-
- News
- Books
Featured Books
- pcb007 Magazine
Latest Issues
Current IssueThe Growing Industry
In this issue of PCB007 Magazine, we talk with leading economic experts, advocacy specialists in Washington, D.C., and PCB company leadership to get a well-rounded picture of what’s happening in the industry today. Don’t miss it.
The Sustainability Issue
Sustainability is one of the most widely used terms in business today, especially for electronics and manufacturing but what does it mean to you? We explore the environmental, business, and economic impacts.
The Fabricator’s Guide to IPC APEX EXPO
This issue previews many of the important events taking place at this year's show and highlights some changes and opportunities. So, buckle up. We are counting down to IPC APEX EXPO 2024.
- Articles
- Columns
Search Console
- Links
- Events
||| MENU - pcb007 Magazine
Characteristics of New Electroless Au/Pd/Au Process for Fine-Line Applications
July 30, 2018 | Tetsuya Sasamura, Ph.D., Tatsushi Someya, et al.Estimated reading time: 2 minutes
Abstract
The characteristics of electroless gold/palladium/gold (IGEPIG) deposit, which has been newly developed for fine-line application as electroless nickel-phosphorus (EN) free, has been compared with that of conventional electroless Ni-P/Pd/Au (ENEPIG) deposit and electroless Pd/Au (EPIG) deposit.
The IGEPIG deposit had excellent wire bonding reliability (WBR) compared with other deposits even if the gold thickness of IGEPIG at the top surface was less than that of the EPIG and ENEPIG deposits. From the results of AES analysis after heat treatment for 16 hours at 175°C, Pd and Cu was hardly detected at the top surface of Au, and it indicated that IGEPIG deposit prevented Cu and Pd diffusion. Also, it was revealed by EBSD (electron back scatter diffraction pattern) analysis that Pd grain size on Au was about ten times bigger than those on a Pd-activated copper surface. It was assumed that the prevention of Pd and Cu diffusion was relative with bigger Pd grain size of IGEPIG deposit.
Solder joint reliability (SJR) of IGEPIG deposit with SAC305 (Sn-3.0Ag-0.5Cu) solder ball is better than that of EPIG deposit, and almost the same with that of ENEPIG deposit. IGEPIG deposit had excellent pattern ability, because of no EN deposit and Pd activator process compared with ENEPIG and EPIG.
Introduction
Recently, the pattern of copper lines and spaces on PCBs has become narrower with the miniaturization of the integrated circuit. If using a conventional ENEPIG process with a nickel thickness of 5–6 µm, it will be easy to cause short circuits between each pattern line because of over-plating. Electroless nickel plating grows both vertically and horizontally, thus increasing the chance of bridging traces when the distance between traces is small. Conversely, the electroless palladium and immersion gold plated deposits are normally quite thin which reduces chance of metal bridging.
In addition, there is the requirement for reducing the EN deposit because less electronic signal loss is necessary for RF (radio frequency) module. As an EN-less or EN-free process, the electroless thin Ni/Pd/Au (thin ENEPIG) or EPIG process has been proposed. However, the pattern ability of thin ENEPIG has some restrictions for extremely fine patterns because a Pd activator process is used. In some cases, residual Pd activator (catalyst) could remain between traces, even with thorough rinsing, and help to serve as sites for extraneous metal plating between traces. And the WBR of EPIG after heat treatment (HT) was inadequate, especially when the gold thickness is less than 0.1 µm. The main factor is that WBR becomes worse by HT is Pd and Cu diffusion to the top surface of Au.
After much examination, we developed the IGEPIG process without Pd activator or any EN deposit as a new process which has excellent WBR and pattern ability. In this study, we introduce the performance of the IGEPIG deposit.
All three finishes discussed are wet plating processes, depositing metals from aqueous solutions. ENEPIG utilizes both immersion reactions (palladium catalyst and immersion gold) and electroless reactions (electroless nickel and electroless palladium). EPIG utilizes immersion reactions (palladium catalyst and immersion gold) and one electroless palladium step. IGEPIG utilizes two immersion reactions (an initial immersion gold and final immersion gold) and one electroless palladium step. All three processes utilize the same aqueous chemical pre-treatment of cleaning, copper micro-etching, and acid dipping.
To read the full version of this article which originally appeared in the June 2018 issue of PCB007 Magazine, click here.
Suggested Items
Indium Corporation Expert to Present on Pb-Free Solder for Die-Attach in Discrete Power Applications
04/30/2024 | Indium CorporationIndium Corporation Product Manager – Semiconductor Dean Payne will present at the Advanced Packaging for Power Electronics conference, hosted by IMAPS, held May 8-9 in Woburn, Massachusetts, USA.
Taiyo Circuit Automation Installs New DP3500 into Fuba Printed Circuits, Tunisia
04/25/2024 | Taiyo Circuit AutomationTaiyo Circuit Automation is proud to be partnered with Fuba Printed Circuits, Tunisia part of the OneTech Group of companies, a leading printed circuit board manufacturer based out of Bizerte, Tunisia, on their first installation of Taiyo Circuit Automation DP3500 coater.
Vicor Power Orders Hentec Industries/RPS Automation Pulsar Solderability Testing System
04/24/2024 | Hentec Industries/RPS AutomationHentec Industries/RPS Automation, a leading manufacturer of selective soldering, lead tinning and solderability test equipment, is pleased to announce that Vicor Power has finalized the purchase of a Pulsar solderability testing system.
AIM Solder’s Dillon Zhu to Present on Ultraminiature Soldering at SMTA China East
04/22/2024 | AIMAIM Solder, a leading global manufacturer of solder assembly materials for the electronics industry, is pleased to announce that Dillon Zhu will present on the topic: Ultraminiature Soldering: Techniques, Technologies, and Standards at SMTA China East. This event is being held at the Shanghai World Expo Exhibition & Convention Center from April 24-25.
AIM to Highlight NC259FPA Ultrafine No Clean Solder Paste at SMTA Wisconsin Expo & Tech Forum
04/18/2024 | AIMAIM Solder, a leading global manufacturer of solder assembly materials for the electronics industry, is pleased to announce its participation in the upcoming SMTA Wisconsin Expo & Tech Forum taking place on May 7 at the Four Points by Sheraton | Milwaukee Airport, in Milwaukee, Wisconsin.