LED Light PCBA
LED is a light emitting diode. It is a moisture and heat sensitive component sealed in an encapsulant (silicon or epoxy). There are bare chips, phosphors and die-bonding glue inside the LED (except for wire-bonded COB LEDs).
After the LED Light PCB is assembled, the single board is separated from the panel. Then perform function test and heat aging test on LED Light PCBA.
LED Light PCB Assembly Type and Method
There are two main types of connecting an LED to a PCB:
(1) LEDs are of the SMD type and LED PCB assemblies are surface mount (SMT) components on a PCB.
(2) The LED is COB LED type, then the LED is directly bonded on the PCB, no need for surface mount and reflow soldering. The two methods are wire bonding and flip chip bonding:
For wire-bonded COB LED PCBs, the chip is connected to the positive and negative pads using gold wires.
For flip-chip COB LED PCBs, the chips with solder balls on the bottom are picked up and placed on the PCB. Then subjected to high temperature forces, the solder balls melt and solidify the chip and PCB. After bonding, all COB LEDs are sealed together with encapsulant.
There are two main methods of connecting an LED to a PCB:
(1) Surface Mount: Surface mount mounts components directly to the PCB surface. This high degree of automation is very useful for LED applications. Place solder paste on the board, place components using a pick and place machine, heat the board to form solder joints and inspect the board.
(2) Through-hole assembly: Through-hole assembly involves drilling holes in the PCB through which the components are inserted. Use solder to hold the parts in place. Numerous checks are performed to ensure accuracy and validity. This method provides a stronger, more durable connection and facilitates effective application when the device is hot.
LED Light PCB Assembly Process
LED Light PCB Assembly is the process of installing electrical components on a PCB.
LED lighting is ubiquitous in our daily life and more and more lighting is being replaced by LED (Light Emitting Diode) solutions. BetonTech has been involved in thousands of LED lighting projects by providing LED PCB and LED PCB assembly services. Let’s see the bellow LED Light PCB Assembly process:
Place LED PCBA Order
The customer places an order after discussing the requirements for PCB assembly. All required files and documentation such as Gerber files and BOM are provided.
Making EQs and Working Gerber
Conduct design for manufacturability (DFM). Our engineers will check the documents provided by the buyer and check if there is any problem to make EQ and Working Gerber for customer confirmation.
Printed Circuit Board Manufacturing
The components are placed on the board, so the first step requires making the PCB. For LED PCB assemblies, the PCB is made of aluminum. Aluminum is an excellent material for durability and heat dissipation. Aluminum PCB has three layers: copper layer, dielectric material, and aluminum base layer.
Components Purchasing
The LED PCB components need to source from different component suppliers. Lead time may take 3-5 days depending on required LED PCB components. Components are purchased against a BOM list. The components generally required for LED PCBs are SMD LEDs, resistors and other components.
Solder paste on PCB
Use solder paste to link the LED PCB components to the LED circuit board. First, using a stencil to make the solder paste smear bare PCB . Because the stencil helps to spread the paste the required places. Apply the paste with a rag. The wiper applies solder paste and removes excess solder paste. Solder paste is applied to place and solder SMDs.
Pick and Place
Once the solder paste has been applied to the PCB, the next step is to place the components. Component placement is an automated process done using machines. Use files to send instructions to machines. This file contains the XY coordinates and rotation of the PCB. The machine places the components according to the instructions.
Reflow Soldering
The PCB will go through a reflow oven in the next step. Due to the heat in the oven, the applied solder melts and forms the connection of the component to the circuit board. After melting, the board is hot, so let it cool before coming out of the oven. Reflow soldering is suitable for SMD. If there are through-hole components, use hand soldering. If the PCB is single sided then wave soldering is also helpful and fast. In wave soldering, molten solder is applied to the bottom of the PCB.
Inspection
There may be some problems after PCB soldering, such as short circuit and missing connectors. So inspection is an important step to ensure the performance of LED PCB components. Faults are detected using AOI (Automated Optical Inspection). Use cameras from various angles to take pictures of PCB assemblies. AOI is a rapid process of thoroughly analyzing and detecting problems.
Then use X-ray Inspection for further inspection. X-rays enable observation of connections under components. Light passes through the PCB assembly and reflects to form an image. The image is then analyzed using image processing methods.
Final Test
To ensure proper functioning and expected results, LED PCB assemblies are subjected to final testing. Testing is carried out by various methods such as flying probe test, functional test and reliability test.
LED PCB Assembly Defects and Solutions
After the LED PCB is assembled, some LEDs may not light up or the light emitted by the LEDs may have serious color difference. LED lights may also have premature light failure with use. You can find out why during the LED PCB design and assembly process.
1. The LED does not light up due to improper wiring
Problem: The LED PCBA panelized board passed the electrical and AOI tests, but after de-boarding, some LEDs do not light up. In this case, we should check the orientation of the LED pads.
