PCBs are the most critical components in modern electronics. They provide both foundational support and electrical connections for electronic devices. Thus, it’s essential to understand how PCBs are manufactured to ensure reliability and performance across various applications and devices.
The article briefly discusses the step-by-step PCB manufacturing process. FC PCBA is one of the renowned PCB manufacturers in China. FC PCBA follows all these manufacturing guidelines and standards to deliver a high-quality end product.
What is the PCB Manufacturing Process?
Printed Circuit Board manufacturing involves making boards that physically hold and electrically connect the electronic components. The manufacturing process transforms raw materials like fiberglass and copper into functional boards through chemical, mechanical, and electrical procedures.
The processes take these raw materials and convert them to boards with tiny pathways to conduct electricity. This process involves removing extra copper to form pathways, layering to construct multi-layer boards, and carefully placing and attaching the electronic parts onto the board. Quality checks should be done to make sure that the boards work fine. We will check the detailed guidelines on the PCB manufacturing process further.
The motto should always be to manufacture reliable, high-performance, cost-effective boards for use in all types of applications like phones, computers, and any other equipment that has an electronic version.
Step-by-Step Guide on PCB Manufacturing Process
Concept and Design
The journey of PCB begins with an idea and concept. At first, the engineers and designers start by defining the purpose and functionality of the PCB. They mostly use specialized software like CAD, a computer-aided design, to create detailed schematic designs and diagrams. It is a must that the circuit boards be designed according to the designs created by engineers. To create these designs, engineers use various software. The popular among them are Altium Designer, Orcad, Pads, KiCad, Eagle, etc. Designers should communicate with their manufacturer which software and version to use. This will prevent problems due to discrepancies between different software versions.
Once the design is finalized, designers export their ultimate PCB design in a manufacturer-supported format. Extended Gerber file format is the most commonly used format in doing this. The commonly dubbed IX274X – extended Gerber format – may be considered a blueprint for the PCB, detailing all information of interest, such as layout, layers, and component placement. This document ensures that the manufacturer’s production process remains an authentic reproduction from the digital design to the physical circuit board.
Material Selection
Selecting suitable PCB materials is crucial for effective PCB performance. Copper Clad Laminate (CCL) is one of the major base materials used in manufacturing PCBs. This is because CCL material can help in effective signal transmission, maintain impedance, and prevent energy loss. The commonly used CCL is FR-4, known for its excellent stability and insulation.
CCL provides the insulation, interconnection, and support within the PCB. At FCPCBA, we use the following method for the CCL manufacturing process:
- Cutting out the prepreg materials in required dimensions.
- Next is the pre-stacking step, where the materials are aligned and layered for the following process of pressing and combining.
- The next step is to combine the layers and press them to form a solid laminate.
- Then, the engineers separate and thoroughly inspect the laminates to ensure the quality of the material.
- Then, finally, the laminate is trimmed to size and packaged as required.
During this whole process, we maintain proper cleanliness, as dust can lead to open or short circuits in the final PCB product.
Printing the PCB Layout
The Plotter Printer is used to print the PCB design. The films produced by this printer provide the board’s details and layers. Looking closely at the PCB designs, you will see that various inks represent various parts of the PCB. For instance, FC PCBA uses color inks to represent the two layers: the inner and outer of the PCB.
For Inner Layers:
- We use black ink to represent the copper traces and circuits.
- While clear ink represents the non-conductive areas like fiberglass base.
Similarly, for Outer Layers:
- We use clear ink to indicate the copper pathways and black ink to show the areas where copper is to be removed.
Etching
Etching is a method of removing unnecessary copper from the PCB manufacturing process. This process is one of the most critical steps, as we need to remove the extra copper for the PCB fabrication method. Etching helps to reveal the pattern on the circuit board. The best way to etch is to use a chemical solution. It helps to dissolve the exposed copper. The etching process can vary in time and the amount of solvent used.
Layering and Lamination
After cleaning and preparing all layers, alignment punches ensure precise stacking. Technicians use an optical punch machine to align inner and outer layers via registration holes.
Once aligned, an automatic optical inspection (AOI) checks for defects, comparing layers to the original Gerber design. If inconsistencies are found, they are displayed for assessment.
Layer-Up and Bond
The layers are fused in two steps: layer-up and bonding. Prepreg (epoxy-coated fiberglass) and thin copper foil are layered with the substrate containing copper traces. This stack is pressed on a steel table with metal clamps, and the process is controlled by a bonding press computer, which heats, applies pressure, and cools the stack.
