PCBs- From Designing To Manufacturing

Have you ever wondered how any electronic component works? What are the key components of any electronic device like your smartphone, Television remote, smartwatch even the wireless earphones or headphones which you are using it right now? The answer is too simple it is just a small electronic plate with some lines and dots in it. And you know it by name of PCB (Printed Circuit Board).

What is the Printed Circuit Board (PCB)?

Printed circuit boards (PCBs) are the boards that are used as the base in most electronics devices — both as a physical support piece and as the wiring area for the surface-mounted and socketed components. Which are mostly made out of fiberglass, composite epoxy, or with any other composite material, Now a day’s most electronic components are denser and used very less power which has become possible due to PCB, It is mainly used in medical devices, Industry Machinery, Aerospace Industry and Automotive Industry making it not only essential but most important component in all electronic devices.

Types of PCB

Based on the functions like cost, heat dissipation, environmentally friendly, material durability, and complexity of any electronic devices PCB has been divided into different types like Single-layer PCB’s, Double-layer PCB’s, Multi-layer PCB’s, Rigid PCB’s, Flexible PCB’s, Flex-rigid PCB’s, High-frequency PCB’s and Aluminum-Backed PCB’s.

How to design a PCB board?

Now to design PCB boards is not easy to figure out, as the right PCB design software can go a long way. Engineers have learned the art of designing PCB boards and one can get benefit it by figuring out the right design. To create a proper PCB board you have to follow some below steps which will give you a proper idea of how to design and by practice you can learn the art of designing your PCB boards.

The earlier method of designing PCB boards by using tapes placed on the drawing sheet is long gone, but instead of that now software is used which are easy and more accurate. Also, simulations are widely been used to run your model to get a proper idea about its working without actually applying on PCB boards and then making it again by doing corrections. It not only saves time but also lots of money can be saved due to these the complexity can also be found out and changes can be made.

Also, Laying out traces for routing and copper placement, or managing the layer needed for solder can become difficult without an accurate and reliable integration from schematic capture to layout due to which knowing your design software becomes more valuable.

Step 1: Create the Schematic

The first stage in the development of a PCB design is to capture the schematic for the circuit. Whether you are generating your design from a template or creating your printed circuit board from scratch, it is probably best, to begin with, the schematic. Also, the components must be decided which will be used in the circuit and how they will be get connected along with the relationships between groups of components in the different schematic. For designing, you can use the components present in the library of your simulation or can design your components with the different parameters.

Step 2: Create a Blank PCB Layout

After the schematic is created you will need to create a blank circuit printed board with a rough estimate of the space and approximate locations of the components, a more detailed component layout can be made for the PCB design. After then you need to compile with schematic the compilation process will include verifying the design and the generation of your several project documents that will allow you to inspect and correct the design before transfer to the file.

Step 3: Designing Your PCB Stackup

When you transfer your schematic information is linked to the file then the component footprints are shown in addition to the board outline specified. Also for this, you will need to define the number of layers although most modern PCB design concepts will start with a 4-layer board on FR4.

Step 4: Defining Design Rules

Since there are too many PCB rules for every design you don’t need to use all those for your design. You can select or deselect the rules by clicking on them making your work easier. Moreover, the rules which you will use, especially for manufacturing, should be in line with the specifications and tolerances for your PCB manufacturer’s equipment. Also, if necessary you can create your own rules and use them depending on the software which you will be using.

Step 5: Place Components

Once the rules are defined you will need to start placing components that you can have your components automatically arranged or you can place them manually. You can also arrange the components in the group and can also define them in a group on the schematic.

Step 6: Insert Drill Holes

After all the components are placed you will need to place your drill holes. If the circuit is too complicated then you need to modify your design to place them with different tools available in the software that you are using.

Steps 7: Routing

Once the basic placement has been completed, the next stage of the PCB design is to route the connections between all the components where the software will routes the physical connections onboard to the netlist from the schematic. To achieve this numbers of the layer are available for connections. This will not only reduce the noise but also it will enable low source resistance connections to be made for the power. This will use a significant amount of computing power with a significant amount of time.

Step 8: Generate Design Files

Before you send your design for manufacturing it is always a good idea to simulate it by running a design rule check. Once your board has passed the final DRC, you will need to generate the design files for your manufacture which should include all the information and data necessary to build your board, along with any notes or special requirements to ensure that your manufacturer is clear on what you require and how to build it exactly. Where the information for the photo plots of the PCB layout is outputted in the form of Gerber files which is a standard format for PCB files. In addition to the Gerber files, drill information is also generated along with the screen print and photo-resist information. However, some manufactures also preferred CAD file format.

How PCB is manufactured?

Once the design is completed, the next step is manufacturing it in large quantities for which it is sent to manufactures, who again process it and then manufactured it. The detailed process of how it is manufactured is given below.

Step 1: Front End Engineering

To achieve this process, each manufacture has their method in this the design are reviewed prepared for manufacturing. Also, a “process card” (traveler) is a set of instructions to travel along with the work as its being completed.

Step 2: Photo Plotting

In this step a laser photoplotter is used to create photo-tools that are used in the solder mask and silkscreen process not only this piece of film is also plotted for each layer.

(Note: In case if you are manufacturing multi-layer PCB’s then different processes like automated optical inspection, oxide, lamination have to need to be done before moving on future steps.)

Step 3: Drilling

To attach different components, linking the copper layer together, or mounting the PCB’s the required numbers of holes are needed to be drilled on PCB boards, which are drilled using advance precision drilling systems that utilize solid carbide cutting tools designed specifically for the fast removal of chips in extremely abrasive materials.

Step 4: Copper Deposition

After the drilling process, a thin coating of copper is chemically deposited on all the exposed surfaces of the panel, including the hole walls, using an electroless plating process. This process is too important as holes are needed to be subsequently electroplated.

Step 5: Plate

In the earlier process, the copper was deposited on holes, but in this process, the copper is also plated on the conductive pattern to meet the design requirements of circuitry.

Step 6: To Remove Extra Copper

After the platting process, the extra copper which spread on the circuitry board is exposed and the copper which will be not covered by tin will get detached through the strip-etch-strip (SES) process. so that only the traces and the pads around the holes and other copper patterns will remain.

Step 7: Solder Mask

Now to prevent solder bridging between components and to protect the copper surface a liquid photo imageable (LPI) solder mask is applied. Also, the panel is exposed to UV light/laser using photolithography so that all exposed solder mask remains while the unexposed solder mask will be removed when processed through the developer.

Step 8: Surface Finish and Electrical Test

The surface finish process is designed to protect the panel from the oxidation of reaming exposed copper which is important because oxidized copper cannot be soldered. The application of each surface finish may vary slightly in the process but involves dipping the panel into a chemical bath to coat any exposed copper with the desired finish. Once it is done an electrical test is performed using a flying probe tester. In this, the boards are tested with the data files supplied by the customer to get the exact output. Once the test is completed the fabrication is done.

Step 9: Final Inspection

Now the last step is to perform the completed inspection process, to ensure that the PCB’s meet both visual and performance standards. An inspector will begin by reviewing all documentation associated with the project, including the process card that describes each manufacturing process performed, and any customer-provided documentation such as a fabrication drawing. Once all things are meet it is ready to get supplied to the customer.