PCB Know How

Generic Standard on PCB Design (IPC2221A)

PCB

Rigid Laminate material (FR4, typically) consisting of a glass epoxy substrate clad with copper on two sides for double sides (0.062” typically)

PCB fabrication Gerber data requirement

1   1) Top Electric (Artwork)

2   2)    Bottom Electric (Artwork)

3   3)    Top Silk (Artwork)

4   4)    Top Resist (Artwork)

5   5)    Plated Through Hole (N.C Drill)

6   6)    Non-Plated Through Hole (N.C Drill)

7   7)    Board Outline (Artwork)

8   8)    Drill Table

    Electrical Clearance

    AC and pulsed voltage > 200V must consider the dielectric and capacitive effect of the substrate in addition to spacing.

     

     Minimum spacing requirements according to withstand voltage are as below

Withstand Voltage (V)	Minimum Spacing (mil)
0 ~ 30	3.9
31 ~ 150	24.0
151 ~ 300	49.2
301 ~ 500	98.4

Electrical Isolation (Creepage Vs Clearance)

     Creepage is the shortest path between two conductive parts measured along the surface of the insulation. Clearance is the shortest distance between two conductive parts measured through air.

     Copper Weight

     1 oz of copper will cover one square foot area when rolled out to a thickness of 0.0014 inch or 1.4 mil.

Copper Weight (oz)	Thickness (inch)
½	0.0007
1	0.0012 ~ 0.0014
2	0.0028

     PCB Surface Finishing

     Different types of PCB finishing are as below

     1)    Hot Air Solder Level (HAL or HASL)

     2)    Hard Gold-Electro plated gold

     3)    Electro Less Nickel Emersion gold

     4)    White Tin

     5)    Organic Solderable Preservative (OSP)

     

     The most common surface finishing we can see is Hot Air Solder Leveling. In this process, Panels are processed through a bath of molten solder, conversing all exposed metal surfaces. High-pressure hot air, directed at both sides of the panel simultaneously, removes excess solder from the holes and surfaces.

     PCB Trace Width vs. Current Table

       A PCB trace width vs. current table helps you understand the relationship between PCB trace width and current carrying capacity so you can determine the required trace width for your printed circuit board design.