Method for electroless nickel-phosphorous alloy deposition onto flexible substrates

• US 9,089,062 B2
• Filed: 01/21/2013
• Issued: 07/21/2015
• Est. Priority Date: 02/16/2012
• Status: Active Grant

• Current Assignee: Atotech Deutschland GmbH (MKS Instruments Incorporated)
• Original Assignee: Atotech Deutschland GmbH (MKS Instruments Incorporated)
• Inventors: Janssen, Boris Alexander
• Primary Examiner(s): Talbot, Brian K
• Application Number:
  US14/368,878
• Publication Number:
  US 20150009638A1
• Time in Patent Office: 911 Days
• Field of Search: 427/99.5, 427/305, 427/438, 427/443.1
• US Class Current: 1/1
• CPC Class Codes: B05D 5/12 to obtain a coating with specific electrical properties
• CPC Class Codes: C23C 18/16 by reduction or substitution, e.g. electroless plating C23C18/54 takes precedence
• CPC Class Codes: C23C 18/1633 Process of electroless plating
• CPC Class Codes: C23C 18/36 using hypophosphites
• CPC Class Codes: C23C 18/50 with alloys based on iron, cobalt or nickel
• CPC Class Codes: H05K 1/028 Bending or folding regions of flexible printed circuits H05K1/0283 takes precedence
• CPC Class Codes: H05K 1/09 Use of materials for the conductive, e.g. metallic pattern
• CPC Class Codes: H05K 2201/032 Materials
• CPC Class Codes: H05K 3/22 Secondary treatment of printed circuits H05K3/1283 takes precedence; embedding circuits in grooves by pressure H05K3/107
• CPC Class Codes: H05K 3/244 Finish plating of conductors, especially of copper conductors, e.g. for pads or lands selective plating methods H05K3/243; finish plating of conductors made by printing techniques H05K3/246; solder as finish H05K3/3457, e.g. by plating H05K3/3473

Abstract

The present invention relates to a method for electroless deposition of a bendable nickel-phosphorous alloy layer onto flexible substrates such as flexible printed circuit boards and the like. The nickel-phosphorous alloy layer is deposited from an aqueous plating bath comprising nickel ions, hypophosphite ions, at least one complexing agent and a grain refining additive selected from the group consisting of formaldehyde and formaldehyde precursors. The nickel-phosphorous alloy layers obtained have a columnar microstructure oriented perpendicular to the flexible substrate and are sufficiently bendable.

Claims

1. A method for electroless deposition of a bendable nickel-phosphorous alloy layer onto a flexible substrate, comprising, in this order, the steps

i. providing a flexible substrate having attached to at least one side a copper circuitry,

ii. contacting the flexible substrate with an aqueous plating bath comprisingnickel ions,

hypophosphite ions,at least one complexing agent anda grain refining additive selected from the group consisting of formaldehyde and formaldehyde precursors,

wherein the contacting deposits the bendable nickel-phosphorous alloy layer onto the copper circuitry attached to at least one side of the flexible substrate.

2. The method for electroless deposition of a bendable nickel-phosphorous alloy layer according to claim 1 wherein the flexible substrate is a flexible printed circuit board.

3. The method for electroless deposition of a bendable nickel-phosphorous alloy layer according to claim 1 wherein the concentration of nickel ions in the aqueous plating bath ranges from 1 to 18 g/l.

4. The method for electroless deposition of a bendable nickel-phosphorous alloy layer according to claim 1 the concentration of hypophosphite ions ranges from 2 to 60 g/l.

5. The method for electroless deposition of a bendable nickel-phosphorous alloy layer according to claim 1 wherein the concentration of the at least one complexing agent ranges from 1 to 200 g/l.

6. The method for electroless deposition of a bendable nickel-phosphorous alloy layer according to claim 1 wherein the at least one complexing agent is selected from the group consisting of carboxylic acids, hydroxycarboxylic acids, and aminocarboxylic acids.

7. The method for electroless deposition of a bendable nickel-phosphorous alloy layer according to claim 1 wherein the concentration of the grain refining additive ranges from 0.001 to 1.0 g/l.

8. The method for electroless deposition of a bendable nickel-phosphorous alloy layer according to claim 1 wherein the formaldehyde precursor is selected from the group consisting of acetals, hemiacetals, aminals, and N,O-acetals.

9. The method for electroless deposition of a bendable nickel-phosphorous alloy layer according to claim 1 wherein the formaldehyde precursor is selected from the group consisting of dimethylol glycol, sodium hydroxymethylglycinate, 1,3-bis(hydroxymethyl) 5,5-dimethyl-imidazolidine-2,4-dione, 1,3,5,7-tetraazatricyclo[3.3.1.1^3,7]decane, benzylhemiformal, 2-bromo-2-nitropropane-1,3-diol, 5-bromo-5-nitro-1,3-dioxane, 1,3-bis(hydroxyl-methyl)-1-(1,3,4-tris(hydroxymethyl)-2,5-dioxoimidazolidin-4-yl)urea, 1,1′

-methylenebis{3-[1-(hydroxymethyl)-2,5-dioxoimidazolidin-4-yl]-urea}, 3,5,7-triaza-1-azoniatricyclo-[3.3.1.1^3,7]-decane-1-(3-chloro-2-propenyl)-chloride, tetramethylolglycoluril, 1,3-bis(hydroxymethyl)2-imidazolidinone, 1,3-bis(hydroxyl-methyl)urea, 2,2,2-trichloroethane-1,1-diol, and 5,5-dimethyl-1,3-dioxane.

10. The method for electroless deposition of a bendable nickel-phosphorous alloy layer according to claim 1 wherein the aqueous plating bath is held at a temperature between 40 and 95°

C. during deposition of the nickel-phosphorous alloy.

11. The method for electroless deposition of a bendable nickel-phosphorous alloy layer according to claim 1 wherein the flexible substrate is contacted with the aqueous plating bath for 1 to 60 min.