{"id":1891,"date":"2026-10-01T16:00:00","date_gmt":"2026-10-01T08:00:00","guid":{"rendered":"https:\/\/www.jingpengpcb.com\/?p=1891"},"modified":"2026-10-02T19:38:01","modified_gmt":"2026-10-02T11:38:01","slug":"enig-process-guide","status":"publish","type":"post","link":"https:\/\/www.jingpengpcb.com\/en\/blog\/enig-process-guide\/","title":{"rendered":"What Should Be Considered in the Chemical Nickel-Gold Plating Process? Causes and Solutions for Color Variations and Rough Plating Surfaces"},"content":{"rendered":"<p>Chemical nickel-gold plating is a versatile wet process that combines solderability, electrical conductivity, wire bonding capability, and heat dissipation in a single process. It is widely used in the manufacture of PCBs (Printed Circuit Boards) and provides critical support for the performance and reliability of electronic products. However, despite the importance of the chemical nickel-gold plating process, various quality issues often arise in practical applications. This article will explore common issues with the chemical nickel-gold plating process and their corresponding solutions.<br \/>\n<img loading=\"lazy\" decoding=\"async\" width=\"1200\" height=\"675\" class=\"alignnone size-large wp-image-12112\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2025\/10\/enepig.jpg\" alt=\"Guide to the Chemical Nickel-Palladium-Gold Plating Process\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2025\/10\/enepig.jpg 1200w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2025\/10\/enepig-300x169.jpg 300w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2025\/10\/enepig-1024x576.jpg 1024w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2025\/10\/enepig-768x432.jpg 768w\" sizes=\"auto, (max-width: 1200px) 100vw, 1200px\" \/><\/p>\n<h2>Table of Contents<\/h2>\n<ol>\n<li><strong>Color Difference Issues<\/strong>\n<ul>\n<li>Analysis of the Causes<\/li>\n<li>Solution<\/li>\n<\/ul>\n<\/li>\n<li><strong>Rough coating<\/strong>\n<ul>\n<li>Analysis of the Causes<\/li>\n<li>Solution<\/li>\n<\/ul>\n<\/li>\n<li><strong>Exposed Copper<\/strong>\n<ul>\n<li>Analysis of the Causes<\/li>\n<li>Solution<\/li>\n<\/ul>\n<\/li>\n<li><strong>Golden Peel<\/strong>\n<ul>\n<li>Analysis of the Causes<\/li>\n<li>Solution<\/li>\n<\/ul>\n<\/li>\n<li><strong>Poor adhesion between nickel and copper<\/strong>\n<ul>\n<li>Analysis of the Causes<\/li>\n<li>Solution<\/li>\n<\/ul>\n<\/li>\n<li><strong>Reaction Mechanisms of Chemical Gold and Chemical Nickel<\/strong>\n<ul>\n<li><a href=\"\/en\/capabilities\/pcb-surface-finishes\/\">Transformation into Gold<\/a>the process<\/li>\n<li>The Nickel Electrolysis Process<\/li>\n<\/ul>\n<\/li>\n<li><strong>Control and Management of the Chemical Nickel-Gold Plating Process<\/strong>\n<ul>\n<li>Preprocessing<\/li>\n<li>Chemical Nickel Plating Tank Management<\/li>\n<li>Chemical Bath Management<\/li>\n<li>Post-processing<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<h2>Color Difference Issues<\/h2>\n<h3>Analysis of the Causes<\/h3>\n<ol>\n<li>The nickel tank is contaminated or has reached the end of its service life, and there is an excessive buildup of organic matter in the tank solution.<\/li>\n<li>There are too many nickel ions in the gold bath.<\/li>\n<li>The palladium concentration in the activation tank is insufficient.<\/li>\n<\/ol>\n<h3>Solution<\/h3>\n<ol>\n<li>Replace the nickel tank to eliminate the source of contamination.<\/li>\n<li>Analyze the nickel content in the gold bath; if it exceeds 0.5 g\/L, replace the bath solution promptly.<\/li>\n<li>Slightly increase the palladium concentration.<\/li>\n<\/ol>\n<h2>Rough coating<\/h2>\n<h3>Analysis of the Causes<\/h3>\n<ol>\n<li>The nickel bath is too reactive.<\/li>\n<li>The filtering is insufficient, and the amplitude of the board's vibration frequency is too low.<\/li>\n<li>Inadequate pretreatment.<\/li>\n<\/ol>\n<h3>Solution<\/h3>\n<ol>\n<li>Slightly lower the temperature, concentration, and pH.