{"id":2190,"date":"2026-04-13T16:51:35","date_gmt":"2026-04-13T09:51:35","guid":{"rendered":"https:\/\/makipos.com\/?p=2190"},"modified":"2026-04-15T14:13:05","modified_gmt":"2026-04-15T07:13:05","slug":"what-is-solder-paste","status":"publish","type":"post","link":"https:\/\/makipos.com\/what-is-solder-paste\/","title":{"rendered":"What Is Solder Paste? Composition, Types and Applications in SMT"},"content":{"rendered":"<p><em><span style=\"font-weight: 400;\">In the electronic circuit board assembly process, solder joint quality is a key factor influencing product performance and reliability. To achieve precise and stable connections between components and printed circuit boards (PCBs), manufacturers depend on a vital material &#8211; solder paste. What is solder paste, what are its main components, and how does it contribute to SMT? This article provides a comprehensive overview.<\/span><\/em><\/p>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_79_2 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">M\u1ee5c l\u1ee5c<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#1_What_Is_Solder_Paste\" >1. What Is Solder Paste?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#2_Composition_of_Solder_Paste\" >2. Composition of Solder Paste<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#21_Solder_Alloy_Powder\" >2.1. Solder Alloy Powder<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#22_Flux\" >2.2. Flux<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#23_Additives\" >2.3. Additives<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#3_Classification_of_Solder_Paste\" >3. Classification of Solder Paste<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#31_Classification_by_Alloy_Composition\" >3.1. Classification by Alloy Composition<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#32_Classification_by_Metal_Particle_Size\" >3.2. Classification by Metal Particle Size<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#33_Classification_by_Flux_Type\" >3.3. Classification by Flux Type<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#34_Classification_by_Flux_Activity_Standards_IPC\" >3.4. Classification by Flux Activity Standards (IPC)<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#4_Applications_of_Solder_Paste_in_SMT\" >4. Applications of Solder Paste in SMT<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#5_Key_Technical_Specifications_of_Solder_Paste\" >5. Key Technical Specifications of Solder Paste<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#6_Storage_and_Handling_of_Solder_Paste\" >6. Storage and Handling of Solder Paste<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#61_Solder_Paste_Storage\" >6.1. Solder Paste Storage<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#62_Preparation_Before_Use\" >6.2. Preparation Before Use<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#63_Precautions_During_Use\" >6.3. Precautions During Use<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#7_How_to_Choose_the_Right_Solder_Paste\" >7. How to Choose the Right Solder Paste<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#71_Selection_by_Alloy_Type\" >7.1. Selection by Alloy Type<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#72_Selection_by_Powder_Particle_Size\" >7.2. Selection by Powder Particle Size<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#73_Selection_by_Flux_Type\" >7.3. Selection by Flux Type<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-21\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#74_Selection_Based_on_Design_and_Manufacturing_Requirements\" >7.4. Selection Based on Design and Manufacturing Requirements<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-22\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#75_Selection_by_Application_Industry\" >7.5. Selection by Application Industry<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-23\" href=\"https:\/\/makipos.com\/what-is-solder-paste\/#Conclusion\" >Conclusion<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"1_What_Is_Solder_Paste\"><\/span>1. What Is Solder Paste?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Solder paste is an essential material in Surface Mount Technology (SMT), used to mount electronic components onto PCB. It is a viscous mixture composed of finely powdered solder alloy and flux, designed to create reliable electrical and mechanical connections after the soldering process.<\/span><\/p>\n<figure id=\"attachment_2191\" aria-describedby=\"caption-attachment-2191\" style=\"width: 1125px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-2191\" src=\"https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste.webp\" alt=\"Solder Paste\" width=\"1125\" height=\"630\" srcset=\"https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste.webp 1125w, https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-300x168.webp 300w, https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-1024x573.webp 1024w, https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-768x430.webp 768w\" sizes=\"auto, (max-width: 1125px) 100vw, 1125px\" \/><figcaption id=\"caption-attachment-2191\" class=\"wp-caption-text\">Solder Paste<\/figcaption><\/figure>\n<p><span style=\"font-weight: 400;\">In the PCBA manufacturing process, solder paste is applied to the PCB surface through a stencil printing process. During reflow soldering, the solder alloy melts and forms strong, permanent joints that ensure excellent electrical conductivity, stability and reliability of electronic products.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Due to its critical role, solder paste directly impacts assembly quality, production efficiency and the lifespan of electronic devices. Therefore, understanding its properties and applications is essential for success in modern electronics manufacturing.<\/span><\/p>\n<h2><span class=\"ez-toc-section\" id=\"2_Composition_of_Solder_Paste\"><\/span>2. Composition of Solder Paste<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Solder paste is a specially engineered mixture designed to ensure optimal soldering performance in SMT. It typically consists of three main components: solder alloy powder, flux and additives. The precise balance of these elements determines solder joint quality, printability and the overall reliability of electronic products.<\/span><\/p>\n<h3><span class=\"ez-toc-section\" id=\"21_Solder_Alloy_Powder\"><\/span>2.1. Solder Alloy Powder<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Solder alloy powder accounts for approximately 85\u201390% of the total weight of solder paste and is composed of ultra-fine metallic particles. Common compositions include:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Leaded alloys<\/strong>: Sn63Pb37.