CN100570910C - Surface Mount LEDs - Google Patents

Abstract

The invention provides a surface mounted LED. In conventional surface mount LEDs of this type, due to repeated external stress, cracks are generated in the molded part of the resin substrate without the copper foil's easy-to-bend part, and there is a problem that the moisture resistance is lowered, and the LED element is likely to deteriorate. According to the present invention, especially in the direction crossing the resin substrate along the short side direction, the front-side electrodes and the back-side electrodes provided on the front and back sides of the resin substrate are formed in a shape that exists on both sides as much as possible, and the number of electrodes supported only by the resin substrate is reduced. The area of the molded part can be reduced, so that the front and back electrodes can withstand external stress, reduce the stress applied to the molded part, and prevent cracks, etc., thereby solving this problem.

Description

Surface Mount LEDs

technical field

The present invention relates to a surface mount type LED chip, and particularly relates to a thin LED chip formed in a shape suitable for illumination of input buttons of miniaturized devices such as mobile phones.

Background technique

FIG. 4 shows an example of such a conventional surface mount type LED 90. For example, a substrate 92 is formed with a glass epoxy resin or the like having a thickness of about 0.05 mm. , and a conductive pattern 92b wired by wires 93 or the like, and one electrode of the LED element 91 is mounted on the conductive pattern 92a by using a conductive adhesive or the like.

In addition, the other electrode is connected to the conductive pattern 92b through wires 93, etc., so that the wiring is performed, and the LED element 91 is sealed with a transparent resin such as epoxy resin with a thickness of about 0.4 mm, thereby forming the molded part 94, and obtaining the overall thickness. Surface-mounted LED 90 of 0.5 mm or less.

In addition, in this conventional example, the substrate 92 located on the inner side of the conductive patterns 92a, 92b is appropriately cut off at both ends of the long side of the substrate 92 by laser processing or the like to form electrodes for surface mounting, and soldering is performed. Enter its differential part, so that the installation height is slightly reduced.

Patent Document 1: Japanese Patent Application Laid-Open No. 8-298345

However, in the above-mentioned conventional surface mount type LED 90, as shown by the corrugated line D in FIG. Cracks and the like are generated from the above-mentioned molded portion 94 part, causing a problem of breakage.

And even if it is not damaged, the above-mentioned molded part 94 is easily deflected due to stress, for example, it will be peeled off from the conductive pattern 92a part where the LED element 91 is installed, and the moisture-proof effect on the LED element 91 is not sufficient. There is a problem that the LED element 91 is degraded, and the solution to these problems has become a problem.

Contents of the invention

As a specific means for solving the above-mentioned problems, the present invention solves the problems by providing a surface-mounted LED as follows: the surface-mounted LED is composed of an LED element; a substrate on which the LED element is mounted; a surface-side electrode, a back side electrode formed on the side of the substrate on which the LED element is mounted and having positive and negative electrodes, and Electrically connected to the corresponding electrode on the surface side; wiring, which electrically connects the LED element and the surface side electrode; and a molding part, which covers at least a part of the LED element, the wiring, and the surface electrode. The positive and negative boundaries of the front-side electrodes and the positive and negative boundaries of the back-side electrodes do not substantially overlap when viewed from a direction perpendicular to the substrate.

According to the present invention, for a substrate formed with glass epoxy resin or the like to a thickness of 0.05 to 0.06 mm, copper foil or the like for forming a conductive pattern is provided on both sides thereof to form a double-sided substrate, and the copper foil or the like is used for reinforcement. In order to increase the strength, and among the conductive patterns formed on both sides of the substrate, the conductive patterns arranged on the surface and the back increase the area facing each other across the substrate, reduce the parts that only rely on the substrate to cope with external stress, and will not deform or stripped.

In particular, in the present invention, in the cross-section in the short side direction of the substrate that is easily deformed by external stress, there is no portion where only the substrate is present, and copper foil is present on at least either side of the front and back regardless of any portion. , so that the two parts contribute to the strength and prevent damage and peeling from the resin part.

