The FR2 PCB is the most recent in a series of boards from the PCB era used by Rayming PCB & Assembly. The design is a lot more complicated than previous designs, and it requires a lot of fine-tuning to get perfect. It also requires 90% less solder by weight. To design this board, you will need to use new software like EagleCad or OrCAD.
This article will take an in-depth look at what you need to do when designing the FR2 PCB using EagleCad and OrCAD. It includes tips on generating your Gerber files correctly to be 3D printed properly. The guide also discusses making sure you set up your board perfectly. As a result, it makes errors less likely to occur during manufacturing.
Overview
The FR2 PCB design consists of many layers, and the FR2 design process is a lot more complicated than other boards. Therefore, to make your life easier, this article will take an in-depth look at the following:
Understanding why the FR2 PCB has so many problems to fix and what you need to do. Testing your board for errors. Doing a physical check for errors. Creating your Gerber files for manufacturing. Making sure any down-hole drill holes have the proper size. So, they don’t cause shorts on your board. Cleaning up the solder mask layer to ensure it is not too thick or too thin could damage components and cause shorts in the future. Fixing misaligned parts of your board.
What is the FR2 PCB?
The FR2 PCB is among the most recent in many boards from the PCB era. Unfortunately, the design proved too complicated, so they removed parts and others to simplify it. The design also has other problems that need fixing before manufacturing. So, this article will go over how to fix them using EagleCad and OrCAD.
Why does it have so many problems?
Most of the problems with this board come from its complex layers and structures. For example, there are a lot of rectangular holes that you will have a hard time making correctly with your etchant. You will have to work harder than with a simpler board to fix these problems.
There are also many tabs for many layers, which adds extra steps to manufacturing because we must cut these tabs before adding the pads and vias. Getting the tabs cut in the correct configuration and position is tricky since they must fit into a small area. A single mistake could cause you to waste time cutting them out correctly and very likely ruin your board.
Testing for errors
It’s official: PCBs have bugs, and it’s impossible to fix all of them. As a result, some errors will always slip through the cracks, even with the best equipment and software. To make sure your board is not full of errors, you need to do a lot of testing after designing it.
One way to test for errors is to do a final burn-in test (FBT) before manufacturing. It simulates several months’ use by connecting your board to a computer. Then, you can either buy an expensive burner-test unit or design one yourself using a breadboard and jumper wires.
Conversely, you can create a “functional” test (FT) using OrCAD. Then, you can test how well your board would function if real-world engineers used it. For example, an FT might test if your board functions ideally when you connect the reset pin to a 5V line or max it out to 12V.
Checking for physical errors/problems
Besides doing FBT and FTs on your board, you will also need to check it for errors physically. We cannot detect some defects cannot by FBTs and FTs, such as shorts, which can severely damage a board during manufacturing. You will need to use an electron microscope or a flat-bed scanner with ARES software installed to find these problems.
Creating your Gerber files
As you can see, designing the FR2 PCB is not easy, and it will cost you quite a bit of time and money to get it right.
Fortunately, EagleCad has options that make generating your Gerber files very easy. For example, to create your Gerber files, you need to do the following:
First, set your design up as normal. Then go File > Plot. In the “Plot Job” dialog box, ensure that you select Gerber-2-Gerber. Also, ensure that you check all layers. To do this, uncheck all layers on the left of your screen and then check them until they appear on the right). Finally, when you are happy with your selections, click OK to generate them.
After creating your Gerber files, you must check them for errors using Gimp Gnome or another image editor like Photoshop. Many errors can occur, such as a large square of metal on your board and missing holes on your vias.
Make sure all holes have the proper size for the drill bit you’re using
The drill bit used for drilling down into polypropylene will require different hole diameters. This helps to prevent the drill bit from overheating and melting the plastic. If you do not specify these hole sizes, then whatever we use will have copper dust. Don’t tear your PCB apart to fix this issue!
When creating your Gerber files, you should make sure that you specify the drill diameter for all of your down-hole holes. In EagleCad, the hole property is under the “StdHole” node’s general properties tab. Type the desired drilling diameter (in inches) into “Drill Diameter,” and all of your down-hole holes will have the proper size. You must make sure that every drill hole has an appropriate diameter and that they are consistent. Otherwise, a thin layer of copper will form between them and create shorts on your board.
Fixing problems with your bottom and top ground planes
Due to its tall and wide shape, the FR2 will be very difficult to drill down properly. The topmost layer of the board is extremely fragile. So, it is essential to make sure that all holes go down into this layer before drilling down into the polypropylene.
When drilling down in FR2, you should always use copper tape on the bottom (and not just any copper tape). Otherwise, you risk breaking your board. The other reason to use copper tape is that it helps keep a hole from cracking as soon as you insert it into the hole. In some cases, one inch of tape won’t be enough, and you may need two inches or more.
Entering your Gerber files into the Gerber2PLUS PCB layout software
This is the easy part. Once you have your Gerber files in a readable format, they can be easily imported into any PCB layout software together with a backplane. This will be an isolation pad. With this information, you can easily create your FR2 PCB and ensure everything has the correct wiring.
Conclusion
The FR2 is a very cryptic design, and it is frustrating to build. On top of that, it’s not the easiest board to build because there are so many pieces. As a result, it’s a challenge for experienced engineers to create. However, it’s also an excellent project for students to get their first experience with microcontrollers.
