Introduction

Hi, we welcome you to this electronic learning platform. In this tutorial, we will get the detailed concept of "Chip On Board"  or COB. If you have ever thought that how compact, powerful, and compact electronic devices are made the answer is chip-on-board technology. Whether you are a DIY electronic hobbyist, a technology enthusiast, or just want to know how your electronic devices are working, a deep understanding of COB will provide you with profitable insights for the electronic miniaturization future.

Through discussing the basics of a chip on board, we will learn how this innovative packaging technology revolutionizing electronic components integration, helps to make small size and more effective devices. We will also cover the industrial advantages and practical application of chips on board, giving you the information you need to appreciate the advancements in modern electronics. So let's get started and review the details of  Chip On Board technology!

What is a Chip on Board PCB?

A Chip On Board (COB) printed circuit board is a packaging method used for the assembly of electronic components on the PCB board. In this method, there is no individual components are configured on the board, but bare integrated circuits are connected on the surface of the board. The use of this technology reduces the use of older packing techniques like ceramic or plastic packaging, and that makes the small size and weight of electronic devices and projects. 

For mounting the chips there are solder bumps or adhesives are used, to make the compact and effective assembly. There are smaller electrical paths created between chip and board due to direct bonding, providing good electrical performance and fewer signal losses. This technology also provides good thermal management as chips are directly connected to heat sinks or thermal pads on the board.

These features good electrical performance, compact size, and good thermal features make this technology best for projects where space is limited like wearable technology, mobile phones, LED lights, and power electronics. This technology also advances the miniaturization and integration of electronic systems.

How Chip-on-boards are Made

1. Substrate Preparation: The PCB board is prepared through a cleaning board surface and applied the adhesive layer of conductive material where chips are bonded

2. Die Attach: The bare chips are getting and positioned on the adhesive-coated areas of the board. There are pick-and-place machines or specialized instruments used to do this process

3. Bonding: When cips are configured, they bonded with a board with the use of conductive solder bumps. This bonding process makes sure a reliable connection between the contact pads of chips and board conductive traces

4. Wire Bonding: In some conditions there are wire bonding is done to connectin bonding pads with board traces by using fine wires. This process helps electrical signals to be transmitted between the chip and board

5. Encapsulation: For the protection of chips and wire bonds from outer components. an encapsulant material can be used on the complete assembly. This material also clear epoxy coating

6. Testing: There are different testing methods used in COB assembly to make sure proper reliability and functionality. Such as temperature cycling, electrical testing, and visual inspection are performed to verify the function of COB

7. Final Assembly: When the chip on board assembly passes all tests, it is now ready to integrate into the final electronic devices like LED lights, phones, or any other projects

PCBasic can also use flip-chip technology to connect the chip face down to the PCB, which can use solder balls pre-applied at the wafer level or use our internal bumping process. Then use the glob top or Dam/Fill packaging process to protect the chip. Most chip-on-board assemblies can also be combined with our fast turnaround service.

For more professional requirements, please contact Pcbasic for a detailed technical review.

Pcb chip technology uses adhesives to connect semiconductor chips directly to the PCB substrate. By wire bonding it to an existing circuit pattern on the board, it is then packaged. Chip on board takes surface mount technology (SMT) to its extreme. The essential difference between COB (chip on board) and SMT is: COB (chip on board) usually involves high lead count, active devices, and does not require ceramic or molded plastic external device packaging.

Dialysis Chip on Board Application

The chip on board is a bare chip directly mounted on the PCB. After connecting the wires, use a ball of epoxy or plastic to cover the chip to connect them. The bare PCB chip is adhered to and wire-bonded to the board, and epoxy resin is poured into insulating and protecting it.

An unpackaged integrated circuit (IC) is mounted on a laminate substrate and signal conditioning or support circuits. When the IC is connected to the corresponding substrate interconnection by gold wire bonding, an electrical connection is formed. A junction coating material can then be applied on top of the chip to protect the chip and wire bonds.

So pcb chip is an excellent choice for miniaturized circuits. When the traditional assembly technology cannot meet the design parameters, a chip on board (COB) solution appears.

On the one hand, the main advantage of a chip on a board is that it reduces the weight and quality of the circuit. When this is a significant issue, chip on board technology is the ideal solution for miniaturizing your circuit.

In addition, chip on board technology brings unique assembly options to system designers. In this technology, the silicon chip is directly glued to the surface of the printed circuit board between the chip and the PCB or AL2O3 to establish electrical connections; an opaque epoxy resin coating is deposited on the chip to protect it from impact and light The harmful effects.

Features and advantages of Chip on board:

1. High and low-pressure design

2. Custom coating

3. Multi-layer, double-sided

4. Functional board test

5. High or low volume

6. Wide temperature range

7. Cost-competitive solution

8. Turnkey application

What are Chip on Board Led Lights?