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Lead-free alloys<\/strong>: SAC305 (Sn96.5Ag3.0Cu0.5).<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">This component determines the melting temperature, mechanical strength and electrical conductivity of the solder joints. The particle size and shape also influence printing accuracy and performance in fine-pitch applications.<\/span><\/p>\n<h3><span class=\"ez-toc-section\" id=\"22_Flux\"><\/span>2.2. Flux<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Flux typically makes up 10\u201315% of the solder paste and plays a vital role in the soldering process. Its primary functions include:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Removing oxide layers from metal surfaces.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Improving wettability and adhesion.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Preventing re-oxidation during heating.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Facilitating the melting and uniform spreading of the solder alloy.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Common types of flux include No-Clean, Water-Soluble and Rosin-Based formulations, each suited to specific manufacturing and cleaning requirements.<\/span><\/p>\n<h3><span class=\"ez-toc-section\" id=\"23_Additives\"><\/span>2.3. Additives<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Additives are incorporated to enhance the performance and stability of solder paste. Their key functions include:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Adjusting viscosity and improving printability.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Minimizing solder paste slump.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Enhancing storage stability and shelf life.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Improving solder joint quality and reducing defects.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Through the precise combination of these three components, solder paste ensures efficient assembly, enhances product quality and optimizes the PCBA manufacturing process.<\/span><\/p>\n<h2><span class=\"ez-toc-section\" id=\"3_Classification_of_Solder_Paste\"><\/span>3. Classification of Solder Paste<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Solder paste is classified based on alloy composition, metal particle size and flux type. Selecting the appropriate type helps optimize the SMT process, improve solder joint quality and ensure the reliability of electronic products.<\/span><\/p>\n<h3><span class=\"ez-toc-section\" id=\"31_Classification_by_Alloy_Composition\"><\/span>3.1. Classification by Alloy Composition<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><span style=\"font-weight: 400;\">&#8211; Leaded Solder Paste:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Common composition: Sn63Pb37.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Offers a low melting point and excellent wettability.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Easy to process and produces reliable solder joints.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Restricted in many applications due to environmental regulations such as RoHS.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">&#8211; Lead-Free Solder Paste:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Typically uses SAC alloys, such as SAC305 (Sn96.5Ag3.0Cu0.5).<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Compliant with RoHS and environmentally friendly.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Widely adopted in modern electronics manufacturing.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Provides high reliability and mechanical strength.<\/span><\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"32_Classification_by_Metal_Particle_Size\"><\/span>3.2. Classification by Metal Particle Size<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Particle size directly affects printing accuracy and the ability to assemble fine-pitch components.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Type 3 (25\u201345 \u00b5m)<\/strong>: Suitable for standard SMT applications.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Type 4 (20\u201338 \u00b5m)<\/strong>: Ideal for fine-pitch and high-density assemblies.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Type 5 (15\u201325 \u00b5m)<\/strong>: Used for ultra-fine-pitch and advanced designs.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Type 6 (5\u201315 \u00b5m)<\/strong>: Applied in microelectronics and ultra-precision printing.<\/span><\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"33_Classification_by_Flux_Type\"><\/span>3.3. Classification by Flux Type<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><span style=\"font-weight: 400;\">&#8211; No-Clean:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Leaves minimal residue after soldering.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Typically does not require post-cleaning.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Helps reduce manufacturing costs and processing time.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">&#8211; Water-Soluble:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Easily cleaned with water.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Suitable for applications requiring high reliability and cleanliness.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">&#8211; Rosin-Based:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Derived from natural rosin.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Provides excellent soldering performance.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Requires cleaning after the soldering process.<\/span><\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"34_Classification_by_Flux_Activity_Standards_IPC\"><\/span>3.4. Classification by Flux Activity Standards (IPC)<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><span style=\"font-weight: 400;\">According to the IPC J-STD-004 standard, flux in solder paste is categorized as follows:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>ROL0, ROL1<\/strong>: Low activity with minimal residue.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>ROM0, ROM1<\/strong>: Moderate activity for general applications.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>ROH0, ROH1<\/strong>: High activity, suitable for difficult-to-solder surfaces.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Understanding these classifications enables manufacturers to select the most appropriate solder paste based on PCB design, technical requirements and industry standards, thereby enhancing assembly efficiency and ensuring product quality in electronics manufacturing.