{"id":4261,"date":"2026-10-22T08:53:10","date_gmt":"2026-10-22T08:53:10","guid":{"rendered":"https:\/\/welleltron.com\/?page_id=4261"},"modified":"2026-10-23T02:13:37","modified_gmt":"2026-10-23T02:13:37","slug":"through-hole-assembly","status":"publish","type":"page","link":"https:\/\/welleltron.com\/ru\/kb\/through-hole-assembly\/","title":{"rendered":"Through\u2011Hole Assembly"},"content":{"rendered":"<style>.kb-table-of-content-nav.kb-table-of-content-id4261_53412e-42 .kb-table-of-content-wrap{padding-top:var(--global-kb-spacing-sm, 1.5rem);padding-right:var(--global-kb-spacing-sm, 1.5rem);padding-bottom:var(--global-kb-spacing-sm, 1.5rem);padding-left:var(--global-kb-spacing-sm, 1.5rem);}.kb-table-of-content-nav.kb-table-of-content-id4261_53412e-42 .kb-table-of-contents-title-wrap{padding-top:0px;padding-right:0px;padding-bottom:0px;padding-left:0px;}.kb-table-of-content-nav.kb-table-of-content-id4261_53412e-42 .kb-table-of-contents-title{font-weight:regular;font-style:normal;}.kb-table-of-content-nav.kb-table-of-content-id4261_53412e-42 .kb-table-of-content-wrap .kb-table-of-content-list{font-weight:regular;font-style:normal;margin-top:var(--global-kb-spacing-sm, 1.5rem);margin-right:0px;margin-bottom:0px;margin-left:0px;}<\/style>\n\n\n<h2 class=\"wp-block-heading\">1. What Is Through-Hole Assembly?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Through\u2011Hole assembly<\/strong> (often abbreviated as THT) is a circuit board manufacturing process where axial, radial, or multi-pin component leads are inserted into pre-drilled <strong>through holes<\/strong> on the printed circuit board and soldered onto pads on the opposite side.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Typical <strong>Through\u2011Hole components<\/strong> include leaded resistors, capacitors, relays, connectors, and certain power-device packages. The specific component package and application determine how it should be mounted and supported.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Three terms need distinction:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Through\u2011Hole technology, or THT:<\/strong> The mounting approach.<\/li>\n\n\n\n<li><strong>Plated Through\u2011Hole, or PTH:<\/strong> A hole with conductive plating along its wall.<\/li>\n\n\n\n<li><strong>Through-hole assembly:<\/strong> The process of installing and joining the components.<\/li>\n<\/ul>\n\n\n<style>.wp-block-kadence-advancedheading.kt-adv-heading4261_03c336-a8, .wp-block-kadence-advancedheading.kt-adv-heading4261_03c336-a8[data-kb-block=\"kb-adv-heading4261_03c336-a8\"]{font-style:normal;}.wp-block-kadence-advancedheading.kt-adv-heading4261_03c336-a8 mark.kt-highlight, .wp-block-kadence-advancedheading.kt-adv-heading4261_03c336-a8[data-kb-block=\"kb-adv-heading4261_03c336-a8\"] mark.kt-highlight{font-style:normal;color:#f76a0c;-webkit-box-decoration-break:clone;box-decoration-break:clone;padding-top:0px;padding-right:0px;padding-bottom:0px;padding-left:0px;}.wp-block-kadence-advancedheading.kt-adv-heading4261_03c336-a8 img.kb-inline-image, .wp-block-kadence-advancedheading.kt-adv-heading4261_03c336-a8[data-kb-block=\"kb-adv-heading4261_03c336-a8\"] img.kb-inline-image{width:150px;vertical-align:baseline;}<\/style>\n<p class=\"kt-adv-heading4261_03c336-a8 wp-block-kadence-advancedheading\" data-kb-block=\"kb-adv-heading4261_03c336-a8\"><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">2. The Through-Hole PCB Assembly Process<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Executing a high-yield <strong>through hole PCB assembly<\/strong> run requires controlled lead preparation, precise insertion, and thermal management.