JPS63249669A - Optical printing head - Google Patents

Abstract

PURPOSE:To obtain an optical printing head achieved in cost reduction, by using a monolithic element wherein a light emitting element (LED) and an LED driver are integrated so as to correspond at a ratio of 1 : 1 to each other. CONSTITUTION:An Si substrate 20 is equipped with a circuit SiIC 21 which drives LED 22. A diffusion resistor 26 forms the ohmic contact with LED 22 and performs the insulating separation from the substrate 20 and said resistor is formed between LED 22 and IC 21. The LED element 22 and the driver element 21 are formed into a pair to be constituted in a monolithic state. LED 22 is allowed to emit light by turning the driver element 21 ON to apply constant voltage VDD. At this time, the current flowing to LED 22 is supplied through the diffusion resistor 26. By this structure, the reduction in manufacturing cost can be achieved.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a light emitting element array (hereinafter referred to as an LED array) as a light source, and a light emitting element in this LED array (hereinafter referred to as an LED).
This invention relates to an optical print head that is connected to a driver that drives the optical print head.

[Conventional technology]

Conventionally, various types of optical print heads have been implemented as this type of optical print head, and for example, there is one shown in FIG. 4.

FIG. 4 is a plan view showing an LED array of an optical print head according to the first conventional example disclosed in Japanese Patent Application Laid-Open No. 61-205153.

In the same figure, 1 is an LED array, and 11 to 1n are LEDs.
, 2t to 2n are electrodes, and this LED array 1 is L
P D 11 to 1n are integrated in an array, and the integration density is L'ED of 10 to 16 elements per 11r11.

The electrodes 21 to 2n are 1 for this LEDlt to 1nK:
LEol 1 to LEol 1 to 1n can be powered by wire bonding connection, which will be described later.

The electrodes 21 to 2n are arranged in a staggered manner to ensure sufficient space for wire bonding connection.

The number of elements of these LEDs 11 to 1n is actually 9 per l chip.
The LED array 1 is formed monolithically with 64 to 128 elements.

An optical print head is constructed by arranging a plurality of I/ED arrays 1 in a straight line on one substrate.

FIG. 5 is a perspective view showing the optical print head.

In the figure, 1 is an LED array, 3 is a substrate on which a plurality of LED arrays 1 are arranged, 4 is a conductive pattern provided on this substrate 3, and 5 is an electrode 21 to 2n of the LED array 1.
This is a bonding wire that connects the conductive pattern 4 on the substrate 3 by wire bonding.

6 is an FPC tape (also called carrier tape) that supplies light emission data and applied voltage to the LED array 1;
7 is a driver that drives the LED array 1, and 8 is a data input terminal of the driver 7.

Here, the conductive pattern 4 on the substrate 3 is L E Dl 1
The pitch is approximately the same as that of ~1n.

As for the operation of the above structure, first, the LED array 1 is mounted and adhered to the substrate 3 by die bonding.

The bonded LED array 1 is connected to a conductive pattern 4 on a substrate 3 via a bonding wire 5.

On the other hand, the output line of the driver 7 (LED array 1
direction) is connected to the conductive pattern 4 on the substrate 3 by laser or thermo-pressure welding.

As a result, the LEDs 11 to 1n correspond to the output lines of the driver 7 at a ratio of 1:1, and a current is supplied to the LEDs 11 to 1n via the bonding wire 5.

Input signals and applied voltages to the driver 7 are supplied by wiring 8 of the FPC tape 6.

FIG. 6 is a perspective view of an optical print head according to a second conventional example.

In the figure, 5 is a bonding wire, 7 is a driver, and 8 is an input signal pattern provided on the substrate 3 as means for supplying input signals to the driver 7.

Regarding the manufacturing procedure of the above configuration, first, an LED is installed on the board 3.
The array 1 and the driver 7 are mounted and bonded together by die bonding or the like.

Next, the electrodes 21 to 2n of the LED array 1 and the output electrode of the driver 7 are directly connected in a 1:1 ratio using the bonding wire 5 (this is called chip-to-chip connection).

On the other hand, the input electrode of the driver 7 is directly connected to the input signal pattern 8 on the substrate 3 via the bonding wire 5 in the same way as the output electrode.

If this second conventional example is compared with the first conventional example, the difference is in the connection method between the driver 7 and the LED array 1.

That is, the connection method of the first conventional example is a method in which the driver output line is once bonded to the pattern 4 on the substrate 3 and then connected to the LED array 1, as shown in FIG.

On the other hand, the connection method of the second conventional example is a method of directly connecting the driver 7 and the LED array 1, as shown in FIG.

In addition, in the first and second conventional examples, two chips of the driver 7 are used for one step of the LED array, but as a connection method of the third conventional example, the electrode structure of the LED array 1 is changed as shown in FIG. If the configuration is not staggered but only in one direction (single-movement extraction method), one chip of the driver 7 is used for one LED array chip (not shown here). 2. It is also possible to form an optical print head using the conventional connection method.

[Problem that the invention seeks to solve]

As explained above, when forming an optical print head, the number of bonds between the LED array and the driver is extremely large, and the bonding pitch accuracy is also required depending on the pitch of the light emitting part, so the connection method between the LED array and the driver is becomes extremely important.

In the second conventional connection method in which the LED array and driver are directly connected, the LED array and driver are connected in a one-to-one manner, so mutual alignment accuracy is required.

Furthermore, the first conventional connection method in which the LED array and the driver are connected via a -H pattern requires twice the number of bonding and man-hours as the second conventional connection method.

Furthermore, in the third conventional connection method in which the electrode structure of the LED array is taken out and connected in only one direction, precision in alignment and bonding pitch between the LED array and the driver is required.

