PCB boards are all around us in every gadget we use. Be it the smartphone or a simple calculator; their function depends on the performance of PCBs.
Do you know what are the PCB circuit boards made of? Have you ever opened up your iPhone to see what’s inside? You would find only a few things, from the digitizer, battery to soldering and of course, the PCB. The logic board is what keeps your iPhone running, and any damage to it results in your phone not being able to power on again. The compact circuit board design of the iPhone X, for instance, has wowed many analysts and techies. It is a feat of engineering that not many companies have been able to surpass.
So, what is it that makes circuit boards so unique? What makes one circuit board better than the other? What does a circuit board consist of?
We have prepared this helpful guide where you can learn about the materials used to make PCBs. You can also get a picture of how a manufacturer produces them. Let’s begin by taking a look at what are the circuit boards made of. Then, we will take a look at how you can make your circuit boards.
1、What are the PCB Circuit Boards Made Of
Circuit boards are also known as printed circuit board or PCBs. They drive the different electronic and electrical equipment and tools that we use every day. Most of the PCBs are formed by combining two or more layers depending upon the complexity and nature of device they will be used in.
PCBs use a variety of materials for their composition. One layer can be made from fiberglass or resin derived from paper. Apart from that other material such as copper, solder mask, and silkscreen layers are also used.
In the next chapter, we will know what materials are the PCB circuit boards made of.
Image 1: PCB
2、What Materials are Circuit Boards Made Of
PCB is generally made from four layers of material which are bonded together by heat, pressure and other methods. Four layers of a PCB are made of the substrate, copper, solder mask, and silkscreen.
The substrate is generally made of fiberglass which is also known as FR4. FR refers to fire retardant and provides the foundation of the PCB. The substrate layer is the thickest layer in any PCB though you will find their thickness to vary. It is the layer that offers rigidity to the PCB.
It can also be made from flexible materials which sometimes can be stretched, too. Recently many innovative materials are also being used to create the substrate some of which are even plant-based.
Some other materials are also used for making the substrate such as epoxy or phenolics. The boards made from epoxy resin suffer from thermal sensitivity, and the lamination can fade of quickly in some instances. You can find these cost-effective boards easily in the market and recognize them by the smell they give off. The material also needs the components to be soldered to it.
Image 2: PCB Material
You can find such substrate materials in cheap devices and low-end consumer electronics. Substrates made from cheap materials such as phenolics come with a low thermal decomposition which results in their delamination. They can also create smoke or char if you happen to hold the soldering iron for a long time on them.
The next layer to be applied to the board is copper which is bonded with the help of industrial adhesive or heat. Copper layer can exist on one side of the PCB, or it may be present on both sides of the substrate. Simple electronic devices make use of PCBs which have copper layer only on one side. Copper layers are much thinner and delicate than the substrate.
The copper used in PCBs is referred to by weight and presented in ounces per square foot. Most common PCBs come with a copper content of 1 ounce of copper per square feet.
While the amount of copper present in the PCB determines the amount of power, it will be able to exchange.
A green top layer of PCB is known as the solder mask and is applied over the copper layer so that they don’t come in contact with other electrical parts. On top of the solder mask, a silkscreen layer is provided to create marks and labels for placement of various components.
Next, let us see how you can develop a custom circuit board using a computer application.
3、Custom Made Circuit Boards
We know that PCBs are complex elements and it can get a bit difficult for hobbyists to design themselves a working circuit. The first thing that you will need is a reliable software with which you can create the blueprint of your PCB.
Then you can use many PCB design solutions such as Eagle from Cadsoft Computer which does an excellent job of designing your PCB.
Prepare Schematic View
You have to prepare the schematic view to create your custom PCB. Access the component library that is present in your design software and places them onto the canvas. Now you have to connect the pins along with the lines that symbolize electrical connections in the software.
The same part number may confuse you a bit as you will find several options to choose from. The different packages can include the surface mounted chip or a Dual in-line package (DIP). If you are a hobbyist or doing a DIY project, then it makes sense to go for significant and noticeable system-in-packages (SIP) or DIPs.
You can find them quickly, and hobby outlets and are far friendly when it comes to soldering them compared to surface mounted devices, which are reserved for commercial applications.
The different packaging options can appear to be similar in the schematic view. However, things will start to appear different when you switch to layout view to begin you designing.
You will need to provide the necessary ground and power signals apart from placing your interconnections and components; you can use the components such as GND, VDD and VCC found in the Eagle library for the job.
You shouldn’t also forget to integrate the connectors on the board so that the ground and power can be employed. At this stage, you will also have to any exterior device you want such as a potentiometer or LEDs.
Your design now needs to go through electrical rule check or ERC after you have put everything in place. The test is crucial to ensure that there is no error present which will hamper the functionality of your circuit board.
Some of the common issues that you mace are wires which appear to be connected but are not in reality. You can check for little dots in your Eagle software which represent the connection intersections of the wires.
Other problems may include ground and power signals that you forgot to connect. So you should remember it that the automated tests won’t tell you if your board is going to carry out the desired action, but it can always validate the electrical properties of your design.
Image 3: Schematic Diagram and Layout View
Access Board Layout View
After you have done everything that you need to do in the schematic view, you have to move over to activate the board layout view. Then you have made the switch, and you will find the components spread randomly in your Eagle software. You will also see that the wires directly hook to the pins.
To make the picture a bit less messy, move the components until they make meaning. For example, you can move the connectors to the edges so that things make sense. You still have much work to do to produce the circuit board. So you have to dedicate signals to the layers but remember that the different layers present in the same layer should not touch each other.