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>+-------------------------------------------------------+\n| 1. Component Lead Bending &amp; Pre-forming               |\n+-------------------------------------------------------+\n                           |\n                           v\n+-------------------------------------------------------+\n| 2. Insertion (Manual Line or Automated AI Machinery)  |\n+-------------------------------------------------------+\n                           |\n                           v\n+-------------------------------------------------------+\n| 3. Soldering Stage (Wave, Selective, or Manual Soldering)|\n+-------------------------------------------------------+\n                           |\n                           v\n+-------------------------------------------------------+\n| 4. Post-Solder Aqueous \/ Solvent Cleaning             |\n+-------------------------------------------------------+\n                           |\n                           v\n+-------------------------------------------------------+\n| 5. Inspection (AOI, X-Ray Barrel Fill, Ionic Testing) |\n+-------------------------------------------------------+\n<\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Lead Preparation:<\/strong> Components arrive in bulk, tape-and-reel, or ammo boxes. Leads must be trimmed and pre-formed to fit pad spacings without placing stress on the component body.<\/li>\n\n\n\n<li><strong>Insertion Methodologies:<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Manual Assembly:<\/strong> A skilled through hole assembly operator manually places complex, irregular, or heat-sensitive connectors onto the board.<\/li>\n\n\n\n<li><strong>Automated Through Hole Assembly:<\/strong> High-speed axial and radial insertion machines automatically punch leads into the PCB at high UPH (Units Per Hour) speeds. <em>(Data needed: specify specific UPH throughput limits comparing high-speed AI equipment against manual assembly lines)<\/em>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Securing Leads:<\/strong> Leads are slightly clinched on the solder side to prevent component floating or displacement during transit to the soldering stage.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">3. Through\u2011Hole vs. SMT: Choosing the Assembly Method<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Through-hole and surface-mount technology should be compared against the actual product requirements rather than ranked by a universal reliability claim.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>Consideration<\/th><th>Through\u2011Hole Assembly<\/th><th>Surface-Mount Assembly<\/th><\/tr><\/thead><tbody><tr><td>Component attachment<\/td><td>Leads pass through board holes<\/td><td>Terminations connect to surface pads<\/td><\/tr><tr><td>Layout requirements<\/td><td>Component holes and associated routing constraints<\/td><td>Footprints and assembly access around surface pads<\/td><\/tr><tr><td>Mechanical design<\/td><td>Evaluate leads, joints, body support, and external loads<\/td><td>Evaluate pads, joints, package, and external loads<\/td><\/tr><tr><td>Manufacturing route<\/td><td>Insertion followed by the approved soldering process<\/td><td>Placement followed by the approved soldering process<\/td><\/tr><tr><td>Rework<\/td><td>Assess access, hole condition, and removal effects<\/td><td>Assess access, pad condition, and package restrictions<\/td><\/tr><tr><td>Selection basis<\/td><td>Component and application requirements<\/td><td>Component and application requirements<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">4. DFM Guidelines for Through\u2011Hole Design and Lead Preparation<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Implementing strict Design for Manufacturability (DFM) rules reduces manufacturing defect rates and avoids costly manual rework.