Most of us have come across PCB and FPCB in our day to day usage of electronic devices. However, few of us have ever taken time to think about how PCBs and PCBA are made. So we keep wondering how the PCBs that drive our appliances including computers and microwaves are actually made. In this article, we delve into what PCBs are, the materials used in making them, the cost and the process of manufacturing them.
What is a PCB and How is it Made?
A printed circuit board refers to a board made of fiberglass, laminate materials or composite epoxy which has conductive pathways that connect to different components such as resistors, transistors, and integrated circuits. It supports and connects components electrically via conductive tracks or pads. Electronic components are soldered onto the PCB to perform a specific function.
The PCB Substrate
Typically, PCBs and Fpcb are made of layers of materials including the base material referred to as substrate which determines whether the PCB is rigid or flexible. Also, the substrate used determines the amount of temperature that your PCB is capable of standing. The substrate can be made by simply laying out the material and spraying it with epoxy resin and rolling it several times until it is of the right thickness.
For a printed circuit board to work, it must have either a layer or layers of copper. Manufacturers may choose to put the layer on the top or either side of the substrate. It is also possible to have several layers which are alternating between the substrate and the copper. We have plenty of PCBs out there with many layers of copper. Some of them have more than 16 copper layers. Usually, the thickness of copper will be thinner than the substrate used. Its primary work is to carry electrons from one point to another. It ensures that electricity is flowing throughout the circuit. Notice that manufacturers attach the copper to the substrate by applying pressure and heat. It makes the base material and the copper to bind before it can be drilled. Copper is one of the materials that can be recovered through a recycling process.
The PCB Soldermask
After the substrate and the copper layers have been fused together, it is necessary that the plating gets protected to reduce chances of the copper getting corroded and damaging. It is, therefore, essential that a solder mask is used to make an additional layer to protect the PCB. The substrate is typically green in color even though the manufacturer may choose any other color depending on the need.
PCB Manufacturing Process
Manufacturing process is vital as it results in one of the tools that are the basis of electronic success. The process starts by assembling the required material including the substrate and copper, attaching the substrate to copper by applying pressure and heat, creating tracks, removing the unwanted copper through the etching process and testing the board to ensure that there are no flows.
Double Sided PCB Fundamentals Introduction
PCB boards have become part of our day to day electronics and are essential components of our modern electronic devices. The boards provide an interface on which components can be soldered. They may be single, double or multi-layered. Single-sided PCB boards are cheap but cannot be deployed in complex situations. As such, it has forced manufacturers to design and manufacture double-sided PCBs which can be used in high density and complex cases.
What is Double Sided PCB
A double-sided PCB refers to one that gives the user the flexibility of interconnecting circuits on either side of the board. It allows the user to have components soldered on the bottom and the top side of the board. They enable the manufacturers to quickly design complex boards that can accommodate more components, which can be used in complex situations. Other than providing interconnection flexibility, the board eliminates electromagnetic interference and makes designing complex circuits easier. The double-sided PCBs have made it possible for PCBs to be used in higher technology applications. Allowing for top layer routing and tracing it to the bottom layer has made PCBs more valuable than before.
Advantages of Double-Sided PCBs
The PCBs offer the engineers more flexibility and have made it possible to increase the circuit density. It is not the case for engineers working on single-sided PCBs. They have limited space to fit the components. Secondly, the double-sided PCBs are cheap and do not put much strain on the users budget. Lastly, since more parts can be populated in a smaller area, the double-sided PCBs are small in size and can fit in a wide range of devices.
PCB Copper Thickness
PCB boards allow for the flow of current between components. They do this by ensuring that the routes on the PCB are not overlapping and have enough space between them. Overlapping of wires can cause short circuits and so using a PCB board with sufficient copper thickness eliminates this problem. Typically, copper thickness is measured in ounces and determines whether the circuit can do the job it is designed for or not.
Copper thickness, therefore, refers to the results you get when 1oz of copper is compressed over an area of one sq. Ft. of PCB. When designing a PCB, the engineers must convert ounces to mills to help them create the PCB. Figure 2 gives an overview of what copper and PCB layers appear like in the form of various layers.
Designing Copper Tracks
The engineers must always remain alert when designing the PCB. They need to ensure that the PCB thickness is enough and can meet the specified needs. Typically, the engineers will keep the thickness at 1 oz to ensure that the PCB can accommodate and allow a specified amount of current to flow through it. Circuits that require more current must have the level of coper thickness increased. The engineers can perform the calculation to determine the amount of copper thickness required when designing a circuit to perform a specified function.
Notice that the more copper a PCB contains, the more it can be applied in circuits. However, use of more copper means that the board may cost more. Also, the thickness of the copper determines how easy it is for the designer to remove the excess copper by etching the PCB. Thus, designers of PCB must evaluate copper thickness before designing a PCB to be put to a specified application.
Heat Sink PCB-The Rules You Need To Know
As the PCB technology advances new challenges emerge and so it is critical that the engineers work round the clock to ensure that the difficulties are overcome. One of the most teething issue that PCB users have had to grapple with is the generation of heat that leads to increased temperatures. It has forced designers to think outside the box and find a way through which they can minimize heat generation and electrical loss. It is for this reason that most circuits will come with a heat sink provision that allows for even distribution of heat to reduce excessive temperatures. For instance in circuits that involve high-speed microprocessor, high heat is dissipated, and if there are no heat sinks to absorb the heat, it can easily damage the component. The IC, in particular, generates a lot of heat and requires a heat sink to absorb and channel the excess heat away from the components.