<\/span><\/p>\n<h2><span class=\"ez-toc-section\" id=\"4_Applications_of_Solder_Paste_in_SMT\"><\/span>4. Applications of Solder Paste in SMT<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<figure id=\"attachment_2192\" aria-describedby=\"caption-attachment-2192\" style=\"width: 1125px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-2192\" src=\"https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-1.webp\" alt=\"Applications of Solder Paste in SMT\" width=\"1125\" height=\"630\" srcset=\"https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-1.webp 1125w, https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-1-300x168.webp 300w, https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-1-1024x573.webp 1024w, https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-1-768x430.webp 768w\" sizes=\"auto, (max-width: 1125px) 100vw, 1125px\" \/><figcaption id=\"caption-attachment-2192\" class=\"wp-caption-text\">Applications of Solder Paste in SMT<\/figcaption><\/figure>\n<p><span style=\"font-weight: 400;\">In SMT, solder paste is used to create both electrical and mechanical connections between electronic components and PCBs. With its excellent conductivity and strong adhesion, solder paste plays a critical role in ensuring product quality and reliability.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>SMD Assembly<\/strong>: Solder paste enables the precise mounting of components such as resistors, capacitors, transistors and integrated circuits (ICs) onto PCBs.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>High-Density PCB Manufacturing<\/strong>: In miniaturized and high-density designs, solder paste ensures accurate deposition and minimizes soldering defects.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Automated SMT Production Lines<\/strong>: Compatible with stencil printing systems and reflow ovens, solder paste enhances productivity, consistency and manufacturing efficiency.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Manufacturing of Modern Electronic Devices<\/strong>: Solder paste is widely used in industries such as consumer electronics, automotive, medical devices, telecommunications and industrial automation.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Thanks to these diverse applications, solder paste has become an indispensable material in modern electronics manufacturing.<\/span><\/p>\n<h2><span class=\"ez-toc-section\" id=\"5_Key_Technical_Specifications_of_Solder_Paste\"><\/span>5. Key Technical Specifications of Solder Paste<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><span style=\"font-weight: 400;\">The technical specifications of solder paste directly affect printability, solder joint quality and SMT process performance. Understanding these parameters enables manufacturers to select suitable materials and optimize PCBA production.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Alloy Composition<\/strong>: Determines the melting temperature and mechanical strength of solder joints. Common alloys include Sn63Pb37 and SAC305.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Powder Particle Size<\/strong>: Classified into Type 3, Type 4 and Type 5, influencing printing accuracy and suitability for fine-pitch components.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Viscosity<\/strong>: Affects stencil printability and the stability of solder paste on PCB surfaces.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Wettability<\/strong>: Indicates the ability of molten solder to spread across pads and component leads.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Metal Content<\/strong>: Typically accounts for 85\u201390% of the paste by weight, impacting conductivity and joint reliability.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Melting Temperature<\/strong>: Must align with the reflow thermal profile to ensure effective soldering.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Stencil Life<\/strong>: Refers to the duration during which solder paste maintains stable performance during printing.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Shelf Life<\/strong>: Indicates the allowable storage period under recommended conditions.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Slump Resistance<\/strong>: Measures the paste\u2019s ability to retain its shape after printing, preventing bridging defects.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Standards and Compliance<\/strong>: Conforms to international standards such as IPC J-STD-005, IPC J-STD-004 and RoHS.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">By carefully controlling and selecting solder paste according to these specifications, manufacturers can improve solder joint quality, reduce production defects and ensure the long-term reliability of electronic products.<\/span><\/p>\n<h2><span class=\"ez-toc-section\" id=\"6_Storage_and_Handling_of_Solder_Paste\"><\/span>6. Storage and Handling of Solder Paste<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<figure id=\"attachment_2193\" aria-describedby=\"caption-attachment-2193\" style=\"width: 1125px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-2193\" src=\"https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-2.webp\" alt=\"Storage and Handling of Solder Paste\" width=\"1125\" height=\"630\" srcset=\"https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-2.webp 1125w, https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-2-300x168.webp 300w, https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-2-1024x573.webp 1024w, https:\/\/makipos.com\/wp-content\/uploads\/2026\/04\/solder-paste-2-768x430.webp 768w\" sizes=\"auto, (max-width: 1125px) 100vw, 1125px\" \/><figcaption id=\"caption-attachment-2193\" class=\"wp-caption-text\">Storage and Handling of Solder Paste<\/figcaption><\/figure>\n<p><span style=\"font-weight: 400;\">Proper storage and handling of solder paste help maintain its material properties, ensure high-quality solder joints and optimize the efficiency of the SMT process. Failure to comply with standard conditions may lead to performance degradation and defects during PCBA production.<\/span><\/p>\n<h3><span class=\"ez-toc-section\" id=\"61_Solder_Paste_Storage\"><\/span>6.1. Solder Paste Storage<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Store at 2\u201310\u00b0C to maintain stability.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Keep containers tightly sealed to prevent contamination and oxidation.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Follow the expiration date and the FIFO (First In, First Out) principle.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Avoid direct sunlight and do not allow the solder paste to freeze.<\/span><\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"62_Preparation_Before_Use\"><\/span>6.2. Preparation Before Use<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Allow the solder paste to reach room temperature for 2\u20134 hours before use.