Rules on PCB construction

Today, let’s introduce primary knowledge on PCB. Here suggest some rules on PCB construction. Mostly are about the information on SMD and DIP assembly.

1. About SMD assembly

In SMD assembly, we must pay attention to the mininum gap between components (capacitors, resistors and IC chips). Usually, we suggest the best gap between independant component and IC chip is 0.5-0.7mm. But, the gap may change according to the configuration of fixture.

2. About DIP assembly

If in DIP assembly, the gap between resistors is 1-3mm, which is wider than SMD assembly. What needs to notice is to make sure enough gap in DIP assembly. Thinking of difficulties of assembly process, nowadays seldom use DIP technology.

3. About the place of decoupling capacitor

Around power port of IC will need to place an decoupling capacitor. The decoupling capacitor should try best near the power port. When a chip have several power ports, each power ports should have a decoupling capacitor.　

4. Independent component on the edge of PCB

Normally, PCB is delivered by panel. So components on the edge of PCB should comply with two rules. The first one is to parallel V-CUT direction. The second is should keep specified gap from the edge, so that to avoid damage on components when making V-CUT.

5. If connect two adjacent PADs, we should make sure they are connected outside of PADs and to avoid connecting as bridge. Moreover, in the meantime, we should notice the width of trace.

6. Traces along with the PAD should keep the same width. If not accordant with electrode size, we should check if short circuit happen or not. 

7. Pay attention that PADs should not have VIAs.

8. Leading wire could not be near the edge of PCB. Further, it’s not allowed to add copper at the edge of PCB or tooling holes.

9. If value of capacitor is big, we should firstly consider if the temperature of capacitor meet the requirement or not. And second assure the capacitor far from the heating area.

10. In the end, we should payment more attention on the technology of SMD assembly of capacitor. When do SMD near heating area, capacitors will be easily deciduous from PCB because of shaking during production.