Description of drawings

FIG. 1 is a cross-sectional view showing an embodiment of a surface-mount LED of the present invention.

Fig. 2 is an explanatory view showing the installation state of the front-side electrode and the back-side electrode of the surface mount type LED of the present invention.

FIG. 3 is an explanatory view showing an example of the shape of a protective layer similarly provided between a front-side electrode and a molding part of a surface-mount LED.

Fig. 4 is a sectional view showing a conventional example.

Detailed ways

Hereinafter, the present invention will be specifically described based on the illustrated embodiments. Shown by number 1 in Fig. 1 is the surface mount type LED1 of the present invention, and in the present invention, the substrate 2 of the surface mount type LED1 also adopts the parts that utilize glass epoxy resin etc. to be formed into the thickness of 0.05～0.06mm, This point is the same as the conventional example.

In addition, copper foils 2a, 2b for forming conductive patterns are pasted on the substrate 2, and one of the LED elements 4 is mounted on one of the copper foils, for example, the copper foil 2a, in a die mount manner. electrode, the other electrode of the LED element 4 is wired on the copper foil 2b by means such as wire bonding realized by the wire 5, and a molding part 6 is formed on the LED element 4 by using a transparent resin such as epoxy resin, so that It has an extremely thin structure with an overall thickness of about 0.4mm, which is the same as the conventional example.

However, in the conventional example, in order to realize the thinning of the surface mount type LED easily, a structure in which a copper foil for forming a conductive pattern is pasted only on the upper surface of the substrate, in contrast to this, in the present invention, the thickness of the surface mount type LED 1 is improved. Strength is the main purpose, and the copper foil is pasted on the upper surface of the substrate 2 to form the front side electrodes 2a, 2b as described above, and is also pasted on the lower surface of the substrate 2 to form the back side electrodes 3a to 3c.

In addition, at this time, of course, the overall thickness is correspondingly increased by one sheet of copper foil, so it can be freely adjusted by using the substrate 2 or the molded part 6 that has been thinned by that much. And, when the copper foil is provided on the front and back in this way, the corresponding parts of the front-side electrodes 2a, 2b and the back-side electrodes 3a to 3c can also be connected in advance by appropriate means such as the connection pattern 8 based on electroless plating. electrical connection etc.

FIG. 2 shows the state where the front-side electrodes 2a, 2b and the back-side electrodes 3a-3c are formed on the substrate 2 as described above. In this FIG. 2, in order to clearly understand the front-side electrodes 2a, 2b and the back The mutual positional relationship of the side electrodes 3 a to 3 c is shown in a state where the substrate 2 is seen through from above. In addition, when producing this kind of LED 1, the substrates 2 are usually produced in a state of being connected in the longitudinal direction, and are separated into individual components by a dicing step in the final step. Describe, and explain.

In the present invention, the front-side electrodes 2a, 2b and the back-side electrodes 3a to 3c are provided as described above, and the respective shapes are studied to eliminate the portion where the strength is maintained only by the substrate 2 in the short-side direction of the substrate 2. At least a part of any part is reinforced by the front-side electrodes (2a, 2b) or the back-side electrodes (3a-3c).

Therefore, even when a bending stress is applied to the substrate 2, the phenomenon that the stress is only received by the relatively soft resin member and the deformation is concentrated in this part does not occur, for example, the phenomenon that the substrate 2 is deformed to cause cracks can be prevented. . And, on the surface side electrode 2a of the substrate 2 formed as described above, the LED element 4 is mounted by die-bonding, and after wiring with the surface side electrode 2b by the wire 5, a transparent resin such as epoxy resin is used, and a mold is used. The molding part 6 is formed by molding, pouring and other means, thereby completing the surface mount LED 1 of the present invention (please also refer to FIG. 1 ).

Here, the results of studies conducted by the inventors to complete the present invention will be described. As described above, when the area of the front-side electrodes 2a, 2b sandwiched between the substrate 2 and the molding part 6 increases, the substrate 2 and the The adhesive force between the molded parts 6 decreases, and the two tend to be easily peeled off.