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Do not use forced heating to accelerate the warming process.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Gently stir according to the manufacturer\u2019s recommendations.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Open the container only after it reaches room temperature to prevent moisture condensation.<\/span><\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"63_Precautions_During_Use\"><\/span>6.3. Precautions During Use<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Maintain the working environment at 20\u201325\u00b0C with 40\u201360% relative humidity.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Control stencil life to ensure consistent printing quality.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Do not reuse printed or contaminated solder paste.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Follow the manufacturer\u2019s technical guidelines.<\/span><\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"7_How_to_Choose_the_Right_Solder_Paste\"><\/span>7. How to Choose the Right Solder Paste<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Selecting the appropriate solder paste plays a crucial role in ensuring solder joint quality, optimizing the SMT process and enhancing the reliability of electronic products. To achieve the best manufacturing performance, companies should carefully evaluate technical factors and specific application requirements.<\/span><\/p>\n<h3><span class=\"ez-toc-section\" id=\"71_Selection_by_Alloy_Type\"><\/span>7.1. Selection by Alloy Type<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Leaded Solder Paste (Sn63Pb37)<\/strong>: Easy to solder with a low melting point, suitable for traditional and legacy applications.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Lead-Free Solder Paste (SAC305)<\/strong>: Environmentally friendly and compliant with RoHS standards, making it the most widely used option in modern electronics manufacturing.<\/span><\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"72_Selection_by_Powder_Particle_Size\"><\/span>7.2. Selection by Powder Particle Size<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Particle size directly affects printing accuracy and solder joint quality.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Type 3<\/strong>: Suitable for standard SMT applications.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Type 4<\/strong>: Ideal for fine-pitch components.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Type 5 and above<\/strong>: Designed for high-density assemblies and microelectronics.<\/span><\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"73_Selection_by_Flux_Type\"><\/span>7.3. Selection by Flux Type<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>No-Clean<\/strong>: Leaves minimal residue and typically requires no post-solder cleaning.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Water-Soluble<\/strong>: Easy to clean and suitable for applications requiring high reliability.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Rosin-Based<\/strong>: Provides effective oxide removal and excellent soldering performance but requires post-solder cleaning.<\/span><\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"74_Selection_Based_on_Design_and_Manufacturing_Requirements\"><\/span>7.4. Selection Based on Design and Manufacturing Requirements<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Compatible with PCB pad sizes and component dimensions.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Suitable for the reflow oven\u2019s thermal profile.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Compliant with IPC standards and product-specific technical requirements.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Optimized for stencil printing performance and defect reduction.<\/span><\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"75_Selection_by_Application_Industry\"><\/span>7.5. Selection by Application Industry<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Consumer Electronics<\/strong>: Focus on cost-effectiveness and production efficiency.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Automotive and Medical Devices<\/strong>: Require high reliability and strict quality standards.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\"><strong>Industrial and Telecommunications Equipment<\/strong>: Demand stable performance in harsh environments.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">In summary, selecting the right solder paste not only enhances PCBA quality but also optimizes production costs and efficiency. Manufacturers should carefully review technical specifications and conduct practical trials to determine the most suitable solution.<\/span><\/p>\n<h2><span class=\"ez-toc-section\" id=\"Conclusion\"><\/span>Conclusion<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Solder paste is an essential material in SMT, playing a decisive role in determining solder joint quality and the reliability of PCBs. A thorough understanding of its composition, classification and applications helps optimize the PCBA manufacturing process. Proper storage and careful selection of solder paste further minimize defects and enhance production efficiency. As a result, it remains a critical factor in ensuring the quality and performance of modern electronic products.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>In the electronic circuit board assembly process, solder joint quality is a key factor influencing product performance and reliability. To achieve precise and stable connections between components and printed circuit boards (PCBs), manufacturers depend on a vital material &#8211; solder paste. What is solder paste, what are its main components, and how does it contribute [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":2194,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[18],"tags":[],"class_list":["post-2190","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/posts\/2190","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/comments?post=2190"}],"version-history":[{"count":11,"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/posts\/2190\/revisions"}],"predecessor-version":[{"id":2205,"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/posts\/2190\/revisions\/2205"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/media\/2194"}],"wp:attachment":[{"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/media?parent=2190"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/categories?post=2190"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/makipos.com\/wp-json\/wp\/v2\/tags?post=2190"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}