Online proceedings - EDA Publishing Association

7-9 October 2009, Leuven, Belgium
Evaluation of Materials for High Temperature IC
Packaging
Robert Klieber, Renee Lerch
Fraunhofer Institute for Microelectronic Circuits and Systems
Finkenstr. 61
D47057 Duisburg, Germany
Abstract- Fast decrease of device dimensions, rapid growth of
the number of elements per integrated circuit device (IC) and
the increasing amount of interconnections between the chip and
the substrate lead to a more complex design and production of
the ICs and to higher demands towards packaging technology
as well. This is especially true in the field of high temperature
electronics with operating temperatures of up to 250°C. We
present an evaluation of materials for both the adhesive and the
encapsulant for packaging of high temperature ICs for this
temperature range. Among the available materials only glassbased
formulations could withstand extended periods of heat
and substantial numbers of temperature cycles. In addition,
samples of high temperature CMOS ICs (capacitive pressure
sensors and EEPROMs) have been successfully assembled
using these materials.
I. INTRODUCTION
Fast decrease of device dimensions, rapid growth of the
number of elements per integrated circuit device (IC) and the
increasing amount of interconnections between the chip and
the substrate lead to a more complex design and production
of the ICs and to higher demands towards packaging
technology as well. The rise in power density due to the
increasing miniaturization of the device size and the interest
of industry for ICs working in high temperature
environments lead to high operation temperatures of the
integrated circuit devices and the encapsulation. Within
automotive, aerospace, space, geothermal wells and nuclear
power applications high temperature devices operate
between 150°C to 600°C. These integrated circuits have to
be protected from mechanical damage, moisture and
radiation, which could negatively affect the device
performance, reliability or lifetime. The proper choice of the
encapsulant therefore enhances the reliability of the IC
devices and improves their mechanical and physical
properties for these high temperatures. While adhesives and
encapsulants are a common technique for die-bonding and
encapsulation of ICs for applications up to 150°C, these
materials fail in high temperature applications for
temperatures higher than 150°C.
II. EXPERIMENTAL SETUP
To monitor the performance of the die attach and the
encapsulant materials, samples have been prepared and
tested in a 250°C ambient and in thermal cycling
experiments, cycling the samples between room temperature
(25°C) and 250°C. At designated time stamps and cycle
amounts tests have been performed at room temperature.
To evaluate the performance of the die adhesives chips of
the size 3 mm 2 were bonded into standard DIL24 ceramic
housings with a gold surface and onto ceramic plates. The
thickness of the adhesives layers was between 20 and 40 μm
after curing. The required die shear force to take off the
chips was measured in accordance with MIL-STD-883
Method 2019 by applying a force parallel to the surface of
the substrate as shown in Fig. 1.
In order to evaluate the performance of the various
encapsulants a die of the size 2x1.5x1 mm 3 was bonded with
the best die adhesive material into a DIL24 ceramic housing.
25 μm thick aluminum bond wires have been used to create
electrical connections between each DIL24 housing pad and
the surface of the die having a gold layer on the top surface.
The electrical connection between the pads of the housing
and the die were tested by a measurement of the resistance
between two contacts of the DIL24 housing as shown in
Fig. 2 after the encapsulation. Also visual inspections of the
encapsulants have been made to reveal defects like flaws and
fractures.
Fig. 1. Schematic drawing of the shear force measurement for the die
attachment test
Fig. 2. Schematic drawing of the conduction measurement for the
encapsulation test
This work was partially funded by the government of the state of North
Rhine-Westphalia as part of the "Hochtemperaturelektronik" program.
©EDA Publishing/THERMINIC 2009 117
ISBN: 978-2-35500-010-2