The reason for this is that the adhesive force between the substrate 2 and the epoxy resin constituting the molded portion 6 is slightly better than that between the surface-side electrodes 2a, 2b and the epoxy resin constituting the molded portion 6, that is, the more The larger the area of the surface-side electrodes 2a, 2b, the more the adhesive force between the substrate 2 and the molded part 6 tends to decrease.

Therefore, the inventors improved the adhesive strength by sandwiching the protective layer 7 which has good adhesive force to both, that is, both the substrate 2 and the molded part 6 . Furthermore, as shown in FIG. 3, by coating the surface of the surface side electrodes 2a, 2b with a protective layer 7, it is also possible to prevent solder from entering the surface side electrodes when the surface mount type LED 1 is mounted on a circuit board or the like by reflow soldering. The surface of 2a and 2b can further improve the strength of the surface mount type LED 1 by causing the molded part 6 to float and destroy the bonding strength.

At this time, if the area to be coated with the protective layer 7 is formed in a wider range, for example, only the range where wire bonding is possible is reserved, and the bonding strength between the substrate 2 and the molded part 6 can be further improved. function and effect. In addition, if the protective layer 7 is made of white or a material whose color is close to the luminous color of the LED element 4, it can also improve the reflection efficiency of light from the LED element 4 when the surface-mounted LED 1 is turned on. , to become brighter.

In addition, referring to FIG. 3 , there is a left-right asymmetrical portion in the front-side electrode 2a, and it is formed in a state where the molding part 6 is mounted, and the substrate 2 can be directly seen because the front-side electrode 2a is not provided on the substrate 2. The blank part of 2 becomes the polarity mark 21a. This is because according to the present invention, the areas of the front side electrodes 2a, 2b and the back side electrodes 3a to 3c are enlarged, so even if the polarity marks 21a are added on the back side, it is difficult to see clearly, and white LEDs are mostly used. Since the fluorescent substance is mixed in the molding part 6 and becomes opaque, even on the surface side, the polarity mark 21a cannot be recognized at the position covered by the molding part.

In addition, when actually carrying out the present invention, it is possible to freely select the necessary parts of the surface side electrodes 2a, 2b to be electroplated, or to use a double-wire method instead of a single-wire method for the LED element 4 to be used. It is not limited. Also, as mentioned above, the use of blue material for the LED element 4 and the addition of a yellow-emitting phosphor to the molding portion 6 to form a white-emitting surface-mount LED 1 can also be freely selected.

As described above, considering the layout pattern in which the substrate 2 is reinforced with copper foil at any part, even when a bending stress is applied from the outside, it does not appear that only the substrate 2 and the molded part 6 are formed relative to each other. The parts with weak bending strength from external stress do not cause cracks in the epoxy resin forming the molding part 6, and as a result, the LED element 4 deteriorates due to humidity, and the reliability of this surface mount type LED 1 can be improved. .

Claims (3)

1. A surface-mounted LED comprising: an LED element; a substrate on which the LED element is mounted; a surface-side electrode formed on a side of the substrate on which the LED element is mounted, and has positive and negative poles; a backside electrode, which is formed on the opposite side of the substrate on which the LED element is installed, has positive and negative poles, and is electrically connected to the corresponding electrode on the surface side; wiring, which connects the The LED element is electrically connected to the surface-side electrode; and a molding part covers at least a part of the LED element, the wiring, and the surface-side electrode, wherein, In any cross-section in the short-side direction of the substrate, there is no region where either the front-side electrode or the back-side electrode is not formed. 2. The surface-mounted LED according to claim 1, wherein a protective layer is coated on the surface of the surface-side electrode. 3. The surface-mounted LED according to claim 1 or 2, wherein a portion of the surface-side electrode not covered by the molding portion is viewed from a plane view in a direction perpendicular to the substrate. is an asymmetric shape.

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