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有时候，在设计电路时，需要用到一个阻值比较小的功率电阻作采样电阻，用来采样大电流。很多时候我们都会采用一个大封装的功率电阻来做，例如2010，1812，功率一般0.5W。但是我们有没有想过用PCB走线来设计一个采样电阻呢？下面介绍用PCB走线设计一个0.05欧姆的方法。

先认识一下物理知识，导体的电阻率公式：R =ρL/S，其中 ρ 是特定导体的电阻率， L 是导体长度， S 是导体截面积。

由上述的导体的电阻率公式可以知道，要用PCB走线设计出0.05欧姆，必须要知道pcb导体的电阻率，走线的长度，走线的横截面积。PCB导体材料是铜，而铜的电阻铜的电阻率查表可得：1.75×10E-08, 走线的横截面积可以由走线宽度和覆铜厚度计算得到，PCB覆铜厚度有1OZ、1/2OZ、1/3OZ等。走线的宽度和长度不能马上知道，需要计算才能得出。为了计算方便，我们可以用EXCEL表格来把一些满足要求的值算出来 。如下所示：

<table border="1" cellpadding="0" cellspacing="0" align="center" >
<tr> <td colspan="6" align="center" valign="middle">R =ρL/S=ρL/(W*T)</td></tr>
<tr>
<td width="102" align="center" valign="middle">铜电阻率ρ</td>
<td width="121" align="center" valign="middle">导线长度L(m)</td>
<td width="122" align="center" valign="middle">导线宽度W(m)</td>
<td width="111" align="center" valign="middle">导线厚度T(m)</td>
<td width="114" align="center" valign="middle">PCB制作铜厚</td>
<td width="138" align="center" valign="middle">导线电阻R(Ω)</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.055</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.0275</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.06</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.03</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.065</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.0325</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.07</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.035</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.075</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.0375</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.08</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.04</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.085</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.0425</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.09</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.045</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.095</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.0475</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.1</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.05</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.005</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.005</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.01</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.01</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.015</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.015</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.02</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.02</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.025</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.025</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.03</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.03</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.035</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.035</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.04</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.04</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.045</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.045</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.05</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.05</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.005</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.007478632</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.01</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.014957265</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.015</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.022435897</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.02</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.02991453</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.025</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.037393162</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.03</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.044871795</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.035</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.052350427</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.04</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.05982906</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.045</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.067307692</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.05</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.074786325</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.055</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.082264957</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.06</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.08974359</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.065</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.097222222</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.07</td>
<td align="center" valign="middle">0.001</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.104700855</td>
</tr>

<tr>
<td width="118" align="center" valign="middle">1.75E-08</td>
<td width="127" align="center" valign="middle">0.15</td>
<td width="119" align="center" valign="middle">0.002</td>
<td width="123" align="center" valign="middle">3.50E-05</td>
<td width="121" align="center" valign="middle">1OZ</td>
<td width="135" align="center" valign="middle">0.0375</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.155</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.03875</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.16</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.04</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.165</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.04125</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.17</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.0425</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.175</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.04375</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.18</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.045</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.185</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.04625</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.19</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.0475</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.195</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.04875</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.2</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">3.50E-05</td>
<td align="center" valign="middle">1OZ</td>
<td align="center" valign="middle">0.05</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.1</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.05</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.105</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.0525</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.11</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.055</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.115</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.0575</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.12</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.06</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.125</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.0625</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.13</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.065</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.135</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.0675</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.14</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.75E-05</td>
<td align="center" valign="middle">1/2 OZ</td>
<td align="center" valign="middle">0.07</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.005</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.003739316</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.01</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.007478632</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.015</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.011217949</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.02</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.014957265</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.025</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.018696581</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.03</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.022435897</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.035</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.026175214</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.04</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.02991453</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.045</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.033653846</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.05</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.037393162</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.055</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.041132479</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.06</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.044871795</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.065</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.048611111</td>
</tr>
<tr>
<td align="center" valign="middle">1.75E-08</td>
<td align="center" valign="middle">0.07</td>
<td align="center" valign="middle">0.002</td>
<td align="center" valign="middle">1.17E-05</td>
<td align="center" valign="middle">1/3 OZ</td>
<td align="center" valign="middle">0.052350427</td>
</tr>
</table>
由上图可知，通过excel表格算出了几组满足要求的数据。

