Several technical challenges exist when manufacturing solid state lighting (SSL) modules and components. The greatest challenge is in keeping up with the changes in LED technology. LED components, such as LED packages and chips, are improving in lumen output, luminous efficacy, and thermal performance at a staggering rate. A successful LED manufacturing organization needs to keep up with these improvements and allot time for educating its employees on new technologies and incremental improvements to LED packages and LED die. Figure 1 shows the luminous efficacy (lumens per watt) of various lighting technologies and their projected improvement through 2020. As you can imagine, staying abreast of the latest technology when it is improving so rapidly is like trying to hit a constantly moving target.
Another technical challenge lies in the need to shift design and manufacturing processes to a new technology. Lighting companies have been using the same technology for a century. LED lighting products need to be designed and manufactured much differently than products consisting of incandescent or florescent bulbs. LED light engines, as they are often referred to, are essentially printed circuit board assemblies (PCBAs) (Figure 2) and their design and assembly is more closely related to the design and manufacture of computers rather than light fixtures. For many lighting companies, it is a large leap to move from developing lighting products as we commonly know them to developing LED-based lighting products.
LEAN manufacturing is the scientific management of improving economic efficiency (Figure 3). It has been driven by the economic change from craft work to mass production. LEAN manufacturing practices are utilized to preserve value while lessening workload. As the adoption of LED illumination products increases, LEAN manufacturing will play an important role in driving down the cost of LED products. There are four basic lean principles used in the manufacturing of LED modules and components:
- Eliminate waste
- Increase speed and response
- Improve quality
- Reduce cost
Experience has shown that forecasting demand for LED products is very difficult. Differing lengths, color temperatures, and geometries are seldom known in advance. A LEAN manufacturing approach has allowed companies to respond to customer demand without the need for finished goods. LEAN principles are not only useful for the manufacturing of LED products but are also useful when designing LED products. This is critical to developing products that can be manufactured using LEAN principles. The designer’s role in using LEAN principles is to achieve the design goal while at the same time reducing or eliminating complexity in the product execution and experience.\
Manufacturing LED lighting products requires certain precautions. Precautions must be taken to control static electricity and contaminants. Because LED lighting products consist of printed circuit board assemblies, they must be handled with care and assembled in the appropriate environment. This is where a cleanroom comes in.
Manufacturing LED products requires a controlled environment, but does not always require a cleanroom. It is essential to control electrostatic discharge (ESD), and this can be done without the use of a cleanroom. Manufacturing floors can be coated in static dissipative flooring and assembly line workers can be grounded through more conventional means. A cleanroom environment is needed to control airborne particulates and contaminants. The necessity of a cleanroom environment is determined by the type of manufacturing being performed. Norlux manufactures hybrid chip-on-board (COB) products utilizing a class 10,000 clean room, while all of Norlux’s products are manufactured in an ESD controlled environment. Different classes of cleanrooms exist and different classifications are dependent on the manufacturing and the environmental sensitivity required (Figure 4).
Chip-on-Board (COB) Manufacturing:
Chip-on-board (COB) manufacturing refers to the direct mounting of a bare chip or die onto a printed circuit board (PCB) with solder or a conductive adhesive. The chip is often wire bonded and covered with an encapsulant to protect the chip and wire bonds and to improve light extraction.
The Chip-on-Board (COB) process often involves 3 main steps (Figure 5):
- Die attachment
- Wire bonding (not needed if flip chip)
Die attachment is the first step in a typical chip-on-board (COB) process. It is usually done with thermally or electrically conductive epoxy, or both. Die can be mounted manually or automatically. Precision die placement is critical before curing and, eventually, wire bonding. Consistent die placement is desirable to ensure interconnect accuracy and repeatability. Chip placement accuracy can be held within +/- 0.002” (X/Y). Typical die sizes ranges from 0.008” to 0.060”. In order to maintain die placement accuracy, a programmable pattern recognition system is employed on automated die attachment systems.
Wire Bonding is the next step after die attachment. The wires are connected from the die to the board by using a manual or automatic wire bonding system. Ultrasonic gold ball bonders and aluminum wedge bonders are typical machines used today. Norlux primarily uses gold ball bonding.
Encapsulation is generally applied for protection. Die and wire bonds are covered with a liquid encapsulant material to help shield components from contamination and mechanical damage, as well as to improve light extraction.
As the trend toward microelectronic LED packaging continues, the introduction of a wider variety of specialized COB LED products will increase.
LED Manufacturing Standards
Currently, no standards exist that are specific to LED manufacturing. However, many LED module and component manufacturers follow industry standards such as IPC (Institute for Printed Circuits) and ISO (International Organization for Standardization).
IPC is an industry association for printed circuit board and electronics manufacturing companies. It was founded in 1957 as the Institute for Printed Circuits. It was later named the Institute for Interconnected and Packaging Electronic Circuits and in 1999 changed to IPC. IPC develops standards and represents all facets of the industry including design, printed circuit board manufacturing and electronics assembly.
Norlux adheres to IPC standards during its design and manufacturing processes. Norlux is also ISO 9000 certified. ISO is a quality management standard for companies and organizations. The ISO standard provides tools for companies who want to ensure that their products and services consistently meet customer’s requirements and that quality is consistently improved. Certification and adherence to such standards is not required by law, but it is in the best interest of anyone looking to develop LED lighting products to be aware of these standards and ensure that their partners follow such standards. Organizations also have the option to test for compliance at agencies such as Underwriters Laboratories (UL) and Intertek ETL (Edison Testing Laboratories). These agencies ensure product safety. The lack of standardization specific to LED manufacturing may be indirectly related to the current high price points of LED lighting products. Regardless of the lack of specific standardization in LED manufacturing, the cost of LED lighting products will continue to decrease, but standardization could accelerate adoption rates and price reductions.
The adoption of LED technology has grown dramatically in merely three to four years. A technology once relegated to toys, indication lights and certain aviation applications has now become cost effective and efficient enough to become mainstream in general lighting applications. With renewed vigor for energy efficiency and environmentally-friendly products, LEDs are now the technology of choice for lighting manufacturers and consumers today. A trip to the doctor or dentist for a checkup, a glance upward on your next flight to turn on your reading light or perhaps even settling in at home under a down light — all of these experiences underscore the relevance of LEDs in your everyday life.
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