-
- 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
PCB Surface Preparation Before Solder Mask on Non-copper Finishes
April 8, 2020 | Nikolaus SchubkegelEstimated reading time: 1 minute
A circuit board is made of copper. Usually, final finishes are applied after the solder mask process. In some cases, for special applications, the final finish may be applied before solder mask. In this case, we have solder mask on ENIG or galvanic nickel-gold. It is also possible to have tin or tin-lead under solder mask; this was an old technology that no longer plays a role today.
The methods for surface preparation of PCBs with copper are very well known. All these methods of pretreatment, chemically or mechanically, increase the surface roughness and ensure good solder mask adhesion. Many technical papers provide details on this topic. Yet, there is almost no literature available on the topic of surface preparation of ENIG or galvanic nickel-gold.
The main criterion for copper preparation is to achieve the desired level of surface roughness. But the gold surface is even, glossy, and very thin. I don’t recommend increasing the surface roughness of the gold, as the gold surface itself will be destroyed. As a consequence, mechanical methods—such as brushing, pumicing, or jet scrubbing—are not applicable to gold.
In addition, chemical microetches, such as mixtures of acids with oxidants, are not recommended. The gold surface generally resists these blends, but due to the fact that the gold thickness is just 0.03–0.07 µm after ENIG, the result is that the gold surface is porous. Acids and oxidants can attack the less noble metals beneath the gold with a negative impact on solderability and reliability. Even after galvanic gold plating with a higher thickness, the surface is porous. In addition, the edges of the tracks are generally not plated, allowing another point of entry for the oxidants.
Nickel-gold Surface (ENIG, ENIIPIG, ENIPIG, Galvanic Ni-Au)
PCBs with a nickel-gold finish can be processed directly over solder mask coating. But to do so, the rinse process following the nickel-gold plating step is good. The rinse water should not exceed 10 µS conductivity. The hold time between ENIG plating and solder mask coating must be held to less than one hour, as well.
To read this entire article, which appeared in the February 2020 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.