<\/li>\n<li>Enhance filtration; it is best to use a 5-micron filter cartridge for edge filtration. At the same time, increase the vibration frequency and amplitude of the plate to remove hydrogen from its surface.<\/li>\n<li>Strengthen pretreatment and check whether the copper surface is rough to prevent the receipt of defective materials.<\/li>\n<\/ol>\n<h2>Exposed Copper<\/h2>\n<h3>Analysis of the Causes<\/h3>\n<ol>\n<li>There is a foreign object on the back.<\/li>\n<li>Incomplete development of the wet film and incomplete rinsing.<\/li>\n<li>Insufficient adhesion of the palladium.<\/li>\n<li>The rinsing time after activation is too long.<\/li>\n<li>Imbalance in the management of the nickel tank solution.<\/li>\n<\/ol>\n<h3>Solution<\/h3>\n<ol>\n<li>Increase scrubbing and tracking the source of foreign objects.<\/li>\n<li>Review and improve the wet film process.<\/li>\n<li>Control the concentration of Cu\u00b2\u207a in the degreasing tank (less than 7 g\/L).<\/li>\n<li>Shorten the rinse time (15 seconds).<\/li>\n<li>Add chemicals strictly according to the specified proportions, and adjust based on the test results.<\/li>\n<\/ol>\n<h2>Golden Peel<\/h2>\n<h3>Analysis of the Causes<\/h3>\n<ol>\n<li>The phosphorus content in the nickel layer is too high.<\/li>\n<li>Passivation of the nickel layer.<\/li>\n<\/ol>\n<h3>Solution<\/h3>\n<ol>\n<li>Use the AA method to analyze phosphorus content, and appropriately reduce the amount of reducing agent added; if that does not work, replace the bath solution.<\/li>\n<li>Avoid exposing the nickel coating to air for too long.<\/li>\n<\/ol>\n<h2>Poor adhesion between nickel and copper (nickel\/copper delamination)<\/h2>\n<h3>Analysis of the Causes<\/h3>\n<ol>\n<li>The copper surface is dirty.<\/li>\n<li>Preprocessing failed.<\/li>\n<\/ol>\n<h3>Solution<\/h3>\n<ol>\n<li>Strengthen pretreatment.<\/li>\n<li>Analyze the Cu+ concentration in the solutions in each tank prior to processing; if the concentration exceeds the limit, replace the solution.<\/li>\n<\/ol>\n<h2>Reaction Mechanisms of Chemical Gold and Chemical Nickel<\/h2>\n<h3>The Process of Transmutation<\/h3>\n<p>When the nickel layer on the PCB surface is placed in the gold plating bath, the nickel layer is attacked by the bath solution, causing nickel ions to dissolve. These dissolved nickel ions are captured by gold cyanide ions, which then deposit a layer of gold onto the nickel surface.<\/p>\n<p>Reaction Mechanism:<\/p>\n<ul>\n<li>Ni \u2192 Ni\u00b2\u207a + 2e<\/li>\n<li>Au(CN)2- + e \u2192 Au + 2CN-<\/li>\n<\/ul>\n<p>The dissolution of one nickel atom can lead to the deposition of two gold atoms. The gold layer contains many open pores, so even though the surface is covered by a layer of gold, the open pores on the nickel surface continue to dissolve, causing the gold layer to continue depositing\u2014albeit at a gradually slower rate.<\/p>\n<h3>The Nickel Electrolysis Process<\/h3>\n<p><strong>Nickel salts:<\/strong> The main component is nickel sulfate, though it also contains nickel chloride and nickel acetate. <strong>Reducing agent:<\/strong> Sodium dihydrogen phosphite (NaH\u2082PO\u2082).<\/p>\n<p><strong>Reaction Mechanism:<\/strong><\/p>\n<ol>\n<li>The hypophosphite ion in sodium dihydrogen hypophosphite is hydrolyzed and oxidized to form a phosphate ion, while simultaneously releasing two active hydrogen atoms that are adsorbed onto the copper-backed palladium surface.<\/li>\n<li>Nickel ions are rapidly reduced on the activated palladium surface and deposited as metallic nickel.<\/li>\n<li>Under the action of catalytic hydrogen, a portion of the hypophosphite ions release phosphorus atoms, which are deposited in the nickel layer.<\/li>\n<li>Under catalytic conditions, some hypophosphite ions will oxidize on their own and generate hydrogen gas, which is released from the nickel surface.