Circuit Card Assembly (CCA) - NextPCB

Introduction to Circuit Card Assembly

Circuit Card Assembly is crucial in manufacturing Printed Circuit Boards (PCBs). All electrical and electronic components are manufactured on PCBs from household appliances and consumer electronics. Many industrial sectors utilize PCBs in their equipment.

While it is common to find PCB in every appliance, it is essential to note the manufacturing and assembly processes. This guide effectively introduces circuit card assembly and its step-by-step process.

In this article,

• Introduction to Circuit Card Assembly
• What is Circuit Card Assembly (CCA)?
• Circuit Card Assembly Components
• Types of Circuit Card Assembly
• Difference Between Circuit Card Assembly and PCB Assembly
• Circuit Card Assembly Steps
• Basic Electronic Components Necessary for Circuit Card Assembly

What is Circuit Card Assembly (CCA)?

A circuit card assembly is a thin, flat piece of dielectric material with traces or conductive paths etched on it. These conductive paths are vital in connecting circuit board components.

The circuit card assembly transforms a bare circuit board into a functional unit by soldering electrical and electronic components on the circuit board.

Circuit card assembly is applicable in several home appliances such as televisions, smartphones, and electronic gadgets. Also, It is also applicable in many industries, including navigation systems, medical imaging systems, monitors, and automobile displays.

Circuit Card Assembly Components

Circuit Assembly is significant in the design of electronic devices. As earlier explained, circuit card assembly is the process of connecting PCB wirings with electronic components. The circuit card assembly comprises four components regardless of the circuitry or application of circuit boards. They are substrate, copper, solder mask, and silkscreen. Let's discuss them.

Substrate

Substrates are the building blocks of circuit card assembly since their function is to hold all electronic components together.

Also, the sheer and mechanical strength comes from the substrate used in its application. Substrates differ in circuit boards, so we have flexible, rigid, rigid-flex, and metal core boards. Substrates comprise fiberglass which is applicable in several circuit boards in various industries and sectors.

Copper

Copper is an essential component of PCBs. The use of copper in circuit card assembly helps to connect electronic components with their conductive traces. During the CCA process, laminate the substrate and copper using heat to ensure that components are firmly in place.

Depending on the application of PCB, single-sided PCBs usually apply a layer of copper on one face of the circuit board or several copper layers.

Solder Mask

If you hold a PCB, you will notice the greenish color on the circuit board. While it is aesthetically pleasing and relaxes the eyes, that is the PCB solder mask. The function of the solder mask is to reduce corrosion and prevents circuit shorts.

During the solder mask apply to the circuit board, it provides a measure of insulation of the copper layer. Also, It aids PCB manufacturers in determining the placement of components during the soldering process.

Silkscreen

The silkscreen is the topmost layer of all circuit boards. This layer includes symbols and texts, enabling users better to understand the circuit board and the board's components. Also, it offers easy repairability as PCB engineers know which component is faulty and replaces it with a replica of the exact specification and standard.

Types of Circuit Card Assembly

There are three significant types of circuit card assembly. They are:

• Surface Mount Technology (SMT)
• Through-Hole Technology (THT)
• Ball Grid Array (BGA)

Surface Mount Technology

Surface Mount Technology or SMT, is the first production technique in PCB Manufacturing. Since the 1960s, many PCB manufacturers used SMTs in their PCBs.

In modern times, SMT has undergone refinements in producing smaller circuit boards. During circuit card assembly, components are firmly fixed on the surface of the PCBs. Also, thanks to SMT, components are fixed on both faces of the circuit board, making it a high-density PCB.

SMT is easily configurable and automated, which attracts PCB manufacturers who want to print circuit boards in large quantities. SMT automatic machines help reduce manual steps and lower labor costs while improving production efficiency.

Through-Hole Technology

When applying through-hole technology, the circuit board is drilled to allow the placement of electrical components with leads. After the drilling and placement, the electrical components are manually or automatically soldered to ensure permanent fixing on the circuit boards.

Through-hole technology is also an early assembly technique in the 1950s. However, with surface mount assembly and the evolution of PCB designs from single-sided to double-sided, it became challenging for THT to be adopted.

Through-hole assembly is excellent for single-sided PCBs, and electrical and electronic components such as capacitors, inductors, and transformers still consider using through-hole assembly.

Ball Grid Array

Ball Grid Array is a surface mount technology, but it is mainly applicable in integrated circuits and microprocessors. This assembly involves permanent mounting using a grid of solder balls on integrated circuit pins on the circuit boards.

The ball grid array process (above) has the following steps:

• Flux dispensed on the balls of a flip-chip component:
• The solder balls are immersed into the flux reservoir;
• The component is removed from the reservoir with the solder balls coated with flux;
• The component is placed on the circuit board.

