Directly mounting a bare semiconductor chip onto a printed circuit board (PCB) and wire bonding the chip to the board constitutes the process known as a chip on board (COB) production. Reduced package size, higher electrical performance, and lower cost are just a few benefits this technology has over conventional packaging solutions. Yet to ensure successful production, it’s crucial to consider several criteria before starting a COB manufacturing process. Therefore, this article will discuss the crucial elements to consider before beginning a COB manufacturing process.
Board Restrictions
When designing a printed circuit board, we must consider board restrictions such as board size and shape. We must first make sure the circuit has enough room. The size and functionality of the finished product are just a couple of the variables that impact the size of a circuit board. Electronic devices are getting smaller and more versatile due to technological advancements and shifts in consumer demand, which also significantly impacts PCB design. Hence, estimating the PCB sizes is essential before beginning the design. If there isn’t enough room, a multi-layer or high-density interconnect (HDI) design might achieve the needed functionality.
In terms of shape, we typically design the PCB into a rectangle. Nevertheless, the PCB must be created into a specific shape for some items with irregular shapes, even though doing so will increase the cost. We must consider the number of layers early in the PCB design process. Although designing a PCB with additional layers costs more, it enables us to design a PCB with more sophisticated features.
Quality Control
Chip-on-board (COB) manufacturing requires quality control to guarantee that the finished product meets electrical and mechanical requirements. Chip installation, wire bonding, encapsulation, and testing are some of the assembly processes essential in COB production. The performance and dependability of the finished product depend on each of these phases.
We can produce a defective product that might not function properly if you do not appropriately carry out any of the phases in the COB manufacturing process. Products with flaws can result in serious issues like decreased performance, system breakdowns, and sometimes even safety risks. Before the delivery of the finished product, quality control assists in finding and fixing any errors.
Several factors highlight the significance of quality control in COB manufacturing:
Component Selection: In the manufacture of COBs, the choice of proper components is crucial. Thanks to quality control, only top-notch components are utilized, lowering the likelihood of failure and ensuring the dependability of the finished product.
Process Control: Manufacturing COBs is a lengthy and intricate assembly procedure. Each process correctly happens, and quality control ensures the finished product satisfies the requirements.
Testing: In manufacturing COBs, testing is a crucial aspect of quality control. It must undergo extensive testing to verify that the finished product satisfies the necessary electrical and mechanical requirements. Functionality, performance, and reliability testing are part of this.
Traceability: Quality control also supports Traceability throughout the COB production process. This entails documenting each component and assembly phase, making it possible to identify the root of any flaws or issues.
Continuous Improvement: The purpose of quality control in COB production is to continuously improve the manufacturing process and the quality of the finished product. This includes determining the source of any difficulties, fixing them, and making enhancements to prevent similar problems from occurring again.
Environmental Considerations
When it comes to making COB devices, it’s essential to think about the environmental impacts. Chemical usage involves stuff like acids, bases, solvents, etc., that can be harmful, so handle and dispose of them carefully. Energy-wise, a lot of energy is helpful in the process, so consider energy-efficient equipment and renewable sources to reduce that. Waste-wise, there’s lots of waste created, so recycle and reuse materials, and mitigate disposable material use. Water usage is also a consideration, so reduce it where you can and ensure you treat wastewater correctly. And lastly, materials – use sustainable, recyclable, and non-toxic ones. All this can help minimize the environmental impact of COB devices and make for a more sustainable future.
Assembly Process
Many assembly procedures create integrated circuits before chip on board (COB) manufacturing (ICs). Some of these procedures include wafer fabrication, photolithography, etching, depositing, dicing, packing, and assembly onto a printed circuit board (PCB). Making silicon wafers, which will serve as the ICs’ substrate, is known as wafer fabrication. A mask is helpful in photolithography to transfer a design from a surface to a silicon wafer. Etching involves scraping away undesirable material.
Deposition entails covering the wafer with a thin layer of metal. Next, we dice the wafer into tiny squares containing one integrated circuit. Finally, we package individual integrated circuits (ICs) into ceramic or plastic packages. Directly mounting the ICs onto the PCB and wire bonding them to the necessary areas of the board constitute an assembly. This method enables high-density packaging and has numerous potential uses.
Wire Bonding
Wire bonding creates electrical contact using small wires and various parameter combinations, including pressure, heat, and ultrasonic wave. We classify it as a solid-phase welding procedure in which an intimate interaction occurs between two materials. One may use the bonding force that may cause the material to deform, making rough surfaces more smooth and separating the contaminant layer. In a year, more than 4 Tera wires bond, most of which are helpful in over 50 billion ICs (incorporated circuits). Along with the older wire bonding approach, several bonding methods are ideal, including Flip-Chip, Tape Automated Bonding (TAB), and Controlled Collapsed Chip Connectivity.
Two common wire bonding types are Ball and Wedge bonds. Wire bonding methods start by joining the bottom of the chip with a chip carrier utilizing natural conductive glue or solder.
Precautions to take when handling COB
Iterative PCBA development is a method for raising quality. Boards must be treated carefully during the manufacturing, production, and storage phases to obtain the highest possible quality. Development precautions include preventing copper traces in the air, utilizing the proper surface finish, eliminating remaining debris, wearing protective gear, being cautious when using equipment, and preventing humidity. Using the right equipment is essential when working with tiny boards since the risk of damage is greater. Moreover, contaminated boards might exhibit inconsistent behavior, making precise testing challenging.
Summary
Chip on Board (COB) manufacturing generally entails wire bonding the chip to the board and directly mounting a bare semiconductor chip onto a printed circuit board (PCB). Therefore, several aspects, including chip selection, PCB design, wire bonding, the assembly process, quality control, and environmental considerations, must be carefully considered while manufacturing COBs.
To ensure that the finished product matches the necessary criteria, wire bonding, a crucial phase in the COB manufacturing process, must be appropriately managed. In addition, chip-on-board (COB) manufacturing requires quality control to guarantee that the finished product meets the necessary electrical and mechanical requirements. Regulation compliance, sustainability, resource conservation, waste minimization, energy conservation, and packaging are all significant environmental factors in COB manufacturing.
It is possible to develop high-quality, dependable COB products that adhere to the necessary specifications by carefully considering these elements.
