{"id":22824,"date":"2024-07-17T15:24:33","date_gmt":"2024-07-17T13:24:33","guid":{"rendered":"https:\/\/www.linseis.com\/thermal-impedance\/"},"modified":"2024-09-13T15:47:21","modified_gmt":"2024-09-13T13:47:21","slug":"thermal-impedance","status":"publish","type":"post","link":"https:\/\/www.linseis.com\/en\/wiki\/thermal-impedance\/","title":{"rendered":"Thermal Impedance"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"22824\" class=\"elementor elementor-22824 elementor-9872\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-9eb8745 e-flex e-con-boxed e-con e-parent\" data-id=\"9eb8745\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-c9533b7 elementor-toc--minimized-on-tablet elementor-widget elementor-widget-table-of-contents\" data-id=\"c9533b7\" data-element_type=\"widget\" data-e-type=\"widget\" data-settings=\"{&quot;headings_by_tags&quot;:[&quot;h2&quot;],&quot;exclude_headings_by_selector&quot;:[],&quot;marker_view&quot;:&quot;numbers&quot;,&quot;no_headings_message&quot;:&quot;No headings were found on this page.&quot;,&quot;minimize_box&quot;:&quot;yes&quot;,&quot;minimized_on&quot;:&quot;tablet&quot;,&quot;hierarchical_view&quot;:&quot;yes&quot;,&quot;min_height&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_tablet&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_mobile&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]}}\" data-widget_type=\"table-of-contents.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div class=\"elementor-toc__header\">\n\t\t\t\t\t\t<h4 class=\"elementor-toc__header-title\">\n\t\t\t\tTable of Contents\t\t\t<\/h4>\n\t\t\t\t\t\t\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--expand\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__c9533b7\" aria-expanded=\"true\" aria-label=\"Open table of contents\"><svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-chevron-down\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M207.029 381.476L12.686 187.132c-9.373-9.373-9.373-24.569 0-33.941l22.667-22.667c9.357-9.357 24.522-9.375 33.901-.04L224 284.505l154.745-154.021c9.379-9.335 24.544-9.317 33.901.04l22.667 22.667c9.373 9.373 9.373 24.569 0 33.941L240.971 381.476c-9.373 9.372-24.569 9.372-33.942 0z\"><\/path><\/svg><\/div>\n\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--collapse\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__c9533b7\" aria-expanded=\"true\" aria-label=\"Close table of contents\"><svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-chevron-up\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M240.971 130.524l194.343 194.343c9.373 9.373 9.373 24.569 0 33.941l-22.667 22.667c-9.357 9.357-24.522 9.375-33.901.04L224 227.495 69.255 381.516c-9.379 9.335-24.544 9.317-33.901-.04l-22.667-22.667c-9.373-9.373-9.373-24.569 0-33.941L207.03 130.525c9.372-9.373 24.568-9.373 33.941-.001z\"><\/path><\/svg><\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<div id=\"elementor-toc__c9533b7\" class=\"elementor-toc__body\">\n\t\t\t<div class=\"elementor-toc__spinner-container\">\n\t\t\t\t<svg class=\"elementor-toc__spinner eicon-animation-spin e-font-icon-svg e-eicon-loading\" aria-hidden=\"true\" viewBox=\"0 0 1000 1000\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M500 975V858C696 858 858 696 858 500S696 142 500 142 142 304 142 500H25C25 237 238 25 500 25S975 237 975 500 763 975 500 975Z\"><\/path><\/svg>\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-8a9139e elementor-widget elementor-widget-heading\" data-id=\"8a9139e\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Scientific Definition<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-ffaef65 elementor-widget elementor-widget-text-editor\" data-id=\"ffaef65\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>In electronic devices the\u00a0<strong>thermal management<\/strong>\u00a0is a crucial performance factor since the overheating of components can lead to failure. The task here is to transfer the\u00a0<strong>generated heat from the electronics to cooling devices<\/strong>, i.e. heat sinks or heat dissipators. However, even the most efficient heat sink cannot dissipate heat optimally if the contact surfaces do not manage the necessary heat transfer. Despite modern manufacturing processes a certain surface roughness remains on which microscopic air inclusions occur.