{"id":10202,"date":"2022-06-08T08:13:00","date_gmt":"2022-06-08T00:13:00","guid":{"rendered":"\/\/m.letratesoro.com\/?p=10202"},"modified":"2022-06-08T15:01:57","modified_gmt":"2022-06-08T07:01:57","slug":"qfn-void-ratio","status":"publish","type":"post","link":"\/\/m.letratesoro.com\/2022\/06\/qfn-void-ratio\/","title":{"rendered":"BTC\u53caQFN\u5c01\u88dd\u4e2d\u8b6f\u540d\u7a31\u53caEPad\u6c23\u6ce1\u7a7a\u6d1e\u7387\u5141\u6536\u6a19\u6e96"},"content":{"rendered":"

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\u9592\u804a\uff01\u5de5\u4f5c\u718a\u6700\u8fd1\u5728\u67e5\u4e00\u4e9b\u95dc\u65bcSMT\u7684\u8cc7\u6599\u6642\uff0c\u767c\u73fe\u5927\u9678\u5c45\u7136\u5c07QFN\u710a\u63a5\u6563\u71b1\u588a\u7684PCB\u710a\u588a\u7a31\u70ba\u300c\u71b1\u6c88\u710a\u76e4\u300d\uff0c\u800c\u5c07QFN\u9019\u985e\u6709ePad\u7684\u96f6\u4ef6\u7a31\u70ba\u300c\u71b1\u6c89\u96f6\u4ef6\u300d\u3002\u300c\u71b1\u6c89\u300d\u5176\u5be6\u662f\u76f4\u8b6f\u82f1\u6587\u3010Heat Sink\u3011\u4f86\u7684\uff0c\u53f0\u7063\u7a31\u4e4b\u70ba\u300c\u6563\u71b1\u7247\u300d\uff0c\u5927\u6982\u662f\u53d6\u5176\u7576\u9ad8\u71b1\u91cf\u5f9e\u8a2d\u5099\u6216\u96f6\u4ef6\u50b3\u905e\u5230Heatsink\u5f8c\uff0c\u71b1\u91cf\u5373\u5f9e\u8a2d\u5099\u6216\u96f6\u4ef6\u4e2d\u6d88\u6563\u4e4b\u610f\uff0c\u8868\u793a\u8a2d\u5099\u6216\u96f6\u4ef6\u5b89\u88dd\u4e86Heatsink\u4e4b\u5f8c\uff0c\u71b1\u91cf\u5c07\u6703\u4e0b\u6c89\u3002<\/font><\/p>\n

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\u4e0d\u904e\u5de5\u4f5c\u718a\u767c\u73fe\uff0c\u82f1\u6587\u4e00\u822c\u6703\u4ee5EPad\u4f86\u7a31\u547c\u9019\u7a2eQFN\u96f6\u4ef6\u4e0a\u7684\u6563\u71b1\u710a\u588a\uff0c\u800cEPad\u5247\u662f\u3010Exposed Pad\u3011\u6216\u3010Exposed central Pad\u3011\u7684\u7c21\u7a31\uff0c\u6211\u5011\u4e00\u822c\u7a31\u4e4b\u70ba\u300c\u5916\u9732\u588a\u300d\u6216\u300c\u5916\u9732\u710a\u588a\u300d\uff1b\u800cEPad\u710a\u63a5\u65bcPCB\u76f8\u5c0d\u61c9\u4f4d\u7f6e\u7684\u710a\u588a\u5927\u591a\u70ba\u63a5\u5730\uff0c\u82f1\u6587\u4e00\u822c\u7a31\u4e4b\u70ba\u3010thermal pad\u3011\uff0c\u53f0\u7063\u7a31\u4e4b\u70ba\u300c\u6563\u71b1\u588a\u300d\uff0c\u8acb\u6ce8\u610f\uff1a\u5c11\u6578\u96f6\u4ef6\u53ef\u80fd\u6703\u6709\u8a0a\u865f\u5f9eEPad\u50b3\u905e\uff0c\u6240\u4ee5\u63a5\u7684\u4e0d\u4e00\u5b9a\u90fd\u662f\u5730(ground)\u3002<\/font><\/p>\n

