Pre-reflow AOI: a tool to improve product yield

Overview

Pre-reflow AOI refers to the technology of automatic optical inspection of print circuit boards before the reflow oven in the SMT assembly process.

Pre-reflow AOI uses optical processing technology and then analyzes the image through software to determine whether there are defects such as missing, offset, reverse, wrong parts, etc.

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Principle

1) Image Processing

Optical image processing technology is the core technology of pre-furnace AOI, which can convert the image on the circuit board into a digital image and analyze the digital image.

The optical image processing technologies used in pre-reflow AOI mainly include the following:

• Image matching technology: By comparing the image of the circuit board with the standard image, it can determine whether there are defects.

• Image analysis technology: By analyzing the image of the circuit board, identifying the location, shape, and size of the components, and judging whether there are any defects.

• Image feature recognition technology: Determine whether there are defects by identifying features in the circuit board image.

2) Software Analysis

Software analysis is another significant component of pre-furnace AOI, which is responsible for analyzing the image to determine whether there are defects.

The software analysis system used by the furnace front AOI has the following main features:

• High precision: It can accurately identify defects.

• High speed: images can be processed quickly.

• Scalability: It can be extended according to the needs of different products.

Test items

AOI before the furnace can detect the following defects:

• Missing components: components are missing from the circuit board.

• Offset: Mounting SMT components in the wrong position.

offset | Pre-reflow AOI | SMT assembly | PCB rework | Highqualitypcb

• Reverse: Component soldering direction is wrong.

• Wrong parts: Using the wrong components on the circuit board.

wrong part | Pre-reflow AOI | SMT assembly | PCB rework | Highqualitypcb

Application

Tablet computers are vital tools for people to work and entertain, and their quality requirements are very high. Pre-furnace AOI can detect and correct problems promptly.

Servers are a significant part of modern information systems. The layout on circuit boards is complex, and pre-furnace AOI can detect and correct problems promptly.

Medical equipment is a significant guarantee for people's lives and health, and the components on the circuit board require very high precision.

Pre-furnace AOI can promptly detect and correct problems during the production of medical devices, thereby ensuring the safety and reliability of medical devices.

Aerospace equipment has very high requirements for product quality and requires pre-furnace AOI to detect and correct problems on time.

Advantage

Reducing PCB rework costs: Pre-furnace AOI can effectively detect problems such as missing parts, misalignment, reverse polarity, etc., thereby reducing the number of circuit rework times and rework costs.

Lowering scrap costs: Pre-furnace AOI can effectively detect defects that cannot be repaired, thereby reducing scrap costs.

Improve production efficiency: Furnace-front AOI can help PCB manufacturers quickly identify and correct problems, thereby improving production efficiency.

In conclusion

Pre-furnace AOI is an inspection before parts are mounted, which can effectively reduce PCB rework costs and scrap costs.

Improve production efficiency, thereby increasing product yield and reducing production costs.

In short, pre-furnace AOI is an indispensable detection method in the PCB SMT assembly process and has significant application value.