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-7a04fb3 elementor-widget__width-initial elementor-widget elementor-widget-image\" data-id=\"7a04fb3\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"800\" height=\"320\" src=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2024\/07\/Tim-Hohlraeume-v2-1024x410.png\" class=\"attachment-large size-large wp-image-9886\" alt=\"\" srcset=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2024\/07\/Tim-Hohlraeume-v2-1024x410.png 1024w, https:\/\/www.linseis.com\/wp-content\/uploads\/2024\/07\/Tim-Hohlraeume-v2-300x120.png 300w, https:\/\/www.linseis.com\/wp-content\/uploads\/2024\/07\/Tim-Hohlraeume-v2-768x307.png 768w, https:\/\/www.linseis.com\/wp-content\/uploads\/2024\/07\/Tim-Hohlraeume-v2.png 1037w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-f3a894e elementor-widget elementor-widget-text-editor\" data-id=\"f3a894e\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><strong>Thermal interface materials, shortly TIMs,<\/strong>\u00a0are designed to fill those voids between components so that the heat transfer is improved significantly. This means also, that the\u00a0<strong>contact resistance<\/strong>\u00a0between the heat generating component and the heat sink should be lowered using the TIM.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-8f63d02 elementor-widget elementor-widget-heading\" data-id=\"8f63d02\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Thermal properties of TIM\u00b4s<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-ec124ef elementor-widget elementor-widget-text-editor\" data-id=\"ec124ef\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>The performance of a TIM depends thus on its <strong>thermal<\/strong> <strong>properties<\/strong>, the most common properties used in industry which are listed in data sheets are thermal conductivity and thermal impedance. Advantageous of having a look onto the thermal impedance of a TIM is that is also reflects the conditions of an application, as it accounts also e.g. the thickness of the material and clamping pressure.<\/p><p>The <a href=\"https:\/\/www.linseis.com\/en\/products\/thermal-conductivity\/\"><strong>thermal<\/strong> <strong>conductivity<\/strong><\/a> is a material-specific property and describes the ability of a material to conduct heat. This means that for thermal management it is advantageous to use a TIM with a high thermal conductivity to improve the cooling effect.<\/p><p>Related to this is the <strong>thermal<\/strong> <strong>resistance<\/strong> which is the ability to resist a heat flow. In contrast to the thermal conductivity, the thermal resistance depends on the thickness of the material. So, for a constant thermal conductivity it means that the thicker the material, the higher the thermal resistance.<\/p><p>Thermal design and the choice of a TIM must consider not only the thermal conductivity of the material but also the <a href=\"https:\/\/www.linseis.com\/en\/wiki\/thermal-contact-resistance\/\"><strong>contact<\/strong> <strong>resistance<\/strong><\/a> between the heat generating component, the TIM and the heat sink. Here, the <strong>thermal<\/strong> <strong>impedance<\/strong> comes into play: it describes the sum of the thermal resistance and the contact resistance, i.e. it is the total opposition that an assembly, which is the material and the material interfaces, presents to the flow of heat.<\/p><p>This means that ideally, the TIM material has a high thermal conductivity and at the same time possesses a low thermal impedance.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-99db763 elementor-widget elementor-widget-heading\" data-id=\"99db763\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Summarized properties:<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-014f6b3 elementor-widget__width-initial elementor-widget elementor-widget-text-editor\" data-id=\"014f6b3\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<ul>\n<li>Thermal conductivity<\/li>\n<li>Thickness of the material contact pressure<\/li>\n<li>Thermal resistance<\/li>\n<li>Contact resistance<\/li>\n<\/ul>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-e5a7e12 elementor-widget elementor-widget-heading\" data-id=\"e5a7e12\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Measurement method<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-de2bf2b elementor-widget elementor-widget-text-editor\" data-id=\"de2bf2b\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>Thermal impedance measurements are typically performed using a <a href=\"https:\/\/www.linseis.com\/en\/instruments\/thermal-conductivity\/tim-tester\/\"><strong>TIM-Tester<\/strong><\/a> which confirm the <a href=\"https:\/\/www.linseis.com\/en\/service-support\/standards-for-thermal-analysis-iso-astm-and-din\/\"><strong>norm ASTM D5470<\/strong><\/a>. It uses a <strong>steady-state<\/strong> <strong>method<\/strong> where a specimen is clamped between a heated and a cooled meter bar. The temperature gradient over the specimen, the resulting heat flux together with the test surface area, which has the same size as the material, are then used for the thermal impedance calculation. The thermal impedance thus measures the specimen thermal resistance plus the <strong>interfacial<\/strong> <strong>thermal<\/strong> <strong>resistance between the material and the test surfaces and is denoted by \u03b8 and given in the unit of m2\u2219K\/W<\/strong>.