PCB Design Process - Introduction to DFM

1> Reduce the PCB assembly process and cost, and try to place the part on the main soldering surface of the PCB.

2> If SMD really needs to be placed on both sides of the mixed-technology PCB, consider selective soldering.

3> The same or similar components should be placed in the same column or row and the polarity should point in the same direction.

4> According to the size and number of uniform distribution components on the PCB to avoid PCBA deformation in the reflow process and wave soldering process.

5> Connectors and sockets should be placed on the main solder surface of the PCBA.

6> Do not design through-hole devices on both sides of the PCB.

7> Allow test or test access.

8> Automatic assembly should be considered in the design to minimize manual operations.

9> Design should consider simple operations.

10> The standard assembly and test requirements should be used in the design unless otherwise specified.

11> Self-check and boundary scan test should be considered in design

PCB edge requirements

Two parallel edges in the direction of the flow of the PCB along its flow allow a 5 mm cut-out.

Features:

Prevents the mechanical equipment chain, clamps and fixture from colliding with the PCB during transportation and assembly, and also prevents SMD parts located on the edge of the PCB from being damaged during manual operation and temporary storage on the line.

PCB board deformation requirements

1. For better placement and fixtures, the maximum degree of PCB bending is:

No more than 0.1 inch (2.5mm) in the direction of the largest dimension of the board

2. Plated through hole technology:

0.001”/inch, (not more than 1.5% of the longest dimension of the board)

SMT/BGA Technology:

0.0075 "/inch, (not more than 0.75% of the longest board size)

Positioning (base hole)

Base hole provides positioning reference for all other drilling and punching holes, as well as PCB assembly equipment

Provide accurate positioning and reduce error accumulation.

Note:

1> The difference between the base hole and the reference mark point;

2> The base hole is on the longest side

3> Standard aperture and distance can reduce waiting time for PCB fabrication and equipment commissioning

Panel design considerations

A panel is a process in which one or more PCBs are arranged on a substrate to make it easy to manufacture (eg process holes, fiducials, etc.)

Panel are divided into sections according to function

The space required for processing

Circuit board

Test point

Board space between boards

Additional connectors for edge-plated connectors