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Method of forming a lead-free bump and a plating apparatus therefor

Inactive Publication Date: 2005-12-22
SHIMOYAMA MASASHI +4
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0010] It has also been found that contrary to the expectation that a decrease in the Ag content of a plated alloy film from the Ag content of the Sn—Ag eutectic composition will incur a rise in the reflow temperature, the melting point of the alloy film does not increase significantly with a decrease in the Ag content, that is, it is not necessary to significantly raise the reflow temperature.

Problems solved by technology

With printing, however, there is a limit in its approach to fine pitches through the use of a metal mask.
However, the formation of bumps by electroplating has the problem that upon reflowing of bumps, voids can be formed in the bumps.
The formation of voids is particularly marked with bumps of an Sn—Ag alloy, lowering the reliability of the bumps.

Method used

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  • Method of forming a lead-free bump and a plating apparatus therefor
  • Method of forming a lead-free bump and a plating apparatus therefor
  • Method of forming a lead-free bump and a plating apparatus therefor

Examples

Experimental program
Comparison scheme
Effect test

example 1

(1) Preparation of Sn—Ag Bump:

[0067] A resist was applied to a thickness of 120 μm on a wafer in such a manner that a number of holes having an opening size of 100 μm are formed, thereby preparing a sample. The plating area of the sample was 149.63 cm2. Plating of the sample was carried out by the following steps under the following conditions.

[0068] (Plating Steps)

[0069] Degassing (10 min)→Pre-cleaning with 10% sulfuric acid (1 min)→Copper plating→Water-cleaning→Ni plating Water-cleaning→Sn—Ag alloy plating

[0070] (Plating Conditions)

[0071] (a) Cu Plating

[0072] Plating bath composition:

Cu2+220g / LH2SO4200g / LHCl5mL / LAdditive5mL / L

[0073] Plating temperature: 25° C.

[0074] Stirring: mechanical stirring (paddle stirring speed 10 m / min)

[0075] Circulation of plating solution: flow rate 2.5 L / min

[0076] Electrode: copper anode, interpolar distance about 7.5 mm, anode mask ø 250 mm

[0077] Cathode current density (total current): 5 A / dm2 (7.48 A)

[0078] Plating thickness: 2 μm

[0079]...

example 2

[0102] Alloy plating was carried out with various proportions of Ag to the total metal in an alloy plating solution, various current densities upon plating and various current application methods, and the respective plated alloy films were subjected to reflowing at 238° C. For the bump thus obtained, measurement of the Ag content and observation of the shape of bump and the presence of voids were carried out in the same manner as in Example 1. The results are shown in table 1.

TABLE 1PlatingPlating conditionsVoltageBumpVoidBallsolutionCurrent densityapplicationAg contentpresent (x)formationAg / Sn (%)(A / dm2)method(wt %)absent (∘)at 238° C.4.33DC5.2x∘4.43DC6.4x∘4.420CHOP4.0x∘4.33DC7.7x∘4.320CHOP5.1x∘1.33DC1.8∘∘1.38DC0.9∘x1.320CHOP1.4∘x2.23DC3.4x∘2.220CHOP2.1∘∘4.13DC4.9x∘3.120CHOP2.9∘∘3.110CHOP3.6x∘3.13DC5.0x∘3.23DC5.8x∘3.220CHOP2.7x∘2.33DC3.5x∘2.320CHOP2.6∘∘

Note:

DC denotes direct current plating, and CHOP denotes intermittent plating

[0103] As apparent from the results shown in Table...

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Abstract

The present invention relates to a lead-free bump with suppressed formation of voids, obtained by reflowing a plated film of Sn—Ag solder alloy having an adjusted Ag content, and a method of forming the lead-free bump. The lead-free bump of the present invention is obtained by forming an Sn—Ag alloy film having a lower Ag content than that of an Sn—Ag eutectic composition by plating and reflowing the plated alloy film.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a lead-free bump and a method of forming the same, and more particularly to a lead-free bump with suppressed formation of voids, obtained by reflowing a plated film of Sn—Ag solder alloy having an adjusted Ag content, and a method of forming the lead-free bump, and also to a plating apparatus for forming such a lead-free bump. [0003] 2. Description of the Related Art [0004] In surface mounting technology of semiconductor devices or the like, it is very important to carry out soldering with high reliability. Although an eutectic solder containing lead (Sn:Pb=63:37) has heretofore been used widely in soldering, in the light of environmental contamination and because of the problem of α-rays generation from lead, development of lead-free soldering is under way. [0005] For example, lead-free soldering by means of printing or electroplating is being studied. With printing, however, there ...

Claims

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Application Information

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IPC IPC(8): C25D3/60C25D5/50C25D21/14H01L21/288H01L21/48H01L21/60H01L23/485H01L23/498H05K3/34
CPCC25D3/60H01L2924/014C25D21/14H01L21/2885H01L21/4853H01L23/49816H01L24/11H01L24/12H01L2224/13099H01L2924/01002H01L2924/01004H01L2924/01013H01L2924/01015H01L2924/01018H01L2924/01022H01L2924/01027H01L2924/01029H01L2924/01033H01L2924/01039H01L2924/01047H01L2924/01074H01L2924/01078H01L2924/01082H01L2924/01092H01L2924/01322H01L2924/14H05K3/3436H05K3/3463H01L2924/01005H01L2924/01006H01L2924/01019H01L2924/01023H01L2924/01076C25D5/505H01L2224/05573H01L2224/05568H01L2224/056H01L2224/11462H01L24/05H01L2924/00014
Inventor SHIMOYAMA, MASASHIYOKOTA, HIROSHIKIUMI, REIKURIYAMA, FUMIOSAITO, NOBUTOSHI
Owner SHIMOYAMA MASASHI
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