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Pin-to-Hole Ratio:<\/strong> The plated through-hole (PTH) diameter must be sized correctly relative to the lead diameter. If the hole is too tight, solder cannot flow up the barrel; if it is too loose, capillary action fails, leaving insufficient solder volume. <em>(Data needed: specify recommended drill-to-lead diameter clearance ratios, typically 0.15mm\u20130.25<\/em> <em>mm allowance)<\/em>.<\/li>\n\n\n\n<li><strong>Thermal Relief Design:<\/strong> <a href=\"https:\/\/welleltron.com\/pcb-pins\/\">Pins<\/a> connected to internal ground or power planes require thermal relief pads with spoke patterns. Without thermal relief, the copper plane acts as a heat sink, drawing energy away during <strong>through hole soldering<\/strong> and causing cold solder joints.<\/li>\n\n\n\n<li><strong>Lead Protrusion &amp; Component Pitch:<\/strong> Adequate clearance around through-hole pads allows automatic insertion heads and selective solder nozzles to navigate without colliding with adjacent SMT parts.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">5. Quality Control and Cleanliness Verification in THT Manufacturing<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">High-density through-hole joints accumulate flux residues inside barrel cavities and under heavy component bodies, making cleaning and verification vital.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Flux Residue Trapping:<\/strong> Wave and selective fluxing apply active organic or rosin-based compounds that can trap active halides inside plated barrels if not flushed thoroughly.<\/li>\n\n\n\n<li><strong>Ionic Contamination Control:<\/strong> Uncleaned flux residues absorb atmospheric moisture, triggering electrochemical migration (ECM) and dendritic growth beneath connectors.<\/li>\n\n\n\n<li><strong>Process Integration with Welleltron Instruments:<\/strong> Contract manufacturers use Welleltron <a href=\"https:\/\/welleltron.com\/pcb-instrument-and-machines\/ionic-contamination-tester\/ionic-contamination-tester-for-pcb-cleaning\/\">ionic contamination<\/a> test equipment to execute accurate ROSE (Resistivity of Solvent Extract) testing on post-cleaned boards. Measuring extract conductivity validates that residual ionic salts fall within acceptable limits before boards move to final enclosure assembly. <\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">6. Common THT Soldering Defects and IPC-A-610 Inspection Criteria<sup><\/sup><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Visual and X-ray inspection protocols evaluate solder joints against international acceptability standards like IPC-A-610.<sup><\/sup><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Insufficient Vertical Barrel Fill:<\/strong> Solder fails to wick up the plated through-hole. IPC-A-610 Class 2 and Class 3 require a minimum of 75% vertical solder fill inside the plated barrel.<\/li>\n\n\n\n<li><strong>Solder Bridging (Shorts):<\/strong> Excess solder creates unwanted conductive pathways between adjacent pins, common when lead protrusion lengths are too long or wave chain speed is miscalibrated.<\/li>\n\n\n\n<li><strong>Solder Icicles and Voiding:<\/strong> Caused by incorrect flux activation, degraded solder purity, or improper temperature profiling during wave exit.<\/li>\n\n\n\n<li><strong>Blowholes and Pinholes:<\/strong> Trapped moisture inside the PCB laminate vaporizes during thermal exposure, outgassing through the molten solder joint and leaving cavities.