HMC258 Datasheet, PDF (5/6 Pages) Hittite Microwave Corporation – GaAs MMIC SUB-HARMONICALLY PUMPED MIXER, 14 - 21 GHz

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MICROWAVE CORPORATION
HMC258
GaAs MMIC SUB-HARMONICALLY
PUMPED MIXER, 14 - 21 GHz
MIC Assembly Techniques
5
Mounting & Bonding Techiniques for Millimeterwave GaAs MMICs
The die should be attached directly to the ground plane eutectically or with conductive epoxy (see HMC general Handling, Mounting,
Bonding Note).
50 Ohm Microstrip transmission lines on 0.127mm (5 mil) thick alumina thin film substrates
are recommended for bringing RF to and from the chip (Figure 1). If 0.254mm (10 mil) thick
alumina thin film substrates must be used, the die should be raised 0.150mm (6 mils) so that
the surface of the die is coplanar with the surface of the substrate. One way to accomplish
this is to attach the 0.102mm (4 mil) thick die to a 0.150mm (6 mil) thick molybdenum heat
spreader (moly-tab) which is then attached to the ground plane (Figure 2).
Microstrip substrates should be brought as close to the die as possible in order to minimize
bond wire length. Typical die-to-substrate spacing is 0.076mm (3 mils).
An RF bypass capacitor should be used on the Vdd input. A 100 pF single layer capacitor
(mounted eutuctically or by conductive epoxy) placed no further than 0.762mm (30 Mils)
from the chip is recommended. The photo in figure 3 shows a typical assembly for the
HMC258 MMIC chip.
Figure 3: Typical HMC258 Assembly
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