\u6c92\u6709\u8aaa\u5c0d\u5cb8\u9019\u6a23\u8a5e\u7ffb\u8b6f\u5f97\u4e0d\u597d\uff0c\u800c\u662f\u4e00\u6642\u770b\u5230\u9019\u500b\u300c\u71b1\u6c89\u96f6\u4ef6\u300d\u7121\u6cd5\u610f\u6703\u662f\u4ec0\u9ebc\u96f6\u4ef6\uff0c\u800c\u4e14\u5c0d\u5cb8\u4f3c\u4e4e\u4e5f\u4e0d\u592a\u7fd2\u6163\u628a\u540d\u8a5e\u505a\u4e2d\u82f1\u5c0d\u7167\u3002<\/font><\/p>\n

\u96f6\u4ef6\u8a2d\u8a08\u88f8\u9732\u710a\u588a(EPad)\u7684\u76ee\u7684\u901a\u5e38\u662f\u7528\u4f86\u589e\u52a0\u5c01\u88dd\u7684\u529f\u8017(power dissipation)\uff0c\u9664\u975e\u6709\u7279\u6b8a\u7684\u9700\u6c42\u4e14\u8207\u96fb\u8def\u8a2d\u8a08\u5de5\u7a0b\u5e2b\u6e9d\u901a\u904e\uff0c\u5426\u5247\u9019\u7a2eEPad\u90fd\u5fc5\u9808\u710a\u63a5\u65bcPCB\u7684\u5c0d\u61c9\u6563\u71b1\u588a\u4f4d\u7f6e\uff0c\u4ee5\u9054\u5230\u6563\u71b1\u4e4b\u76ee\u7684\u3002\u56e0\u6b64EPad\u710a\u63a5\u65bcPCB\u7684\u7a7a\u6d1e\u7387\u5c31\u8b8a\u5f97\u975e\u5e38\u7684\u91cd\u8981\u3002<\/font><\/p>\n

\uff08\u5c0d\u65bc\u5927\u9678\u90a3\u4e9b\u76dc\u6587\u7db2\u7ad9\uff0c\u8907\u88fd\u8cbc\u4e0a\u672c\u7ad9\u6587\u7ae0\u5f8c\uff0c\u5c45\u7136\u9084\u6539\u6210\u81ea\u5df1\u516c\u53f8\u7684\u540d\u5b57\uff0c\u611f\u5230\u7121\u6065\uff01\u6587\u7ae0\u5167\u5bb9\u90e8\u4efd\u9632\u6b62\u8907\u88fd\u7de8\u6392\u53ef\u80fd\u9020\u6210\u60a8\u95b1\u8b80\u7684\u4e0d\u4fbf\uff0c\u8acb\u898b\u8ad2\uff01\uff09<\/font><\/em><\/p>\n

QFN\u53caBTC\u7684EPad\u710a\u63a5\u6c23\u6ce1\u7a7a\u6d1e\u7387(void ratio)<\/font><\/h2>\n

\u4e00\u822c\u5efa\u8b70QFN(Quad Flat No Lead)\u53caBTC(Bottom Termination Components)\u5e95\u9762EPad\u710a\u63a5\u7684\u7e3d\u6c23\u6ce1\u9762\u7a4d(void ratio)\u6700\u597d\u53ef\u4ee5\u63a7\u5236\u5728EPad\u9762\u7a4d\u768450%\u4ee5\u5167\u3002<\/font><\/p>\n

\u5728IPC-7093\u898f\u7bc4\u4e2d\u6709\u4e00\u500b\u5be6\u9a57\u7814\u7a76\u7d50\u8ad6\uff0c\u8aaa\u660e\u53ea\u8981EPad\u6563\u71b1\u710a\u588a\u7684\u6c23\u6ce1\u4e2d\u7a7a\u9762\u7a4d\u4e0d\u8d85\u904e50%\uff0c\u5c31\u5e7e\u4e4e\u4e0d\u6703\u5c0d\u6563\u71b1\u8207\u96fb\u8def\u7522\u751f\u8ca0\u9762\u5f71\u97ff\u3002\u7576\u7136\uff0c\u9019\u500b\u5be6\u9a57\u53ea\u662f\u91dd\u5c0d\u5c11\u6578\u7522\u54c1\u7684\u71b1\u963b(thermal resistance)\u6240\u4f5c\u7684\u5be6\u9a57\uff0c\u5404\u5bb6\u7522\u54c1\u5c0d\u71b1\u963b\u53ca\u71b1\u5c0e\u7387(Thermal conductivity)<\/font>\u7684\u9700\u6c42\u53ef\u80fd\u4e0d\u540c\uff0c\u5efa\u8b70\u8981\u8207\u7522\u54c1\u8a2d\u8a08\u8005\u6e9d\u901a\u5f8c\u78ba\u5b9a\u3002<\/font><\/p>\n

