The longest thing you can see on the street is the LED display. With the rapid development of society, the LED display has been fully integrated into our daily life. The basic semiconductor digital tube is composed of seven strip LED chips arranged as shown in Figure 12. Its specific structure includes "reflector type", "strip seven-segment type" and "single-chip integrated multi-digit digital type". YONGS LED display will introduce his structure to everyone.
(1) The matrix tube (light-emitting diode dot matrix) can also be produced by a process similar to the monolithic integrated multi-digit digital display.
(2) The strip-shaped seven-segment digital tube belongs to the mixed package form. It is to divide the gallium phosphide or gallium phosphide wafer that has been prepared as a die into one or several LED light-emitting strips, and then stick the same seven strips on the Japanese-shaped "Kovar" frame, and use pressure welding The process connects the inner leads and encapsulates them with epoxy resin.
(3) The single-chip integrated multi-digit digital display is on the luminescent material substrate (large wafer), using integrated circuit technology to produce a large number of seven-segment digital display graphics, select qualified chips by dicing, and align them on the printed circuit. On the board, lead out the leads by pressure welding process, and then cover the "fisheye lens" shell on it. They are suitable for use in small digital meters.
(4) The production method of symbol tube and meter tube is similar to that of digital tube.
(5) The reflective cover type digital tube is generally made of white plastic into a seven-segment shell with a reflective cavity, and a single LED is pasted on a printed circuit board that is aligned with the seven reflective cavities of the reflective cover, and the bottom of each reflective cavity is The center position is the LED chip. Before installing the reflector, connect a φ30μm silicon-aluminum wire or metal lead between the chip and the corresponding metal strip on the printed circuit by pressure welding, drop epoxy resin into the reflector, and then connect the printed circuit with the chip. The board is aligned with the reflector and then cured.
The encapsulation method of the reflector type digital tube has two types: empty seal and solid seal. The solid encapsulation method adopts epoxy resin of scattering agent and dye, which is mostly used in one- or two-bit devices. The air-sealing method is to cover the filter and homogenizing film on the top. In order to improve the reliability of the device, the chip and the bottom plate must be coated with transparent insulating glue, which can also improve the light efficiency. This method is generally used for digital display (or symbol display) with more than four digits.
