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Electrode Using Mixed Sizes of Powder

IP.com Disclosure Number: IPCOM000077828D
Original Publication Date: 1972-Sep-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Tu, KN: AUTHOR

Abstract

The amount of porosity and the interconnections between them in sintered electrodes can be reduced, by using mixed sizes of Ag (or Ag alloy) powder as the paste material. A method is described herein to reduce the porosity in the sintered product, by using mixed sizes of powder instead of high temperature.

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Electrode Using Mixed Sizes of Powder

The amount of porosity and the interconnections between them in sintered electrodes can be reduced, by using mixed sizes of Ag (or Ag alloy) powder as the paste material. A method is described herein to reduce the porosity in the sintered product, by using mixed sizes of powder instead of high temperature.

Microstructure of electrodes shows a lot of interconnected porosities. These porosities have been estimated to occupy as high as 20% of the total volume of the electrode. They not only serve as deep penetration paths for the liquid solder, but also provide a much larger reaction interface between solder and electrode during processing. Such reaction has been found undesirable because it leads to the corrosion of Ag.

Heretofore, the electrode has been sintered at higher temperature (from 825 degrees C to 900 degrees C) in order to reduce the amount of porosity.

Ag (or Ag alloy) powder of approx. 3 microns diameter and Pd powder of approx. 500 angstroms diameter were used. Since these two kinds of powder are far apart in their sizes, Pd powder will stick to each Ag powder and form a coating layer during mixing them together, as shown in Fig. 1. The packing of such powder will leave a large volume of voids among them.

By using mixed sizes of Ag (or Ag alloy) powder, e.g., half of 5 Mu and half of 1 Mu powder, the smaller powder serves to fill in the voids among the larger ones, as shown in Fig. 2. It not only gives higher pack...