JPH1131876A - Circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board wherein a void or blow hole is prevented from occurring, when a semiconductor part is mounted. SOLUTION: On a rear surface of the package of a semiconductor part, a grounding layer is provided instead of a grounding lead terminal. On the front surface of a circuit board 10 where a semiconductor part is mounted, a grounding pattern 11 is formed while facing the grounding layer. A through- hole 12 is provided at a part of the grounding pattern 11 of the circuit board 10. When a semiconductor part is mounted on the circuit board 10, the grounding layer and the grounding pattern 11 are soldered. Here, the gas of flux contained in the solder and the air taken in a molten solder are evacuated via a through- hole, as well as between the grounding layer and the grounding pattern 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a circuit board for mounting a semiconductor component operating at a high frequency.

[0002]

2. Description of the Related Art In order to reduce the size of electronic devices, the density of electronic components constituting electronic circuits has been dramatically increased.
For this reason, most electronic components are generally mounted by soldering the electrode terminals of the electronic component to pads that are part of a circuit pattern formed on the surface of the circuit board.

Next, an outline of a mounting method will be described. First,
A mask formed in a predetermined shape is superimposed on the surface of the circuit board on which the circuit pattern has been formed. Thereafter, a solder paste is printed on the surface of the pad using a squeegee. Further, after the electronic component is placed on the circuit board such that the electrode terminals of the electronic component and the pads are overlapped with each other, the electronic component is passed through a reflow furnace to melt the solder paste. As a result, the electrode terminals and the pads are electrically connected via the solder.

There is also known a method of melting a solder paste using a laser beam without using a reflow furnace. In this method, as described in JP-A-4-73911, a solder paste is applied to a substrate on which electronic components are mounted.
An opening for releasing gas of flux contained in the solder paste generated when the strike is melted and air taken in the molten solder is provided at least partially from the side end of the electronic component. It is provided so as to be exposed.

In recent years, semiconductor components operating at a high frequency are often used as electronic components in mobile communication devices such as PHS, switching power supplies, and the like. Generally, a semiconductor component has a semiconductor element and a lead terminal electrically connected to the semiconductor element, and the semiconductor element and the lead terminal are packaged with a resin. When designing an electronic circuit using a semiconductor component that operates at a high frequency, the number of the lead terminals is desirably small because the lead terminal of the semiconductor component functions as an inductance component. Accordingly, for semiconductor components operating at high frequencies, products have been developed in which the number of lead terminals is reduced by eliminating the ground lead terminals.

As shown in FIG. 5, in a semiconductor component 1 which operates at a high frequency without a ground lead terminal, a ground layer 2 made of, for example, gold plating is used instead of the ground lead terminal.
Is a package of resin or ceramic of the semiconductor component 1
A ground terminal of a semiconductor element (not shown) forming the semiconductor component 1 and a ground layer 2 is formed on the bottom surface of the semiconductor device, and is electrically connected directly.

When the semiconductor component 1 is mounted on the circuit board 3, a ground pattern 4 is formed on the surface of the circuit board 3 facing the ground layer 2, and the ground layer 2 and the ground pattern 4 are connected to each other. They are electrically connected via the solder 5. A lead terminal 6 other than the ground terminal of the semiconductor component 1 is electrically connected via a solder 5 to a pad 7 which is a part of a circuit pattern formed on the surface of the circuit board 3.

Further, since the grounding layer 2 and the grounding pattern 4 are connected via the solder 5, heat generated in the semiconductor element constituting the semiconductor component 1 is not affected by the grounding pattern via the grounding layer 2 and the soldering 5. -Efficient escape to 4 For this reason, the temperature rise of the electronic circuit designed using the semiconductor component 1 is reduced,
Malfunction due to temperature rise can be prevented.

[0009]

However, when the semiconductor component 1 is mounted on the circuit board 3, the heat applied to melt the solder paste can easily escape to the ground pattern 4, so that the ground layer 2 and the ground can be removed. There is a problem that the temperature near the pattern 4 does not rise uniformly. As a result, the solder paste is hardly melted, and the temperature of the reflow furnace must be set relatively high.

On the other hand, if the semiconductor component 1 is held at a high temperature for a long time, the semiconductor element will be thermally damaged due to the heat resistance of the junction of the semiconductor element constituting the semiconductor component 1. Therefore, the time required for holding in the reflow furnace had to be as short as possible. As a result, the flux gas contained in the solder paste generated when the solder paste is melted, and the air taken into the molten solder,
The space between the grounding layer 2 and the grounding pattern 4 did not escape sufficiently, causing voids 8 and blowholes 9 to be generated. For this reason, there has been a problem that the position shift and the inclination of the semiconductor component 1 occur. Also, the ground layer 2 and the ground pattern
In this case, the bonding area with the heat sink 4 is reduced, so that the high frequency grounding characteristics and the heat radiation effect are deteriorated. Further, when the heat cycle is used, the connection strength is significantly reduced. There was also a problem of lack of electrical reliability.

