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Coercivity control of Electrolessly Deposited Cobalt Phosphorus

IP.com Disclosure Number: IPCOM000075138D
Original Publication Date: 1971-Aug-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

DePew, JR: AUTHOR

Abstract

Coercivity of cobalt-phosphorus deposited by chemical reduction from baths of the cobalt cation-hypophosphite anion type is dependent upon many variables.

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Coercivity control of Electrolessly Deposited Cobalt Phosphorus

Coercivity of cobalt-phosphorus deposited by chemical reduction from baths of the cobalt cation-hypophosphite anion type is dependent upon many variables.

Plating thickness is normally one of the variables affecting coercivity. By using a specific hypophosphite anion concentration in a citrate complexed bath, in which the ratio of citrate anion to cobalt cation is about 2:1, coercivity can be made practically independent of deposit thickness. For example, utilizing plating baths having compositions of: CoS0(4).7H(2)O 17.5 gm/1

NaH(2)PO(2).H(2)O 17.0 to 30.0 gm/1

Na(3)C(6)H(5)O(7).2H(2)O 35.0 gm/1

(NH(4))(2)SO(4) 66.0 gm/1

pH at 80 degrees C 8.7. certain relationships between coercivity and thickness are noted, as shown in Fig. 1. Curve 11 represents the monatomically decreasing coercivity with increasing thickness relationship, for a bath having a NaH(2)PO(2).H(2)O concentration of 17.0 gm/1. In the high concentration range of reductant concentration, for example, NaH(2)PO(2).H(2)O at 30.0 gm/1, coercivity monatomically increases with increasing thickness as shown by curve 13. However, at 23.5 gm/1 of NaH(2)PO(2).H(2)O, coercivity becomes practically independent of deposit thickness, as indicated by curve 15. It is also noted that coercivity becomes substantially linear at thicknesses greater than 2000 angstroms for the lower and higher reductant baths.

Additionally, it has been previously reported t...