JP2650236B2 - Manufacturing method of LED array light source - Google Patents

Description

The present invention relates to a method for manufacturing an LED array light source used for reading a document of a facsimile terminal.

(B) Conventional technology Conventionally, an LED (light emitting diode) is used as a light source for an image sensor, and the light output of the LED varies due to variations in epitaxial growth and the like. Therefore, as shown in FIG.
DD ₁ to D ₄ and method of the resistor R for the light quantity adjustment is connected in series are often used. In this image sensor light source (LED array light source), a wiring pattern is formed on an insulating substrate, an LED chip is die-bonded, and the LED chip and the wiring pattern are wire-bonded to connect four LEDs in series. Then, by applying a probe to the LED chip to actually apply a current to cause the LED chip to emit light, the resistance value R _{0 at} which the amount of light emitted from the LED chip becomes optimal is determined. A chip resistor R having a resistance value closest to this _R0 is selected, mounted on the circuit board, and the four LED chips and the chip resistor R are connected in series.

However, since the types of resistance values of the chip resistors are limited, it is difficult to accurately adjust the light output of the LED chip. Therefore, a light source for an image sensor shown in FIG. 6 has already been filed by the present applicant (Japanese Utility Model Application No. 1-87590).

The light source for an image sensor according to the prior application will be described with reference to its manufacturing process. First, a wiring pattern 13,14,15,16,17 on the circuit board, so as to straddle between the wiring patterns 16 and 17, different resistors R ₁ to R ₆ of each resistance value print form . LED chips D _{1 to} D ₄ on the wiring pattern 15
Are die-bonded, and the LED chips D _{1 to} D ₄ and the wiring patterns 15 and 16 are bonded to each other with a wire w.
ED chip D ₁ to D ₄ are connected in series. Then by applying a probe, by applying a current to the LED D ₁ to D _4, the light output to determine the value R ₀ of the adjustment resistor for the optimization. Then, the resistors R _{1 to} R ₆ are connected to each other so as to obtain a value closest to the adjustment resistance value R _0.
Alternatively, two or more elements are selected, and the wiring pattern 17 where the resistor is located and the wiring pattern 14 are bonded by the wire w '.

In this method of manufacturing a light source for an image sensor, the number of combinations of resistors can be increased, and a very large variety of combined resistance values can be obtained. Therefore, the light output is adjusted more accurately than when a chip resistor is used. can do.

In the above-mentioned problems the conventional method of manufacturing an image light source sensor (C) to be Solved by the Invention To form a resistor R ₁ to R ₆ is a resistor paste was printed on a circuit board, and firing the I have. Therefore, since the circuit board is exposed to high temperatures, the material of the circuit board is limited to ceramic or glass. However, these materials have poor workability and increase the cost. Further, the formed resistor R ₁ to R _6, each requires trimming for adjusting to a predetermined value, there is a problem that manufacturing process becomes complicated.

The present invention has been made in view of the above, and an object of the present invention is to provide a method of manufacturing an LED array light source that can use an inexpensive circuit board having better workability and that has a simplified manufacturing process.

(D) Means and Actions for Solving the Problems In order to solve the above problems, the method for manufacturing an LED array light source according to the present invention forms one electrode on a strip-shaped insulating substrate in the long side direction of the insulating substrate. At the same time, the other electrode is formed in the long side direction in opposition to the one electrode, and the LED chip is die-bonded along the one electrode and wire-bonded to the one electrode to incorporate a plurality of resistors. And a resistor built-in chip having a pad for connecting each resistor, die-bonding along the other electrode so that the pad is along the long side direction of the insulating substrate,
In order to obtain a resistance value at which the light output of the LED chip is optimal, one or two or more resistors of the chip with a built-in resistor are selected, and the pads of the resistor and the other electrode are wire-bonded, The LED chip is connected to a resistor.

According to the method of manufacturing the LED array light source of the present invention, since the chip with the built-in resistor in which the resistor is formed in advance is directly die-bonded, it is not necessary to fire the resistor at a high temperature as in the related art. An inexpensive material having excellent workability, such as a substrate, can be used.

Further, since it is not necessary to perform trimming adjustment of the resistor, the manufacturing process can be simplified.

(E) Embodiment One embodiment of the present invention will be described below with reference to FIGS.

In the LED array light source according to this embodiment, four LEDs are connected in series to form one block, and the light output of each block is adjusted by a chip with a built-in resistor.

FIG. 1 shows a part of a wiring pattern of a printed circuit board 2 of an LED array light source according to an embodiment. The printed circuit board 2 is a strip-shaped one as shown in FIG. 4, and as the material of the printed circuit board itself, glass epoxy which is inexpensive and has excellent workability is used, but ceramic or glass may be used. it can.

The wiring patterns formed on the printed circuit board 2 include an anode electrode (one electrode) 3, a cathode electrode (the other electrode) 4, LED patterns _5-1 , _5-2 , _5-3 , _5-4 , Wire bonding pattern 6, resistor built-in chip pattern 7
It consists of. As can be seen from FIG. 1, the anode electrode 3 and the cathode electrode 4 are formed facing the long side direction of the printed circuit board 2. Also LED chip
D ₁ , D ₂ , D ₃ , and D ₄ are provided along the anode electrode 3, and the resistor built-in chip 8 is provided along the cathode electrode 4. The LED patterns 5 _-1 , 5 _-2 , 5 _-3 , 5 _-4 , the wire bonding pattern 6 and the resistor built-in chip pattern 7
The LED pattern _5-1 is provided for each block, and is integrated with the anode electrode 3.

