Electronics Manufacturing

An Ultimate Guide to the Electronics Manufacturing Process

Electronics Manufacturing Process

The Electronics Manufacturing Services (EMS) market has grown significantly over the years because demands for electronic products like computers, mobile phones, Smart TV, and wearables are on an upward trajectory. The positive trend is particularly evident in the Asia-Pacific region where there is a concentration of electronics manufacturers boosted by government policies. Most EMS companies can offer a range of services like design, assembly, testing, and product packaging as original equipment manufacturers (OEMs) continue to outsource these types of services. In this article, steps involved in electronics manufacturing process will be written in sequential order.

  • Electronics Design and Development
  • PCB Fabrication
  • PCB Assembly
  • PCB Testing
  • PCB Inspection
  • IC Programming
  • Box Build Assembly
  • Final Functional Testing

Electronics Manufacturing

Electronics Design and Development

The design and development phase in an electronic manufacturing process includes the generation of schematics showing the circuitry and connections. A schematics diagram is designed and developed by mapping out the location of components and plotting out logic diagram that represents electrical connections. This is typically done using a CAD (Computer-aided Design) software which is a readable format where you can easily drag the lines and symbols into a virtual sheet while the software automatically tracks the connections and checks design rules for violations. Drawings and electronic symbols represent the parts such as resistors, capacitors, transistors, and diodes. Each part also has a line that is referred to as a pin with a designated unique number for each connection.

PCB Fabrication

Once the design is finished, the next step in electronic board manufacturing process is the PCB fabrication. To put it briefly, PCB fabrication refers to putting together layers that make up the circuitry. The Printed Circuit Board is sometimes referred to as the “substrate” as it is the physical board where electronic components are being mounted on. The usual raw base material used in PCB fabrication is an epoxy glass fabric laminate called FR-4 with known advantages in terms of electrical and mechanical properties. Below are basic steps involved in the electronic circuit board manufacturing process.

  • Panel Preparation and Image Transfer: The Gerber file is the standard input format during image transfer which allows fabricators to automatically transfer the design data to a computer-aided manufacturing system (CAMS) for each layer including copper layers, solder mask and component placement.
  • Etching: In the etching process, the boards are immersed in a chemical bath to remove unwanted copper. Only copper pattern based on the transferred design should remain. Etching time is controlled to avoid shorts and damage to the tracks. After the etching process, the PCB is rinsed with water to completely remove residual etchant solution.
  • Drilling: Holes or vias are drilled into the panel to connect the layers. This can be done using two methods: mechanical drilling and laser drilling. Mechanical drilling uses a regular drill bit while a laser is best for very small holes.
  • Plating: After the vias are drilled into the boards, copper is plated into the inner layer either through electroplating or electroless plating. Electroplating is the process where the metal is deposited into a material by ionizing a source and drawing the ions thru an electric field. In electroless plating, a chemical reaction is required to attract the plating material into the surface.
  • Solder Masking: In electronic circuit board manufacturing process, corrosion and oxidation are the common potential problems that may arise due to exposure to air during succeeding operations and applications. To protect the board, solder mask is applied and subsequently cured with UV. The solder marks help guide and align the solder during reflow.
  • Silkscreen: If you look very closely to a PCB, you will see tiny labels on various parts of the board which are used for reference. These designated labels allow engineers and operators to quickly locate the components when debugging the PCB.

PCB Assembly

The next step in electronics manufacturing process is assembling components into the fabricated PCB. The most-used technology is called Surface Mount Technology (SMT). Listed below are the general processes involved in PCB assembly.

  • Solder Paste Printing: In this electronic board manufacturing process, a solder material, more commonly called as “solder paste”, is printed into the boards based on the circuit pattern for the stencil uploaded through a machine program containing the CAD tool. The solder paste is composed of a metal solder and a flux which serves as protection against oxidation.
  • Component Placement: A pick-and-place machine picks up and places the component into the pad with solder paste. The alignment of the components is critical during the electronics manufacturing process to avoid quality defects like missing components and open or short circuits.
  • Reflow Soldering: Reflow is a common method in the electronics manufacturing process to melt and cure the solder material to achieve ideal joint and connection in the PCB substrate. The reflow machine consists of heating zones that are programmed based on an optimum temperature profile. An inert gas, usually Nitrogen, is required to eliminate potential oxidation during the heating process.

