What are the key aspects of PCB quality inspection standards?

Date：2022-10-21 15:01:28Views：658

PCB (printed circuit board) can be divided into rigid PCB and flexible PCB. The former can be divided into three types: single-sided PCB, double-sided PCB and multi-layer PCB. After PCB manufacturing, inspection must be carried out to determine whether the quality is compatible with the design requirements. Differences in PCB quality levels lead to differences in complexity and testing and inspection methods. So far, rigid double-sided PCBs and multilayer PCBs account for relatively large applications in electronic products, and sometimes flexible PCBs are used in some cases. Now let's introduce the quality inspection standards of PCB.

The first thing to say is about the performance level of PCB

PCB performance level

In order to reflect the increasing complex programs, functional performance requirements and inspection and test frequency, PCB has specified three general levels.

Class I general electronic products

Including consumer products, some computers and their external equipment, suitable for occasions where the appearance defect is not important but the main requirement is the function of the printed board of the finished product.

Secondary durable electronic products

Including communication equipment, complex commercial machines and instruments. These devices have high performance and long service life, which require uninterrupted work but are not critical. Such appearance defects of printed boards are allowed.

Three level high reliability electronic products

Including those continuous functions or functions that work immediately once required is critical equipment. These equipment are not allowed to have downtime, and must be able to work normally when necessary, such as life support equipment or aviation control system. This grade of printed boards is applicable to occasions where high assurance level and application are critical.

The quality inspection of PCB generally includes appearance inspection, connectivity inspection and solderability inspection.

1、 Appearance inspection standard for PCB

1. Whether the surface of PCB circuit board is smooth and flat, and whether there are bumps or scratches. Whether there are missing holes, wrong holes or copper foils around the through-hole are broken.

2. For the integrity of the wire pattern, cover the PCB with a photographic negative, and measure whether the wire width and shape meet the requirements. Whether there is any trachoma or broken wire on the printed wire, whether there is any serrated notch on the edge of the line, and whether the wires that should not be connected are short circuited.

3. Whether the outer edge size of PCB meets the requirements.

2、 PCB board connectivity inspection standard

Multi layer PCB circuit board needs connectivity inspection. Usually, use a multimeter to check whether the PCB circuit is connected.

3、 Solderability inspection standard for PCB

Inspect the wetting ability of solder to PCB graphics when soldering components to PCB.

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