Crucial Factors to Consider When Designing Custom PCB Boards

Printed circuit boards are available in most electronic devices and even the small gadgets we carry about. When you check your mobile phone, you will see a small green board. That board is a circuit board and it is responsible for the functioning of your PCB.

PCB manufacturers can fabricate circuit boards to meet the demands and specifications of their customers. As a PCB user, you can customize your boards according to your specifications. Customized PCBs are regarded as custom PCBs.

What is a Custom PCB?

A custom PCB is a circuit board fabricated according to a specification. The materials and components used in this PCB are according to a particular specification. This PCB comprises strips of conductive material and small electronic components. Custom PCB manufacturers integrate your own PCB design layout. This printed circuit board is usually customized based on the PCB specifications required by a client.

Also, custom bare boards are advanced circuits suitable for high-volume applications whereby requirements don’t usually change. PCB manufacturers always work with their customers to design printed circuit boards according to needed specifications. Also, they quote engineering costs to meet design requirements.

Mission-critical equipment requires custom made PCB. Custom made PCBs are advanced circuits ideal for use in mission-critical or expensive applications. For instance, these advanced circuits are crucial in industries like energy, mining, manufacturing, and transportation. Also, custom board manufacturing involves more rigorous standard test.

With custom circuit boards, you can have a PCB that meets your design requirements, rather than matching your design with an already fabricated PCB. Also, custom PCB manufacturers usually have an engineering team that conducts design for manufacturing to review all manufacturing processes.

The complexity and budget of your PCB project will determine your need for a custom printed circuit board. Also, custom boards can make assemblies more organized, easier to service, and smaller. These advanced circuits give you total control over all the stages involved in the PCB production process.

Layers of a Custom PCB

Custom printed circuit boards comprise some layers. These layers are very crucial in a PCB.

Substrate

This serves as the foundation of a custom PCB. This substrate is usually made from fiberglass or other PCB materials. Also, the substrate layer can have one or more substrates.

Copper

The copper layers of a custom board is usually thinner than the substrate. Copper is a conductive material widely used in PCB fabrication. Also, the power of a PCB depends on the amount of copper present in the circuit. The copper layer helps to transmit electrical current.

Solder mask

Solder mask protects the conductive traces of the bare boards from unfavorable conditions. The solder mask is a green color material applied over the copper.

Silkscreen

Silkscreen is usually applied on top of the solder mask layer. The silkscreen offers details on parts and components on the board. It creates labels and marks for placing different components on the board.

Steps in Designing a Custom PCB

There are some steps aimed at designing a custom circuit board.

Use a PCB design software

There are several PCB design software applications. These applications help you to create the schematic of your printed circuit board. EAGLE and CAD are examples of PCB layout software.  Also, these applications help a PCB artist to achieve the best design.

Film generation

You can generate the film after creating finalized PCB diagram of the PCB layout.

Hole drilling

The hand machine and CNC machine are the two types of drilling machines. CNC machines are automatic while hand machines are manual.

Image fixing

This step involves placing a copper layer on a laser printer. Laser printers help to print layouts on the circuit board.

Etching

This involves the use of various chemicals to get rid of useless copper on the printed circuit board.

Testing

Here, the PCB manufacturer checks the board’s functionality. Testing is an integral aspect of PCB manufacturing.

After completing the PCB design, you will need Gerber files. The gerber file describes the PCB images.  Also, the Gerber file comprises a series of data for every conductive layer of the  PCB. Gerber files play a crucial role in the design and manufacturing process of a custom PCB.

Types of Custom PCB

Single sided

This type of custom circuit board has one substrate. A conductive layer of copper offers protection to a side of the substrate. Also, there is a solder mask on the copper layer. This PCB comprises silkscreen used to mark the PCB parts. In a single sided PCB, components are on one side of the PCB. Also, these boards are often used in simple electronic manufacturing. Single sided PCB is budget-friendly.

Double sided

A double sided PCB features two conductive layers with each layer attached to the two sides of the substrate. Also, double sided PCBs are more commonly used than single sided PCBs. Double sided boards have holes in them. These holes connect one circuit to the other side. The surface mount technology is widely integrated in this process.

Multilayer

Multilayer PCBs have more functions compared to double layer PCBs. Also, multilayer boards have multiple substrates connected by insulating materials. These advanced circuits have more than two copper layers. multiple layer boards can feature more than 10 layers. Also, these boards have numerous benefits among which is the space saving benefits.

Rigid boards

Rigid circuit boards have several rigid layers. These boards don’t twist, flex, or bend. Also, these boards integrates fiberglass as its base material.

Flex boards

Flex PCBs have flexible substrate that can bend, twist, or flex. You can form a desired shape for your flexible PCBs. Also, these boars can fit into any desired form.

Rigid-flex boards

The rigid-flex boards combine the rigid and the flexible boards. Therefore, they have the properties of both flexible and rigid boards. Also, these boards allow you to attach a hard PCB to a flexible PCB.

