bare pcb

Bare PCB: Its Technology, Design, and Fabrication

The bare PCB plays a significant role in the fabrication of a printed circuit board. Without this board, there won’t be a PCB. Most times, people confuse the bare PCB board with a PCB. The bare PCB board is an essential material in PCB. This board serves as the fundamental base in which manufacturers place components. This article aims to provide vital information about a blank PCB.

What is a Bare PCB?

A bare PCB is a blank board designed for the production of a printed circuit board. This board comprises a metal coating, substrate, and conductive pathways. Bare PCBs boards are available so that engineers can mount electrical components. These boards feature no electrical components. As printed circuit boards are a core material in electronics devices, so is a bare board to a PCB.

A bare board helps the production of several types of PCB. Circuit board manufacturers can’t do anything without this board. A bare PCB is also known as a blank PCB board. Manufacturers mount all electronic components on this board. The bare PCB board provides electrical and mechanical support for circuit production.

The difference between a blank PCB and a PCB is the electronic components mounted on it. The blank circuit board simply refers to the condition of a PCB before electronic components are mounted on it.  A board with copper traces, but no components on it, is referred to as a bare PCB board.

Blank PCB boards are specifically designed with the aim of configuring and populating them with electronic components.  These boards are the skeleton or foundation of any PCB design. PCB manufacturers can determine component placements via a bare PCB layout.

 

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Blank PCB Board: Materials Used For Fabrication

A blank PCB board comprises different types of materials. The three primary materials manufacturers use are PTFE, Fr-4, and metal. These materials play a significant role in the fabrication process of a bare PCB.  The functionality of a blank PCB depends on the material used for its manufacturing. To ensure the durability of a blank PCB, other materials like silicon are also used.

PTFE

Polytetrafluoroethylene is an ideal material used for fabricating a blank PCB board. This material is weather-resistant and has no adhesion. PTFE, also known as Teflon is widely used due to its high speed.

FR-4

This material is commonly used in the production of a bare PCB. FR-4 comprises an epoxy laminate sheet reinforced with glass. FR refers to flame retardant while the 4 means glass-reinforced epoxy resin.

Metal

The metal used for the fabrication of a bare PCB board can either be iron, aluminum, or copper. However, copper is the most common metal used. This is because of its conductive nature. Copper offers mechanical stability and durability.

Blank Circuit Board Design

There are increasing demands in the production of electronic devices. This has had an impact on blank PCB design. Since these boards are the foundation material in which components are installed, they have to be well-fabricated.  Bare PCB designers should ensure they carry out the design process carefully. A good design will guarantee a good board. Therefore, we will discuss the design process of a bare PCB below.

The design and output

The circuit board you intend to use must have a layout. This layout must be designed by software. You can use software like OrCAD, Eagle, KiCad, or Altium Designers for the layout. After creating the PCB design, export the design. The design needs to be exported into a format.

You will convert the design into an output format. The designer can do this by making use of the extended Gerber. This software encodes important data like component notations, tracking layers, and apertures. The blank board needs to go through some checks to ensure there are no errors.

After this, you have to plan other elements like the size of the hole. This also includes the track width, board edge spacing, and trace hole spacing. The designer forwards the file to the boarding house for production. It is important the design fulfils the requirements for minimum tolerance.

Create the schematic files

The schematic files are used to make photo films. The designer then uses the films to image the bare board. You can use plotters to achieve a detailed PCB design. At this stage, the manufacturer will have a plastic sheet featuring a negative film.

The negative photo film will represent conductive copper parts. You can then use the plotter to create a film layer.

Steps in Fabricating Bare PCB

Drilling

Drilling involves the creation of holes for via connections. Here, the foundation for vias is created. This is an important process for the fabrication of bare PCB. The blank PCB drilling process requires serious attention. This is because any error can lead to losses.

Hole Metallization

The already drilled blank PCB boards go through a conveyorized line. Then, the holes are lined with a thin layer of carbon which serves as the cathode.

Photo Mech

This stage involves laminating the drilled bare PCB with photosensitive film plating resist. A direct imaging machine then images the board.

Plating

The manufacturer copper plates the bare printed circuit board. The technique used here is known as periodic pulsed plating. It involves plating copper evenly down small holes and on the tracks’ surface. Manufacturers must take measures to ensure the right amount of copper is in each panel.

Etching

This stage involves the removal of the unwanted copper from the bare PCB board. The manufacturer dips the board in an etching solution to remove the unwanted copper. The etching solution comprises ferric chloride. It is important to pay attention to this process to avoid over or under etching.

 

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Solder mask application

The manufacturer applies a solder mask to the two sides of the bare printed circuit board. This will help protect the copper surface. In addition, it will prevent solder-shorting of components in the process of board assembly. Solder mask prevents the disconnection of traces.

