The patent's assignee for patent number 8816384 is
News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to a semiconductor apparatus useful in, for example, a light-emitting diode (LED) print head in an electrophotographic printer.
"Referring to FIG. 45, a conventional LED print head 900 includes a circuit board 901 on which are mounted a plurality of LED array chips 902 having electrode pads 903, and a plurality of driver integrated circuit (IC) chips 904 having electrode pads 905. The electrode pads 903, 905 are interconnected by bonding wires 906 through which current is supplied from the driver IC chips 904 to LEDs 907 formed in the LED array chips 902.
"For reliable wire bonding, the electrode pads 903, 905 must be comparatively large, e.g., one hundred micrometers square (100 .mu.m.times.100 .mu.m), and the LED array chips 902 must have approximately the same thickness as the driver IC chips 904 (typically 250-300 .mu.m), even though the functional parts of the LED array chips 902 (the LEDs 907) have a depth of only about 5 .mu.m from the surface. To accommodate the needs of wire bonding, an LED array chip 902 must therefore be much larger and thicker than necessary simply to accommodate the LEDs 907. These requirements drive up the material cost of the LED array chips 902.
"As shown in plan view in FIG. 46, the electrode pads 903 may need to be arranged in a staggered formation on each LED array chip 902. This arrangement further increases the chip area and, by increasing the length of the path from some of the LEDs 907 to their electrode pads 903, increases the associated voltage drop.
"Light-emitting elements having a thin-film structure are disclosed in Japanese Patent Laid-Open Publication No. 10-063807 (FIGS. 3-6, FIG. 8, and paragraph 0021), but these light-emitting elements have electrode pads for solder bumps through which current is supplied. An array of such light-emitting elements would occupy substantially the same area as a conventional LED array chip 902."
As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "A general object of the present invention is to reduce the size and material cost of semiconductor apparatus.
"A more specific object is to reduce the size and material cost of a semiconductor apparatus comprising an LED array and its driving circuits.
"The invented semiconductor apparatus includes a substrate having at least one terminal. A thin semiconductor film includes at least one semiconductor device, the thin semiconductor film being disposed and bonded on the substrate. An individual interconnecting line formed as a thin conductive film extends from the semiconductor device in the thin semiconductor film to the terminal in the substrate, so the semiconductor device is electrically connected to the terminal.
"The semiconductor device may be an LED. The thin semiconductor film may include an array of LEDs, and the substrate having at least one terminal may include an integrated circuit that drives the LEDs. Compared with conventional semiconductor apparatus comprising an LED array chip and a driving-IC chip which is different from the LED array chip, the invented semiconductor apparatus has a reduced material cost because the LED array is reduced to a thin film and the overall size of the apparatus is reduced. The overall size of the apparatus is reduced because the large wire bonding pads conventionally used to interconnect the LEDs and their driving circuits are eliminated. Furthermore, the distance between the LEDs and their driving circuits can be reduced because of the elimination of the large wire bonding pads."
For additional information on this patent, see:
Keywords for this news article include: Electronics,
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