In LED PCB design, it is necessary to remember that the direction of the LED pad is preferably perpendicular to the stretching direction of the PCB. Especially aluminum LED PCB with V-cut board. If the direction of the LED pad is the same as the stretching direction of the PCB, the bending force when the board is divided may break the gold wire, resulting in an open circuit.
Solution: In the LED PCB design, try to make the LED pads perpendicular to the stretching direction of the PCB.
2. LEDs that are not baked before assembly have color difference
Problem: If the LEDs have been unpacked for a while, remember that it is necessary to bake the LEDs before LED PCB assembly.
If there is moisture inside the LED and you don't bake it, during reflow soldering, the water vapor will expand rapidly inside and cause the glue to break. As a result, the path of the light changes and the color of the light appears more yellow than a qualified LED.
Solution: Store the LED in an airtight moisture-proof storage condition with a humidity indicator card inside. If the LED has been unpacked or wet, please bake it at 70°C for 24 hours before LED PCB assembly.
3. The flexible LED light bar does not light up due to low temperature solder paste
Problem: If you use low temperature solder paste to solder the flexible LED PCB, after reflow soldering, the solder paste may come off and cause an open circuit. Why? Because low temperature solder paste will become brittle after reflow soldering (Peak temperature for lead-free soldering is 245°C to 265°C.). However, the flexible LED strip is often bent during use, which will cause the solder joints to fall off, so it is not suitable to use low-temperature solder paste to solder the flexible LED PCB.
Solution: When selecting the type of solder paste, please ensure that the viscosity, wettability, and melting point of the solder paste match the LED PCB and product use.
4. Premature light failure due to poor heat dissipation
Problem: LED light decay means that the brightness of the LED becomes low after working for a period of time, which is probably caused by poor heat dissipation. The LED cannot effectively dissipate heat, and the temperature of the LED will become higher and higher during operation. At high temperature, the phosphor and die-bonding glue inside the LED will deteriorate, and the light efficiency of the chip will decrease. In addition, the encapsulant turns yellow.
Solution: Pay attention to LED PCB thermal management, PCB substrate material, copper thickness, effective heat transfer area, etc.
Advantages of LED Light PCBA
- Lower Power Consumption: Replacing incandescent lamps with LED lamps can reduce power consumption by more than 80%.
- Longer lifespan: LEDs generally have a lifespan of more than 20,000 hours, and can be used around the clock for 3 years, 25 times longer than incandescent lamps. Not only can save costs, but also reduce the frequency of replacement.
- Greater Efficiency: Incandescent lamps emit more heat. LED lights can reduce this by up to 20%. This means that unnecessary heating can be reduced while using more powerful LED lights.
- Smaller size: Due to the small size, LED lights can have various sizes and can be applied in different places respectively. Manufacturers can add LEDs to anything, whether it is electronic equipment or cars, even traffic lights and signs on the road also add LED lights.
- Eco-Friendly: Compared to other bulbs, LED lights do not contain mercury. So, LEDs have less impact on the environment and are easier to dispose of.
Where can LED Light PCBA be applied?
LED Light PCBA offers excellent energy efficiency, low cost and maximum design flexibility, so it can be incorporated into many lighting applications.
Telecommunications: LED indicators and displays are always used in telecommunications equipment due to the surrounding machinery and they have a great ability to transfer heat. Therefore, aluminum-based LED Light PCBA has played an important role in its application.
Automotive: Aluminum LED Light PCBA is also used in indicator lights, brake lights and headlights of cars, among other applications. There are a few factors that make aluminum pcbs ideal in the automotive industry, such as durability and competitive pricing.
Computers: LED displays and indicator lights are gaining popularity in computer applications. Due to the heat sensitivity of computer mechanics, the Aluminum LED Light PCBA is an ideal solution. Besides LED applications, aluminum PCBs are also used in computer components such as power supply units and CPU boards because of their ability to dissipate and transfer heat.
Medical: Lighting tools used in surgical operations and medical examinations often use high-power LED lights, and these LED lights usually use aluminum PCBs, mainly because of the durability and heat transfer capabilities of aluminum PCB LEDs-this ensures that medical equipment works properly Runs regardless of the number of patients cycled through the infirmary. In addition to lighting tools, aluminum PCBs are also frequently used in medical scanning technology.
Get the Best
LED PCB Assembly Services
Beton Technology can provide the best LED PCB assembly service. We are one of the well-known LED PCB assembly manufacturers in China.
Our quality management system complies with international standards and is ISO, RoHS and UL certified. We ensure high quality and fast turnaround LED PCB assembly services. We have a wide variety of pre-designed LED PCB assemblies, and you can also order custom assemblies based on your needs. Also, we are good at turnkey PCB Assembly services. We'll handle everything from the first step to the last. For more information and details, please feel free to contact us at Cathy@beton-tech.com.