# US 8,740,047 B2 · Method of manufacturing electronic apparatus, electronic component-mounting board, and method of manufacturing the same

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- Number: US 8,740,047 B2
- Document ID: US8740047B2
- Status: Granted
- Kind: B2
- Application number: 14/023,608
- Filed: 2013-09-11
- Published: 2014-01-09
- Granted: 2014-06-03
- Earliest claimed: 2008-11-28
- Assignees: Fujitsu Limited
- Applicants: Fujitsu Limited
- Inventors: Seiki Sakuyama; Toshiya Akamatsu; Masateru Koide
- Web page: https://patentgrep.com/patent/US8740047B2

## CPC

- H05K 1/0271: {Arrangements for reducing stress or warp in rigid printed circuit boards, e.g. caused by loads, vibrations or differences in thermal expansion}
- H05K 3/3436: {having an array of bottom contacts, e.g. pad grid array or ball grid array components}
- H05K 3/346: Solder materials or compositions specially adapted therefor
- H10W 70/098: {Applying pastes or inks, e.g. screen printing (H10W70/095 takes precedence)}
- H10W 70/099: {Connecting interconnections to insulating or insulated package substrates, interposers or redistribution layers}
- H10W 74/012: {of encapsulations on active surfaces of flip-chip devices, e.g. forming underfills}
- H10W 74/15: on active surfaces of flip-chip devices, e.g. underfills
- H05K 3/3485: Application of solder paste, slurry or powder (using printing techniques to form the desired conductive pattern of the printed circuit by applying conductive material H05K3/12)
- H05K 2201/10977: Encapsulated connections
- H10W 72/01251: {Changing the shapes of bumps}
- H10W 72/072: {of bump connectors}
- H10W 72/07236: {Soldering or alloying}
- H10W 72/07255: {changes in materials}
- H10W 72/073: {of die-attach connectors}
- H10W 72/241: {Dispositions, e.g. layouts}
- H10W 72/252: {comprising solid metals or solid metalloids, e.g. PbSn, Ag or Cu}
- H10W 72/2524: {Eutectic alloys}
- H10W 90/701: {characterised by the relative positions of pads or connectors relative to package parts}
- H10W 90/724: {between a chip and a stacked insulating package substrate, interposer or RDL}
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A method of manufacturing an electronic apparatus including a first and a second components, includes: forming a first solder bump on one of the first component and the second component; forming a second solder bump on the other one of the first component and the second component; bringing the first solder bump into contact with the second solder bump at a temperature higher than the liquidus temperature of any of the first and the second solder bumps such that the first and the second solder bumps are fused together to form a solder joint of an alloy having a lower liquidus temperature than any of the first and the second solder bumps; and solidifying the solder joint between the first and the second component.

## Claims

### Claim 1

An electronic component mounting board comprising:
a circuit board;
an electrode formed on the circuit board;
a first solder bump formed on the electrode, the first solder bump containing Bi in the range from 85 to 90 wt % as a base component and containing Sn; and
a solder layer formed on the first solder bump, the solder layer containing Sn having a larger weight ratio than the first solder.

### Claim 2 (depends on 1)

The electronic component mounting board according to claim 1, wherein
the first solder bump further contains at least one metal selected from a group consisting of Au, Ag, Cu, Sb, Ni, Ge, and Zn in the range from 0.01 to 1 wt. %.

### Claim 3 (depends on 1)

The electronic component mounting board according to claim 1, wherein
the solder layer contains Sn higher than or equal to 90 wt. %.