COB Packaging Technology

DeRun   Views:5648    05/19-2013

Compared with other packaging technology, COB technology, low price (only about 1/3 of the same chip), to save space, mature technology. But any new technology first appeared can not be perfect, COB technology there is a need to reprovision welding machines and packaging machines, sometimes not keep pace with the PCB patch more stringent environmental requirements and can not be repaired and other shortcomings.

Some chip-on-board (COB) the layout of the IC can be improved signal performance, because they remove most or all of the package, also is to remove most or all of the parasitic device. However, along with these techniques, there may be some performance issues. In all of these designs, the lead frame sheet or BGA flag, the substrate may not be well connected to VCC or ground. Possible problems, including the problem of the coefficient of thermal expansion (CTE) and poor substrate connection.

Substantially consists of three types:
The first category: small power LED straw hat made of LED energy-saving lamps, power supply with RC step-down circuit. Straw hat LED continue to use the indicator LED package, epoxy resin, making the LED chip can not dissipate the heat, severe decline of light, a lot of white LEDs in use for some time, the color temperature becomes high, and gradually into a bluish, become dim. Manufacturers committed to developing low-light failure straw hat LED, the light fades, but because there is no change package still did not change much. LED energy-saving lamps such products, as a transitional product, low prices, poor quality.

The second category: made by 3528 or 5050 power LED energy-saving lamps, power commonly used RC Buck circuit, there are some manufacturers using constant current circuit, compared to the straw hat LED, SMD LED heat slightly better thermally conductive substrate, in line with the aluminum plate, can part of the heat export. However, due to the heat of the LED or neglected, many medium-power SMD LED energy-saving lamps, radiators, still use the plastic shell is still serious, the light fades. RC Buck low-end power, grid voltage instability, the current fluctuations in the brightness fluctuations, affordable, quality slightly better.

Third category: the power SMD LED made of LED energy-saving lamps, power commonly used constant current isolated circuit, a constant current, such as 5W LED, usually 5 watt LED chip series, constant current 300mA current source power supply, wide voltage power supply, power fluctuations, the current does not change, the luminous flux to maintain a constant brightness, 5 patch.

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