JP2592436Y2 - Mounting structure of surface mount components - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for soldering a surface mount electronic component to a substrate. In order to promote the reduction in size and size of electronic devices, it is essential to use surface mounting technology. That is, it is because individual electronic components can be reduced in size and mounting density can be increased.

On the other hand, when a target circuit is constructed by assembling electronic components, the reliability in manufacturing is determined by the reliability of soldering. That is, it is necessary that the electrical connection be made securely and the mechanical connection be made securely.

On the other hand, there is a problem that the heat generation density is increased in accordance with the promotion of reduction in size and thickness, and the reliability of soldering is reduced with respect to thermal stress. Therefore, it is required to establish a mounting structure that can ensure high reliability against thermal stress.

[0004]

2. Description of the Related Art FIG. 4 is a view for explaining a soldering state of a surface mounting component, and is a view of a soldered state viewed from a side of a soldering surface. In this figure, a power transistor is illustrated as an example of the surface mounting component 2, and a structure is shown in which an electrode 4 serving also as an electrode and a heat sink is soldered to the pattern _3-1 of the printed circuit board 1. .

That is, the pattern 3 _{-1 of the} printed circuit board 1
This is a structure in which an electrode and a heat sink 4 of the surface mounting component 2 are connected by solder 5. Also, the lead 6 of the surface mounting component 2
Is a structure connected to another pattern _3-2 by solder 7.

In an element such as a power transistor for surface mounting, which has a large allowable power loss and a large amount of heat generation, some electrodes 4 have a function as a heat sink. Then, the electrode 4 is connected to the pattern 3 of the printed circuit board 1.
_By soldering to _-1 , the heat is dissipated through the pattern 3-1 to achieve an effective element cooling.

[0007]

An invention to be Solved] However, in order to electrode 4 and the solder 5 of the surface mount component 2, the thermal expansion coefficient of the pattern 3 _-1 of the printed circuit board 1 are different, the solder cracks and interfaces to the soldering point There is a problem of peeling and severe breakage. That is, when a thermal stress is applied to the soldering portion, the stress is generated in the surface direction of the soldering surface, that is, in FIG. 4, in the lateral direction of the drawing.

[0008] Such solder cracks, interfacial peeling and breakage at the soldered portion significantly reduce the reliability of soldering, and interfacial peeling and breakage cause failure because electrical connection is not ensured.

Further, even if the electrical connection is ensured in the solder crack state, if heat is radiated through the soldered portion, the thermal resistance rises and the performance of the surface mounting component increases. If it is reduced and increased, the element itself of the component will eventually fail. Incidentally, such a problem is particularly likely to occur in a component having a large area for the soldering electrode or in a case where the component generates a large amount of heat.

[0010] The technical problem of the present invention is to solve the above-mentioned problems in the soldering of surface mounting components and to establish a mounting structure that enhances the reliability of soldering against thermal stress, thereby improving the reliability of electronic equipment. To improve the quality.

[0011]

FIG. 1 is a diagram for explaining the basic configuration of the present invention. More specifically, FIG. 1 illustrates a case where the soldering electrodes of the surface mounting parts and the pattern of the printed circuit board are provided with irregularities. FIG. FIG. 1 is a view of the soldered state viewed from the side of the soldering surface.

The present invention is characterized in that the soldering surface of the soldering electrode of the surface mounting component and the soldering surface of the pattern other than the through-hole of the printed circuit board are provided with a mounting structure having irregularities.

[0013]

That is, the surface on which the soldering electrode 4a of the surface mounting component 2a is to be soldered, and the soldering electrode 4a
This is a mounting structure in which projections and depressions are provided so as to fit each other with the surface of the substrate 1a to which the solder 4a is to be soldered on the pattern 3a which is not a through hole.

[0015]

According to the mounting structure of the present invention, the stress generated in the surface direction of the soldering surface due to the thermal stress can be dispersed by the unevenness of the soldering surface. as a result,
Solder cracks, interface peeling and breakage are less likely to occur at the soldered locations.

Further, since the soldering area is increased by the unevenness, the soldering strength is also increased, and the soldering becomes more robust against the stress generated by the thermal stress.

[0017]

[0018]

In this mounting structure, the stress generated in the surface direction of the soldering surface due to thermal stress is applied to the uneven surface of the soldering electrode 4a of the surface mounting component 2a and the pattern 3a of the substrate 1a. Occurs in the direction. Therefore, stress does not concentrate on a specific location. That is, soldering with high reliability against thermal stress can be performed.

The soldering is performed in such a manner that the irregularities provided on the soldering electrode 4a of the surface mounting component 2a and the irregularities provided on the pattern 3a of the substrate 1a are fitted. Therefore, the stress generated in the soldering surface direction due to the thermal stress is dispersed in each of the irregularities, and the stress dispersing action is large.

[0021]

Next, an example of a mounting structure according to the present invention will be specifically described.