Next, LED chips D ₁ , D ₂ , D ₃ and D ₄ are die-bonded on the LED patterns 5 _-1 , 5 _-2 , 5 _-3 and 5 _-4 , respectively. A chip 8 with a built-in resistor is die-bonded on the pattern 7 for a chip with a built-in resistor, and the pattern 8 c extends along the long side direction of the printed circuit board 2. Resistance built-in chip 8, as shown in FIG. 2, the silicon chip 8a diffused resistor R ₁ to R ₆ are formed on the one end of the diffusion resistance R ₁ to R ₆ are electrically connected with aluminum wirings 8b ing. Thus, the diffusion resistance R ₁ to R ₆ are connected in parallel as shown in Figure 3. The other ends of the diffusion resistances R _{1 to} R ₆ and the wiring 8b have pads
8c,..., 8c, 8d are formed.

The LED chips D ₁ , D ₂ , D ₃ , and D ₄ each have a wiring pattern 5
_-2 , 5 _-3 , 5 _-4 , 6 are bonded by wire w. Thereby, as shown in FIG. 3, the LED chips D ₁ , D ₂ ,
D ₃ and D ₄ are connected in series.

In this state, apply the probe (not shown) and actually
The chips D ₁ , D ₂ , D ₃ and D ₄ emit light, and the light output is measured. And the value R ₀ of the adjusting resistor, such as the light output is optimized to determine, so that the smallest combined resistance to the value R ₀ of the adjusting resistor obtained 1 from among the resistors R ₁ to R ₆ or 2 Select the above. Then, the pad 8c of the selected resistor and the cathode electrode 4, and the pad 8d and the wire bonding pattern 6 are bonded by the wire w '. Since there are many combinations of resistors, fine adjustment of the resistance value is possible, and the light output of the LED chips D ₁ , D ₂ , D ₃ , and D ₄ can be adjusted with high accuracy.

For each block diagram, After completion the bonding wires w ', LED chip D _1, ..., D ₄ and resistors built-in chip 8
Is protected with a resin (not shown).

Finally, the cover 9 is attached to the printed circuit board 2 with screws 11 as shown in FIGS. The cover 9 has a plastic lens 10 and has LED chips D ₁ ,.
The illuminance of the light of No. _{4 on} the document surface is secured.

In this embodiment, one or two or more of the six resistors are selected and connected in parallel. However, the number of resistors in one resistor built-in chip is six.
The present invention is not limited to this, and a configuration in which the selected resistors are connected in series may be adopted.

Also, the number of LEDs in each block is not limited to four, and the design can be changed as appropriate.

(F) Effect of the Invention Since the method for manufacturing the LED array light source of the present invention is configured as described above, there is an advantage that an inexpensive and highly processable insulating substrate such as a glass epoxy substrate can be used. In addition, there is an advantage that the manufacturing process can be simplified. Also, since the pads of the chip with a built-in resistor are arranged along the long side direction of the insulating substrate, not only the advantage that the LED array can be manufactured without enlarging in the short side direction of the insulating substrate but also the desired Regardless of the number of wires connecting the pad of the resistor and the other electrode according to the resistance value, the length of the wire is constant, and there is no problem such as broken wire or contact between the wire and other parts. Has advantages.

[Brief description of the drawings]

FIG. 1 is a view for explaining wiring pads on a printed circuit board of an LED array light source according to one embodiment of the present invention, and FIG.
An enlarged plan view of a chip with a built-in resistor applied to this embodiment,
FIG. 3 is a diagram showing one block of an equivalent circuit of the LED array light source of the embodiment, and FIGS. 4 and 5 are the same LE.
FIG. 6 is an external plan view and an external side view of the D array light source.
FIG. 7 is a diagram illustrating a wiring pattern on a printed circuit board of an LED array light source according to the prior application, and FIG. 7 is an equivalent circuit diagram of a conventional LED array light source. 2: Printed circuit board, 3: Anode electrode, 4: Cathode electrode, _5-1・ 5 _-2.5・ 5 _-3・ 5 _-4 : Pattern for LED, 6: Pattern for wire bonding, 7: Pattern for chip with built-in resistor , 8: resistance built-in chip, 8c · 8d: _{pad, R 1 · ... · R 6} : resistor.

Continuation of the front page (56) References JP-A-62-268170 (JP, A) JP-A-61-156780 (JP, A) JP-A-63-48954 (JP, A) , U) Japanese Utility Model Showa 63-180957 (JP, U)

Claims (1)

(57) [Claims] An electrode is formed on a strip-shaped insulating substrate in the direction of the long side of the insulating substrate, and the other electrode is formed in the direction of the long side in opposition to the one electrode. A chip with a built-in resistor comprising a plurality of built-in resistors and pads for connecting each of the resistors is bonded to the LED chip by die bonding and wire bonding to one electrode along the Die bonding is performed along the other electrode along the long side direction, and one or more resistors of the resistor built-in chip are selected so that a resistance value at which the light output of the LED chip is optimal is obtained. And a method of manufacturing an LED array light source in which the resistor pads and the other electrode are wire-bonded to connect the LED chip and the resistor.