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Stacked LED structure to achieve a compact multi-channel optical coupler - optical coupler - Communications Industry by big tree
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Stacked LED structure to achieve a compact multi-channel optical coupler - optical coupler - Communications Industry by BIG TREE
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| Article Posted: 06/29/2010 |
| Article Views: 32 |
| Articles Written: 1033 - MORE ARTICLES FROM THIS AUTHOR |
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Stacked LED structure to achieve a compact multi-channel optical coupler - optical coupler - Communications Industry |
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Business,Business News,Business Opportunities
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The core of modern optical coupler is input LED And optical output Detector . They are separated by insulating the light transmission medium. Photodetector can be a phototransistor, optical transistor can be with Diode And can also be integrated detector / logic IC . Most of the optical couplers have been UL1577, CSA and IEC / DIN EN/EN60747-5-2 set out the basic Security Standards.
In some cases, people especially want to improve a package in the number of optical couplers to optimize production costs, savings Board Space. For example, in computer systems, in an integrated package of more than two-channel optical coupler, can significantly reduce the parallel interface and serial interface, the number of components and board space, such as RS232/485/422, SPI (serial external based interface) and between IC (I2C) bus. Multi-channel optical coupler in industrial control, test and measurement, PLC (Programmable logic controller) health care system, Fieldbus interface and data acquisition; in POE (Power over Ethernet) and circuit boards and other interconnection Communicate Applications; in Plasma Flat Monitor And other Consumption Home Appliances Both provide the same advantages.
Ago to more than two optical coupler into a DIP / surface mount package, the casting is a big challenge. The main issues from the existing packaging technology, LED light box, a positive feature.
Some of the difficulties include: * Increase the manufacturing process, process complexity increases;
* Channel optical coupler between the light leakage / crosstalk;
* As a result of difficulties in isolation material placed IC Increasing the number of issues related to chip;
* As required leadframe and package graphics, need to clear a much larger package.
Optical coupler manufacturing technology The work of the optical coupler is based on LED light emitted through the transparent insulating medium to the photodetector, this medium provides 2.5kV - 6 kV range High pressure Insulation. Optical coupling depends on the photoconductive material. Insulation material through the light guide itself or through additional dielectric material to achieve light transmission. In any case, LED arrangement, optical materials, dielectric materials and the IC will directly affect the optical coupling and high-voltage insulation performance. In general, the optical coupler package similar to traditional integrated circuit package, but it uses a unique process steps and the necessary materials to form optical, high voltage insulation to meet the requirements. The following table sets out the various casting manufacturing method of optical coupler, introduced the unique material, process and constraints.
Double-casting process Figure 1 casting optical coupler package use the double-casting process
Figure 2 optical coupler package molding dielectric material used in place processes
Single channel optical coupler in the two-casting process, LED and IC by Mold Connected to two different lead frame and welding line. Then use the welding together of the two leadframes. After soldering in the lead frame, LED direct-to-IC, LED located above the IC. Then, the combination of a good use of white light transmission lead frame molding compounds, constitute a light guide device, the light from the LED transmitted to the photoelectric detector on the IC. White compound also provides a high-voltage insulation capabilities. Finally, the components are cast using opaque compounds to form the final package outline.
Dielectric material placed Process Placed in the dielectric process, LED and IC are arranged with the same dual casting process. But it does not use a white compound, but in between the LED and IC using silicon resin to form a light guide device. In addition, it placed between the LED and IC a dielectric optical transmission devices, the formation of high-voltage insulation. Finally, the devices use non-transparent casting compound casting.
Figure 3 casting optical coupler package use plane technology
Plane technology Process in the plane, LED and IC lead frame and welded in line with the same plane. Then use a layer of transparent silicone, with similar dome-shaped cover LED and IC. Silicone provides a light guide capacity. To prevent the escape of light, transparent silicone resin used in another layer of white paint. Therefore, the light from the LED will be reflected in the dome to the IC on the inside. Finally, the device package using the opaque molding compounds.
Stacked LED Technology Figure 4 is the optical coupler cross-section, in which LED directly stacked on the photoelectric detector IC. This method of stacking the main realization of LED back light LED technology is developing.
Figure 4 optical coupler cross-section, in which LED directly stacked on top of photo detector IC
Photodiode chip uses two transparent layers: SiO2 Passivation / Polyimide insulation and light transmission. LED connections using a transparent layer is firmly connected to the optical diode. IC using silver Epoxy resin Through the die connected to the lead-frame. Dielectric material used to connect to the IC optical conductivity on epoxy resin. LED light conductive epoxy mold used to connect to the dielectric material. Finally, the use of welding wire and casting components. It is connected using a standard mold process, the completion of all placed, packaged in a single transparent casting compound to complete casting.
Stacked LED advantages High integration: through the use of traditional IC component equipment stacked LED packaging technology greatly enhances the functionality and flexibility. In essence, Transmitter - Detector chip set can be integrated into any required package.
Reduce process steps: The method reduces the process steps, it is a more efficient manufacturing methods.
Light, small package: The total package height is determined by a simple IC, LED, LED ultra-thin polyimide and the thickness of the combination of a high degree of welding wire.
Figure 5 compares the various manufacturing processes have the package height.
Figure 5 LED back light Figure 6 is a positive light-emitting LED and through traditions BenQ The back end of the cross-section of light-emitting devices. Table 4 shows its properties.
Figure 6 traditional LED light absorbing substrate and the transparent front substrate cross-section of the back light LED
On the back of the illuminated LED, the active layer grown on a transparent substrate, doping depends on the required emission wavelength. Emitting region in the wafer fabrication workers I am China Product writer, reports some information about cheap wetsuits , rip curl wetsuits.
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