Accordingly, an object of the present invention is to provide a circuit board for mounting a semiconductor component operating at a high frequency to solve the above problem.

[0012]

The present invention is configured as follows to achieve the above object. That is, first, the circuit board on which the semiconductor component is mounted has a ground pattern formed at a position facing the ground layer provided on the bottom surface of the semiconductor component and soldered to the ground layer,
A through hole is formed in the ground pattern.

During the soldering, the gas of the flux contained in the solder paste and the air taken in the molten solder generated between the ground layer and the ground pattern pass through the through holes. Scatter.

Second, the circuit board on which the semiconductor component is mounted has a ground pattern formed at a position facing the ground layer provided on the bottom surface of the semiconductor component and soldered to the ground layer. A groove for exposing the insulating substrate is formed in the ground pattern portion, at least one end of which is a peripheral edge of the ground pattern.

During soldering, the flux gas contained in the solder paste and the air taken into the molten solder generated between the ground layer and the ground pattern are diffused through the grooves. I do.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A circuit board 10 according to claim 1 will be described with reference to FIGS. Note that the same components as those in the related art will be described using the same numbers. In addition, only the portion of the circuit board 10 on which the semiconductor component 1 operating at a high frequency is mounted will be described.

As shown in FIG. 1, a pad 7 which is a part of a circuit pattern and a ground pattern 11 are provided on the surface of a circuit board 10 on which the semiconductor component 1 is mounted. Pad 7
When the semiconductor component 1 is mounted on the circuit board 10, it is electrically connected to a lead terminal 6 connected to a semiconductor element (not shown) constituting the semiconductor component 1. The ground pattern 11 is formed so as to face the ground layer 2 provided on the bottom surface of the resin package of the semiconductor component 1. Generally, the ground pattern 11 is formed in the same shape as the ground layer 2 so as to make the circuit board 10 small. When the ground pattern 11 is formed larger than the ground layer 2, the heat radiation effect of the semiconductor component 1 is increased.

Further, a ground pattern 11 of the circuit board 10 is provided.
, At least one or more through-holes 12 are formed. The through-hole 12 is provided to fulfill the function of degassing. For this reason, the opening of the through hole 12 is formed in such a size that it is not blocked by the decrease in the capillary of the molten solder. The through holes 12 are generally formed using a drill. Therefore, the inner diameter of the through hole 12 is usually formed to a size of about 300 μm used for a through hole. In addition, the through holes 12 are formed by considering the shapes of the ground layer 2 and the ground pattern 11 so that the gas of the flux and the air taken into the molten solder are not easily diffused.
1 is formed at the center. The number of the through holes 12 is appropriately selected in consideration of the size or shape of the ground pattern 11.

Next, an outline of the mounting method will be described. First,
A mask formed in a predetermined shape is superimposed on the surface of the circuit board 10 on which the circuit pattern has been formed. Thereafter, a solder paste is printed on the surfaces of the pad 7 and the ground pattern 11 using a squeegee. Further, the semiconductor component 1 is mounted on the circuit board 10 so that the lead terminals 6 and the pads 7 of the semiconductor component 1 overlap. At this time, the ground layer 2 and the ground pattern 11 overlap. Thereafter, the circuit board 10 on which the semiconductor component 1 is mounted is passed through a reflow furnace to melt the solder paste. Since the heat applied to melt the solder paste easily escapes to the ground pattern 11, the temperature rise of the ground pattern 11 is slower than that of the pad 7. For this reason, the temperature of the reflow furnace is set higher than in the case where a semiconductor component operating at a high frequency provided with a grounding lead terminal instead of the grounding layer 2 is mounted.
The holding time in the reflow furnace is set short.

At this time, the gas of the flux generated between the ground layer 2 and the ground pattern 11 and the air taken into the molten solder are not limited to the space between the ground layer 2 and the ground pattern 11. The air is diffused using the through holes 12 as airways. As a result, between the ground layer 2 and the ground pattern 11, the occurrence of the void 8 and the blow hole 9 is prevented.

In the circuit board 10 described above, the circuit board 10
Although the through hole 12 is formed in the portion of the ground pattern 11 in the above, the present invention is not limited to this. The first circuit board 13 according to claim 2 will be described with reference to FIG.

On the surface of the circuit board 13, a pad 7 which is a part of a circuit pattern and a ground pattern 14 are provided.

