JPH0888409A - Led array head - Google Patents

Abstract

PURPOSE: To provide an LED array head, which can prevent the short circuits between neighboring electrodes and can improve the yield of products even if the applied amount of adhesive agent is large and the excess of adhesive agent is squeezed out in die bonding. CONSTITUTION: An LED array head is constituted by die-bonding many LED array chips 3 on a substrate 1 at minute neighboring intervals. In the this LED array head, a containing part 11 for containing the excess of adhesive agent 10a, which is squeezed out in die bonding, is provided at a part corresponding to the neighboring end parts of the LED array chips at the substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED (light emitting diode) array head used as a light source for an optical printer or the like, and particularly to a short circuit which occurs when an LED array chip is die-bonded onto a substrate with an adhesive. Prevented L
The present invention relates to an ED array head.

[0002]

2. Description of the Related Art LEDs, semiconductor lasers and the like are used as light sources for optical printers. In particular, unlike the laser beam head, the LED array head has the advantage that it has no mechanically movable parts and that the device can be made smaller and its durability can be improved.

As shown in FIG. 3, the LED array head has an insulative substrate 1 provided with conductive wiring including a die bonding pattern 7 for mounting an LED array chip 3 (31 ... 3n). Then, a large number of LEDs are formed on the die bonding pattern 7 (71 ... 7n) on the substrate 1.
A band-shaped light source is formed by adhering the array chips 3 adjacent to each other at a minute interval X with an electrically conductive adhesive 10. In this case, the LED array chip 3 is mounted on the die bonding pattern 7 after applying the adhesive 10 on the die bonding pattern 7, and is fixed by pressure bonding and drying of the adhesive 10.

Generally, the distance X between the LED array chips 3 is set to 2 in order to match the distance between the light emitting points in each chip and the distance between the light emitting points located at the ends facing the chip as much as possible.
It is set to 0 to 30 μm. In particular, since the LED array chip 3 on the substrate 1 uses the adhesive surface electrode on the back surface of each chip as a common electrode for each light emitting point in the chip, it is permissible to short-circuit between the electrodes of the adjacent LED array chips 3. Not done.

[0005]

However, the above L
In the ED array head, as shown in FIG. 3B, when the surplus adhesive 10a is extruded between the adjacent LED array chips 3 by pressure bonding during die bonding, the surplus adhesive 10a becomes the LED array chip 3. There has been a problem that the gap accumulates in the gap X between them and a short circuit between adjacent electrodes is likely to occur. As described above, if the amount of the adhesive applied is large, a short circuit or the creep of the adhesive to the chip surface occurs, and if the amount is small, the bondability deteriorates, and in either case, there is a problem that the yield of the product is reduced. As a countermeasure against this, it is required to precisely control the application amount and application area of the adhesive agent, but the present situation is that no adequate adequate amount control method has been proposed yet.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and prevent a short circuit between adjacent electrodes even if a large amount of adhesive is applied and excess adhesive is extruded during die bonding. It is an object of the present invention to provide an LED array head capable of improving the yield of products.

[0007]

In order to achieve the above-mentioned object, the LED array head according to claim 1 is an LED array head formed by die-bonding a large number of LED array chips adjacent to each other at a minute interval on a substrate. An accommodation section for accommodating the excess adhesive extruded at the time of die bonding is provided in a portion of the substrate corresponding to the adjacent end of the LED array chip.
It should be noted that, for example, a concave portion, a groove, a slit, a through hole, or the like can be applied as the accommodation portion.

An LED array head according to a second aspect of the invention is characterized in that the accommodating portion in the LED array head according to the first aspect comprises a through hole formed so as to penetrate the substrate.

[0009]

According to the LED array head of claim 1,
Since the accommodation portion for accommodating the surplus adhesive extruded at the time of die bonding is provided in the portion corresponding to the adjacent end portion of the LED array chip on the substrate, even if the adhesive coating amount is large, Even if the surplus adhesive is extruded at the time of bonding, the surplus adhesive is accommodated in the accommodating portion and does not accumulate in the gap between the adjacent LED array chips. As a result, short circuits between adjacent electrodes are prevented, and the yield of products can be improved.

Further, according to the LED array head of the second aspect, since the accommodating portion is formed of a through hole formed so as to penetrate the substrate, it is the same when the through hole for the electrode is formed on the substrate. Can be easily formed by the above method.

[0011]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a diagram schematically showing an embodiment of the present invention in which only an LED array mounting portion of an LED array head is shown for convenience of explanation, and FIG. 2 is a plan view showing a detailed configuration of the LED array head on a substrate. It is a figure.

In FIG. 2, reference numeral 1 is an LE of an optical printer.
An insulative substrate made of, for example, ceramics, which constitutes a main part of the D array head, and the surface of the substrate 1 is made of an electrically conductive material including a die bonding pattern to be described later made of, for example, Cu coating or Au coating by plating and photoetching. Wiring 2 is provided. On the substrate 1, a large number of LED array chips 3 (31 ... 3n) are mounted in a strip shape or in a straight line in the central portion of the substrate 1 so as to be adjacent to each other at a minute interval (20 to 30 .mu.m). The driving IC 4 is provided.