Chip on board led refers to the direct mounting of LED chips on a substrate such as SiC or sapphire to produce LED arrays. COB LED is a newer and more advanced market entrant. Compared with the old LED technology, they have many significant advantages.

For example, pcb chipled technology exhibits a higher lumen density. This is achieved using multiple diodes, while older LED iterations usually only use one DIP LED or three SMD LEDs. Using more diodes in the LED means that there will be higher and more uniform light intensity while reducing the space occupied. No matter how many diodes there are on the chip, COB (chip on board) technology also uses a single circuit design with two contacts to make LEDs simpler.

Other advantages of a chip on board led include:

1. Highly compact and small size design;

2. Greater intensity, especially at close range;

3. High uniformity even when working at close range;

4. More straightforward single circuit design;

5. Excellent thermal performance to improve stability and reliability.

Chip on Board Packaging Process

Compared with other packaging technologies, pcb chip technology is inexpensive (only about 1/3 of the same chip), saves space, and has mature craftsmanship. However, any technology cannot be perfect when it first appeared. Chip On Board technology also has disadvantages such as the need for additional welding machines and packaging machines, sometimes the speed cannot keep up, and the stricter environmental requirements of the PCB patch, and the inability to maintain it.

The layout of a certain chip on board can improve IC signal performance because they remove most or all of the packages and remove most or all of the parasitic components. However, with these technologies, there may be some performance issues. Since pcb chip has a lead frame chip or BGA logo in all these designs, the substrate may not be well connected to VCC or ground. Therefore, possible problems with Chip on Board technology include the coefficient of thermal expansion (C TE) issues and poor substrate connections.

Step 1: Crystal expansion

The expansion machine is used to uniformly expand the entire LED chip film provided by the manufacturer so that the tightly arranged LED die attached to the film's surface is pulled apart to facilitate the thorn crystal.

Step 2: Adhesive

Place the expanded crystal ring on the backing machine surface where the silver paste layer has been scraped and put the silver paste on the back. Some silver paste. Suitable for bulk LED chips. Use a dispensing machine to spot an appropriate amount of silver paste on the PCB printed circuit board.

Step 3: Pierce the LED chip on the PCB

Put the crystal expansion ring prepared with silver paste into the piercing crystal holder. And the operator will pierce the LED chip on the PCB with a piercing pen under the microscope.

Step 4: Put the pierced PCB in a thermal cycle oven

Put the pierced PCB printed circuit board in a thermal cycle oven and let it stand for some time. After the silver paste is cured, take it out (not for a long time, otherwise the coating of the LED chip will be yellowed, that is, oxidized. Causing difficulties). If there is LED chip bonding, the above steps are required; if there is only IC chip bonding, the above steps are canceled.

Step 5: Stick the chip

Use a dispenser to put an appropriate amount of red glue on the IC position on the PCB. And then use an anti-static device to correctly place the IC die on the red glue or black glue.

Step 6: Drying 

Put the glued die in a thermal cycle oven on a large flat heating plate and let it stand at a constant temperature for a while, or it can be cured naturally (a longer time).

Step 7: Bonding (wire bonding)

The aluminum wire bonding machine is used to bridge the chip (LED die or IC chip) with the aluminum wire of the corresponding pad on the PCB board; that is, the inner lead of the COB is welded.

Step 8: Pre-test

Use special inspection tools (different equipment for COB for other purposes, simply high-precision stabilized power supply) to inspect the COB board and re-repair the unqualified board.

Step 9: Dispensing 

A glue dispenser is used to place an appropriate amount of the prepared AB glue on the bonded LED die. And the IC is packaged with black glue and then packaged in appearance according to customer requirements.

Step 10: Curing

Put the sealed PCB printed circuit board into a thermal cycle oven and let it stand at a constant temperature. Different drying times can be set according to requirements.

Step 11: Post-test

The packaged PCB boards are then tested for electrical performance with special testing tools to distinguish between good and evil.

Summary

Chip-On-Board (COB) technology has revolutionized the electronic world and provides different advantages than conventional packaging techniques. As there is direct bonding of bare chips on board, the chip on board made the small, less weight, and more effective electronic devices. The removal of bulk packaging and shorter electrical paths provides good electrical performance, fewer signal losses, and good thermal management. This technique is also important for the miniaturization of electronic components and paved the way for cutting-edge and compact technology in different industries. 

COB provides different applications from small mobile phone devices to lighting systems and automobile applications. As we move toward a future where electronics are seamlessly integrated into our lives and offer improved functionality and performance, embracing COB's promise empowers engineers, designers, and consumers alike.