Ball grid array circuits have more connections and density making them suitable for circuit boards in CPUs or mobile phones.

Difference Between Circuit Card Assembly and PCB Assembly

Keeping up with PCB terminologies can be pretty challenging. However, circuit card assembly and PCB Assembly refer to the same process of assembling bare circuit boards. Hence, they are interchangeable.

Circuit Card Assembly Steps

The steps involved in circuit card assembly transform a bare circuit into a printed circuit board. The following steps are as follows:

Applying Solder Paste Using Stencil

The first step in circuit card assembly is the application of solder paste on the bare circuit board. The solder paste's components are the solder metal and the flux.

The solder paste is also lead-free, with its principal constituent being Tin. Also, the flux assists the solder in melting and gluing the melted solder to the circuit board surface.

To ensure the proper spread of the paste on the circuit board, PCB manufacturers use PCB stencils. The stencil follows the set PCB design and is carefully fit on top of the bare circuit board. After application, the stencil is carefully removed, and the solder paste stays in the designated areas on the circuit board.

Automated Pick and Place Components

This next step is the pick and place process, where components are picked and placed on the circuit board. For SMT, an automated pick and place machine puts necessary electronic components on the board's surface.

The reason for the use of automated machines is that they are faster, more precise, and less prone to errors. Also, handling tiny components can cause weariness and eyestrain after prolonged hours of manually picking and placing the components.

Some pick-and-place machines put small amounts of adhesive to secure the components further. Yet, it can be disadvantageous, especially if the components' placement is misaligned from the original PCB design specification.

For through-hole technology, there is a drilling process, and automated THT machines place components with leads inside the circuit board.

Reflow Soldering

Reflow soldering is the next stage after components are placed on the solder paste of the PCBs. The solder paste must harden the components to stick to the board. Hence the reflow process places the PCB on a conveyor belt and travels through a huge reflow oven.

The oven heats the board to about 250 ℃, which melts the solder paste equally. Then, it goes through several cooling and solidifying processes till the surface mount devices and components are permanently fixed on the circuit board.

For two-sided circuit card assembly, special consideration is needed. Each side is stenciled and reflowed separately, with the side fewer, with the fewer side going first before the other side.

Inspection and Quality Control

The finished CCA circuit board will undergo an inspection to check if components are still in place during the reflow process, leading to poor connections. It is vital to prevent these defects to ensure the qualification for final tests.

Standard inspection techniques are x-rayed inspection, manual checks, and automatic optical inspection. For larger CCA batches, automated optical inspection is an excellent inspection technique.

Final Inspection and Functional Test

The final stage of circuit card assembly is functional testing, which indicates whether the circuit board is operational. Regular testing is vital throughout the assembly process to ensure proper workability of the PCB in its application.

The functional tests offer simulations of real-world scenarios and check out the performance of the PCB, such as its electrical and mechanical performance.

Basic Electronic Components Necessary for Circuit Card Assembly

Resistors

A resistor is a passive electrical component that opposes the current flow. Since resistance is necessary for all electrical circuits, resistors are not misplaced. In several PCBs, resistors are color-coded in stripes and help regulate voltage and current across each electronic component in the PCB.

Capacitors

Capacitors are passive electrical components that store electric charges in an electric field. Similar to the operations of a battery, they store electrical energy, which they can transmit when required in the circuit. However, capacitors can charge and discharge in a split second.

Capacitors help in blocking direct currents while allowing alternating currents to pass through. Also, they assist in regulating a power supply's output, which is useful in electrical transmission systems.

Inductors

Inductors are passive electronic components that store energy in a magnetic field and release it back into the circuit when needed. In contrast to capacitors, it blocks alternating current while direct current passes through it.

Diode

A diode is a semiconductor component that allows electric current to flow in one direction while restricting current flow in another direction. It helps in the rectification process where alternating current is converted to a direct current.

Transistors

Transistors have revolutionized the electronics industry and have become a vital component in PCBs. They switch and amplify components in a circuit. Their multifunctional nature and prolonged shelf life make them excellent in circuit card assembly.

Two kinds of transistors employed in PCBs include Bipolar Junction Transistors (BJT) and Field Effect Transistors (FET).

Conclusion

Circuit card assembly involves several processes and technology that make it a necessary step in the PCB industry. Relevant information regarding CCA has been extensively considered in this article.

Circuit card assembly is advantageous as it allows complex PCB designs to be produced efficiently and quicker. PCB manufacturers can take advantage of this information to improve their assembly process.

It is imperative to consider circuit card assembly in your PCB design. NextPCB delivers excellent quality PCBs using the CCA process. If you have any information regarding the process involved in circuit card assembly, reach out to us via PCB quote page.