1、当覆铜厚度是1OZ，走线宽度是1mm，走线长度是10cm时，PCB走线导体电阻计算出来的结果是0.05Ω。
2、当覆铜厚度是1/2OZ，走线宽度是1mm，走线长度是5cm时，PCB走线导体电阻计算出来的结果是0.05Ω。
3、当覆铜厚度是1/3OZ，走线宽度是1mm，走线长度是3.5cm时，PCB走线导体电阻计算出来的结果是0.052Ω。
4、当覆铜厚度是1OZ，走线宽度是2mm，走线长度是20cm时，PCB走线导体电阻计算出来的结果是0.05Ω。
5、当覆铜厚度是1/2OZ，走线宽度是2mm，走线长度是10cm时，PCB走线导体电阻计算出来的结果是0.05Ω。
6、当覆铜厚度是1/3OZ，走线宽度是2mm，走线长度是7cm时，PCB走线导体电阻计算出来的结果是0.05Ω。

算出了满足阻值要求的PCB走线宽度和长度后，已经可以在PCB上画过这段导线了。例如，其中一组满足要求的数据的画法如图：

<center><img src="http://mouser.eetrend.com/files/2021-01/wen_zhang_/100060826-118831-1.j…; alt=“” width="600"></center>

但是，我们还要知道所设计的这个“电阻”的载流能是多大，如果需要流过的电流很大，而设计出来的“电阻”载流能力比它小，就有烧毁的可能。导体的载流能力可以用以下计算方法计算，

<center> I=KT<sup>0.44</sup>A<sup>0.725</sup> </center>

（K为修正系数，一般覆铜线在内层时取0.024，在外层时取0.048，T为最大温升，单位为摄氏度(例如，60℃)，A为覆铜截面积，单位为平方MIL(不是毫米mm，注意是square mil.)

同样用excel表格计算PCB走线载流能力，把以上满足条件的几组数据设计出来的导线的载流能算出来，如下图所示:

