1. Our Mission:
Symtx develops
custom test
systems for
electronics
manufacturers,
to enable them
to meet their
production goals.
symtxr e a l l i f e s o l u t i o n s t o r e a l t e s t p r o b l e m s
application note
Customer
Problem:
The research
department of
a major
semiconductor
manufacturer
wanted to test
the reliability
of solder
connections
associated
with their
integrated circuit (IC) packages. The
objective of this study was to provide a
better understanding of the mechanisms
leading to failure, and use the knowledge to
improve IC reliability. Due to the already
low failure rate of these connections, a
system was required to accelerate the
normal life cycle and failure rate by rapidly
cycling the internal temperature of the chip
packages in a carefully
controlled environ-
ment.
Key Test
Requirements:
• Precise control of
the internal
junction tempera-
ture across mul-
tiple packages
Power Cycling System
The PCS interface panel, capable
of cycling 64 chip packages
simultaneously.
VXI modules used for temperature monitoring
• Ability to define independent tempera-
ture profiles
• Accurate timing to synchronize the
temperature cycling with a separate
solder joint monitoring system
• Automatic calibration of the internal
temperature reference
• Graphical user interface, easily oper-
ated by personnel without extensive
training
Background:
The packages used to house integrated
circuits are subject to temperature changes
as they are used within electronic equip-
ment. The resulting expansion and contrac-
tion of the chip package, in conjunction
with other factors, causes solder joint failure
during the life of the equipment. This
customer planned to study these failure

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phone: 512.328.7799
fax: 512.328.7778
internet: www.symtx.com
West Coast:
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o u r s t o r y c o n t i n u e s...
mechanisms in order to obtain a better
understanding of their cause, possible cures
and the degree to which these failures can
be predicted in advance.
Studying these failures required a system
to accurately control and cycle the internal
temperature of the packages. A separate
system (also provided by Symtx) was used
to monitor and record changes in the solder
joint resistance over time.
Most standard package types were to be
evaluated using this system, including dual-
inline package (DIP), gull-wing (GW) and
ball-grid array (BGA). Because overall
flexibility was a prime customer concern,
the system was required to interface with
any type of IC package. A unique interface
board was developed for each type while a
common interface to the control system was
maintained.
Solution:
A test system was designed to simulta-
neously control the operation of 64 devices,
each with independent temperature profiles.
The internal temperature of each package is
held within a few degrees of the user's
specification.
A power supply is used to heat an internal
power resistor within each package. This
resistor is capable of heating the internal
semiconductor junction in excess of 100° F.
The internal temperature of the IC is then
measured using a reference diode located
on the same substrate. The voltage versus
temperature transfer curve of this diode is
accurately calibrated by the system, then
used as feedback to control the IC tempera-
ture. This results in a closed loop system,
capable of maintaining a temperature
setting of 25° to 100° F with tight accuracy,
for any user selected profile.
The system consists of a combination of
standard VXI equipment and custom
electronics. Monitoring is handled using a
DMM and FET multiplexors to read back the
junction voltage (temperature) of the
reference diodes. Control of the power
applied to each package is handled by a
custom interface board, under direction of
the system computer (PC).
Software provided with the system allows
the user to independently define the
temperature profile to be followed by each
device. The resulting profile is then moni-
tored, controlled and recorded for later
analysis. Complete system self test is also
included for automatic detection and
diagnosis of a hardware failure, should one
occur.
System Implementation:
Symtx worked directly with the manufac-
turer to determine their needs and provide a
solution within their time and budget
constraints.
Several design and system reviews were
held before delivering the test solution,
which was engineered concurrently and
completed before the customers' final DUT
design release.
Instrumentation List:
HP E1401B C-size VXI mainframe
HP E1483A VXI Interface
HP E1411B DMM
HP E1330B Digital I/O
HP E1351A FET MUX
HP E1353A Thermocouple FET MUX
HP Z2467A Solid State MUX