<\/li>\n<\/ol>\n<h2>Control of Each Process Step in Chemical Nickel-Gold Plating<\/h2>\n<h3>Preprocessing<\/h3>\n<ol>\n<li><strong>Brushing and Polishing:<\/strong> Gently brush the board surface with a high-mesh nylon brush (1,000\u20131,200 mesh) to remove dirt and oxides. After brushing, be sure to wear clean gloves when handling the board to prevent spots from appearing on the surface during subsequent processes.<\/li>\n<li><strong>Defatting:<\/strong> To remove oils and organic matter, only nonionic surfactants should be used, as they provide only a wetting effect. Avoid using surfactants that are too strong, to prevent static electricity from building up on the surface of the solder mask or the substrate, which could lead to nickel leaching and bath contamination.<\/li>\n<li><strong>Micro-etching:<\/strong> Typically, micro-etching the copper to a depth of 30\u201340 \u03bcm is sufficient. If small spots of exposed copper appear, this may be due to incomplete development in the wet film process or insufficient rinsing after development. In such cases, the micro-etching time can be appropriately extended to resolve the issue.<\/li>\n<li><strong>Pickling:<\/strong> Used to remove copper salts produced by micro-etching.<\/li>\n<li><strong>Pre-activation:<\/strong> When using palladium chloride as an activator, it can be pre-activated with hydrochloric acid to remove contaminants from the previous bath and protect the activation tank.<\/li>\n<li><strong>Activation:<\/strong> Use ionic palladium chloride (or other precious metals such as palladium sulfate or ruthenium sulfate) as an activator; the concentration should ideally be maintained between 30 ppm and 60 ppm.<\/li>\n<\/ol>\n<h2>Chemical Nickel Plating Tank Management<\/h2>\n<h3>Composition and Control of Tank Solution<\/h3>\n<p>The formulation of the plating bath is generally a supplier\u2019s trade secret; its main components include nickel salts, reducing agents, and various organic additives. Control measures involve the following parameters:<\/p>\n<ul>\n<li><strong>pH:<\/strong> It is generally between 4.6 and 5.2. You can adjust it using citric acid or ammonium hydroxide, but be sure to add them slowly and in small increments.<\/li>\n<li><strong>Temperature:<\/strong> Above 80\u00b0C to ensure the reaction in the bath proceeds smoothly.<\/li>\n<li><strong>Phosphorus content:<\/strong> Typically, the range is 6\u201381 TP3T; if the content is too low, it will affect corrosion resistance and solderability, while if it is too high, it will affect the quality of the nickel layer.<\/li>\n<li><strong>Ni\u00b2\u207a content:<\/strong> Typically, it ranges from 4.6 to 5.2 g; if the concentration is too low, it will affect the deposition rate, and if it is too high, it will cause the bath solution to become unstable.<\/li>\n<li><strong>Additives:<\/strong> These include complexing agents, accelerators, and stabilizers. It is important to periodically raise the temperature and perform a test plating to maintain the quality and activity of the bath solution.<\/li>\n<\/ul>\n<h2>Chemical Bath Management<\/h2>\n<h3>Composition and Control of Tank Solution<\/h3>\n<p>The main component of the gold leach tank is potassium auricyanide, with a gold content of approximately 63.81 TP3T. Key control points include:<\/p>\n<ul>\n<li><strong>pH:<\/strong> Remain between 5.1 and 6.1.<\/li>\n<li><strong>Reaction Mechanism:<\/strong> Gold deposition occurs through an electroplating reaction. In the early stages of the reaction, the deposition rate is relatively fast; as time progresses, the gold layer can continue to deposit only through sparing dissolution.<\/li>\n<\/ul>\n<h2>Post-processing<\/h2>\n<p>After completing the chemical nickel-gold plating process, the PCB must be cleaned as soon as possible, preferably with hot water, to ensure that no moisture remains. In addition, gold-plated PCBs should not be stored in an acidic environment to prevent oxidation of the gold layer. It is best to separate them with paper pads to maintain the integrity of the gold surface.