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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Power electronic substrate</span></span>

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The role of the <b><a href="Wafer_(electronics)" title="Wafer (electronics)">substrate</a> in <a href="Power_electronics" title="Power electronics">power electronics</a></b> is to provide the interconnections to form an electric circuit (like a <a href="Printed_circuit_board" title="Printed circuit board">printed circuit board</a>), and to cool the components. Compared to materials and techniques used in lower power <a href="Microelectronics" title="Microelectronics">microelectronics</a>, these substrates must carry higher currents and provide a higher voltage isolation (up to several thousand volts). They also must operate over a wide temperature range (up to 150 or 200 °C).

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<div class="mw-heading mw-heading2"><h2 id="Direct_Bonded_Copper_(DBC)_substrate">Direct Bonded Copper (DBC) substrate</h2></div>

<p>DBC substrates are commonly used in <a href="Power_module" title="Power module">power modules</a>, because of their very good <a href="Thermal_conductivity" class="mw-redirect" title="Thermal conductivity">thermal conductivity</a>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> They are composed of a ceramic material tile with a sheet of <a href="Copper" title="Copper">copper</a> bonded to one or both sides by a high-temperature oxidation process (the copper and substrate are heated to a carefully controlled temperature in an atmosphere of nitrogen containing about 30 ppm of oxygen; under these conditions, a copper-oxygen eutectic forms which bonds successfully both to copper and the oxides used as substrates). The top copper layer can be preformed prior to firing or chemically etched using <a href="Printed_circuit_board" title="Printed circuit board">printed circuit board</a> technology to form an electrical circuit, while the bottom copper layer is usually kept plain. The substrate is attached to a <a href="Heat_spreader" title="Heat spreader">heat spreader</a> by soldering the bottom copper layer to it.

</p><p>A related technique uses a seed layer, photoimaging, and then additional copper plating to allow for fine lines (as small as 50 micrometres) and through-vias to connect front and back sides. This can be combined with polymer-based circuits to create high density substrates that eliminate the need for direct connection of power devices to heat sinks.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>One of the main advantages of the DBC vs other power electronic substrates is their low <a href="Coefficient_of_thermal_expansion" class="mw-redirect" title="Coefficient of thermal expansion">coefficient of thermal expansion</a>, which is close to that of <a href="Silicon" title="Silicon">silicon</a> (compared to pure <a href="Copper" title="Copper">copper</a>). This ensures good thermal cycling performances (up to 50,000 cycles).<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> The DBC substrates also have excellent electrical insulation and good heat spreading characteristics.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

</p><p>Ceramic material used in DBC include:

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<ul><li><a href="Alumina" class="mw-redirect" title="Alumina">Alumina</a> (Al<sub>2</sub>O<sub>3</sub>), commonly used because of its low cost. It is however not a really good thermal conductor (24-28 W/mK) and is brittle.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></li>

<li><a href="Aluminium_nitride" title="Aluminium nitride">Aluminium nitride</a> (AlN), which is more expensive, but has far better thermal performance (> 150 W/mK).</li>

<li><a href="Silicon_nitride" title="Silicon nitride">Silicon nitride</a> (SiN) (90 W/mK)</li>

<li>HPS (Alumina w/ 9% ZrO<sub>2</sub> doped) (26 W/mK)</li>

<li><a href="Beryllium_oxide" title="Beryllium oxide">Beryllium oxide</a> (BeO), which has good thermal performance, but is often avoided because of its toxicity when the powder is ingested or inhaled.</li></ul>

<div class="mw-heading mw-heading2"><h2 id="Active_Metal_Brazed_(AMB)_substrate">Active Metal Brazed (AMB) substrate</h2></div>

<p>AMB consists of a metal foil soldered to the ceramic baseplate using solder paste and high temperature (800 °C – 1000 °C) under vacuum. Although AMB is electrically very similar to DBC, it is typically suited for small production lots due to the unique process requirements.

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<div class="mw-heading mw-heading2"><h2 id="Insulated_Metal_substrate_(IMS)">Insulated Metal substrate (IMS)</h2></div>

<p>IMS consists of a metal baseplate (<a href="Aluminium" title="Aluminium">aluminium</a> is commonly used because of its low cost and density) covered by a thin layer of <a href="Dielectric" title="Dielectric">dielectric</a> (usually an epoxy-based layer) and a layer of copper (35 μm to more than 200 μm thick). The <a href="FR-4" title="FR-4">FR-4</a>-based dielectric is usually thin (about 100 μm) because it has poor thermal conductivity compared to the ceramics used in DBC substrates.

</p><p>Due to its structure, the IMS is a single-sided substrate, i.e. it can only accommodate components on the copper side. In most applications, the baseplate is attached to a heatsink to provide cooling, usually using <a href="Thermal_grease" class="mw-redirect" title="Thermal grease">thermal grease</a> and screws. Some IMS substrates are available with a copper baseplate for better thermal performances.