Drilling and Plating
Drilling creates precise and accurate holes for through-hole components and vias, helping to enable the electrical connections between the PCB layers. Automated machines ensure the accuracy of hole size and placement, which is crucial for the PCB’s performance.
Then the PCB is plated after drilling to provide the electrical pathways. Cleaning and immersing the PCB in an electroplating bath are required steps in this process. These pathways are created by copper ions deposition onto the PCB surface and with the drilled holes. Reliable connection depends on the high-quality plating, so process control and close observations are the most important to ensure the PCB’s longevity and functionality.
Solder Mask Application
This process involves applying non-conductive epoxy ink to protect the copper traces from oxidation and facilitate soldering during assembly. It is made of three main colors: green, blue, and red. It covers everything except the areas where components will be soldered.
Silkscreen Printing
Silkscreen printing applies layers of ink traces to identify areas of the PCB, components, warning signals, logos, and marks. The layer is used on the component side. However, it can also be applied on the solder side.
The ink used is non-conductive epoxy ink. There are two standard silkscreen printing techniques: Liquid Photo Imaging and Direct Legend Printing.
Liquid Photo Imaging is a traditional method. It involves coating the board with a photo-resistive chemical, which is then exposed to UV light passed through a photomask that contains a desired design. The areas exposed to UV light harden, while the unexposed areas can be washed away. This method is usually used when the line widths exceed four millimeters.
Direct Legend Printing, on the other hand, is a modern and more reliable silk screen printing method. It uses an inkjet printer to apply acrylic ink directly onto the board. The ink pattern is provided from the CAD data. The ink is cured with UV light as it is printed.
Surface Finishing
A proper surface finish is required on PCB boards. This is because the copper traces are prone to oxidation when exposed to air. Another essential function of surface finish is that this layer serves as a solderable surface. There are many surface finishes to choose from. We can have options like Electroless Nickel Immersion Gold (ENIG), Electrolytic Nickel Gold, Immersion Silver, and Organic Solderability Preservatives– just to name a few. The best choice depends on factors like cost, application environment (e.g., high heat, vibration), and whether lead-free materials are needed. Most modern finishes avoid lead to protect the environment these days.
Assembly
Before the PCB assembly process starts, manufacturers often subject the PCB board to several functionality checks. One such check is the DFM check. It’s an acronym for “Design for Manufacturability”. Manufacturing companies use design files to perform a DFM check. This helps to identify any redundant, missing, or problematic features in the design that might cause assembly issues in the final PCB. Manufacturers use an automated DFM/DFA system, which provides high-speed and accurate checks. After the check has been performed, the assembly involves the following steps:
First, apply solder paste to the PCB using a stainless stencil for precise placement. The paste is a mix of 96.5% tin, 3% silver, and 0.5% copper.
Next, a pick-and-place machine positions the surface-mount devices (SMDs) onto the solder-pasted PCB.
It is then heated in a reflow oven to around 250°C, melting the solder paste and bonding the SMDs. It then cools to form secure joints. The assembled PCB is inspected manually and with AOI machines and X-ray inspection to find defects like shorts or misalignments.
Finally, Plated Through-Hole components are inserted manually or by wave soldering, which automates the process by washing molten solder over the bottom of the board.
Quality Control and Testing
Quality control in PCB involves various testing methods to ensure the reliability and functionality of the boards.
One of them is In-circuit testing. It uses capacitance tests to check for open/short circuits, component values, and IC operation. Spring-loaded pogo pins press into designated test points to measure resistance and verify solder connections.
Another test: Automated Optical Inspection utilizes 2D/3D cameras to capture PCB images and compare them to schematics. The Flying Probe Test, a non-powered method, checks for open/short circuits, capacitance, resistance, inductance, and diode issues using needles on a CAD grid probe. Another method, X-ray inspection (AXI), examines solder connections, barrels, and internal traces, which is useful for components like ball grid arrays (BGA).
Some of these tests are performed in real-world conditions that mimic the working environment, while others are performed under exaggerated conditions. One such test is the burn-in test. In this test, the PCB is subjected to continuous power at maximum capacity, typically for 48 to 168 hours. Thus, the test is performed in elevated voltage and temperature to ensure its functionality even in critical conditions.
Conclusion
The FC PCBA PCB manufacturing process ensures precision, reliability, and functionality. Each step is executed carefully and meets the highest quality standards, from the design concept to the material selection, printing etchings, and assembly.
So, experience the difference with FC PCBA, one of the best PCB manufacturers in China, for your next PCB project. Visit us today and request a quote to know more about PCB projects.