<\/li>\n<\/ul>\n\n\n\n<pre class=\"wp-block-preformatted\"> <code>      ACCEPTABLE (Class 2\/3)                    DEFECT (Insufficient Fill)\n      \n    |  |  | Solder |  |  |                   |  |  |          |  |  |\n    |  +--+--------+--+  |                   |  +--+          +--+  |\n    |  |  |  Lead  |  |  |                   |  |  |  Lead    |  |  |\n====+==+==+========+==+==+====           ====+==+==+==========+==+==+====\n    |  |  |  &gt;&gt;&gt;&gt;  |  |  |                   |  |  |  Air     |  |  |\n    |  |  | &gt;= 75% |  |  |                   |  |  |  Gap     |  |  |\n    |  |  | Barrel |  |  |                   |  |  | &lt; 75%    |  |  |\n    |  |  |  Fill  |  |  |                   |  |  | Fill     |  |  |\n====+==+==+========+==+==+====           ====+==+==+==========+==+==+====\n    |  +--+--------+--+  |                   |  +--+--------+--+  |\n    |  |  | Solder |  |  |                   |  |  | Solder |  |  |\n<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">7. Frequently Asked Questions on Through-Hole Assembly<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Q1: When should a hardware design specify THT over SMT?<\/strong>\n<ul class=\"wp-block-list\">\n<li><em>A:<\/em> THT is preferred when components experience strong mechanical forces (e.g., switches, heavy connectors), carry high current\/voltage loads, or operate in high-vibration environments like automotive or aerospace systems.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Q2: What is the minimum acceptable vertical barrel fill for IPC Class 3 THT joints?<\/strong>\n<ul class=\"wp-block-list\">\n<li><em>A:<\/em> Under IPC-A-610 standards, Class 3 high-reliability electronics require a minimum of 75% vertical solder fill inside the plated through-hole barrel.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Q3: How does selective soldering protect nearby surface-mount devices?<\/strong>\n<ul class=\"wp-block-list\">\n<li><em>A:<\/em> <strong>Selective soldering<\/strong> uses targeted miniature solder nozzles and drop-jet fluxers to apply heat strictly to specific through-hole pins, keeping thermal exposure away from neighboring SMT parts on the board bottom.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Q4: What Should Be Checked After Through-Hole Rework?<\/strong>\n<ul class=\"wp-block-list\">\n<li><em>A:<\/em> Inspect the affected connection, hole and pad condition, nearby components, and cleanliness. Complete the required electrical or functional retesting and document the release decision.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>1. What Is Through-Hole Assembly? Through\u2011Hole assembly (often abbreviated as THT) is a circuit board manufacturing process where axial, radial, or multi-pin component leads are inserted into pre-drilled through holes on the printed circuit board and soldered onto pads on the opposite side. Typical Through\u2011Hole components include leaded resistors, capacitors, relays, connectors, and certain power-device&#8230;<\/p>","protected":false},"author":1,"featured_media":0,"parent":2541,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_uag_custom_page_level_css":"","_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"left","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"footnotes":""},"categories":[],"tags":[],"class_list":["post-4261","page","type-page","status-publish","hentry"],"taxonomy_info":[],"featured_image_src_large":false,"author_info":{"display_name":"lucaismilelove@gmail.com","author_link":"https:\/\/welleltron.com\/ru\/blog\/author\/luciasmilelovegmail-com\/"},"comment_info":0,"_hostinger_reach_plugin_has_subscription_block":false,"_hostinger_reach_plugin_is_elementor":false,"spectra_custom_meta":{"_uagb_previous_block_counts":["a:90:{s:21:\"uagb\/advanced-heading\";i:0;s:15:\"uagb\/blockquote\";i:0;s:12:\"uagb\/buttons\";i:0;s:18:\"uagb\/buttons-child\";i:0;s:19:\"uagb\/call-to-action\";i:0;s:15:\"uagb\/cf7-styler\";i:0;s:11:\"uagb\/column\";i:0;s:12:\"uagb\/columns\";i:0;s:14:\"uagb\/container\";i:0;s:21:\"uagb\/content-timeline\";i:0;s:27:\"uagb\/content-timeline-child\";i:0;s:14:\"uagb\/countdown\";i:0;s:12:\"uagb\/counter\";i:0;s:8:\"uagb\/faq\";i:0;s:14:\"uagb\/faq-child\";i:0;s:10