Anodic Bonding Specification

Overview

We tested a number of glass and metal plate samples provided by CRS Electronics for the successful formation of metal-to-glass hermetical seals using anodic bonding.

Background

Note: Information used has been taken from micro-scale research papers which may not apply to macro-scale, bulk material anodic bonding. Contractor must posess sufficient knowledge to extrapolate expertise of any micro-scale knowledge to macro-scale bulk application.

Experimental Setup

Equipment

1. High Voltage Power Supply
   1. 0-1.5kV (one paper spoke of range up to 3.5KV)
   2. mA max current output
   3. Suitable electrode to connect to samples
2. Hotplate
   1.  Temperature controller with maximum temperature of 600 Deg C
   2.  Thermocouple or other temperature sensor to Hotplate temperature controller
3. Cleaning Solution (Piranha)
4. Polisher to polish sample bonding surfaces to at least less than 0.1 um rms roughness
5. Vice to clamp metal and glass sample together with controlled pressure
6. Ammeter (1-10mA)

Procedure

1. Use standard anodic bonding procedure of preparing the samples by cleaning, polishing to ensure adequate smoothness and then placing on the anodic bonding apparatus. Consideration must be given to fabricating the proper electrical contact.
2. Apply the anodic bonding to various permutations, noting the bonding resistance to liquid (hermetic seal), bonding strength and thermal stress (microcracks and other stress indicators).
3. Vary parameters to create the best bond (effective hermetic seal, acceptable thermal stress and bonding strength)

Provided Test Samples

• 7740 Pyrex glass wafers – 2 to 5’’ diameter
• 7052 Pyrex glass wafers – 2 to 5’’ diameter
• Aluminum plate – 2 to 5’’ diameter and 0.25’’ thickness
• Aluminum silicon – 2 to 5’’ diameter and 0.25’’ thickness
• AlSiC – 2 to 5’’ diameter and 0.25’’ thickness
• Kovar plate – 2 to 5’’ diameter and 0.25’’ thickness

Measurement

1. Apply the anodic bonding to the Hermetic seal – Determine, recommend and apply best technique for testing for bonding resistance to liquids. Possible tests from papers worth considering from micro-scale applications are Nitrogen with fluorescent label (Briand, Weber, & Rooij, 2003) and Hellium leak detector less than 5 x10-10 cc He/second (Wallis, 1975)
2. Thermal stress and bonding strength test (Briand, Weber, & Rooij, 2003)