As an excellent PCB design engineer, you need to master some necessary design concepts so that you can design a better board. Today, let’s learn about the “three properties” of standard PCB: manufacturability, testability, and reliability.
Manufacturability of PCB
Design for manufacturability (DFM) takes manufacturability and testability into consideration from the beginning of product development and design, so that design and manufacturing are closely linked to achieve the goal of one-time success from design to manufacturing. This is the most effective way to ensure the quality of PCB design.
The manufacturability of printed circuit boards should mainly consider the following factors:
a) The processing capacity, process level and assembly requirements of the equipment;
b) Under the premise of meeting the use, use less fine wire holes, special-shaped holes and slots;
c) The number of layers of the printed circuit board should be minimized;
d) The overall dimensions should comply with the provisions of GB/T9315;
e) If there are no special requirements, FR-4 (GF) foil-clad boards are recommended.
Testability of PCB
Design for testability (DFT) is a technology that adapts to the test needs of the development of integrated circuits. The main task is to design specific test circuits and adjust the structure of the tested circuits to improve the testability of the circuits, that is, controllability and observability.
The testability requirements of printed circuit boards are as follows:
a) The type and format of the test data should meet the requirements of the test equipment;
b) The component holes and power (ground) lines (layers) should be easy to test;
c) When using fixed probe testing, the test points should be arranged at the intersection of the grid, otherwise, detection points should be set. Positioning holes should be set on both sides of the X direction in the board;
d) When using mobile probe testing, optical positioning marks should be set at the four corners of the board;
e) There should be no non-conductive materials on all test points.
Reliability of PCB
Reliability is easy to understand from the literal meaning. When we say “reliable”, we mean “trustworthy”. Reliability refers to the nature and degree of reliability, which means whether the user can trust the product when using it, and how much it can normally, accurately and stably play its functions and performance.
There are many factors that affect the reliability of printed circuit boards. Under the premise of meeting the use requirements, the following requirements should be considered:
a) Use common materials and popular processing technology as much as possible;
b) The design should be simple, symmetrical in structure and evenly laid out;
c) The number of layers of the printed circuit board should be as small as possible, and the diameter and aperture of the connection plate, the width and spacing of the wire should be as large as possible;
d) The board thickness-aperture ratio should be as small as possible, generally not more than five to one.