<table border="1" align="center" cellpadding="0" cellspacing="0">
<tr>
<td colspan="7" align="center" valign="middle">I=KT<sup>0.44</sup>A<sup>0.725</sup>&nbsp;&nbsp;=KT<sup>0.44</sup>（W*TC）<sup>0.725</sup></td>
</tr>
<tr>
<td width="114" align="center" valign="middle">修正系数K</td>
<td width="109" align="center" valign="middle">最大温升T(OC)</td>
<td width="112" align="center" valign="middle">线宽（mil）</td>
<td width="42" align="center" valign="middle">mm</td>
<td width="81" align="center" valign="middle">铜厚（mil）</td>
<td width="53" align="center" valign="middle">mm</td>
<td width="92" align="center" valign="middle">最大电流I(A)</td>
</tr>
<tr>
<td align="center" valign="middle">0.024</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">39.37</td>
<td align="center" valign="middle">1</td>
<td align="center" valign="middle">1.37795</td>
<td align="center" valign="middle">0.035</td>
<td align="center" valign="middle">2.63049194</td>
</tr>
<tr>
<td align="center" valign="middle">0.024</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">39.37</td>
<td align="center" valign="middle">1</td>
<td align="center" valign="middle">0.688975</td>
<td align="center" valign="middle">0.0175</td>
<td align="center" valign="middle">1.59143985</td>
</tr>
<tr>
<td align="center" valign="middle">0.024</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">39.37</td>
<td align="center" valign="middle">1</td>
<td align="center" valign="middle">0.460629</td>
<td align="center" valign="middle">0.0117</td>
<td align="center" valign="middle">1.188563511</td>
</tr>
<tr>
<td align="center" valign="middle">0.024</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">78.74</td>
<td align="center" valign="middle">2</td>
<td align="center" valign="middle">1.37795</td>
<td align="center" valign="middle">0.035</td>
<td align="center" valign="middle">4.347941802</td>
</tr>
<tr>
<td align="center" valign="middle">0.024</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">78.74</td>
<td align="center" valign="middle">2</td>
<td align="center" valign="middle">0.688975</td>
<td align="center" valign="middle">0.0175</td>
<td align="center" valign="middle">2.63049194</td>
</tr>
<tr>
<td align="center" valign="middle">0.024</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">78.74</td>
<td align="center" valign="middle">2</td>
<td align="center" valign="middle">0.460629</td>
<td align="center" valign="middle">0.0117</td>
<td align="center" valign="middle">1.964577383</td>
</tr>
<tr>
<td align="center" valign="middle">0.048</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">39.37</td>
<td align="center" valign="middle">1</td>
<td align="center" valign="middle">1.37795</td>
<td align="center" valign="middle">0.035</td>
<td align="center" valign="middle">5.260983881</td>
</tr>
<tr>
<td align="center" valign="middle">0.048</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">39.37</td>
<td align="center" valign="middle">1</td>
<td align="center" valign="middle">0.688975</td>
<td align="center" valign="middle">0.0175</td>
<td align="center" valign="middle">3.1828797</td>
</tr>
<tr>
<td align="center" valign="middle">0.048</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">39.37</td>
<td align="center" valign="middle">1</td>
<td align="center" valign="middle">0.460629</td>
<td align="center" valign="middle">0.0117</td>
<td align="center" valign="middle">2.377127021</td>
</tr>
<tr>
<td align="center" valign="middle">0.048</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">78.74</td>
<td align="center" valign="middle">2</td>
<td align="center" valign="middle">1.37795</td>
<td align="center" valign="middle">0.035</td>
<td align="center" valign="middle">8.695883604</td>
</tr>
<tr>
<td align="center" valign="middle">0.048</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">78.74</td>
<td align="center" valign="middle">2</td>
<td align="center" valign="middle">0.688975</td>
<td align="center" valign="middle">0.0175</td>
<td align="center" valign="middle">5.260983881</td>
</tr>
<tr>
<td align="center" valign="middle">0.048</td>
<td align="center" valign="middle">60</td>
<td align="center" valign="middle">78.74</td>
<td align="center" valign="middle">2</td>
<td align="center" valign="middle">0.460629</td>
<td align="center" valign="middle">0.0117</td>
<td align="center" valign="middle">3.929154766</td>
</tr>
</table>

由上图可知，

1、当覆铜厚度是1OZ，里层走线宽度是1mm，PCB走线导体的载流能力60度最大温升时是2.63A。

2、当覆铜厚度是1/2OZ，里层走线宽度是1mm，PCB走线导体的载流能力60度最大温升时是1.59A。

3、当覆铜厚度是1/3OZ，里层走线宽度是1mm，PCB走线导体的载流能力60度最大温升时是1.19A。

4、当覆铜厚度是1OZ，里层走线宽度是2mm，PCB走线导体的载流能力60度最大温升时是4.35A。

5、当覆铜厚度是1/2OZ，里层走线宽度是2mm，PCB走线导体的载流能力60度最大温升时是2.63A。

6、当覆铜厚度是1/3OZ，里层走线宽度是2mm，PCB走线导体的载流能力60度最大温升时是1.96A。

7、当覆铜厚度是1OZ，外层走线宽度是1mm，PCB走线导体的载流能力60度最大温升时是5.26A。

8、当覆铜厚度是1/2OZ，外层走线宽度是1mm，PCB走线导体的载流能力60度最大温升时是3.18A。

9、当覆铜厚度是1/3OZ，外层走线宽度是1mm，PCB走线导体的载流能力60度最大温升时是2.38A。

10、当覆铜厚度是1OZ，外层走线宽度是2mm，PCB走线导体的载流能力60度最大温升时是8.70A。

11、当覆铜厚度是1/2OZ，外层走线宽度是2mm，PCB走线导体的载流能力60度最大温升时是5.26A。

12、当覆铜厚度是1/3OZ，外层走线宽度是2mm，PCB走线导体的载流能力60度最大温升时是3.93A。

有了以上这些结果，我们就可以根据实际情况选择合适的数据来设计出满足我们要求的阻值的PCB导线。

本文转载自：PCB和原理图设计与共享
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