Each light emitting point electrode in the LED array chip 3 is electrically connected to the corresponding electrode of the driving IC 4 by a bonding wire 5. Further, a connector 6 for obtaining an input signal is provided at one end on the board 1,
The connector 6 is electrically connected to the wiring 2. The substrate 1 thus configured is attached to a housing made of, for example, an aluminum plate together with a light converging rod lens array and the like to form an LED array head.

The LED array mounting portion of the substrate 1 will be described in more detail. As shown in FIGS. 1 (a) and 1 (b), the LED array chip is provided in the central portion of the substrate 1 along the longitudinal direction thereof. The bonding patterns 7 (71 ... 7n) are applied discontinuously for every three. The bonding pattern 7 continues to the back side electrode of the substrate 1 through a through hole 8 formed through the substrate 1 for each pattern and is used as an external connection terminal. Further, on the substrate 1, a housing portion 11 for housing the excess adhesive 10a extruded during the die bonding is provided at a portion corresponding to the adjacent end portion of the LED array chip 3. The accommodating portion 11 of the present embodiment is formed of a round hole-shaped through hole formed so as to penetrate the substrate 1 similarly to the through hole 8. Then, a conductive adhesive 10 such as a silver epoxy resin is applied onto the bonding pattern 7 by, for example, a screen printing method or a transfer method,
The LED array chip 3 is placed thereon and fixed by pressure bonding and drying of the adhesive.

In the LED array head having the above-described structure, the housing portion 11 for housing the surplus adhesive 10a extruded during die bonding is provided in the portion of the substrate 1 corresponding to the adjacent end portion of the LED array chip 3. Since it is provided, even if the adhesive 10 is applied in a large amount, the die bonding pattern 7 and the LE can be used at the time of die bonding.
Even if the surplus adhesive 10a is extruded from between the D array chips 3, the surplus adhesive 10a flows down by its own weight, is accommodated in the accommodating portion 11, and is solidified.

Therefore, since the excess adhesive 10a does not accumulate in the gap X between the adjacent LED array chips 3,
Short circuits between adjacent electrodes can be prevented in advance, and the product yield can be improved. In addition, since the accommodating portion 11 is formed of a through hole formed so as to penetrate the substrate 1, it is possible to easily form the through hole 8 for an electrode in the substrate 1 by a similar method, which is troublesome. And there is no cost.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like within the scope not departing from the gist of the present invention. Also included in the present invention. For example, as the material of the substrate 1, an insulating material such as glass epoxy resin can be applied in addition to ceramics. The wiring 2 including the die bonding pattern 7 formed on the substrate 1 is
For example, thick film printing such as Pd-Ag or plating may be used. Further, the adhesive 10 may be solder or the like, for example. Further, in the above-described embodiment, the through hole is used as the housing portion 11 for housing the surplus adhesive 10a, but the housing portion may be, for example, a recess, a groove, a slit, or the like, in addition to the through hole. Further, the accommodating portion may be formed in a predetermined pattern, for example, a strip pattern.

[0018]

In summary, according to the present invention, the following excellent effects can be obtained.

(1) According to the LED array head of the first aspect, a housing portion for housing the surplus adhesive extruded during die bonding is provided in a portion of the substrate corresponding to the adjacent end portion of the LED array chip. Because it is
Even if a large amount of adhesive is applied and excess adhesive is extruded at the time of die bonding, the excess adhesive is accommodated in the accommodating portion and is not accumulated in the gap between the adjacent LED array chips and is adjacent to each other. It is possible to prevent a short circuit between the electrodes and improve the product yield.

(2) According to the LED array head of the second aspect, since the accommodating portion is formed of a through hole formed so as to penetrate the substrate, the same applies when forming a through hole for an electrode on the substrate. Can be easily formed by the above method.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an embodiment of an LED array head according to the present invention, in which (a) is a plan view and (b) is a sectional view.

FIG. 2 is a plan view showing in detail a configuration of a LED array head on a substrate.

FIG. 3 is a diagram schematically showing a main part of a conventional LED array head, in which (a) is a plan view and (b) is a sectional view.

[Explanation of symbols]

 1 Substrate 3 LED Array Chip 10a Excessive Adhesive 11 Housing

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04N 1/036 A

Claims (2)

[Claims] 1. An LED array head formed by die-bonding a large number of LED array chips adjacent to each other at a minute interval on a substrate, at the time of the die-bonding to a portion of the substrate corresponding to an adjacent end of the LED array chip. An LED array head, characterized in that a housing portion for housing a surplus adhesive that has been extruded is provided. 2. The LED array head according to claim 1, wherein the housing portion comprises a through hole formed so as to penetrate the substrate.