The professional version of the Eagle solution comes with an auto-layout feature that can route the signals with a single click. However, for users of the standard version, you have to take things in your own hands. You may also find a design solution from your PCB manufacturer to take care of this step.
After you have laid down the signals, the time has come to run the DRC or the design check. The check ensures that holes drilled too close to a signal line. It also notifies you if the traces are not at an optimum distance from each other or the edge of the board.
You can customize the rules, and sometimes your PCB vendor will offer a file that can be integrated with Eagle solution with specified DRC values. Then you can move ahead and upload your design files if your project passes the DRC.
You should utilize a particular layer to add silk screen lettering to the top. The printing will help you know which component fits whereby presenting part numbers and outlines. That enables you to avoid mistakes like placing a 100K resistor instead of a 1K one.
A Gerber file reveals the language of PCB design, and the 3each board can have many files associated with them. You will have a separate file for specifications of the solder pads and different files for each layer. The drill files also carry the specifications of the drilling.
You can then upload the design with your manufacturer who can use another program to present the final look of the layers, and you can also find out if the components are the right size to fit the holes.
With this, you have come to the end of creating a custom circuit board using design software. In the next chapter, we will explore how a manufacturer produces PCBs.
Image 4: Layout View
4、How are Circuit Boards Made
By now you know how to custom design your PCB by reading the earlier chapter. The technology of PCB is complicated, and it needs to go through a multi-stage manufacturing process. You also have to choose a manufacturer who has all the high precision equipment to bring your project to life. We are going to discuss the PCB manufacturing process in brief just for you.
1. Making the Substrate
You can think of PCBs as sandwiches which come in multiple layers. The base material that is found in the middle is known as the substrate. Then the substrate material is responsible for giving width to the PCB. You can view a PCB from the side angle and find that the thickest layer is the substrate.
Traditionally PCBs were made with fiberglass substrate which is rigid. Nowadays you can find a substrate material which is flexible. Many materials can be, but one common option is using special plastic for the substrate which can tolerate high temperatures.
The material used to make the substrate is generally spread out, the manufacturer then dips it or sprays it with epoxy resin. Next, the material is rolled on to get the desired thickness just like you roll your pie crust using a rolling pin.
The rollers stop rolling when the substrate reaches the desired thickness and passes to the next step, and the substrate is now placed in the oven so that it turns out solid and firm by curing it. After the completion of this step, you have created the very first layer of your PCB.
2. The Copper Layers
The copper layers are essential to carry electricity throughout your PCB. Depending on the purpose, PCBs have a simple or complex design. Apart from the foundation layer of the substrate, copper layers are another essential component.
Your PCB cam comes with a single layer of copper applied to the top or two layers on both sides of the substrate. The PCB can also have numerous layers with other copper and substrate. Some PCBs used in advanced devices or smartphones have more than 12 or 16 layers of copper.
Copper layers are much lesser in width than the substrate layers, and you won’t have any electricity flowing through your circuit if they are absent.
The manufacturer can use a combination of different methods to bond the copper to the surface of the substrate. Any standard methods involve using heat, pressure, and adhesive so that the copper layers are fixed firmly on the substrate. You can take your PCB for drilling after the copper has bonded with the substrate.
For your device to function, the PCB needs to transmit the charge to the right points from one layer to another layer in the board. You will have to create holes referred to as via for the cost to be able to flow through. The manufacturer has several options to drill holes on the PCB and may use a CO2 laser, UV laser or other equipment.
The accuracy and efficiency of the drilling machine determine the preciseness and complexity of the PCB.
You have to clean the holes of any debris or any material that might have been left behind after the process of drilling. They can also be deburred to get any additional material clinging to the PCB. After that, the inner sides of the vias are coated with copper so that it can carry the charge from one layer of the circuit board to another.
Next, you have to print the pattern of the circuit on the PCB. The manufacturer can deploy the copper accurately following the design to get the pattern on board. Otherwise, they may apply copper to the entire board and then remove the copper to etch out the circuit pattern.
The PCB may be subjected to an alkaline bath to remove any extra unnecessary copper.
What you need to add now is the other components such as transistors, capacitors or LEDs on the PCB. You can solder the components on to the PCB using a soldering iron. Before adding the components, the PCB is passed through a succession of electrical tests using a grid tester or flying probe to ensure there are no short circuits or open connection.
Your manufacturer may also use a machine to pump out the parts to your PCB.
Image 5: Copper Patterns
3. The Final Solder Mask
The metals which remain exposed on the circuit board have a chance to get damaged. A nature of copper is to corrode, which will render your PCB useless. You can adequately protect the copper plating and other components of the PCB by adding an extra protective layer on top.
Generally, manufacturers use gold, nickel or tin-lead to plate specific vulnerable parts of the PCB. To top it all, the manufacturer provides another layer on top called the solder mask.
The green color that you see in PCBs is due to the application of the solder mask layer, the solder mask also has some other functions apart from covering and protecting all the metal parts that don’t need to form a connection with anything, the layer of solder mask also ensures that current flows to the right places following absolute paths.
Sometimes you may also find a layer of silkscreen on top of the solder mask which is used to carve labels on necessary parts.
After everything is done, the manufacturer will trim and shed off any extra material or unnecessary parts that are not required in your PCB.
Image 6: Green Solder Mask
Circuit boards can be difficult to create, especially since there are many factors involved. For one, you need to ensure that you use copper, and use the right soldering. Knowing what circuit boards are made of could help you see the circuit board you need for your business.
Creating circuit boards require adept knowledge and precision equipment. You also need to have a reliable and experienced manufacturer who can build PCBs accurately following your specifications. Contact us for custom manufacturing of circuit boards to bring your project to life!