The first thing to note is that the ounce (OZ) itself is a unit of weight. The conversion formula for ounces and grams (g) is: 1OZ≈28.35g.

　　In the PCB circuit board industry, 1OZ means the thickness of copper with a weight of 1OZ evenly spread on an area of 1 square foot (FT2). It uses the weight per unit area to express the average thickness of the copper foil. Expressed by the formula, 1OZ=28.35g/FT2 (FT2 is square feet, 1 square foot=0.09290304 square meters).

　　Specifically, it can also be said that the conversion method of PCB circuit board thickness is as follows:

　　First of all, we know that the density constant of copper and the conversion formula of related units are as follows:

　　The density of copper ρ=8.9g/cm3

　　1 centimeter (cm) = 10 millimeters (mm); 1 millimeter (mm) = 1000 microns (um)

　　1mil≈25.4um

　　1FT2≈929.0304cm2

　　1mil≈25.4um

　　According to the mass calculation formula m=ρ×V(volume)=ρ×S(area)×t(thickness), knowing that the weight of copper foil divided by the density and area of copper is the thickness of copper foil!

　　Known from the previous article, 1OZ=t×929.0304cm2×8.9g/cm3=28.35g

　　Therefore, t=28.35÷929.0304÷8.9cm≈0.0034287cm=34.287um≈34.287÷25.4mil≈1.35mil

　　"It can be seen that the thickness of 1OZ copper foil is about 35um or 1.35mil.

　　Copper thickness 1.OZ (0.035mm) Copper thickness 1.5OZ (0.05mm) Copper thickness 2.OZ (0.07mm)

　　One, the relationship between the line width of the PCB board and the current:

　　first calculate the cross-sectional area of the track, most of the PCB circuit board copper foil thickness is 35um (if you are not sure, you can ask the PCB manufacturer), multiplied by the line width is the cross-sectional area, pay attention to the conversion to square millimeters. There is an empirical value of current density, which is 15-25 A/mm2. Call it the upper cross-sectional area to get the flow capacity.

　　thick copper circuit board

　　2. Data:

　　The calculation of the current carrying capacity of the PCB has always lacked authoritative technical methods and formulas. The experienced CAD engineers can make more accurate judgments relying on personal experience. But for CAD novices, it can be said that they have encountered a problem.

　　The current carrying capacity of the PCB board depends on the following factors: line width, line thickness (copper foil thickness), and allowable temperature rise. Everyone knows that the wider the PCB circuit board traces, the greater the current-carrying capacity. Here, please tell me: Assuming that under the same conditions, a 10MIL trace can withstand 1A, how much current can a 50MIL trace withstand, is it 5A? The answer is naturally no. Please see the following data from international authorities:

　　The unit of line width is: Inch (inch inch=25.4millimetres mm) 1oz. Copper=35 microns thick, 2oz.=70 microns thick, 1OZ=0.035mm1mil.=10-3inch.

　　In the experiment, the voltage drop caused by the wire resistance caused by the wire length must also be considered. The tin on the process welding is only to increase the current capacity, but it is difficult to control the volume of the tin. 1OZ copper, 1mm wide, generally used as a 1-3A ammeter, depending on your cable length and voltage drop requirements.

　　The maximum current value should refer to the maximum allowable value under the temperature rise limit, and the fusing value is the value at which the temperature rise reaches the melting point of copper. The temperature rise of Eg.50mil1oz is 1060 degrees (that is, the melting point of copper), and the current is 22.8A.

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