PCB Assembly Visual Inspection

Geospace Technologies Contract & Manufacturing Division

April 28, 2022

Analysts expect the market for printed circuit boards (PCBs) to be worth more than $75 billion by 2027. In this dynamic market, you need to offer the highest quality products to stay competitive.

If flawed boards reach your customers, you can lose money through warranty payments or returns—even face lawsuits. Your reputation could also suffer, resulting in a loss of trust from your clients.

A comprehensive testing and verification process helps you avoid these negative outcomes.

PCB assembly visual inspection is a critical part of the inspection process. Combined with early design review and automated inspection techniques, visual inspection helps you produce a higher-quality product.

We’re providing a guide about PCB visual inspection and how it fits into a well-designed inspection plan.

Design Review

The quality control process for PCB assembly starts before production begins. A design review can identify potential issues before they cause problems during assembly.

A Design for Manufacturing (DFM) check looks at how the PCB design could be optimized. It finds ways to prevent and eliminate aspects of the design that could cause manufacturing inefficiencies. A DFM also identifies any design errors that could cause problems in assembly.

Design for Excellence (DFX) focuses on creating higher-quality products at the design stage. Its goals are to improve quality, lower costs, and accelerate the product development cycle.

A comprehensive design review should result in a product that needs fewer alterations. The inspection process during assembly goes more smoothly with fewer defects.

Manual visual inspection is the most basic form of PCB inspection. Visual inspection can occur after many steps in the PCB assembly process.

Visual inspection is a simple procedure. However, it requires an experienced and knowledgeable inspector.

PCB Visual Inspection Process

To conduct a manual visual inspection, an inspection staff member looks over the board with the naked eye or through magnification. The inspector first compares the board to the design documents. This part of the inspection verifies that the board meets all the design specifications.

Next, the inspector looks for common defects. The type of defect depends on the type of board, its components, and the stage in production.

For example, after solder paste printing and device placement, an inspection will look for contaminating solder paste. This inspection will also check to see if any components are missing.

A PCB assembly visual inspection can include checking items such as:

Surface quality
Dimensions of the assembly
Clarity and completeness of conductive patterns
Quality of pad plating
Quality of coating

The inspection staff can examine almost every aspect of the board.

Benefits of Manual Visual Inspection

PCB visual inspection has several advantages. It’s simple and doesn’t require specialized equipment other than magnification. It’s less expensive than other testing methods.

Visual inspections are often the most cost-effective method for prototypes and low-volume runs.

Visual inspections are also rapid. You can do a visual inspection after almost any phase of the production process.

Visual Inspection in the PCB Assembly Inspection Process

Visual inspection is an essential method for testing and verification during PCB assembly. It works well in combination with other methods, and you get a more complete picture of the quality of the board.

There are several automatic inspection technologies available for PCB assembly.

Electrical Part Verification and Paste Inspection

Electrical part verification and paste inspection look at the solder. Electrical part verification uses an automated optical inspection to look for soldering defects.

Paste inspection looks for defects in the solder paste, and it can find problems in the application process.

Automated Optical Inspection

Automated optical inspection uses multiple light sources and at least one still or video camera. The machine combines the pictures into a complete image of the board. Geospace operates a 3D inspection machine that utilizes both optical and laser to more accurately map and analyze the deposit to ensure the best quality.

The system compares the image to what the PCB should look like. It gets this information from the design specifications or an approved model.

Automatic Laser Test

An automatic laser test system uses lasers to scan the PCB and take measurements. It measures the height. Automatic laser testing provides data in real-time about the solder paste printing process.

X-Ray Inspection

X-ray inspection allows the examination of components that are difficult to see using visual inspection techniques. For example, x-ray systems let you see solder connections beneath chip packages, and you can see beneath leads to inspect the heels of solder joints.

An x-ray inspection can be manual or automated.

In-Circuit Testing

In-circuit testing lets you test individual components of the PCB and measure their performance.

A fixture with sensor points connects to the relevant points on the board. Software for the in-circuit tester tells the system which tests to perform, and it establishes the pass or fail criteria.

In-circuit testing will identify the vast majority of defects.

Flying Probe Testing

Flying probe testing is also called fixtureless in-circuit testing. It’s a type of in-circuit test, but it doesn’t use fixtures, which lowers the cost of the test.

Flying probe testing can adapt to new boards quickly and easily. It’s ideal for prototypes and small-volume production.

Functional Circuit Test

A functional circuit test comes at the end of the PCB assembly process. It uses a functional tester that simulates the final working environment of the PCB. The test evaluates whether the PCB performs according to specifications.

Ensuring Quality in the PCB Assembly Process

PCB assembly visual inspection is an essential part of ensuring the quality of your product. Visual inspection combined with automated inspection techniques provides the data necessary to eliminate defects.

Geospace Technologies is a PCB assembly manufacturer with the top-tier quality standards you expect. Starting with the design review process, we work with you to create a higher-quality product. Our inspection process uses a full range of techniques including visual inspection with 10x optical and digital microscopes.