<\/p>\n

\u6b64EPad\u710a\u63a5\u7a7a\u6d1e\u7387(solder void ratio %)\u7684\u5be6\u9a57\u4f7f\u7528\u7684BTC\u70ba48\u8173\u6578\u4e14\u9577\u5bec\u70ba 7mm x 7mm\u5927\u5c0f\u7684\u5c01\u88dd\uff0c\u5728PCB\u6563\u71b1\u588a\u8a2d\u8a08\u67094×4\u500b1.0mm\u9593\u8ddd(pitch)\u76840.3mm\u5c0e\u901a\u5b54(via)\u3002\u5716\u7247\u7684\u7e31\u5ea7\u6a19\u70ba\u71b1\u963b\u03b8JA<\/sub>(thermal resistance)\uff0c\u6a6b\u5750\u6a19\u70ba\u7a7a\u6d1e\u7387(Solder void %)\u3002<\/font><\/p>\n

\u6700\u5f8c\uff0c\u63d0\u9192\u96fb\u8def\u53ca\u96fb\u8def\u677f\u8a2d\u8a08\u8005\u5011\u4e00\u4ef6\u4e8b\uff0cSMT\u5de5\u5ee0\u70ba\u4e86\u907f\u514d\u932b\u818f\u5728\u5927\u710a\u588a\u7684\u878d\u932b\u904e\u7a0b\u4e2d\u56e0\u5167\u805a\u529b\u800c\u7fa4\u805a\u81f3\u67d0\u4e00\u5340\u57df\u800c\u5c0e\u81f4\u96f6\u4ef6\u9802\u9ad8\uff0c\u9020\u6210\u96f6\u4ef6\u50be\u659c\uff0c\u6700\u5f8c\u5f62\u6210\u55ae\u5074\u5403\u932b\u4e0d\u826f\u4e4b\u73fe\u8c61\uff0c\u6703\u5728\u958bEPad\u92fc\u677f\u6642\u505a\u4e95\u5b57\u5f62\u3001\u7530\u5b57\u884c\u3001\u7c73\u5b57\u5f62\u6216\u689d\u7d0b\u5f62\u72c0\u7684\u958b\u5b54\uff0c\u5176\u932b\u818f\u8986\u84cb\u7387\u5927\u6982\u53ea\u6703\u6709EPad\u9762\u7a4d\u768450\uff5e60\uff05\uff0c\u5982\u679cPCB\u7684\u6563\u71b1\u588a(thermal pad)\u4e0a\u53c8\u6709\u904e\u591a\u672a\u585e\u5b54\u96fb\u934d\u7684\u5c0e\u901a\u5b54(vias)\uff0c\u70ba\u4e86\u907f\u514d\u932b\u818f\u6d41\u5165\u5230\u9019\u4e9bvias\u9020\u6210\u932b\u91cf\u4e0d\u8db3\u4ee5\u53ca\u6ea2\u6d41\u5c0d\u677f\u5b50\u53e6\u4e00\u9762\u9020\u6210\u932b\u73e0\u6216\u77ed\u8def\u7b49\u554f\u984c\uff0c\u5728\u932b\u818f\u5370\u5237\u6642\u90fd\u6703\u7279\u610f\u907f\u958b\u9019\u4e9bvias\uff0c\u9019\u53ef\u80fd\u4f7f\u5f97EPad\u710a\u63a5\u7684\u6c23\u6ce1\u7a7a\u6d1e\u7387\u589e\u52a0\u5927\u65bc50%\uff0c\u751a\u81f3\u4f86\u523070\uff05\u7684\u7a7a\u6d1e\u7387\uff0c\u90a3\u5c31\u53ef\u80fd\u4f7f\u5f97\u71b1\u963b\u589e\u52a0\u3001\u71b1\u5c0e\u7387\u964d\u4f4e\u4e26\u5f71\u97ff\u5230\u6563\u71b1\u7684\u6548\u679c\u3002<\/font><\/p>\n

\n

\u5ef6\u4f38\u95b1\u8b80\uff1a<\/font>
QFN\u5c01\u88dd\u5728SMT\u7d44\u88dd\u7684\u710a\u63a5\u54c1\u8cea<\/font><\/a>
BGA\u3001QFN\u5c0e\u901a\u5b54\u5728\u588a(Vias-in-pad)\u7684\u7f3a\u9ede\u53ca\u8655\u7406\u539f\u5247<\/font><\/a>
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