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-80d22bb elementor-widget__width-initial elementor-widget elementor-widget-image\" data-id=\"80d22bb\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"300\" height=\"90\" src=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2024\/07\/Formel-300x90-1.png\" class=\"attachment-large size-large wp-image-9911\" alt=\"\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">A: area of the meter bars, [m2] TH: temperature of the hot meter bar surface in contact with the specimen, [K] TC: temperature of the cold meter bar surface in contact with the specimen, [K] Q: heat flow, [W]<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-3112811 elementor-widget elementor-widget-text-editor\" data-id=\"3112811\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>As the contact resistance\u00a0<strong>varies depending on the specimen surface and the pressure<\/strong>\u00a0applied by the test surfaces onto the tested material, the pressure is recorded by the TIM-Tester. The thickness of the specimen is also measured<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-6712c86 elementor-widget elementor-widget-spacer\" data-id=\"6712c86\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-8d131a1 e-con-full e-flex e-con e-child\" data-id=\"8d131a1\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t<div class=\"elementor-element elementor-element-0011d84 e-con-full e-flex e-con e-child\" data-id=\"0011d84\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-f70640f elementor-widget elementor-widget-text-editor\" data-id=\"f70640f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>With the TIM-Tester one can determine the\u00a0<strong>apparent thermal conductivity<\/strong>\u00a0as well, so the<strong>\u00a0thermal conductivity specific<\/strong>\u00a0to the test conditions. For this one needs to exclude the interfacial thermal resistance. This can be done by firstly measuring and plotting the thermal impedance in dependence on different specimen thicknesses. This results in a straight line whose inverse of the slope is the apparent thermal conductivity and the intercept at thickness zero corresponds to the contact resistance at the two test surfaces.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-35de7f8 e-con-full e-flex e-con e-child\" data-id=\"35de7f8\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-7df98d7 elementor-widget elementor-widget-image\" data-id=\"7df98d7\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"768\" height=\"512\" src=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2024\/07\/TIM-Tester-Nahaufnahme-768x512-1.jpg\" class=\"attachment-large size-large wp-image-9924\" alt=\"\" srcset=\"https:\/\/www.linseis.com\/wp-content\/uploads\/2024\/07\/TIM-Tester-Nahaufnahme-768x512-1.jpg 768w, https:\/\/www.linseis.com\/wp-content\/uploads\/2024\/07\/TIM-Tester-Nahaufnahme-768x512-1-300x200.jpg 300w\" sizes=\"(max-width: 768px) 100vw, 768px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-6f1cdb9 elementor-widget elementor-widget-spacer\" data-id=\"6f1cdb9\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"spacer.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<div class=\"elementor-spacer\">\n\t\t\t<div class=\"elementor-spacer-inner\"><\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Thermal management is a decisive factor in electronic devices, as overheating of components can lead to failures. The aim is therefore to transfer the heat generated by the electronics to a cooling device, e.g. a heat sink or heat sink.<\/p>\n","protected":false},"author":3,"featured_media":9875,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[106],"tags":[],"class_list":["post-22824","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-wiki"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/posts\/22824","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/comments?post=22824"}],"version-history":[{"count":0,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/posts\/22824\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/media\/9875"}],"wp:attachment":[{"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/media?parent=22824"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/categories?post=22824"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.linseis.com\/en\/wp-json\/wp\/v2\/tags?post=22824"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}