At least one groove 15 is formed in the ground pattern 14 of the circuit board 13. The groove 15 is formed so as to extend from the periphery of the ground pattern 14 to the vicinity of the center of the ground pattern 14. If the molten solder adheres to the inner wall of the groove 15, the groove 15 will be closed.
Does not function as an airway for diffusing the gas of the flux or the air taken into the molten solder. For this reason, the groove 15 is formed in the circuit board 1 below the ground pattern 14.
3 is formed so as to expose the surface of the insulating substrate 16. Since the insulating substrate 16 is formed of, for example, a substrate formed by impregnating glass fiber with an epoxy resin or a ceramic substrate, molten solder does not adhere thereto, and the groove 15 is not closed.

The groove 15 is formed by a chemical method such as pattern etching so that the width of the groove 15 is about 300 μm. The groove 15 is provided with a ground pattern.
In consideration of the shape of the solder 14, the flux gas and the air taken into the molten solder are formed in a portion where it is difficult to diffuse.

Further, the number of grooves 15 depends on the ground pattern 14.
Is appropriately selected depending on the size or the shape of. Groove 15
When a plurality of grooves 15 are formed, the grooves 15 may be formed radially, may be formed in parallel, or may be formed to intersect. Further, the groove 15 may be formed so as to divide the ground pattern 14. In the case where the ground pattern 14 is divided into a plurality of parts by the groove 15, when each part of the divided ground pattern 14 is grounded, it is possible to efficiently release the heat generated in the semiconductor component 1. it can.

The grooves 15 may be formed by a physical method such as cutting using an end mill instead of using a chemical method. Referring to FIG.
The second circuit board 17 according to the above will be described.

The circuit board 17 has a groove 19 formed by cutting using an end mill in the ground pattern 18.

When cutting the ground pattern 18 using an end mill, not only the ground pattern 18 but also the surface layer of the insulating substrate 16 is removed. For this reason, the bottom surface of the groove 19 is lower than the surface of the insulating substrate 16, and the depth of the groove 19 is deeper than the groove 15 formed by a chemical method. Therefore, if the width of the groove 19 is the same, the cross-sectional shape of the groove 19 becomes larger than that of the groove 15 formed by using a chemical method, and the gas of the flux and the air taken in the molten solder are diffused. The effect as an airway increases.

[0029]

The present invention has the following effects because it has the above-described configuration. That is, the gas of the flux generated between the ground layer and the ground pattern and the air taken into the molten solder not only come from between the ground layer and the ground pattern but also through the through holes or grooves. Is also distracted. As a result, generation of voids and blowholes between the ground layer and the ground pattern is prevented. For this reason, misalignment and inclination of the semiconductor component are less likely to occur. Therefore,
The yield when mounting a semiconductor component operating at a high frequency on a circuit board is improved. Further, since the bonding area between the ground layer and the ground pattern of the semiconductor component becomes constant, the variation in the high-frequency characteristics of the semiconductor component is reduced, and the reduction of the heat radiation effect can be prevented. Further, even when a circuit board mounted in a state where a heat cycle is applied is used, a remarkable decrease in connection strength can be prevented, and electrical reliability is improved.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit board according to claim 1, FIG. 1A is a part of a top view, and FIG.
It is sectional drawing in A '.

FIG. 2A is a diagram showing a semiconductor component mounted on the circuit board according to claim 1; FIG. 2A is a part of a top view, and FIG.
FIG. 2 is a cross-sectional view taken along line AA ′ in FIG.

3 (a) is a part of a top view, and FIG. 3 (b) is a circuit board of FIG. 3 (a); FIG.
It is sectional drawing in A '.

4 (a) is a part of a top view, and FIG. 4 (b) is a circuit board of FIG. 4 (a);
It is sectional drawing in A '.

5A and 5B are diagrams in which semiconductor components are mounted on a conventional circuit board, FIG. 5A is a part of a top view, and FIG. 5B is a view taken along a line AA ′ in FIG. It is sectional drawing.

[Explanation of symbols]

 Reference Signs List 10 circuit board 11 ground pattern 12 through hole

Claims (2)

[Claims] A circuit board on which a semiconductor component is mounted, the circuit board having a ground pattern formed at a position facing a ground layer provided on a bottom surface of the semiconductor component and soldered to the ground layer; A circuit board, wherein a through hole is formed in a ground pattern portion. 2. A circuit board on which a semiconductor component is mounted, the circuit board having a ground pattern formed at a position facing a ground layer provided on a bottom surface of the semiconductor component and soldered to the ground layer. A circuit board, wherein a groove for exposing an insulating substrate is formed in at least one end portion of the ground pattern portion as a peripheral edge of the ground pattern.