PCBs have allowed engineers to connect components in a circuit in a more organized manner eliminating the need to have many wires that are crossing each other and which may lead to accidents.
Notice that the modern technology allows for the large-scale production which significantly reduces costs. This article introduces you to learn more about PCB, the material used in manufacturing them, the cost and the process they undergo.
1、What Is A PCB And How Is It Made?
A Printed Circuit Board (PCB) 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 electrical components via conductive tracks or pads. Electronic components are soldered onto the PCBs to perform some specific functions.
Figure 1 PCB Board
The PCB Substrate
PCBs and FPCB are made of layers of materials including the base material (referred to as a substrate), which determines whether a PCB is rigid or flexible. Also, the substrate used determines the temperature range that your PCB can withstand.
The substrate is often made by laying out the material directly and spraying it with epoxy resin and rolling it several times to an acceptable thickness. Another critical consideration is PCB's permittivity/permeability. This feature is of the essence when designing boards for devices with high-frequency signals.
For a printed circuit board to work, it must have either a single layer or multi-layers of copper. Manufacturers may choose to put the layer of copper on the top or both sides of the substrate. It is also possible to have several layers which alternate between the substrate material 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 is thinner than the substrate used. The primary role of copper is to carry electrons from one point to another. Manufacturers bind the copper to the substrate by applying a combination of heat and pressure.
This binding process secures the bond between the copper and the substrate. This process makes it resistant to breakage during the drilling process. Copper is also 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 copper oxidizing and corroding in a way that can damage the PCB. It is, therefore, to use a solder mask when making additional layers to protect the PCB.
The substrate is typically green in color. But then, the manufacturer may choose any other color depending on his/her need.
PCB Manufacturing Process
The process of manufacturing PCBs starts by assembling the required material (including the substrate and copper). The substrate is then attached to the copper by applying pressure and heat.
Lastly, the process also involves the creation of tracks, removal of unwanted copper through an etching process and testing the board for flaws before production.
2、Double Sided PCBs Fundamentals Introduction
PCB boards have increasingly become part of our day-to-day electronics. The boards provide an interface on which components can be soldered.
PCBs may be single, double or multi-layered. Single-sided PCB boards are cheap, but they cannot be deployed in complex situations. As such, it has forced manufacturers to design and manufacture double-sided PCBs that can be used in high density and complex cases.
2.1 What is Double-Sided PCB
Figure 2 Double Sided PCB
A double-sided PCB is a type of PCB that offers engineers the flexibility of interconnecting circuits and components on either side of the board. It allows the user to have components soldered on both the bottom and the top side of the PCB. They enable the manufacturers to design complex boards that can accommodate more components for use in complex situations.
Other than providing interconnection flexibility, the boards also eliminate electromagnetic interference. This ability makes designing complex circuits a lot easier. The double-sided PCBs have also made it possible to use PCBs in higher technology applications.
Allowing for top layer routing and tracing to the bottom layer has made PCBs more valuable than before.
2.2 Advantages of Double-Sided PCBs
Double-sided PCBs offer engineers more flexibility. They also house increment in the circuit densities over time. These factors do not apply to engineers working on single-sided PCBs. Single-Sided PCBs have limited space to fit the components.
Secondly, double-sided PCBs are nowadays cheaper and do not squeeze much from your daily budget.
Lastly, since more parts can be populated in a smaller area, double-sided PCBs are small in size and can fit be utilized to manufacture smaller-sized devices.
3、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, PCB copper thickness is measured in ounces and determines whether the circuits can do the job it is designed for or not.
Figure 3 PCB Copper Thickness
3.1 PCB Copper Thickness
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.
3.2 Designing Copper Tracks
Engineers must always remain alert when designing PCBs. They need to ensure that the PCB thickness is enough to meet all that a circuit needs.
As an engineer, you should keep the thickness at 1oz. to ensure that the PCB can accommodate the specified amount of current that should flow through it.
Circuits that require more current must have their copper thickness increased to minimize resistance. PCB engineers can perform the calculation to determine the amount of copper thickness needed when designing a circuit to perform a specific function.
The thickness of the copper can at times affect the cost of the PCB board. Also, the thickness of the copper determines how easy it is for the designer to remove the excess copper through etching the PCB.
Thus, designers of PCB must evaluate thickness before designing a PCB to be put to a specified application.
4、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 overcome the difficulties.
The generation of heat that leads to increased temperatures on boards is an issue that most engineers strive to overcome. This challenge has forced designers to think outside the box and find ways through which they can minimize heat generation and electrical loss.
The invention of the heat sinks is one such attempt to regulate the circuit temperatures. Heat sinks help to distribute heat evenly and minimize excessive concentrated temperatures.