(1) First Embodiment FIG. 2 is a diagram for explaining a first embodiment, in which the present invention is applied to the conventional mounting structure shown in FIG. (A) is a view of the soldered state viewed from the side of the soldering surface,
(b) is a first example diagram for explaining the formation state of the irregularities on the soldering surface, and (c) is a second example diagram for explaining the formation state of the irregularities on the soldering surface.

In this embodiment, irregularities are provided on the soldering surface of the electrode / radiator plate 4b of the power transistor 2b, and irregularities are provided on the pattern 3-1a which is not a through hole of the printed board 1b so as to fit the irregularities. ing.

The shape of the irregularities is a short shape when viewed from the side of the soldering surface as illustrated in FIG. 2A. However, there are various variations in the shape of the soldering surface. That is, FIG. 2B shows an example in which the electrodes are provided in a stripe shape, and FIG. 2C shows an example in which the electrodes are provided in a lattice pattern. In addition, various variations such as a circle shape can be considered.

On the other hand, in the method of forming such concavities and convexities, the surface mounting component can be formed by a press die used for punching a lead frame by a press. In the case of using a ceramic for the base material 9c in the pattern of the printed circuit board, the pattern printing is repeated a plurality of times, and the pattern printing is selectively performed so as to form an uneven pattern on the pattern _3-1a. By doing so, target unevenness can be formed.

It is also possible to provide a structure in which the base material (ceramic) is provided with irregularities in advance. By forming irregularities on the ceramic surface at the stage before firing the green sheet, and then performing pattern printing, it is possible to achieve the desired purpose. Irregularities can be formed.

When a resin-based material is used as the substrate 9c of the printed circuit board, it is possible to form the desired unevenness by adjusting the etching depth of the pattern etching.

That is, in the case of a resin-based substrate, a substrate in which the thickness of the patterning electrode before etching is formed slightly larger is used, a basic pattern is formed in the first etching, and then a second etching is performed. Only the concave portions of the pattern where the irregularities are to be formed are etched. The second etching for forming the concave portion is stopped before the pattern is completely removed, and a concave portion having a desired depth is formed.

Of course, it is also possible to adopt a configuration in which irregularities are provided in advance on the substrate of the substrate. In this case, a pattern having irregularities can be formed by one etching.
That is, before forming an electrode to be a pattern on the surface of the substrate, the substrate is formed with irregularities. For reference, desired irregularities can be formed on the soldering surface of the surface mounting component by selective etching.

(2) Other Embodiments FIG. 3 is a view for explaining another embodiment, in which all of (a), (b) and (c) are soldered as viewed from the side of the soldering surface. FIG. That is, (a) is a diagram illustrating a saw-tooth uneven shape, (b) is a diagram illustrating a sinusoidal uneven shape,
(c) is a diagram illustrating a trapezoidal uneven shape.

In each of the examples shown in FIGS. 3A, 3B, and 3C, the electrodes 4c, 4d, and 4e of the surface mounting
This is an example of a mounting structure in which c, 3d, and 3e are provided with projections and depressions in a state where they fit each other. However, a mounting structure in which unevenness is provided on only one of them may be adopted.

As described above, according to the mounting structure of the component for surface mounting according to the present invention, the stress in the soldering surface direction generated by the thermal stress can be dispersed by each of the irregularities, so that it is further improved. Is obtained. Therefore, due to the difference in the coefficient of thermal expansion between the surface mounting component and each of the solder and the substrate, there is no occurrence of a solder crack, interface peeling or breakage at the soldered portion. As a result, the reliability of an electronic device employing the surface mounting technology can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a basic configuration of the present invention, specifically, a diagram illustrating a case in which a pattern is formed on a pattern of a soldering electrode of a surface mounting component and a printed board;
This figure is a view of the soldered state viewed from the side of the soldering surface.

FIG. 2 is a diagram for explaining the first embodiment, in which the present invention is applied to the conventional mounting structure shown in FIG. 4; (A) is a view of the soldered state viewed from the side of the soldering surface,
(b) is a first example diagram for explaining the formation state of the irregularities on the soldering surface, and (c) is a second example diagram for explaining the formation state of the irregularities on the soldering surface.

FIG. 3 is a view for explaining another embodiment, and is a view in which all of (a), (b), and (c) are soldered as viewed from the side of a soldering surface. That is, (a) is a diagram illustrating a saw-tooth uneven shape, (b) is a diagram illustrating a sinusoidal uneven shape,
(c) is a diagram illustrating a trapezoidal uneven shape.

FIG. 4 is a view for explaining a soldering state of the surface mounting component, and is a view of the soldered state as viewed from a side surface of a soldering surface.

Claims (1)

(57) [Scope of request for utility model registration] In a mounting structure for soldering a surface mounting component (2a) to a substrate (1a), a surface for soldering a soldering electrode (4a) of the surface mounting component (2a); on each side performing soldering not a through-hole of the substrate (1a) electrode for the (4a) soldering patterned (3a), providing the irregularity as mutually fitted to each other, surface mount, wherein Mounting structure of parts for use.