5
Bonding and Handling Procedures for Beam Lead Diodes
1. Storage
Under normal circumstances, storage of beam lead
diodes in Avago supplied wae/gel packs is sucient.
In particularly dusty or chemically hazardous environ-
ments, storage in an inert atmosphere desiccator is
advised.
2. Handling
In order to avoid damage to beam lead devices, par-
ticular care must be exercised during inspection,
testing, and assembly. Although the beam lead diode
is designed to have exceptional lead strength, its small
size and delicate nature requires that special handling
techniques be observed so that the devices will not be
mechanically or electrically damaged. A vacuum pickup
is recommended for picking up beam lead devices, par-
ticularly larger ones, e.g., quads. Care must be exercised
to assure that the vacuum opening of the needle is suf-
ciently small to avoid passage of the device through
the opening. A #27 tip is recommended for picking up
single beam lead devices. A 20X magnication is needed
for precise positioning of the tip on the device. Where a
vacuum pickup is not used, a sharpened wooden Q-tip
dipped in isopropyl alcohol is very commonly used to
handle beam lead devices.
3. Cleaning
For organic contamination use a warm rinse of trichlo-
roethane, or its locally approved equivalent, followed by
a cold rinse in acetone and methanol. Dry under infrared
heat lamp for 5–10 minutes on clean lter paper. Freon
degreaser, or its locally approved equivalent, may
replace trichloroethane for light organic contamination.
• Ultrasonic cleaning is not recommended.
• Acid solvents should not be used.
4. Bonding
Thermocompression: See Application Note 979 “The
Handling and Bonding of Beam Lead Devices Made
Easy”. This method is good for hard substrates only.
Wobble: This method picks up the device, places it on
the substrate and forms a thermo-compression bond all
in one operation. This is described in the latest version
of MIL-STD-883, Method 2017, and is intended for hard
substrates only.
Resistance Welding or Parallel-GAP Welding: To make
welding on soft substrates easier, a low pressure welding
head is recommended. Suitable equipment is available
from HUGHES, Industrial Products Division in Carlsbad,
CA.
Epoxy: With solvent free, low resistivity epoxies
(available from ABLESTIK and improvements in dispens-
ing equipment, the quality of epoxy bonds is sucient
for many applications.
5. Lead Stress
In the process of bonding a beam lead diode, a certain
amount of “bugging” occurs. The term bugging refers
to the chip lifting away from the substrate during the
bonding process due to the deformation of the beam by
the bonding tool. This eect is benecial as it provides
stress relief for the diode during thermal cycling of the
substrate. The coecient of expansion of some substrate
materials, specically soft substrates, is such that some
bugging is essential if the circuit is to be operated over
wide temperature extremes.
Thick metal clad ground planes restrict the thermal
expansion of the dielectric substrates in the X-Y axis.
The expansion of the dielectric will then be mainly
in the Z axis, which does not aect the beam lead
device. An alternate solution to the problem of dielec-
tric ground plane expansion is to heat the substrate to
the maximum required operating temperature during
the beam lead attachment. Thus, the substrate is at
maximum expansion when the device is bonded. Sub-
sequent cooling of the substrate will cause bugging,
similar to bugging in thermocompression bonding or
epoxy bonding. Other methods of bugging are pre-
forming the leads during assembly or prestressing the
substrate.
