OZ is a unit of weight. Why is it used to represent thickness in PCB?

OZ is a unit of weight. Why is it used to represent thickness in PCB?

First of all, ounces (oz) itself is a unit of weight. The conversion formula of ounces and grams (g) is 1oz ≈ 28.35g.

In the PCB industry, 1oz means the thickness of copper with a weight of 1oz evenly spread over an area of 1 square foot (ft2).?

It represents the average thickness of copper foil by the weight per unit area. Expressed by the formula, that is, 1oz = 28.35g/ft2 (ft2 is square foot, 1 square foot = 0.09290304 square meter).

Specifically, the conversion method between length and thickness is as follows:

Firstly, we know the density constant of copper and the conversion formula of relevant units are as follows:

Density of copper ρ= 8.9g/cm3

1 cm (CM) = 10 mm (mm); 1 mm (mm) = 1000 microns (UM)

1mil≈25.4um

1 FT2≈929.0304cm2

1mil≈25.4um

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

As we know from the above, 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

Therefore, 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 2.5mm OZ(0.07mm)