Tin electrodeposits having properties or characteristics that minimize tin whisker growth

a technology of tin electrodes and tin whisker, which is applied in the direction of printed circuit aspects, conductive pattern reinforcement, and semiconductor/solid-state device details, etc. it can solve the problems of reducing the efficiency of electronic circuits, and reducing the occurrence of so as to minimize or prevent tin whisker formation or growth, and the effect of less prone to tin whisker formation or

Inactive Publication Date: 2007-01-11
TECHNIC INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0018] The invention also relates to an improvement in a tin plated electronic component that includes a copper surface upon which a fine grained tin deposit is present. The improvement comprises minimizing or preventing tin whisker formation or growth by providing the tin deposit with one or more of (a) a fine grained structure so that the tin deposit is less prone to tin whisker formation or growt...

Problems solved by technology

When pure tin is used and is applied to a copper or copper alloy substrate, the resulting deposit suffers from interdiffusion of base material copper into the tin deposit and subsequent formation of copper-tin intermetallic compounds.
While these copper-tin compounds can be brittle and may impair the usefulness of the tin coated component, their presence also results in compressive stress formation in the tin deposit.
The presence of such whiskers is undesirable due to the very fine line definition required for modern circuitry, since these whiskers can form both electrical shorts and electrical bridges across insulation spaces between conductors.
The whiskers may create shorts or introduce failures into electronic circuitry.
However, this approach does not fully address or necessarily ...

Method used

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Examples

Experimental program
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Effect test

example 2

[0037] Tin was electroplated from a mixed acid sulfate electrolyte (“Technistan EP” from Technic Inc) onto a Cu alloy substrate (Cu99.85%, Sn0.15%) at a current density of 150 A / ft2 for a period of time sufficient to obtain an average of 10 μm tin deposit thickness. The grain size of the tin deposit was measured and found to be 1-2 microns avg. grain diameter. The deposit was subjected to high temperature & humidity (HTH) testing of 155 deg C. for 16 hrs (in an uncontrolled humidity environment) followed by 97 deg C. / 99% relative humidity (RH) conditions for 8 hrs. This deposit was measured by SERA and the tin oxide thickness on the surface was found to be 68 angstroms. This deposit was subjected to the high heat & humidity whisker test condition specified by JEDEC STANDARD JESD22A121 “Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes”, specifically: high temperature / humidity storage of 60° C. / 90% RH for 3000 hrs. Upon completion of the whisker test method, the maximum ...

example 3

[0038] Tin was electroplated from a mixed acid sulfate electrolyte (“Technistan EP” from Technic Inc. which also contained a phosphorous compound at a concentration of 4 g / l in the plating solution as described in U.S. patent application Ser. No. 2004 / 0099340 A1) onto a Cu alloy substrate (Cu99.85%, Sn0.15%) at a current density of 150 A / ft2 for a period of time sufficient to obtain an average of 10 μm tin deposit thickness. The grain size of the tin deposit was measured and found to be 1-2 microns avg. grain diameter. The deposit was subjected to high temperature & humidity (HTH) testing of 155 deg C. for 16 hrs (in an uncontrolled humidity environment) followed by 97 deg C. / 99% relative humidity (RH) conditions for 8 hrs. This deposit was measured by SERA and the tin oxide thickness on the surface was found to be 43 angstroms. This deposit was subjected to the high heat & humidity whisker test condition specified by JEDEC STANDARD JESD22A121 “Measuring Whisker Growth on Tin and Ti...

example 4

[0039] Tin was electroplated from a mixed acid sulfate electrolyte (“Technistan EP” from Technic Inc. which also contained a phosphorous compound at a concentration of 4 g / l in the plating solution as described in U.S. patent application Ser. No. 2004 / 0099340 A1) onto a Cu alloy substrate (Cu99.85%, Sn0.15%) at a current density of 150 A / ft2 for a period of time sufficient to obtain an average of 10 μm tin deposit thickness. After tin plating the substrate was placed into a solution containing a phosphorous compound (phosphoric acid@70 ml / l)+sodium gluconate at 50 g / l. The grain size of the tin deposit was measured and found to be 1-2 microns avg. grain diameter. The deposit was subjected to high temperature & humidity (HTH) testing of 155 deg C. for 16 hrs (in an uncontrolled humidity environment) followed by 97 deg C. / 99% relative humidity (RH) conditions for 8 hrs. This deposit was measured by SERA and the tin oxide thickness on the surface was found to be 35 angstroms. This depo...

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Abstract

A method of reducing tin whisker formation by creating a tin deposit which is inherently less prone to tin whisker formation or growth facilitated by oxide presence or corrosion reactions on the tin deposit surface. This is obtained by one or more of: (i) the deposition of a fine-grained tin deposit having an average grain diameter in the range of 0.05 to 5 microns; (ii) a phosphorous compound in the solution that is used to electroplate the tin deposit so that that the deposit incorporates trace amounts of phosphorous which in turn reduces tin whisker formation by preventing surface oxides even when exposed to heat or humidity; or (iii) a phosphorous compound, mercaptan, or organic or organo-metallic compound in a solution that applies a protective coating to the surface of a previously electroplated tin deposit, wherein the protective coating acts to minimize or prevent oxide formation or corrosion of the tin deposit during exposure to heat or humidity. Such tin deposits containing 80% to 100% by weight of tin exhibit minimal to no tin whisker growth.

Description

[0001] This application claims the benefit of U.S. provisional application No. 60 / 698,550 filed Jul. 11, 2005, the entire content of which is expressly incorporated herein by reference thereto.FIELD OF INVENTION [0002] The present invention relates to a method for depositing tin in a manner to reduce, minimize or prevent tin whisker growth from such deposits, as well as to electroplated components formed by such a method. More particularly, the invention relates to a modification or treatment of the deposit to render it less prone to whisker growth. In particular, prevention of oxide formation and / or corrosion reactions on the tin deposit surface or post treatment of the deposit surface has been found to be effective for this purpose. BACKGROUND OF THE INVENTION [0003] The use of a tin or tin alloy electroplated deposit has become increasingly important in fabricating electronic circuits, electronic devices and electrical connectors because of the benefits that such deposits provide...

Claims

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Application Information

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IPC IPC(8): C25D3/30
CPCC25D3/30C25D3/32C25D5/48H05K3/244H05K3/282H01L2924/0002H05K2201/0769H01L2924/00H01L23/495H05K3/24
Inventor SCHETTY, ROBERT A. III
Owner TECHNIC INC
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