What Is PCB Design And Layout?

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PCB design is one of the most important factors in designing an electronic product. Once you have a layout or schematic design in mind as a raw form, it becomes easier to transfer it into a circuit.

PCB design allows you to have a reliable model, and it is also very cost-effective. This is because you keep testing it on the PCB design before actually making it, and there is an already build network for wiring.

There is a lot more to PCB design and layout. To know more about it, read on.

 

PCB

 

What is PCB?

PCB stands for Printed Circuit Board. It is also called a printed wiring board.

Previously, the circuit boards were constructed with a point to point wiring, and this created so much hassle. The wires would overlap so much, and the connections were not even so secure. It all came to rest as soon as PCB was introduced.

The best thing about PCB design is that the gauze wire is already present at each connection point, sealed with a gas-tight link.

PCB has lines and pads which you can connect many connectors and components to each other without them being too messed up.

Composition of PCB

PCB design is made on a board that apparently looks like a single layer, but it is composed of many layers. Each layer is embossed on one another and then made in such a way to give an impression of a circuit board.

Let us talk about the four main layers, which are most common and heat-fixed on top of one another.

Silkscreen

The uppermost layers that you see are green in color, and it is the solder, but as we are starting from the first layer, it is the silkscreen. The white or silver writing you see above the green is the silkscreen.

This white is used to make any annulations and bold the connection points, wiring, and pads. Any specification or labeling is also done with the silkscreen label.

Solder mask

Solder is that green color you see in circuit boards. It is the second layer and the most visible one. Usually, the solder mask is in green color, but it can be of any other color. Some PCB designs use red solder as well.

The solder mask is to cover the inner copper. It basically acts as an insulator to copper so that it cannot come in contact with any other metal.

Solder mask is generally applied to all of the circuits, but a few traces of silver are left for the connection points and SDM pads.

Copper

Copper is used as a laminating material in PCB. It is used to laminate the substrate. A very thin layer of copper is used. Usually, copper is laminated above and below the substrate covering it from all sides. Some of the manufacturers of PCB design also prefer one-sided lamination, but it is not that durable.

The thickness of copper is dependent on the weight per ounce square foot. Commonly, one ounce of copper is used per square foot, making the thickness less than 35 micrometers.

FR4

FR4 is a fiberglass material used as a substrate for PCB. It is a heat-resistant plastic that is used as the main core layer. Using a good quality substrate is very crucial. It is what the base of material depends on. As for the thickness of FR4, the common thickness is 1.6mm but as thin as 0.8mm is also used.

Some people also use epoxies and phenolic because they are cheap. But we don't recommend them because they char and smoke when coming in contact with iron. Other than that, they also give off a bad smell when it comes in contact with heat.

 

pcb

 

Basic steps for PCB design

Now we have talked about the basic composition for a PCB design board, let us move on to the next step, which is making the PCB design. Here are the basic steps to make PCB. We are not going into too much detail, but it will give you a good idea of how this all works.

These are the basic 6 steps in making the PCB design.

1. The Basic Concept

You know that you need a PCB; the first thing to think of before making is to know where it will be used in the final product. It is the basic concept, and you can know where it is needed. According to that, the wiring points and interconnection with other circuits are considered.

In the basic concepts, the temperature range and other environmental concerns are also considered.

2. Schematic design

After the basic concept, then comes the schematic design. You will have to draw what you need for this particular PCB design. Write all the dimensions on a piece of paper or in your notes. Also, mention the number of wires or other raw materials needed.

Along with all these basic designs, mention the costs of each item which is to be used. This part of the schematic design can be updated along with other steps as well as you proceed with making the PCB design.

3. Block diagram

Before moving actually to make the PCB onboard, you can make the basic conceptual diagram on a piece of paper or your computer. Just make boxes and label them where you will have a certain component, there will be the wiring and which points will be constrained to it.

Once you have all these things aligned, it becomes easier, later on, to work on the actual PCB design.

4. Component placement

After the block diagram comes to the actual component placements. Component placement can take time because it is quite obvious that the components might not always work. You have to keep alternating the positions to see which works the best for you.

5. Routing

After placing each component, you have to decide the routing of each one of them on the circuit board.

6. Testing

Finally comes the first pass testing, where you see that each connection is tight and works as you have placed. The testing part directly corresponds to routing and component placement.

After each testing, you will have to counter-check the component placements and routing.

Few factors to keep in mind when making PCB layout design

PCB design can be messed with the smallest of errors. Here are a few factors which will help you minimize the errors. Keep them in mind when making the PCB layout design.

1. Manufacturing processes

Every type of PCB design has its own manufacturing process, which will suit the needs, so make sure you are aware of which will suit the needs.

2. Board constraints

Before you make the board, you should know the right size of board needed. The board's dimensions should be set considering its placement in the final product and the number of components you need to fix on it.

3. Materials and components

You should have all the components and materials needed for the PCB design before you actually start working on it. Having all of them beforehand makes the process easier, and in case any one of them is not available, you can use an alternative.

4. Placement

Component placement is what takes the most time in making the PCB design. You should know where to place each circuit, hole, and connection. It should be smooth and also minimize other glitches.

5. Orientation

When placing the components, make sure they are oriented in a specific order. Those parts which are similar to one another should be placed next to each other.

6. Organisation

To reduce the assembly hassle, one thing which you can do beforehand is that organize each part according to when it is used. Keeping things organized also ensures that the process is streamlined and that you don't miss any steps.  

7. Pad and hole dimensions

Pad and hole dimensions should be fixed on the board so that each component is placed in alignment with them.

8. Thermal check

Finally comes the thermal check. Although the materials used are the ones already been used for a long time, but they should be checked before use. Give them the heat that limit it can reach to see if they will work with the circuit or not.

Conclusion:

Throughout the PCB design process, you should keep testing the board to see if it works well. PCB design is easy to make, and once you have a layout, it is easier for you to use in the future as well.

The PCB is important because these small circuits are the backbone for any electronic product these days. These small chips-sized circuit boards can cover all the mess for so many wires.

So by the end of this, we hope that you know how you can make a PCB design of your own and you are aware of what to avoid.

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