JP2001024004A - LED chip mounting structure - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent silver paste unnecessary for bonding between an LED chip and a substrate to the outside of a bonding area to prevent the silver paste from creeping up to the upper surface of the LED chip. SOLUTION: In a chip type LED in which an electrode pattern on a substrate and an LED chip are joined by a silver paste, a groove for guiding extra silver paste for the joining to the outside of the joining area in a joining area of the LED chip of the pattern electrode. Is formed, and the liquefied silver paste is guided outside by capillary action.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention discharges extra conductive paste, such as silver paste, which does not contribute to bonding between an LED chip and an electrode pattern in a chip type light emitting diode (hereinafter, referred to as LED) to the outside of the bonding area. The present invention relates to a chip LED that prevents the silver paste from creeping up on the chip surface.

[0002]

2. Description of the Related Art LEDs are used as display lamps for various electric appliances because of their advantages such as low operating voltage, fast response speed and long operating life. Particularly in recent years, chip LEDs for surface mounting have been frequently used in order to meet the demand for miniaturization of electric equipment.

In general, a chip (type) LED is composed of a set of electrodes formed so as to extend from the front surface to the back surface of an insulating substrate, a light emitting element mounted on one of the electrodes, and a light emitting element on the other side. And a resin sealing portion in which a metal wire connecting the electrodes is sealed with a transparent or translucent resin. A chip-type LED having such a configuration is mounted on a printed circuit board, and the blinking of the chip-type LED indicates a switch 0N / OFF of various electric devices and various indicators are displayed.

[0004]

SUMMARY OF THE INVENTION Printed circuit board and LED
The bonding with the chip is performed by attaching a silver paste to a substrate or the like by, for example, pin transfer, and placing an LED chip thereon and curing the paste. However, since the LED chip itself is small, it is not easy to accurately apply a certain amount of silver paste to a substrate or the like, and therefore, the amount of silver paste attached (transfer amount) varies (variation in viscosity, P
It is unavoidable that a difference in adhesion due to IN transfer occurs. In addition, if the amount of the silver paste to be attached is insufficient, the bonding may be insufficient. Therefore, the amount of the silver paste may be slightly large. However, if the amount is too large, the following problems may occur depending on the LED.

That is, when the LED is used for displaying a button of an electric device, for example, a mobile phone, it may be easier to view the display by diverging the light emitted from the LED in the horizontal direction as much as possible. In such a case, fine irregularities are formed on the LED surface by, for example, etching so as to suppress the total reflection of light on the side surface of the LED chip. In such an LED chip, if the amount of the silver paste attached to the substrate or the like is too large, the heat applied when the silver paste is cured causes the epoxy resin in the silver paste to liquefy, and the liquefaction causes the silver paste to become capillary. Due to this phenomenon, there is a problem that the microscopic unevenness on the side surface of the chip is crawled up to cause a short circuit on the LED chip surface. FIG. 5 explains this state, and shows a process for joining the LED chip 1 to the electrode pattern 3 on the substrate 2. First, FIG.
As shown in FIG. 5A, an electrode pattern is formed on a substrate, and a silver paste 4 is adhered thereon by a transfer pin 5 (FIG. 5B,
C) Then, the LED chip 1 is mounted thereon (FIG. 5D).
When heated in that state, the epoxy resin in the silver paste becomes liquid, and the silver paste creeps up on the top surface of the LED through fine irregularities on the side surface of the LED due to the capillary phenomenon.
A short circuit occurs on the chip surface (FIG. 5E).

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an electrode pattern formed on a substrate, in which a groove having a shape that easily causes a capillary phenomenon is formed, and excess paste is released. , Leaving the necessary paste only on the back side of the chip,
This is to prevent the silver paste from creeping up on the chip surface. Specifically, according to the first aspect of the present invention, in a chip-type LED in which an electrode pattern on a substrate and an LED chip are bonded by a conductive paste, extra silver for the bonding is provided in a bonding area of the LED chip of the pattern electrode. A chip LED in which a groove for guiding a paste to the outside of the bonding area is formed.

According to a second aspect of the present invention, in the chip LED according to the first aspect, the groove for guiding the conductive paste out of the bonding area guides the liquefied silver paste out of the mounting area by capillary action. It is a chip LED characterized by the above.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. The present invention utilizes the above-described problem of capillary phenomenon to form a groove on the electrode pattern where the capillary phenomenon is likely to occur, so that the conductive paste such as extra silver paste adhered to the substrate or the like can be externally formed. To prevent the paste from creeping up on the chip surface. That is, FIGS. 1A and 1B each show L for comparison.
1A shows an electrode pattern 3 of a substrate 2 on which an ED chip is mounted, and no groove is formed in the electrode pattern of the conventional substrate shown in FIG. 1A. On the other hand, in the electrode pattern of the present invention shown in FIG. 1B, a cross-shaped groove 3A which is formed by etching or press working or the like in order to allow excess silver paste to escape from the joining area is described. The shape of the groove 3A is not limited to the cross shape as shown in the figure, but may be any shape such as a radial shape as long as it is a groove shape extending from the LED chip mounting portion to the outside.

