the overall
total cost of test.
Even before multi-die modules, IDMs,
foundries, and off-shore assembly and
test suppliers would implement multiple
insertions for wafer-level, device-level,
and package-level testing. As part of
that process, stable electrical contact at
each stage is critical for data reliability
and to assure fault identification.
Figure 1 highlights the broad future Figure 2: Examples of test contactor cleaning (TCC) unit designs that emulate various device page types and
facilitate auto contactor cleaning (ACC) execution within a high-volume test cell.

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