:\"uagb\/forms\";i:0;s:17:\"uagb\/forms-accept\";i:0;s:19:\"uagb\/forms-checkbox\";i:0;s:15:\"uagb\/forms-date\";i:0;s:16:\"uagb\/forms-email\";i:0;s:17:\"uagb\/forms-hidden\";i:0;s:15:\"uagb\/forms-name\";i:0;s:16:\"uagb\/forms-phone\";i:0;s:16:\"uagb\/forms-radio\";i:0;s:17:\"uagb\/forms-select\";i:0;s:19:\"uagb\/forms-textarea\";i:0;s:17:\"uagb\/forms-toggle\";i:0;s:14:\"uagb\/forms-url\";i:0;s:14:\"uagb\/gf-styler\";i:0;s:15:\"uagb\/google-map\";i:0;s:11:\"uagb\/how-to\";i:0;s:16:\"uagb\/how-to-step\";i:0;s:9:\"uagb\/icon\";i:0;s:14:\"uagb\/icon-list\";i:0;s:20:\"uagb\/icon-list-child\";i:0;s:10:\"uagb\/image\";i:0;s:18:\"uagb\/image-gallery\";i:0;s:13:\"uagb\/info-box\";i:0;s:18:\"uagb\/inline-notice\";i:0;s:11:\"uagb\/lottie\";i:0;s:21:\"uagb\/marketing-button\";i:0;s:10:\"uagb\/modal\";i:0;s:18:\"uagb\/popup-builder\";i:0;s:16:\"uagb\/post-button\";i:0;s:18:\"uagb\/post-carousel\";i:0;s:17:\"uagb\/post-excerpt\";i:0;s:14:\"uagb\/post-grid\";i:0;s:15:\"uagb\/post-image\";i:0;s:17:\"uagb\/post-masonry\";i:0;s:14:\"uagb\/post-meta\";i:0;s:18:\"uagb\/post-taxonomy\";i:0;s:18:\"uagb\/post-timeline\";i:0;s:15:\"uagb\/post-title\";i:0;s:20:\"uagb\/restaurant-menu\";i:0;s:26:\"uagb\/restaurant-menu-child\";i:0;s:11:\"uagb\/review\";i:0;s:12:\"uagb\/section\";i:0;s:14:\"uagb\/separator\";i:0;s:11:\"uagb\/slider\";i:0;s:17:\"uagb\/slider-child\";i:0;s:17:\"uagb\/social-share\";i:0;s:23:\"uagb\/social-share-child\";i:0;s:16:\"uagb\/star-rating\";i:0;s:23:\"uagb\/sure-cart-checkout\";i:0;s:22:\"uagb\/sure-cart-product\";i:0;s:15:\"uagb\/sure-forms\";i:0;s:22:\"uagb\/table-of-contents\";i:0;s:9:\"uagb\/tabs\";i:0;s:15:\"uagb\/tabs-child\";i:0;s:18:\"uagb\/taxonomy-list\";i:0;s:9:\"uagb\/team\";i:0;s:16:\"uagb\/testimonial\";i:0;s:14:\"uagb\/wp-search\";i:0;s:19:\"uagb\/instagram-feed\";i:0;s:10:\"uagb\/login\";i:0;s:17:\"uagb\/loop-builder\";i:0;s:18:\"uagb\/loop-category\";i:0;s:20:\"uagb\/loop-pagination\";i:0;s:15:\"uagb\/loop-reset\";i:0;s:16:\"uagb\/loop-search\";i:0;s:14:\"uagb\/loop-sort\";i:0;s:17:\"uagb\/loop-wrapper\";i:0;s:13:\"uagb\/register\";i:0;s:19:\"uagb\/register-email\";i:0;s:24:\"uagb\/register-first-name\";i:0;s:23:\"uagb\/register-last-name\";i:0;s:22:\"uagb\/register-password\";i:0;s:30:\"uagb\/register-reenter-password\";i:0;s:19:\"uagb\/register-terms\";i:0;s:22:\"uagb\/register-username\";i:0;}"],"_edit_lock":["1792724352:1"],"rank_math_internal_links_processed":["1"],"_edit_last":["1"],"rank_math_seo_score":["66"],"_wp_page_template":["default"],"rank_math_title":["Through\u2011Hole 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What Is Through-Hole Assembly? Through\u2011Hole assembly (often abbreviated as THT) is a circuit board manufacturing process where axial, radial, or multi-pin component leads are inserted into pre-drilled through holes on the printed circuit board and soldered onto pads on the opposite side. Typical Through\u2011Hole components include leaded resistors, capacitors, relays, connectors, and certain power-device...","_links":{"self":[{"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/pages\/4261","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/comments?post=4261"}],"version-history":[{"count":2,"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/pages\/4261\/revisions"}],"predecessor-version":[{"id":4291,"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/pages\/4261\/revisions\/4291"}],"up":[{"embeddable":true,"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/pages\/2541"}],"wp:attachment":[{"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/media?parent=4261"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/categories?post=4261"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/welleltron.com\/ru\/wp-json\/wp\/v2\/tags?post=4261"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}