<\/p>\n<h2>Quality Risks in Upstream Processes Affecting the Chemical Nickel-Gold Plating Process<\/h2>\n<p>The chemical nickel-gold plating process itself may not have any major issues, but it is often affected by the quality of upstream processes, particularly solder mask whitening and copper exposure in the form of \"star spots.\" These issues typically stem from quality defects in the wet film process.<\/p>\n<ol>\n<li><strong>Self-Flux Welding:<\/strong> The quality of the solder mask ink is a determining factor, but as long as the process parameters are properly controlled, the severity of the issue can be minimized. Choosing the right ink is crucial.<\/li>\n<li><strong>Speckles of Raw Copper:<\/strong> This is a problematic issue, primarily caused by the wet film development process, as well as the rinsing and drying steps that follow. To address this issue, we need to start by improving the wet film process.<\/li>\n<\/ol>\n<h2>Concluding Remarks<\/h2>\n<p>Quality control in the chemical nickel-gold plating process is a challenging task, especially since potential quality issues often do not become apparent until after the product is put into production at the customer\u2019s site. However, as long as standard operating procedures are strictly followed, the likelihood of problems occurring is significantly reduced. By sharing his experience, the author hopes to receive guidance and assistance from peers in the industry.<\/p>\n<p>In the chemical nickel-gold plating process, it is crucial to carefully control each step and parameter. Only by ensuring the quality and stability of every stage can a high-quality nickel-gold plating layer be achieved, one that offers multifunctional characteristics such as weldability, electrical conductivity, wire bonding capability, and heat dissipation\u2014making it the preferred process for PCB surface treatment.<\/p>\n<p><strong>Further Reading<\/strong>\uff1a<a href=\"\/en\/blog\/enepig\/\">Guide to the Chemical Nickel-Palladium-Gold Plating Process<\/a> \u00b7 <a href=\"\/en\/blog\/printed-circuit-board-humidity\/\">Analysis and Solutions to Humidity Issues in Printed Circuit Boards<\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>\u5316\u5b66\u954d\u91d1\u9540\u5c42\u662f\u4e00\u79cd\u591a\u529f\u80fd\u7684\u6e7f\u5236\u7a0b\uff0c\u96c6\u5408\u4e86\u53ef\u710a\u63a5\u3001\u53ef\u63a5\u89e6\u5bfc\u901a\u3001\u53ef\u6253\u7ebf\u4ee5\u53ca\u53ef\u6563\u70ed\u7b49\u529f\u80fd\u4e8e\u4e00\u8eab\u3002\u5b83\u88ab\u5e7f\u6cdb\u5e94\u7528\u5728PCB [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":12112,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"slim_seo":{"title":"What Should Be Considered in the Chemical Nickel-Gold Plating Process? Causes and Solutions for Color Variations and Rough Plating Surfaces","description":"What are some common issues with the chemical nickel-gold plating process? Taking color variation and surface roughness in the plating layer as examples, this article analyzes the causes related to chemicals and temperature and provides practical solutions that can be implemented immediately."},"_slim_seo_primary_term_category":0,"_slim_seo_primary_term_post_tag":0,"footnotes":""},"categories":[406,26],"tags":[],"class_list":["post-1891","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-pcb-manufacturing","category-blog"],"_links":{"self":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/1891","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/comments?post=1891"}],"version-history":[{"count":5,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/1891\/revisions"}],"predecessor-version":[{"id":19472,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/1891\/revisions\/19472"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/media\/12112"}],"wp:attachment":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/media?parent=1891"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/categories?post=1891"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/tags?post=1891"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}