HL1.JUN–McKenzie–SC
PGA socket exhibits controlled impedance
Patented ground plane transforms socket contacts into coaxial-type
transmission lines
At the heart of a new pin-grid-array socket from McKenzie Technology is a
patented ground plane that achieves a matched-impedance signal path. The
ZGA (impedance-controlled pin-grid-array) socket meets the needs of
designers using chips whose clock speeds approach 100 MHz. The socket
uses selective metallization of a high-performance molded liquid-crystal
polymer to create interconnected ground planes around the contact housing.
Metallized traces are plated onto the socket's molded liquid-crystal
polymer insulator, forming ground planes and tubes. The company
custom=designs the metallization pattern on the contact housing to match
the user's impedance requirements. Typically, the socket will be designed
to maintain a 50-ohm matched impedance. The ground planes encircle each
signal pin and interconnect via plated through-holes that are
interstitched around each contact. Ground pins are inserted in the
through-holes to couple the electrical ground of the motherboard to the
socket ground planes and tubes. The result is a coaxial-style transmission
line running throughout the socket and onto the motherboard. In tests,
the socket exhibited an inductance of 2 nH, compared with 2.4 nH for a
conventional PGA socket. Crosstalk is 0.6% to 0.3% over a dc to 1-GHz
range, compared to 10% over the same range for a standard PGA socket.
Characteristic impedance is 40 ohms, compared to 70 ohms for a standard PGA.
The socket is initially available in a 168-pin configuration for the
Intel 66-MHz 80486 microprocessor and a 273-pin configuration for the
Pentium microprocessor. (Pentium socket, part number ZGA
273H509B-2119-001, $12.21 ea/1,000–4 weeks ARO.) McKenzie Technology
Fremont, CA Debra Woods 510-651-2700 Fax 510-651-1020
CAPTION: use only photo, not diagram
The ZGA socket from McKenzie Technology has a patented design that
creates interconnected ground planes for a controlled-impedance signal
path.
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