PCB Inspection

  • Automated Optical Inspection: During PCB assembly, some defects can be encountered that may have impact on the quality of the boards. A perfect process is a myth and variations are inherent in electronics manufacturing process, thus, controls should be discussed with the contract manufacturers to ensure that only good PCBs are shipped. Automated Optical Inspection (AOI) is an efficient way to check the PCB using a reference good image. The AOI system should be programmed with optimum resolution, contrast and brightness to ensure accurate detection.
  • X-ray Inspection: Another method to inspect the PCB is through X-ray inspection. As there are limitations to optical inspection, X-ray inspection is also performed to check visual anomaly on the boards like voids and insufficient solder paste. X-ray inspection is carried out by inserting the PCB into a vacuum chamber while allowing a source to emit X-ray. As the X-ray hits the samples with varying, thickness, density and atomic number, images are formed based on the X-ray absorption of each material type of the PCB components. Darker areas on the image imply higher absorption of thicker and denser materials.

Electronics Manufacturing Services

PCB Testing

A critical step in electronic board manufacturing process is the verification of functionality and connectivity of the boards through testing. There are several methods to test the boards that vary based on equipment type, cost, and ease of use.

  • In-Circuit Testing (ICT): For mass production, the In-Circuit Testing is the most practical method to test the circuitry. This test method makes use of a fixture with pogo pings to test the probe locations of the PCB or the Device-Under-Test (DUT). ICT provides immediate detection of assembly faults by giving straightforward alert of the affected node in the electronic manufacturing process.
  • Flying Probe Testing: For prototype and small-scale testing, the Flying Probe Testing is the preferred method. This type of testing does not require a custom fixture. The test equipment consists of movable probes that can access the test points in X and Y directions. The boards are aligned and clamped in place through software control.
  • Functional Testing: In functional testing, the PCB undergoes testing that simulates the electrical environment which the boards will go through during application. This is to verify the functionality of the board as part of quality verification during the electronic manufacturing process. The test set-up inputs a signal pattern to the PCB and check the overall performance with a result of Pass or Fail. A functional test enclosure consists of a fixture such as that in ICT testers, but lesser in number of required nails.

We have learned that the printed circuit board, with size even smaller than your palm, goes through a long and elaborate electronics manufacturing process. The quality of the PCB and its functional performance is highly dependent on the above-listed processes, so adherence to the process flow and controls is significant.

IC Programming

After PCB testing, the electronic manufacturing process moves toward IC programming, or integrated circuit programming. And what is IC programming in the electronic circuit board manufacturing process? To put it simply, it is a process of loading software code into programmable integrated circuits. Specialized tools like IC programmer will be used to finish this process so that integrated circuits can be used in command of software code.

Here is typical process:

  • Programming in a specific language
  • Creating a binary file
  • Starting the programming process

Box Build Assembly

Next, another step involved in the electronics manufacturing process is box build assembly. Enclosure or “box” is needed so as to assemble PCBA, wire harness or other HMI elements into the enclosure where these electronics components are packaged. Usually, a custom or off-the-shelf enclosure acts as the defining feature of box build assembly because it is an option for prototyping or volume production.

Final Functional Testing

The final step in electronic board manufacturing process is final function testing (FTC), which aims to test the functionality of PCB boards before shipping. After functional test, the circuit board will be used in various sectors if no failure detected. Therefore, it is necessary to make sure that final products meet design requirements and specifications and check their reliability and performance. To do this, seeking FTC service should not be ignored in the electronics manufacturing process.

Conclusion

In summary, after explaining the electronics manufacturing process, I guess you may have a brief understanding of electronics manufacturing process. This process involves design, fabrication, assembly and testing. And it includes many technologies, electronic components, production methods and relevant equipment. As a saying goes, it is much easier said than done. If you want to make your own PCB board, you’d better carry out these steps to the letter.

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