Next, a case where an LED chip is bonded using the substrate formed as described above will be described. A silver paste is applied to the groove forming area of the electrode pattern by, for example, pin transfer, and an LED chip is placed thereon. 2A and 2B
3A and 3B are a side view and a plan view showing a state where an LED is mounted on an electrode pattern on a substrate, respectively. As shown, the excess silver paste 4 protrudes to the side of the LED chip. Next, when heating to cure the silver paste 4,
The epoxy resin in the silver paste is liquefied, and the excess silver paste 4 escapes to the outside through a groove 3A formed in the substrate immediately before curing due to capillary action. FIGS. 2C and 2D show this state. As a result of the extra silver paste escaping to the outside, the required minimum amount of silver paste can be left on the back side of the LED chip 1 almost uniformly. Therefore,
According to the present invention, even if the silver paste 4 is excessively placed on the substrate 2, the excess portion escapes to the outside through the groove 3A due to the capillary phenomenon. There is no possibility that the LED chip 1 will short-circuit due to crawling.

FIG. 3 shows a second embodiment of the present invention, in which the present invention is applied to bonding of a frame 10 and an LED chip 1 in an LED lamp, instead of bonding to a substrate in the first embodiment. It shows. When the LED chip 1 is joined to the frame 10 with the silver paste 4, the epoxy resin in the silver paste becomes liquid by heating when the silver paste is solidified, and the silver paste becomes a capillary phenomenon due to minute irregularities on the surface of the LED chip. As a result, the LED chip rises to the upper surface and causes a short circuit. In the present embodiment, as shown in FIG. 4, since the groove 3A is formed on the frame so as to extend outside the joining area in the radial direction, when the silver paste 4 becomes liquid immediately before curing, the excess silver paste is used. Escapes from the bonding area along the groove by capillary action, and as a result, only a minimum amount of the stable silver paste 4 can be left on the back surface of the LED chip 1. Therefore, even if the amount of the silver paste is large or the amount of the paste slightly varies, the amount of the paste remaining on the back surface of the LED chip can be stabilized to a minimum substantially constant amount.

[0011]

According to the first and second aspects of the present invention, when excess conductive paste such as silver paste is released to the outside of the bonding area during bonding of the LED chip, the excess conductive paste is liquefied by heating. In addition, there is no danger of the LED chip crawling up due to the capillary phenomenon and shorting the LED chip upper surface. In addition, as a result of discharging excess paste, a minimum amount of paste can be left in the bonding area on the back surface of the LED chip, and the amount of paste for bonding can be stabilized at a substantially constant level.

[Brief description of the drawings]

FIG. 1 is a diagram showing an electrode pattern of a chip LED.

FIG. 2 is a diagram illustrating a process in which a silver paste escapes outside a bonding area.

FIG. 3 is a diagram illustrating a process similar to FIG. 2;

FIG. 4 is a view showing an electrode pattern of a frame in the LED lamp.

FIG. 5 is a diagram for explaining the creeping-up of silver paste in a conventional chip LED.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... LED chip, 2 ... board, 3 ... electrode pattern, 3A
... grooves, 4 ... silver paste, 5 ... transfer pins, 10 ... frame

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[Procedure amendment]

[Submission date] September 24, 1999 (1999.9.2)
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] LED chip mounting structure

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention discharges extra conductive paste, such as silver paste, which does not contribute to bonding between an LED chip and an electrode pattern in a chip type light emitting diode (hereinafter, referred to as LED) to the outside of the bonding area. The present invention relates to an LED chip mounting structure that prevents a conductive paste such as a silver paste from creeping up on a chip surface.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

Means for Solving the Problems The present invention was made in consideration of the aforementioned problems, a substrate or a lead frame
Create a groove prone shape of capillarity electrode pattern on the beam, escape the excess paste, leaving only the required paste-chip back side, and as Ru prevents creeping of the silver paste on the chip surface Things. Specifically, the invention according to claim 1 is a mounting structure of an LED chip for bonding an LED pattern and an electrode pattern on a substrate or a lead frame by a conductive paste, wherein the bonding area of the LED chip of the pattern electrode is A mounting structure for an LED chip, wherein a groove for guiding an extra conductive paste to the outside of the bonding area for bonding is formed.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

[0007] The invention of claim 2 is described in claim 1.
In the mounting structure of the LED chip, a groove for guiding a conductive paste to the outside of the bonding zone, the mounting structure of the LED chip, characterized in that the liquefied conductive paste and guides before described置区outside by capillary action It is.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

FIG. 3 shows a second embodiment of the present invention, in which the present invention is applied to bonding of a frame 10 and an LED chip 1 in an LED lamp, instead of bonding to a substrate in the first embodiment. It shows. When the LED chip 1 is bonded to the electrode pattern of the frame 10 with the silver paste 4, the epoxy resin in the silver paste becomes liquid by heating when the silver paste is solidified, and the silver paste becomes fine irregularities on the surface of the LED chip. As a result, capillary action causes the LED chip to go up and cause a short circuit. In the present embodiment, as shown in FIG. 4, since the groove 3A is formed on the frame so as to extend outside the joining area in the radial direction, when the silver paste 4 becomes liquid immediately before curing, the excess silver paste is used. Escapes from the bonding area along the groove by capillary action, and as a result, only a minimum amount of the stable silver paste 4 can be left on the back surface of the LED chip 1. Therefore, even if the amount of the silver paste is large or the amount of the paste slightly varies, the amount of the paste remaining on the back surface of the LED chip can be stabilized to a minimum substantially constant amount.

Claims (2)

[Claims] 1. In a chip type LED in which an electrode pattern on a substrate and an LED chip are joined by a conductive paste, an extra silver paste for the joining is put out of the joining area in a joining area of the LED chip of the pattern electrode. A chip LED in which a guide groove is formed. 2. The chip LED according to claim 1, wherein the groove for guiding the silver paste out of the bonding area guides the liquefied conductive paste out of the mounting area by capillary action. Characterized chip LED.