Metallic Heat Sinks
This type of a heat sink can be attached to the PCB body by tightening it with a screw on the through the hole. In some other cases, the heat sink may be pasted on the body using epoxy or even a thermal tape. In cases where the heatsink comes with springs and clips, it is possible to fit them on the component that heats up.
Notice that a heat sink for PCB play a critical role especially where the PCB is to be used in circuits with a massive flow of current. For instance, discrete semiconductors such as IGBTs, TRIACS, and MOSFET generate a lot of heat which must find its way out of the PCB via a heat sink.
SMD Components with built-in Heat Sink
We have plenty of SMD components that come with inbuilt heat sinks they include PMICs and MOSFET. These devices have an integrated heat sink which may be attached to the body and connected to the drain.
Heat Sink PCB Thermal Design Considerations
From this discussion, it is evident that power devices must have a proper PCB layout and should come with a heat sink to take care of thermal issues that may arise as the device is being used.
Design guidelines to consider when dealing with heat sinks
- For a heat sink to dissipate one Watt of power at a temperature of about 40℃ it should have a cross-section of 2.4 in2. If an external cooling fan is used the values reduces to about 1.2 in2 per watt.
- If you try these two methods, but you discover that it is not working, it is recommended that you use heat sinks.
- Notice that the above parameters assume that copper layer will generally be coupled with components that generate heat and that the copper will be extended to the edges of the board. The copper layer will thus behave as the thermal layer of your PCB.
- When more than 1 component that generates a lot of heat is to be used on PCB, it is recommended that you place them a few inches away from each other. It allows the PCB to be heated evenly.
- The heat transfer is always higher when the PCB has more vias. The vias are in thermal contact with the parts of the component that is generating heat.
- In case of high powered applications, it recommends that you consider using PCBs with an increased copper weight between the planes.
Manufacturing Costs Breakdown
PCB assembly and production is a tedious activity that entails so many steps. It is concerned with numerous activities that include collecting the materials, preparing and fabrication them into PCBs. It also involves etching the PCBS, laminating, drilling and packaging them. Each of these steps come with their cost which consists of the total cost of manufacturing the PCBs, which must be included in the final selling price. How To Make PCB Manufacturing Cost Breakdown from each part?
The Cost of Material
To be able to understand the cost of PCB manufacturing, it is critical that we consider the layers that the PCB has, the material used in manufacturing it and the size of the PCB. The cost of the raw materials is the primary factor that determines the final cost of PCBs.
Gold, nickel, copper, silver, fiberglass, lead, epoxy resin, a variety of chemicals, and nickel are some of the materials that must be used in manufacturing PCBs. You also need to estimate the number of the components that need to be assembled. Also, the type of the PCB to be assembled is critical as it helps determine the final cost of the PCB. Manufacturing double sided PCB is more costly than single sided PCB.
Double-sided PCBs use more solder and requires that you make use of the SMT machine programming. This increases the cost of these PCBs. Similarly, manufacturing multi-layered PCB is more costly than the production of double-sided PCB.
Notice that the essential items that increase the cost of PCBs are not just limited to the cost of the material but also the thickness of the PCBs, the Impedance they should come with, and the diameter of the hole are all critical. The components to be included, the distance the PCB must be transported before it is sold. Also, other peripheral factors must also be considered when computing the cost of the PCBs.
Other aspects that add to the cost of PCBs is the thickness of the copper used. Using thick copper increases impedance and allows the PCBs to be deployed in areas that require more current. Other external factors such as energy, water, and transportation cost may increase the cost of production and must be included in the computation of the cost of producing PCBs.
Cost of Labour
Notice that the cost of labor is also critical in determining the final price of manufacturing PCBs. It refers to the price of all the factors used by the fabricators. Manufacturers will also have to include other overhead expenses in the final cost of PCBs. The cost of equipment, security, lighting, water, and other small overhead expenses must all be considered in determining the final cost of producing every single PCB. Other additional overheads such as treatment of wastewater system, approvals, zoning, and permits are all important and will be used in the cost of producing PCBs.
It is one of the most important raw material used in producing printed circuit board. The size of the panel used is important when calculating the overall cost. Boards that take up less panel will cost less. Also, those that use panels that fit better will be less costly.
The Quantity of Pieces Produced
The quantity of the pieces required is critical because it determines the method of production to be used. Mass production of PCBs requires the use of efficient and automated processes that reduce the cost significantly.
The time it takes to manufacture the PCBs. We can provide both regular delivery service & express service; expedited boards can be shipped out within 24-48 hours! You can choose suitable service according to your schedule. We will try our best to make PCB Manufacturing Cost Breakdown with the best quality.
Having taken you through what PCBs are and some of the factors that determine the ultimate cost of PCBs, I bet you are better placed to make your next order. To make your work easier, visit wellpcb.com now and place your order online.
Please note that without special remarks, all the price we quoted is based on the normal delivery. You need to indicate on online quote system or contact us about the expedited order; your order will be processed as the top priority. (Please note that our current production will affect the time, call us if time is urgent for)
For the Special board, please contact us for details:
► Special Material Requirements
► Shielding Layers
► Blind and or Buried Vias
► Rigid-Flex constructions with more than 2 Flex Layers
► Special Surface Treatment
WellPCB, registered in Australia, is a daughter company of Uniwell Circuits Co., Ltd, which has two modern PCB factories, founded in April 2007.WELLPCB is Focusing on Printed Circuit Board Fabrication and PCB Assembly Turnkey Services, to meet the requirement of High Quality, low cost, fast delivery, easy ordering from customers around the world.