In most cases, the PCBs we design and use are regular rectangular shapes, but there are many times when we need to design circuit boards with irregular shapes such as circular, circular, and hollow, and the PCB design of these shapes is often difficult. . This article will introduce how to design these irregularly shaped PCBs.
Tujia Lichuang PCB Model
Nowadays, the size of the PCB is shrinking, and the function in the circuit board is more and more. With the increase of the clock speed, the design becomes more complicated. So let's take a look at how to deal with more complex circuit boards.
Simple PCB board outlines can be easily created in most EDA Layout tools. For example, to create EDA software, you can easily complete the design and export of various PCB schematics. However, when the board shape needs to be adapted to a complex housing with a high degree of restriction, it is not so easy for PCB designers because the functions in these tools are not the same as those of the mechanical CAD system. Complex circuit boards are mainly used in explosion-proof enclosures and therefore suffer from many mechanical limitations.
It may take a long time and not be effective to rebuild this information in EDA tools. Because, it is very likely that mechanical engineers have already created the shell, board outline, mounting hole position and height restrictions that PCB designers need.
Due to the radian and radius in the board, the rebuild time may be longer than expected even if the board is not complex in shape.
Tujia Lichuang PCB Model
However, from today's consumer electronics, you will be surprised to find that there are many projects that are trying to incorporate all the features in a small package that is not always rectangular. The first thing you think of is smart phones and tablets, but there are many similar examples.
If you return your rented car, you might see the waiter scanning the car with a handheld scanner and then wirelessly communicating with the office. The device is also connected to a thermal printer for instant receipt printing. In fact, all of these devices use rigid/flexible circuit boards where conventional PCB boards are interconnected with flexible printed circuits so that they can be folded into small spaces.
How to import a defined mechanical engineering specification into a PCB design tool?
Reusing these data in mechanical drawings can eliminate duplication of work and, more importantly, eliminate human errors.
We can use DXF, IDF or ProSTEP format to import all the information into the PCB layout software to solve this problem. This will not only save a lot of time, but also eliminate possible human errors. Next, we will learn about these formats one by one.
Figure LCEDA's PCB design work
DXF
DXF is the oldest and most widely used format, mainly used to electronically exchange data between mechanical and PCB design domains. AutoCAD developed it in the early 1980s. This format is mainly used for two-dimensional data exchange.
Most PCB tool vendors support this format, and it does simplify data exchange. DXF import/export requires additional features to control the layers, different entities, and units that will be used in the exchange process.
A few years ago, 3D functions began to appear in PCB tools, so there was a need for a format that could transfer 3D data between mechanical and PCB tools. As a result, Mentor Graphics has developed the IDF format, which has since been widely used to transfer board and component information between PCBs and machine tools.
IDF
Although the DXF format includes circuit board dimensions and thickness, the IDF format uses the X and Y positions of the component, the component position number, and the Z-axis height of the component. This format greatly improves the ability to visualize the PCB in a 3D view. The IDF file may also include additional information about the banned areas, such as height restrictions at the top and bottom of the board.
The system needs to be able to control what will be included in the IDF file in a similar way to the DXF parameter settings. If some components do not have height information, the IDF export can add missing information during the creation process.
Another advantage of the IDF interface is that either side can move the component to a new location or change the board shape, then create a different IDF file.
The disadvantage of this approach is that the entire file representing the board and component changes needs to be re-imported, and in some cases it may take a long time due to the size of the file.
In addition, it is difficult to determine what changes have been made through the new IDF file, especially on larger boards. IDF users can eventually create custom scripts to determine these changes.
Figure LCEDA's PCB design work
STEP&ProSTEP
In order to better convey three-dimensional data, designers are looking for an improved way, STEP format came into being. The STEP format can convey the board size and component layout, but more importantly, the components are no longer a simple shape with only height values.
The STEP component model provides a detailed and complex representation of the components in three dimensions. Board and component information can be transferred between the PCB and the machine. However, there is still no mechanism for tracking changes.
In order to improve the exchange of STEP files, we have introduced the ProSTEP format. This format moves the same data as IDF and STEP, and is a great improvement – ​​it can track changes, and it can also provide functionality that works in the discipline's original system and reviews any changes after the baseline is established.
In addition to viewing changes, PCB and mechanical engineers can also approve all or individual component changes in the layout, board shape modification. They can also suggest different circuit board sizes or component locations. This improved communication establishes an ECO (engineering change order) that has never existed before between ECAD and machinery groups.
Most ECAD and mechanical CAD systems now support the use of the ProSTEP format to improve communication, which saves a lot of time and reduces the costly mistakes that complex electromechanical designs may bring.
More importantly, engineers can create a complex board shape with additional constraints, and then electronically pass this information to avoid someone from reinterpreting the board size incorrectly, saving time.
Conclusion:
If you have not used these DXF, IDF, STEP, or ProSTEP data formats to exchange information, you should check their usage. Consider using this electronic data interchange to stop wasting time recreating complex circuit board shapes.