For instance, in circuits that involve high-speed microprocessor, a lot of heat is dissipated. Without heat sinks to absorb the heat, the high temperatures are capable of damaging the component.
The ICs, in particular, generate much heat and require heat sinks to absorb and channel the excess heat.
Figure 4 Heat Sink
4.1 Metallic Heat Sinks
This type of a heat sink can be attached to a board by tightening it with a screw 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 it into the component that heats up.
Notice that a heat sink on PCBs plays a critical role; especially where a PCB is to be used in circuits with a massive flow of current. For instance, discrete semiconductors such as IGBTs, TRIACS, and MOSFET generate much heat which must find its way out of the PCB (often via a heat sink).
4.2 SMD Components with built-in Heat Sink
We have plenty of SMD components that come with inbuilt heat sinks. Such components include the PMICs and MOSFET. These devices have an integrated heat sink which may be attached to a circuit and then connected to a drain.
4.3 Heat Sink PCB Thermal Design Considerations
From the above discussions, it is evident that power devices must have a proper PCB layout and heat sink(s) to take care of thermal issues that may arise when the device is in use.
4.4 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 the two proposed methods fail to work, it is recommended that you use generic heat sinks.
• Notice that the above parameters assume that copper layers will generally be coupled with components that generate heat. Also, the copper will be extended to the edges of the board. The argument then implies that the copper layer will behave as the thermal layer of your PCB.
• When more than 1 component that generates much 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.
5、Manufacturing Costs Breakdown
PCB assembly and production is a tedious activity that entails so many steps. It involves the processes of collecting the materials, preparing them 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?
5.1 The Cost of Material
Figure 5 PCB Materials
The cost of the raw materials is the primary factor that determines the final price of PCBs. When understanding the cost of manufacturing, it is critical that we consider the layers of a PCB, the material used in manufacturing it and the size of the PCB.
Gold, nickel, copper, silver, fiberglass, lead, epoxy resin, and a variety of chemicals 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. For instance, manufacturing a 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. These requirements increase 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 holes.
The cost also needs to include the components, transport the PCB distance. Other peripheral factors must come to play when computing the value of the PCBs.
The thickness of the copper used is one of the factors that affect the production cost. 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 as well.
5.2 Cost of Labour
Notice that the cost of labor is also critical in determining the final price of manufacturing PCBs. Manufacturers will also have to include other overhead expenses in the final cost of PCBs. These costs are expenses from the labor working on the fabrication of a PCB.
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 should also be part of the billing of PCBs.
5.3 Board Size
A panel is one of the essential raw materials used in producing printed circuit board. The size of the panel used is necessary when calculating the overall cost of a PCB. Boards that take up a less panel area will cost less. Also, those that use panels that fit better will be less costly.
5.4 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.
5.4 Lead Time
Lead time is the time it takes to manufacture a PCB. We can provide both regular delivery service & express service; expedited boards can be shipped out within 24-48 hours. You can choose a suitable service according to your schedule.
We often try our level best to make PCB Manufacturing Cost Breakdown without compromising our quality.
The delivery time of our factory also assured.
Figure 6 Delivery Time Assurance
We have other Ultimate Guides to reduce PCB Cost. If you got some interest, you could check them out here.
Having taken you through what PCBs are and some of the factors that determine the ultimate cost of PCBs; I bet you are now better placed to make your PCB order. We simplified this process. Just visit wellpcb.com and place an online order.
Please note that without special remarks, all the price we quoted is based on the standard delivery. So, you need to indicate our online quote system or contact us about an expedited order. In so doing, your order will be processed as a top priority request. (Please note that our current production will affect the time, call us if time is of the essence).
For the Special board, please contact us for details:
► Special Material Requirements
► Shielding Layers
► Blind and or Buried Vias
Figure 7 PCB Vias
► Rigid-Flex constructions with more than 2 Flex Layers
► Special Surface Treatment
Why Choose WellPCB
WellPCB, registered in Australia, is a daughter company of Uniwell Circuits Co., Ltd, which has two modern PCB factories, founded in April 2007.
We are focused on Printed Circuit Board Fabrication and PCB Assembly Turnkey Services. As WELLPCB, we aim to meet the goal of producing high quality and low-cost PCBs. We are dedicated to deliver faster and ease ordering from customers around the world.
With brand new equipment and total production area over 10,000 square meters; we are capable of producing 100,000 square feet of 2-32 layer PCBs and delivering over 5000 varieties monthly.
We can provide quick turns to meet 24-48 hour delivery for double-sided PCBs, 72-hour for four to eight layers and 120-hour for ten layers or higher PCBs.