Screen printing

In this stage, the manufacturer presses some ink on a mesh screen. This is one of the final stages in the bare PCB board fabrication. Screen printing helps to specify important information on the bare PCB. It is used to identify parts, logos, and marks on the bare board.

Finishing

This involves using electroless nickel immersion gold or silver for exposed copper pads. It is equally important to verify the coating thickness with an X-ray fluorescence instrument.

Inspection

This is an important part of the fabrication process. Here, the manufacturer inspects the PCB panels thoroughly.

Possible Errors in Bare PCB Board Manufacturing

During the manufacturing of a bare printed circuit board, some defects may likely occur. Therefore, it is important we discuss the possible defects and their solutions.

Extra holes

All blank PCBs have holes in them. These holes are regarded as through-holes. They go through the blank board entirely. These holes function as the signals that carry conductive vias. These signals create an interconnection between the PCB’s layers.

However, these holes can be too much. Extra holes in your board can cause errors during the fabrication of the blank PCB. They can reduce the available space and also the routing area meant for signal tracing.

Inadequate or Excessive Copper

This is another error blank circuit board manufacturers are likely to encounter. Copper is the primary material used for making traces on a blank board. Since copper is a conductive material, it helps to transmit signals quickly. However, inadequate or excessive copper can lead to defects on the blank circuit board. Inadequate copper might result in short-circuits while excessive copper might result in corrosion.

Short Circuit Problem

This happens when some wires that shouldn’t come into contact touch each other. A short circuit can cause very high currents to flow via the circuit. A short circuit may also occur when some electrical current bypass. Many designers face short circuit problems during the fabrication of a bare PCB. However, this problem can be solved by replacing the wire. If this isn’t done, your blank PCB won’t function well.

Bare Printed Circuit Board Testing

It is important you test a blank PCB board before using it for the manufacturing of a PCB. This bare board needs to be tested to verify its functionality. As a bare board manufacturer, you can’t guarantee the functionality of your board without testing it.

It is wrong to start mounting components on a bare board without conducting proper tests. Manufacturers can risk having dead boards if they fail to test their bare PCBs. Earlier detection of any defects will save you a lot. So, what is Bare PCB testing? Bare PCB testing involves verifying the continuity and isolation of the electrical connections on a bare board.

There is continuity testing and isolation testing. In the isolation testing, the manufacturer verifies that there is the resistance between two different electrical connections. While continuity testing is carried out to ensure the circuits have no open points.

Types of Bare Board Test Systems

There are two types of blank PCB board test systems which are;

  • Flying probe test

The flying probe test involves driving a set of “flying probes” to the net ends. A CNC machine is used for this process. It involves using two or more probes for each side, bottom, and top. The flying probe test doesn’t need a custom fixture attached to the circuit. This test is ideal for both small and large production volumes. The limitation of this test is the time per test.

  • The Bed of nails test

The bed of nails test system is a custom fixture that holds the PCB. It then uses custom spring-loaded pogo pins to test the PCB. The pins can test a good number of points simultaneously.

Why Testing Is Important

The major reasons for testing are functionality and reliability. Testing helps you to keep track of all the through-holes, vias, and traces. A bare board is solid before mounting expensive components on it. Although bare PCB testing may be a costly and time-consuming process, it is very important.

Bare board testing can save time, money, and effort in the long run. It helps you to prevent the cost of repair and maintenance of a board. When testing is carried out, manufacturers can detect any errors or defects on the bare board on time.

Testing bare boards helps to ensure reliability. PCBs are always densely populated during miniaturization. Therefore, it is crucial to ensure your bare PCB can solder the expensive components. The slightest error in a blank PCB will make an electronic assembly malfunction. This board is the foundation of an electronic system. When it fails, the entire system does. Therefore, it is important to build a good foundation.

Benefits of a Blank PCB Board

The bare PCB board offers a lot of benefits. PCB manufacturers understand the impact of these boards in their manufacturing process. These boards offer mechanical support to the components, traces, and pads. They are the substrates that house all other components.

Most electronic devices feature a bare PCB board. However, one should note that this board doesn’t feature any component. These blank boards are available in even the smallest devices. The circuit connections on this board allow the routing of electrical current between the components on the board.

Another great benefit of this board is its low electronic noise. The type of materials used for the production of these boards is responsible for this feature.  Furthermore, a blank circuit board features a coating of copper. This enables the board to provide an effective flow of electricity when electronic components are on the board.

Conclusion

The diverse range of industries that utilize blank PCBs has led to the increasing demand for this board. Blank circuit boards are the support system of electronic components. These boards act as interconnection and support to a printed circuit board. Bare PCBs have both mechanical and electrical properties. The manufacturing process of this PCB board is a complex one; however, there are rules that guide this process.

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