Korean Institute of Surface Engineering

pISSN : 1225-8024 | eISSN : 3399-8403


공학

한국표면공학회지 (55권2호 102-119)

Deposition behavior of cyanide-free electroless Au plating solution using thiomalic acid as complexing agent and aminoethanethiol as reducing agent and characteristics of plated Au film

티오말산을 착화제로 하고 아미노에탄티올을 환원제로 하는 비시안계 무전해 Au 도금액의 석출 거동 및 도금 특성

한재호a,*, 김동현b
Jaeho Hana,*, DongHyun Kimb

a주식회사 이씨텍, b주식회사 엠에스씨
aECTECH Co., Ltd., Incheon, 226165, Republic of Korea bMSC Co., Ltd., Incheon, 21698, Republic of Korea

DOI : 10.5695/JSSE.2022.55.2.102

Abstract

Gold plating is used as a coating of connecter in printed circuit boards, ceramic integrated circuit packages, semiconductor devices and so on, because the film has excellent electric conductivity, solderability and chemical properties such as durability to acid and other chemicals. As increasing the demand for miniaturization of printed circuit boards and downsizing of electronic devices, several types of electroless gold plating solutions have been developed. Most of these conventional gold plating solutions contain cyanide compounds as a complexing agent. The gold film obtained from such baths usually satisfies the requirements for electronic parts mentioned above. However, cyanide bath is highly toxic and it always has some possibility to cause serious problems in working environment or other administrative aspects. The object of this investigation was to develop a cyanide-free electroless gold plating process that assures the high stability of the solution and gives the excellent solderability of the deposited film. The investigation reported herein is intended to establish plating bath composition and plating conditions for electroless gold plating, with thiomalic acid as a complexing agent. At the same time, we have investigated the solution stability against nickel ion and pull strength of solder ball. Furthermore, by examining the characteristics of the plated Au plating film, the problems of the newly developed electroless Au plating solution were improved and the applicability to various industrial fields was examined. New type electroless gold-plating bath which containing thiomalic acid as a complexing agent showing so good solution stability and film properties as cyanide bath. And this bath shows the excellent stability even if the dissolved nickel ion was added from under coated nickel film, which can be used at the neutral pH range.

Keywords

cyanide-free plating; electroless Au plating; Immersion plating; Autocatalytic plating; complexing agent; reducing agent; deposition rate; solderability.