NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.

AX and RTAX-S FPGA Bond Wires

Background

In previous generation Actel FPGAs such as the RT54SX (0.6 µm, MEC), the RT54SX-S (0.25 µm, MEC), and the RTSX-SU (0.22 µm, UMC), gold ball bonds were used on aluminum pads.  A concern is the formation of intermetallic compounds as a result of the two unlike metals, as they diffuse into one another.  Early generation Actel devices utilized aluminum wires.  Other FPGA manufacturers also use gold wire and ball bonds.  Please see reference 1 below for additional data.

References and Additional Reading:

1. FPGA Reliability
2. NASA Goddard Space Flight Center Wire Bond Website

AX and RTAX-S Technology

Both AX and RTAX-S FPGAs are 0.15 µm devices fabricated at UMC.  The AX, which is used for commercial, industrial, and military applications utilizes gold bond wires.  The RTAX-S, designed for space applications, has been designed for aluminum bond wires.  The images below show representative bonds and pads, contrasting the AX and RTAX-S FPGAs.

AX: A SEM image showing the the gold ball bonds.		RTAX-S: A SEM image showing the inner and outer row of die pads with 1.0 mil diameter aluminum wedge bonds.

For additional images of bonds and pads at different magnifications, click here.

 

RTAX-S and AX Application Notes

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Last Revised: November 27, 2005
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