M541 Datasheet, PDF (1/9 Pages) M/A-COM Technology Solutions, Inc. – Bonding, Handling, and Mounting Procedures for Chip Diode Devices

Application Note
M541
Bonding, Handling, and Mounting Procedures for
Chip Diode Devices
M/A-COM Products
Rev. V3
Discussion
Chip Diode devices for use in integrated circuits and
hybrid integrated circuits have proliferated in the last few
years. Today circuit designer is faced with a multiplicity
of alternatives in the involving tradeoffs of particular ad-
vantages and disadvantages. The obvious advantages in
the use of chip diodes in hybrid integrated circuit applica-
tions are their very small size and potentially lower cost.
Small size and simplicity of structure give the benefit of
minimal parasitics, but as the size of the diode becomes
smaller, handling and production problems increase. By
outlining our conclusions, we hope to help the designer
overcome some of the difficulties encountered when
using chips in MIC applications. M/A-COM Tech manu-
factures a large selection of chip and packaged diodes
for hybrid integrated circuits. Obviously not all diode
types are available in all configurations. Characteristics
such as breakdown voltage or capacitance may limit the
size of the chip or its form.
Silicon Chip Devices
CERMACHIP™ PIN Diodes
Oxide Passivated PIN Chips
Beam Lead PINs
Snap Varactor Chips
Tuning Varactor Chips
MNS Chip Capacitors
Schottky Chips
Beam Lead Schottky Diodes
PF transistor Chips (Low Noise)
Silicon Chip Devices
Gunn Diodes
GaAs Tuning Varactors
Beam lead GaAs Tuning Varactors
GaAs Multipliers
GaAs Schottky Mixers
GaAs Abrupt and Hyperabrupt Tuning Varactors
GaAs Beam lead Schottky
Microstrip Packages and Chip Carriers
Chip diodes usually require specialized equipment for die
attachment to the circuit and for wire or strap bonding to
the top of the chip. These operations require a clean
work environment and special handling equipment such
as vacuum pickups, hot gas bonders and/or thermal
compression bonding equipment.
Not all MIC circuits require chips. In many cases
(especially for conventional stripline circuits) a hybrid
circuit package or carrier will give satisfactory results and
can be handled much more easily without a large invest-
ment in fabrication equipment. M/A-COM Tech supplies
a broad band of diodes in stripline or carrier packages.
Chip Bonding Methods
The biggest problem in using chip diodes is the damage
encountered when assembling chips into circuits. In gen-
eral, the value of the integrated circuits far exceeds the
cost of the chip itself. When packaged diodes are used,
the critical die attach and top contract operations are per-
formed by M/A-COM tech and all devices are RF tested
after assembly into the package. When the circuit fabrica-
tor performs the die attach and wire bonding operation on
a complex substrate, he /she runs the risk of losing or
damaging a chip during the bonding operation which can
results in the loss of the whole circuit or in an expensive
rework cycle.
The most common problems that arise when bonding
chips to the circuit are: the introduction of excessive series
resistance, especially under forward bias conditions due to
the improper bonding of the chip to the ground plane; poor
reliability due to the entrapment of fluxes under the bond;
and mechanical failure of the bond under thermal shock or
temperature cycling. All three conditions are the results of
improper wetting of the die to the ground plane and are
usually caused by inadequate cleanliness or inadequate
bonding conditions,
The Influence of the Circuit Board on
Chip bonding Methods
Selection of the chip bonding method must take into con-
sideration the characteristics of the circuit board material
being used.
Stripline teflon fiberglass circuits should be soft soldered.
Most eutectic solders melt at temperatures too high (250-
300ºC) to be used with teflon fiberglass boards. Conduc-
tive epoxies can also be used, but the results may not be
reliable. The use of Gunn diodes on teflon fiberglass cir-
cuits is not recommended because the major problem in
operating these diodes is removal of heat. It is absolutely
essential that eutectic solders or thermal compression
bonding be used to bond these diodes to achieve the best
thermal resistance. Soft solders and conductive epoxies
are not acceptable methods for bonding Gunn diodes. The
use of beam lead diodes with teflon fiberglass boards is
not generally recommended. Because these boards are
flexible, they may bend during or after bonding and cause
the diode leads to break.
In many cases conductive epoxies will give good results
with little or no complex equipment required. Although the
high temperature and long them reliability of this type of
band is not generally as good as eutectic solder, the use
of conductive epoxies is an acceptable and sample way to
fabricate most circuits.
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