{"id":2605,"date":"2025-03-18T08:06:09","date_gmt":"2025-03-18T00:06:09","guid":{"rendered":"https:\/\/www.jingpengpcb.com\/?p=2605"},"modified":"2026-10-02T17:34:00","modified_gmt":"2026-10-02T09:34:00","slug":"reasons-for-poor-soldering-of-circuit-boards","status":"publish","type":"post","link":"https:\/\/www.jingpengpcb.com\/en\/blog\/reasons-for-poor-soldering-of-circuit-boards\/","title":{"rendered":"Analysis of the Causes of Soldering Defects on Printed Circuit Boards"},"content":{"rendered":"<p>For most people working with SMT processes, when they encounter soldering defects on SMD components, they often first suspect some common causes, such as poor solder paste printing, oxidation due to expired solder paste, oxidation of SMD component leads, or an improperly adjusted reflow soldering temperature profile.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-10145\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/reasons-for-poor-soldering-of-circuit-boards.jpg\" alt=\"Poor Soldering on the Circuit Board\" width=\"667\" height=\"376\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/reasons-for-poor-soldering-of-circuit-boards.jpg 667w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/reasons-for-poor-soldering-of-circuit-boards-300x169.jpg 300w\" sizes=\"auto, (max-width: 667px) 100vw, 667px\" \/><\/p>\n<p>However, there is another reason that is often overlooked: the thickness of the tin plating on the circuit board.<\/p>\n<p>In the past, we were more familiar with how the thickness of the gold and nickel layers affects soldering. However, can a tin layer that is too thin on a tin-plated circuit board lead to poor soldering?<\/p>\n<p>This article will present some relevant data and perspectives to help readers better understand this issue.<\/p>\n<h2>Case Studies of Defects in HASL Boards and Solder Paste<\/h2>\n<p>A study analyzed the causes of poor solder uptake on the second side of HASL boards following reflow soldering. Metallographic section analysis revealed that the pads exhibiting poor solder uptake had already undergone complete copper-tin alloying, and this copper-tin alloy was no longer capable of providing solderability.<\/p>\n<p>Further inspection of the unsoldered blank PCBs from the same batch, followed by cross-sectional analysis, revealed severe alloy exposure on the solder pads of the unsoldered PCBs. The cross-section analysis also indicated that the copper-tin alloy had formed to a thickness of approximately 2 \u00b5m. Considering that the alloy would increase in thickness subsequently, it can be inferred that the original tin plating thickness was likely less than 2 \u00b5m. Therefore, the root cause is that the tin plating was too thin (less than 2 \u00b5m), resulting in the copper-tin alloy being exposed on the surface of the pads and unable to provide sufficient tin to bond with the solder paste, thereby affecting the solder uptake of the pads.<\/p>\n<h2>Troubleshooting Single-Side Soldering Defects<\/h2>\n<p>Another article summarized opinions from various sources, focusing primarily on the impact of tin spray thickness on the SMT process. Although the article compiled a range of viewpoints, the majority of the conclusions attributed the soldering defects to the tin spray being too thin.<\/p>\n<p>The recommended tin plating thickness depends on the type of pad:<\/p>\n<ul>\n<li>For large copper areas, it is recommended that the tin plating thickness be at least 100 \u00b5m (2.5 \u00b5m).<\/li>\n<li>For QFPs and peripheral components, the recommended tin plating thickness is 200 \u00b5m (5.0 \u00b5m) or greater.<\/li>\n<li>For BGA solder pads, a tin plating thickness of 450 \u00b5m (11.4 \u00b5m) or greater is recommended.<\/li>\n<\/ul>\n<p>Although increasing the tin plating thickness can resolve the issue of solder rejection when the second side passes through the reflow soldering process, it is worth noting that thicker tin plating may be less favorable for components with fine-pitch pins, as it can easily lead to short circuits. Furthermore, the PCB manufacturing process also affects the thickness of the tin plating on the solder pads; smaller pads typically have a thinner tin plating layer.<\/p>\n<hr \/>\n<h2>Frequently Asked Questions<\/h2>\n<h3>1. Why does the thickness of the tin plating on a circuit board affect solder quality?<\/h3>\n<p>The thickness of the tin plating affects the adhesion between the solder pad and the solder paste. If the tin plating layer is too thin, it cannot provide enough tin to bond with the solder paste, resulting in poor soldering.<\/p>\n<h3>2. How should the tin plating thickness be selected for tin-plated boards?<\/h3>\n<p>The tin plating thickness should be selected based on the type of pad. For large copper areas, a tin plating thickness of at least 100 \u00b5m is recommended, while QFP, peripheral components, and BGA pads require a thicker tin plating layer.<\/p>\n<h3>3. Does the manufacturing process for tin-plated boards affect the thickness of the tin coating?<\/h3>\n<p>Yes, the manufacturing process for tin-plated boards can affect the thickness of the tin plating. Smaller pads typically have a thinner layer of tin plating.<\/p>\n<h3>4. What problems can arise from an excessively thick tin plating layer?<\/h3>\n<p>An excessively thick tin plating layer may adversely affect components with fine-pitch leads, potentially leading to short circuits.<\/p>\n<h3>5. How can soldering defects be resolved?<\/h3>\n<p>Methods for resolving soldering defects include selecting the appropriate solder paste thickness, optimizing the soldering process, and ensuring the quality of the solder paste and SMD components.<\/p>","protected":false},"excerpt":{"rendered":"<p>\u5bf9\u4e8e\u5927\u90e8\u5206\u73a9SMT\u5de5\u827a\u7684\u670b\u53cb\uff0c\u5f53\u78b0\u5230SMD\u96f6\u4ef6\u710a\u9521\u4e0d\u826f\u7684\u95ee\u9898\u65f6\uff0c\u5f80\u5f80\u9996\u5148\u6000\u7591\u5230\u4e00\u4e9b\u5e38\u89c1\u539f\u56e0\uff0c\u6bd4\u5982\u9521\u818f\u5370\u5237\u4e0d\u826f\u3001 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":10145,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"slim_seo":{"title":"Analysis of the Causes of Soldering Defects on Printed Circuit Boards","description":"What causes poor soldering? Using tin-plated boards as an example, this article explains how tin plating thickness affects solderability and provides solutions for thickness selection and process control\u2014to avoid focusing solely on solder paste and furnace temperature."},"_slim_seo_primary_term_category":0,"_slim_seo_primary_term_post_tag":0,"footnotes":""},"categories":[26],"tags":[333],"class_list":["post-2605","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","tag-333"],"_links":{"self":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/2605","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=2605"}],"version-history":[{"count":1,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/2605\/revisions"}],"predecessor-version":[{"id":19281,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/2605\/revisions\/19281"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/media\/10145"}],"wp:attachment":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/media?parent=2605"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/categories?post=2605"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/tags?post=2605"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}