What Are Crossed Boards (X-out PCB) in PCB Manufacturing

In the PCB (Printed Circuit Board) manufacturing process, panelization is a common practice. Panelization involves arranging multiple circuit boards on a larger panel to improve production efficiency, reduce material waste, and lower costs. However, during this process, the occurrence of "crossed boards" can significantly impact product quality, production costs, and delivery timelines. This article will provide a detailed explanation of what crossed boards are, why they occur, how to control their proportion, and their impact on PCB production.

What Are "Crossed Boards"?

Some people may wonder, what is the "X" on a PCB? Why are there cross lines on the PCB? In fact, this is what we call a "crossed board." "Crossed boards" (also referred to as X Boards, X-out PCB, or Cross-out boards) are defective circuit boards on a panel that have been damaged or misaligned during processing, cutting, or other production steps. These boards are often marked with an "X" to indicate their defective status. They may fail to meet the required quality standards, leading to issues such as electrical short circuits, damaged pads, or broken traces. Typically, crossed boards are the result of improper cutting, equipment malfunction, or human error. 
In the production of panelization, the occurrence of crossed boards means that one or more circuit boards within the panel have been affected, making them unsuitable for use. This phenomenon has significant implications for product quality, production efficiency, and cost.

Why mark with an "X" instead of scrapping the entire panel?

This involves a cost issue. For example, if a large panel contains ten small PCB boards and one of them is defective, scrapping the entire panel due to one faulty board would significantly increase the PCB manufacturer's costs. Crossed boards are an inevitable issue in panelization, as defects can occur in any production process. As long as production continues, defective products are bound to happen.

Should I Accept Crossed Boards?

HQ NextPCB, based on industry standards and production requirements, handles crossed boards in two ways: accepting crossed boards and not accepting crossed boards.

1. Not Accepting Crossed Boards:

• Increased Costs: In situations where crossed boards are not accepted, PCB manufacturers typically incur additional labor and equipment costs to reprocess the defective boards. The presence of crossed boards leads to material waste and reduced production efficiency, which often results in extra charges for the customer.
• Strict Quality Standards: When crossed boards are not accepted, production processes are typically stricter, ensuring that every board leaving the factory meets high-quality standards without any defects.

2. Accepting Crossed Boards:

• Prototype Stage: During prototype production, a higher tolerance for crossed boards may be allowed because the primary focus is on design and functionality verification, rather than on cosmetic or precision defects.
• Small to Medium Batch Production: In small to medium batch production runs, customers may tolerate a certain proportion of crossed boards. The acceptable percentage is calculated based on the number of boards (pcs) and depends on factors such as board complexity and panelization quantity.

The following is a general guideline of HQ NextPCB, Note: The panel quantity P refers to the number of pieces on one SET panel. When P ≥ 20, the maximum allowable number of crossed boards per panel is 5, and the highest acceptable crossed board ratio is 10%.

NextPCB's online quote system allows you to choose whether to accept crossed boards, and you can view the price difference between accepting or not accepting them.

PCB Quote Online

Impact of Crossed Boards

1. Impact on Production Costs:

Crossed boards typically mean that additional resources will be required to rework or scrap the affected boards, raising overall production costs. In cases where crossed boards are not accepted, PCB manufacturers often pass these additional costs on to the customer, making the final price higher than expected. For example, they have to produce extral PCBs to meet the customer's order quantity requirements.

2. Impact on Delivery Schedules:

Crossed boards can lead to delays in delivery. If a significant number of crossed boards are produced, the manufacturer may need to rework, repair, or recheck the affected boards, which could extend the overall production timeline. Timely delivery is often a key factor for customers, and crossed boards increase the risk of delays.

3. Impact on Quality:

Crossed boards can directly impact the electrical performance and reliability of the PCB, especially in high-frequency, high-density, and high-precision applications. Even small damages to pads, traces, or vias could cause functionality issues in the final product. Excessive crossed boards negatively affect the quality and reliability of the PCB, particularly in applications for advanced electronic devices.

Controlling the Proportion of Crossed Boards

Of course, controlling the proportion of crossed boards is an important issue that PCB manufacturers need to address during production. PCB Manufacturers determine the acceptable proportion of crossed boards based on different production requirements, board complexity, and panel design. For customers, the main decision is whether to accept crossed boards and the acceptable ratio. PCB manufacturers will provide corresponding advice and solutions in this process to ensure a balance between product quality and production costs.

1. Optimizing Panel Design:

Panel design is one of the key factors in controlling the occurrence of crossed boards. An optimized design not only improves production efficiency but also reduces the likelihood of defects during the manufacturing process. For example, by improving panel layout, boards are less likely to be misaligned or damaged during cutting or separation.

2. Improving Manufacturing Processes and Equipment Precision:

Crossed boards often result from issues during the cutting, drilling, or polishing processes. Improving the precision of production equipment and optimizing cutting processes are crucial steps in reducing the occurrence of crossed boards. Additionally, regular maintenance and calibration of equipment can help ensure high production accuracy and stability.

3. Implementing Stringent Quality Control Standards:

During production, manufacturers should set appropriate quality control standards based on the complexity of the batch and the number of boards on a panel. By managing the proportion of crossed boards differently for small, medium, and large batch production, manufacturers can effectively control the impact of crossed boards on overall product quality.

4. Employee Training and Operational Standards:

Human error is a significant factor contributing to the occurrence of crossed boards. Proper training for employees is essential to ensure they are proficient in operating machinery and following quality standards. This reduces the risk of mistakes and ensures that the final product meets the required specifications.
At NextPCB, as a professional and reliable PCB manufacturing and assembly service provider, they are committed to offering cost-effective panel designs that help customers reduce costs and improve efficiency. Their experienced engineers work closely with clients to provide optimized panelization solutions tailored to specific production needs, ensuring both quality and cost savings throughout the production process.

Conclusion

While the occurrence of crossed boards in PCB manufacturing is unavoidable, their impact on production cost, delivery time, and product quality can be minimized with proper design, process optimization, and quality control. Manufacturers should adopt effective measures to manage crossed board acceptance standards and control their proportion to meet customer expectations while maintaining high production efficiency and quality standards. Through these efforts, manufacturers can maintain their competitiveness in the highly demanding PCB industry and provide high-quality products to customers.
From the customer's perspective, the decision to accept crossed boards largely depends on the specific needs of the project. Customers can choose whether to accept crossed boards based on their quality requirements and budget. Generally, accepting a certain percentage of crossed boards can be a more cost-effective option, particularly for less critical applications or smaller production runs, where the economic benefits of accepting some defects outweigh the potential cost of scrapping whole panels. This flexibility allows customers to tailor their PCB orders according to both their technical and financial needs.