Why you need a Custom PCB?

A custom printed circuit board is ideal for use in highly specialized electronic products. Traditionally, most PCBs has the same model since custom made boards were expensive. Recently, rapid development in the electronics industry has resulted in more demand for fully customized boards. It is now common to design and fabricate custom PCBs.

Most PCB prototype manufacturing companies are now looking at the benefits of custom boards instead of going for off-the-shelf PCBs. There are several benefits of integrating a custom PCB for your project.

Exceptional performance

In terms of performance, custom PCBs function well. PCB prototype will have a clearer benefit if it performs better than custom boards. However, a circuit board designed from the scratch to meet a particular specification will operate with better efficiency. Custom boards are specially fabricated to meet the demands of a specific application.

Reduced cost and size

Designing a custom board can help to reduce cost and size. Printed circuit boards will demand less resource to manufacture when there is reduction in size. Therefore, this will help to minimize manufacturing cost of custom PCBs. While it can be more expensive to fabricate a single custom PCB, any additional cost can be reduced when operating at a large scale.

Longer serviceable life

One of the greatest benefits of custom PCBs is that they have longer shelf life than conventional boards. Mass produced boards can have poor solders and loose wires. This can affect the functionality of the electronic product.

Technical advantages

A custom circuit allows you to have absolute control over the manufacturing of your board. You have control over the placement of every piece of copper on your board. Therefore, this enables you to mitigate some properties of your printed circuits.

Limitations of Custom PCB

There are some reasons why people don’t choose the custom circuit. Some of these reasons are highlighted below:

Flexibility

A custom circuit board isn’t reconfigurable. When a PCB is the prototype stage, it is enticing to change some things. For instance, if you discovered a hardware bug or you needed to include a feature, you might want to change some things. There are two major concerns about flexibility when designing a custom board. These questions are “ what if there is a change in the board requirement” and “what happens when there is a hardware bug?”

Some PCB projects need flexibility. However, custom circuit boards don’t offer the flexibility needed in most cases. It is easier to change the design requirements of a standard PCB compared to a custom PCB.

Cost

It is more expensive to design custom circuit boards than standard PCBs. This is because there are certain specifications for these boards.  There are several factors that influence the cost of manufacturing custom printed circuit board. Some of these factors include the size of the board, tooling costs, and number of layers.

Timeline

Custom board often require more design time and initial tooling. Also, it is difficult to revise these boards several times.  

Important Consideration in Custom PCBs

There are certain things that play a significant role in a custom printed circuit board.

Silkscreen legend

Silkscreen legend is available on the top or bottom of a custom PCB surface. Also, silkscreen offers details concerning part numbers and component placement. Silkscreen legend is useful in the repair and production of circuit boards. With advancement in technology, PCB manufacturer enables component printing on PCB surface.

Schematic

The schematic plays a crucial role in custom board manufacturing. A schematic is a drawing that displays the functions of a printed circuit board at a conceptual level. Also, it helps to document the components of a printed circuit board in a readable manner. A schematic is crucial in the PCB design process.

Average thickness

 The specification of your custom board determines its thickness. However, most custom boards have 1.58mm thickness. However, some dense SMT PCBs have thickness of 0.79mm. Therefore, this helps to drill small vias. A custom printed circuit board can have a thickness of 2.3mm.

Trace width

There are different trace widths. Also, trace widths feature different properties that can impact the performance of a custom PCB. For example, a thin trace has a higher resistance. The minimum trace width used by most PCB manufacturer is 0.006 inch. Also, this value is enough for the majority of digital and analog applications of circuit board.

Trace clearance

This refers to the distance between two conductive traces on a circuit board. Also, trace width and spacing is a crucial consideration in custom circuit boards. The traces must not be too close to each other. Otherwise, the solder can cause shorts in the traces. Also, the printed circuit board can become too bulky of the traces are too far apart.

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Other Factors to consider during Custom PCB Fabrication

Drill hole size tolerance

The drill hole size tolerance compensates for any variation in plating, material, and machining among others. When calculating the minimum drill hole size, you will need to deduct the tolerance value from the specification value. However, you will need to add up the specification and tolerance value. The custom board hole should be wider than the component’s lead diameter, at least 0.007 inches.

Fiducial

Fiducials are alignment marks and tooling holes align layers. Also, the recommended fiducial for a custom board should be a 1mm diameter solid circle. Therefore, this enables the entire board to be easily mounted in a pick and place machine.

Design for manufacturability

Design for manufacturability, which is popularly known as DFM, checks for any possible issues of design flaws before commencing with custom circuit manufacturing. Also, DFM detects any defects and makes correction. This analysis helps to cut down cost by figuring out the areas the design could be more efficient.  DFM detects issues like acid traps, inadequate annular ring, and starved thermals among others.

Conclusion

Printed circuit boards are core parts of any electronic device and as such, it is crucial to integrate a high quality solution that matches your application. A custom board offers this advantage. Also, custom boards are crucial for mass production printed circuit boards.