{"product_id":"mica-insulator-sheet-for-bu508a-to-218-to-247","title":"Mica Insulator Sheet for BU508A (TO-218 \/ TO-247)","description":"\u003ch5\u003eDescription\u003c\/h5\u003e\n\u003cp\u003eThe \u003cstrong\u003eMica Insulator Sheet for BU508A\u003c\/strong\u003e is a precision-cut thermal management and electrical isolation pad designed specifically for large, high-power transistors. Because heavy-duty components like the famous BU508A (used heavily in CRT television horizontal deflection circuits) operate at extreme voltages and generate massive heat, they must be bolted to large metal heatsinks. However, the metal mounting tab on the back of the transistor is electrically live.\u003c\/p\u003e\n\n\u003cp\u003eAvailable at Tomson Electronics, this pre-cut mica pad solves that problem. Placed directly between the transistor and the heatsink, it acts as an impenetrable electrical wall (preventing a catastrophic short circuit) while still allowing the heat to pass through efficiently. Perfectly sized for \u003cstrong\u003eTO-218, TO-247, and TO-3P\u003c\/strong\u003e transistor packages, it comes with the mounting screw hole already cleanly punched out to save you time on the repair bench.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003ePeople also search for:\u003c\/strong\u003e bu508a mica pad, to-247 mica insulator, to-218 thermal pad, crt transistor insulator, high voltage mica sheet.\u003c\/p\u003e\n\n\u003chr\u003e\n\n\u003ch5\u003eSpecifications\u003c\/h5\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Natural Muscovite Mica\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatible Packages:\u003c\/strong\u003e BU508A, TO-218, TO-247, TO-3P\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePre-Punched Hole:\u003c\/strong\u003e Yes (Standard 3mm \/ M3 screw clearance)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOperating Temperature:\u003c\/strong\u003e Up to 500°C\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDielectric Strength:\u003c\/strong\u003e \u0026gt; 20 kV\/mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFunction:\u003c\/strong\u003e High electrical isolation with excellent thermal conductivity\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch5\u003eApplications\u003c\/h5\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCRT TV \u0026amp; Monitor Repair:\u003c\/strong\u003e Safely mounting high-voltage horizontal deflection transistors (like the BU508A or BU2520A) to their chassis heatsinks.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAudio Amplifiers:\u003c\/strong\u003e Isolating large TO-247 power MOSFETs and bipolar transistors in high-fidelity audio output stages.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePower Supplies:\u003c\/strong\u003e Mounting high-current voltage regulators and switching transistors in switch-mode power supplies (SMPS) or welding inverters.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch5\u003eFrequently Asked Questions (FAQ)\u003c\/h5\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Do I need to use thermal paste with this mica pad?\u003c\/strong\u003e\u003cbr\u003e\nA: Yes! Mica is naturally stiff and has microscopic surface imperfections. To ensure maximum heat transfer, you must apply a very thin, even layer of silicone thermal grease (heatsink compound) to \u003cem\u003eboth sides\u003c\/em\u003e of the mica pad before bolting the transistor down.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Why use a mica pad instead of a modern grey silicone thermal pad?\u003c\/strong\u003e\u003cbr\u003e\nA: Modern silicone pads are convenient because they don't require thermal paste, but they generally have a lower dielectric breakdown voltage and cannot survive the extreme heat transients that natural mica can. For a high-voltage part like the BU508A (which can see 1500V spikes), traditional mica remains the safest and most reliable industry standard.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQ: Will I need a plastic washer for the screw as well?\u003c\/strong\u003e\u003cbr\u003e\nA: Yes. Because the metal mounting screw passes through the live transistor tab and into the grounded heatsink, you must use a small plastic insulating \"shoulder washer\" (sometimes called a bush) on the screw head to completely isolate the screw from the transistor.\u003c\/p\u003e\n\n\u003ch5\u003ePackage Includes\u003c\/h5\u003e\n\u003cul\u003e\n\u003cli\u003e1 × Mica Insulator Sheet for BU508A (TO-218 \/ TO-247 \/ TO-3P)\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"TOMSON ELECTRONICS","offers":[{"title":"Default Title","offer_id":48386665152750,"sku":"HSK-03369","price":0.45,"currency_code":"INR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/2132\/9029\/files\/MICA_SHEET_BV_508A.jpg?v=1784984966","url":"https:\/\/www.tomsonelectronics.com\/products\/mica-insulator-sheet-for-bu508a-to-218-to-247","provider":"Tomson Electronics ","version":"1.0","type":"link"}