PCB Tech - ​How to deal with more complex PCB circuit boards

We expect that a complete PCB board is usually a regular rectangle. Although most designs are rectangular, many designs require irregular circuit boards, which are usually not easy to design. This article describes how to design irregular-shaped PCBs.

Nowadays, the size of PCB is shrinking, the function of circuit board is getting bigger and bigger, with the increase of clock speed, the design becomes more and more complicated. Let's see how to deal with more complex circuit boards.

Simple PCI board shapes can be easily created in most Edayout tools. However, it is not easy for PCB designers when the shape of the circuit board needs to adapt to a complex enclosure with height restrictions. Because the functions of these tools are different from mechanical CAD systems. Complex circuit boards are mainly used for explosion-proof enclosures, so they are subject to many mechanical limitations.

Rebuilding this information in EDA tools may take a long time, and it has no effect. Because the mechanical engineer may have created the mounting hole position and height restrictions of the housing circuit board shape required by the PCB designer.

Due to the arc and radius in the circuit board, even if the shape of the circuit board is not complicated, the reconstruction time may be longer than expected.

However, from today's consumer electronics products, you will be surprised to find that many projects are trying to add all the functions into a small package, which is not always rectangular. The first thing you think of is smartphones and tablets, but there are many similar examples.

If you return to the rental car, you can see the attendant using a handheld scanner to read the car information and communicate wirelessly with the office. The device will also be connected to a thermal printer for instant receipt printing. In fact, all these devices use rigid/flexible circuit boards, and traditional PCB circuit boards are connected with flexible printed circuits so that they can be folded into a small space.

How to introduce the defined mechanical engineering standards into PCB design tools

Reusing these data in mechanical drawings can eliminate duplication of work.

We can use DXFIDF or ProStep format to input all the information into PCB Layout software to solve this problem. This not only saves a lot of time, but also eliminates possible human error. Next, we will learn about these formats one by one.

DXF is one of the most widely used formats between the mechanical and PCB design domains. Auto Card was developed in the early 1980s. This format is mainly used for QR data exchange.

Most PCB tool suppliers support this format, and it does simplify data exchange. DXF introduction/guidance requires additional functions to control the different entities and units of the layer used in the switching process.

A few years ago, three-dimensional functions began to appear in PCB tools, and three-dimensional data needs to be transferred between machinery and PCB tools. Therefore, Mentor Graphics developed the IDF format, followed by the transmission of circuit board and component information between the PCB and the machine tool.

Although the DXF format includes the size and thickness of the circuit board, the IDF format uses the number of components in the X and Y positions and the height of the component on the Z axis. This format greatly improves the role of the PCB in the three-dimensional view. The IDF file can also be included in other information in the forbidden area, such as the top and bottom of the circuit board.

The system needs to control the content contained in IDF files in a manner similar to DXF parameters. If some components do not have height information, the missing information can be added during the creation process.

Another advantage of the IDF interface is that either party can move the component to a new location or change the shape of the circuit board, and create a different IDF file.

The disadvantage of this method is that in some cases, because the size of the file may take a long time, the circuit board and components need to be re-introduced to change the entire file.

In addition, it is difficult to determine which changes are made through a new IDF file, especially on larger circuit boards. IDF users can finally create custom feet to determine these changes.

In order to better transmit 3D data, designers are looking for an improved step format. The step format can transmit the size of the circuit board and the layout of the component, but more importantly, the component is no longer a simple shape, only the height value.

The STEP component model provides a detailed and complex description of the components in a three-dimensional form. The circuit board and component information can be transferred between the PCB and the machine. However, there is still no mechanism to track changes.

In order to improve the exchange of step files, the ProStep format was introduced. This format can move the same data as IDF and steps, and has a great improvement-it can be tracked and changed. It can also work in the original system of the theme and review any changes after setting a baseline.

In addition to checking for changes, PCB and mechanical engineers can also approve all or individual components that modify the shape of the circuit board. They can also suggest different board sizes or component locations. An ECO (Project Change Order) that has never appeared before was established between ECAD and the Machinery Group.

Currently, most ECAD and mechanical CAD systems support the use of professional step formats to improve communication. This saves a lot of time and reduces the cost of complex electromechanical design.

More importantly, engineers can create a complex circuit board shape and transmit it electronically to prevent anyone from misunderstanding the size of the circuit board. So as to achieve the goal of saving time.

The conclusion is that if you have not used these DXFIDFSTEP or ProSTEP formats to exchange information, you should check their usage. Consider using this electronic data exchange to stop wasting time to create complex circuit board shapes.