</p><p>Compared to a classical printed circuit board, the IMS provides a better heat dissipation. It is one of the simplest ways to provide efficient cooling to <a href="Surface_mount_technology" class="mw-redirect" title="Surface mount technology">surface mount components</a>.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Other_substrates">Other substrates</h2></div>

<ul><li>When the power devices are attached to a proper <a href="Heatsink" class="mw-redirect" title="Heatsink">heatsink</a>, there is no need for a thermally efficient substrate. Classical <a href="Printed_circuit_board" title="Printed circuit board">printed circuit board</a> (PCB) material can be used (this method is typically used with <a href="Through-hole_technology" title="Through-hole technology">through-hole technology</a> components). This is also true for low-power applications (from some milliwatts to some watts), as the PCB can be thermally enhanced by using thermal vias or wide tracks to improve <a href="Convection" title="Convection">convection</a>. An advantage of this method is that multilayer PCB allows design of complex circuits, whereas DBC and IMS are mostly single-sided technologies.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup></li></ul>

<ul><li><a href="Flexible_electronics" title="Flexible electronics">Flexible substrates</a> can be used for low-power applications. As they are built using <a href="Kapton" title="Kapton">Kapton</a> as a dielectric, they can withstand high temperatures and high voltages. Their intrinsic flexibility makes them resistant to <a href="Thermal_cycling" class="mw-redirect" title="Thermal cycling">thermal cycling</a> damage.</li>

<li>Ceramic substrates (<a href="Thick_film_technology" class="mw-redirect" title="Thick film technology">thick film technology</a>) can also be used in some applications (such as automotive) where reliability is of highest importance.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Compared to DCBs, thick film technology offers a higher degree of design freedom but may be less cost-efficient.</li>

<li>The thermal performances of IMS, DBC and thick film substrate are evaluated in <i>Thermal analysis of high-power modules</i> Van Godbold, C., Sankaran, V.A. and Hudgins, J.L., IEEE Transactions on Power Electronics, Vol. 12, N° 1, Jan 1997, pages 3–11, ISSN 0885-8993 <a rel="nofollow" class="external autonumber" href="https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=554164">[4]</a> (restricted access)</li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://rogerscorp.com/-/media/project/rogerscorp/documents/advanced-electronics-solutions/english/product-information/curamik-ceramic-substrates-product-information-and-data-sheet.pdf">"Rogers DBC Datasheets"</a> <span class="cs1-format">(PDF)</span>.</cite></span>

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<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.hytel.com/film.htm">Source: Hytel Group, manufacturer of copper on ceramic substrates</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/19990222160039/http://www.hytel.com/film.htm">Archived</a> 22 February 1999 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a></span>

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<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.curamik.com/sprache2/n160349/n.html">Source: Curamik, manufacturer of DBC</a></span>

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<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text">Source: Liu, Xingsheng (February 2001). "Processing and Reliability Assessment of Solder Joint Interconnection for Power Chips". Virginia Tech Dissertation <a rel="nofollow" class="external autonumber" href="http://hdl.handle.net/10919/26691">[1]</a></span>

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<li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text">Source: Liu, Xingsheng (February 2001). "Processing and Reliability Assessment of Solder Joint Interconnection for Power Chips". Virginia Tech Dissertation <a rel="nofollow" class="external autonumber" href="http://hdl.handle.net/10919/26691">[2]</a></span>

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<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.bergquistcompany.com/ts_thermal_clad.cfm">Source: The Bergquist company</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20060208112338/http://www.bergquistcompany.com/ts_thermal_clad.cfm">Archived</a> 8 February 2006 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a></span>

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<li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.aitechnology.com/products/thermalinterface/thermclads/">Source: AI Technology, Inc</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070928054657/http://www.aitechnology.com/products/thermalinterface/thermclads/">Archived</a> 28 September 2007 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a></span>

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<li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><i>Thermal Management in High-Density Power Converters </i>, Martin März, International Conference on Industrial Technology

ICIT'03 Maribor, Slovenia, 10–12 December 2003 <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20070613210444/http://www.iisb.fraunhofer.de/de/arb_geb/pub_les/02_03.pdf">"Archived copy"</a> <span class="cs1-format">(PDF)</span>. Archived from <a rel="nofollow" class="external text" href="http://www.iisb.fraunhofer.de/de/arb_geb/pub_les/02_03.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 13 June 2007<span class="reference-accessdate">. Retrieved <span class="nowrap">6 May</span> 2006</span>.</cite><span class="cs1-maint citation-comment"><code class="cs1-code">{{cite web}}</code>: CS1 maint: archived copy as title (link)</span> (pdf document, last accessed 6/5/06)</span>

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<li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text">Quick presentation of several applications and features of the thick film substrates <a rel="nofollow" class="external autonumber" href="https://web.archive.org/web/20060109065356/http://www.welwyn-tt.co.uk/pdf/brochures/HybridBrochure.pdf">[3]</a></span>

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