Therefore, the first. Second. All of the connection methods in the third conventional example have a problem in that the number of connections is large and manufacturing is extremely difficult.

Therefore, this invention was made by focusing on the above-mentioned problems, and its purpose is to reduce the number of connections to facilitate manufacturing, improve reliability, and reduce costs. The purpose of the present invention is to provide an optical print head.

[Failure to solve the problem]

In accordance with the above object, the present invention includes LEDs and L of an LED array.
The gist of this invention is to use a monolithic element in which a silicon IC and an LED are monolithically integrated so that the ED drive driver corresponds to 1=1.

[Effect]

Regarding the manufacture of optical print heads, first of all, LED
LED array! = A monolithic element is used, in which a silicon IC and an LED are monolithically integrated so that the LED drive driver corresponds to the LED drive driver at a ratio of 1:1. Attach with adhesive.

Next, the input signal line of the wiring pattern on the substrate and the electrode pad portion of the monolithic element are connected with a bonding wire.

Therefore, the above-mentioned problem can be eliminated.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a sectional view showing a monolithic element used in the optical print head according to the embodiment.

In the same figure, 20 is a Si substrate, and this Si substrate 2
0 is silicon I, which is an IC for the circuit that drives the LED 22.
C (hereinafter referred to as 5iIC) 21.

23 is the optical and 5i IC2 between adjacent LEDs 22
This element isolation layer 23 is provided on the substrate 20 around the LED 22, for example.

24 is a wiring section connecting the LED 22 and the 5i IC 21, and 25 is an electrode pad section.

26 is a diffused resistor provided between the LED 22 and the 5i IC 21 and the Si substrate 20. The diffused resistor 26 forms an ohmic contact with the LED 22 and also provides insulation separation from the Si substrate 20.
This allows a resistance to be formed between C21 and C21.

27 is an insulating layer provided on 5iI021 or the like.

In this way, the LED element 22 and the driver element 21 form a pair, and for example, 64 to 128 elements are monolithically constructed on one chip.

FIG. 3 is a diagram showing an equivalent circuit of the monolithic element.

For convenience, the explanation will be based on FIG. 3. The 5i IC 21 has a logic circuit (register) and a driver (transistor) section that cause the LED 22 to emit light or emit light first.

IJil: To make D22 emit light, set driver 21 to
At this time, apply constant voltage VDD as “ON” state.
The current flowing through the LED 22 is diffused resistor (current limiting resistor) 2
6.

FIG. 1 is a perspective view showing an optical print head using the monolithic element.

In FIG. 1, reference numeral 3 denotes one branch of a substrate, on which a plurality of monolithic elements 30 are linearly arranged.

The electrode pad portions of these monolithic elements 30 and the wiring pattern 8 on the substrate 3 are connected by bonding wires 5, and a logic circuit and a constant voltage are supplied by connector coupling to an input connector 32 for an interface that conducts electricity with the wiring pattern 8. It is now possible to do so.

22 is an LED light emitting part, and 31 is a conductive adhesive.

Next, the manufacturing procedure of the LED print head having the above structure will be explained.

First, a plurality of monolithic elements 30 are linearly mounted on one substrate 3 and bonded with a conductive adhesive 31.

Next, the input signal line of the wiring pattern 80 on the substrate 3 and the electrode pad portion of the monolithic element 30 are connected with the bonding wire 5.

The number of connections is approximately 96 to 7 per 30 monolithic elements.

Thereby, the space between the electrode pad portions can also be sufficiently widened.

Furthermore, when driving the LED light emitting section 22, by supplying logic circuit signals such as a light emission data signal and a clock signal and a constant voltage to the input connector 32! The LED light emitting section emits all 22 lights.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, L
Since the configuration uses a monolithic element in which silicon ICs and LEDs are monolithically integrated so that the LEDs and drivers of the ED array correspond in a 1:1 ratio, the following effects can be obtained.

(1) A structure using a monolithic element provides a highly reliable element.

(2) Because of the monolithic element structure, an extremely simple linear arrangement structure can be achieved.

(3) Since the bonding wire is only required at the input section of the monolithic element, the number of connections can be significantly reduced and reliability can be improved.

(4) High definition and miniaturization of the head can be achieved, and manufacturing costs can also be reduced.

(5) Even if a defective element occurs, it can be replaced extremely easily.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an optical print head according to an embodiment;
FIG. 2 is a cross-sectional view showing a monolithic element of an optical print head, FIG. 3 is an equivalent circuit diagram of the monolithic element, FIG. 4 is a plan view showing an LED array of the first conventional optical glint head, and FIG. FIG. 6 is a perspective view showing a first conventional optical print head, and FIG. 6 is a perspective view showing a second conventional optical print head. 3... Board 5... Bonding wire 8...
Wiring pattern 20...St board 21...5iI
C22...LED 23...Element isolation layer 24.
...Wiring part 25...Electrode pad part 26...Diffused resistance 27...Insulating layer 30...Monolithic element 3
1... Conductive adhesive 32... Input connector patent applicant Representative of Oki Electric Industry Co., Ltd. Patent attorney Takashi Kanakura 31: Re-examination 32: Input connector scraping; Inburi] Tohe = J'E Show T4 Touhami Zukan 1 Figure Monolithi, Cliff W view of Riso ÷ 27:
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Claims (1)

[Claims] 1. In an optical print head formed by connecting a light emitting element array and a driver for driving the light emitting elements of the light emitting element array, the light emitting elements of the light emitting element array and the driver are arranged in a ratio of 1:1. An optical print head characterized by using a monolithic element in which a silicon IC and a light emitting element are monolithically integrated in a corresponding manner.