JP2013080778A - Printed board, circuit board, and electronic component mounting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printed board which obtains sufficient solder wicking regardless of an area of a mat pattern, eliminates the need of manual soldering, and reduces the process cost for mounting an electronic component.SOLUTION: A through hole 2, to which a lead 10a of an electronic component 10 is soldered, and a mat pattern 4 are formed on an insulative substrate 1a so as to be separated from each other. A conductor 8 extending toward the through hole 2 is joined to an electrode 7 of the mat pattern 4, and a tip of the conductor 8 faces at least a part of the through hole 2 being spaced away therefrom and serves as a soldered part 8a, which is soldered together when the lead 10a of the electronic component 10 is soldered to the through hole 2.

Description

  The present invention relates to a printed circuit board, a circuit board, and an electronic component mounting method.

  Generally, when an electronic component is soldered to a printed circuit board, a lead of the electronic component is inserted into a through hole provided in the printed circuit board, and molten solder is brought into contact with the surface opposite to the surface where the lead is inserted. By bringing the molten solder into contact with the printed circuit board, the molten solder wets the inner peripheral surface of the through hole, and is filled into the through hole and solidifies to be soldered.

  However, in a through-hole where a circuit is connected to a so-called solid pattern and the lead of an electronic component is inserted, the heat of the molten solder escapes from the solid pattern during soldering, and the solder gets wet while the through-hole gets wet. It will solidify.

  Since the electronic component is held by the solder filled in the through-hole, if it is solidified in the middle of wetting up, the solder filling amount is not sufficient, so that a so-called poor soldering occurs. When the solder finish is poor, there is a problem that the holding strength is lowered, the solder is cracked, and there is a high possibility of disconnection.

  Therefore, as a conventional technique for improving solder rise, for example, there is a technique in which a thermal land for heat retention is provided around a through hole in a printed board (see, for example, Patent Document 1). In the technique of Patent Document 1, when the printed circuit board is brought into contact with the molten solder, the solder is solidified in the course of getting up the through hole by holding the solder on the thermal land and warming the through hole portion. I try to prevent it.

  In addition, there is a technique in which a through hole for heat retention is formed on the outer periphery of a through hole in a printed board (see, for example, Patent Document 2). In the technique of Patent Document 2, the solder enters the through hole at the same time as the solder enters the through hole, and heat is supplied from the solder that has entered the through hole into the through hole, so that the through hole is wetted up. This prevents solder solidification.

  Both of the above two technologies are technologies that improve the solderability by supplying heat to the through-hole, but improve the solderability by adopting a structure that does not allow heat to escape from the through-hole to the solid pattern. There is also a technique (see, for example, Patent Document 3). In the technology of Patent Document 3, a solid pattern is formed from the through hole by providing a slit between the conductive film and the solid pattern provided from the inner peripheral surface of the through hole to both surfaces of the printed circuit board so as not to contact each other. The heat escape to is suppressed. Then, when soldering, a first step of soldering the lead of the electronic component to the through hole and a second step of soldering the soldered portion by hand soldering to the solid pattern across the slit The soldering of the electronic component and the solid pattern is completed in two steps.

Japanese Patent Laying-Open No. 2005-12088 (Summary, FIG. 1) JP 2003-69202 A (summary, FIG. 3) JP-A-6-61630 (page 3, FIG. 1)

  In Patent Document 1 and Patent Document 2, since heat is input to the through hole from its periphery, a decrease in the temperature of the solder in the through hole can be suppressed, which is effective in improving the solderability. However, since the conductive film of the through hole is connected to the solid pattern, heat escape to the solid pattern always occurs, and as the area of the solid pattern becomes wider, the effect of improving the soldering property is reduced. is there.

  In Patent Document 3, since the through hole and the solid pattern are formed apart from each other, there is no heat dissipation through the pattern, and a good solder finish can be obtained. However, as described above, after soldering the lead of the electronic component to the through hole, it is necessary to manually solder the through hole and the solid pattern, which increases the processing cost.

  Moreover, in patent document 3, in the stage which the 1st process of soldering the lead of an electronic component to a through hole is complete | finished, depending on the shape of an electronic component, the soldering location in a 2nd process is hidden by the electronic component itself and cannot be seen. There is a case. For example, the case where the electronic component is of a type in which the lead extends straight from the lower surface of the resin portion is applicable, and in this type of electronic component, since the soldering location is located directly under the resin portion, the soldering location is It cannot be seen from the electronic component mounting side. For this reason, manual soldering cannot be performed, so this type of electronic component cannot be mounted substantially. Thus, there are many inconveniences in a printed circuit board that requires manual soldering work.

  Moreover, the soldering iron used in the second step of manual soldering generally has a small heat input. For this reason, the heat escapes from the solid pattern during the soldering operation, and it takes time to melt the portion to be soldered, resulting in a problem that the soldering time becomes long. Further, when the soldering time is long, there is a problem that the adhesion of the through hole conductive film is peeled off.

  The present invention has been made to solve the above problems, and can obtain sufficient soldering regardless of the area of the solid pattern, and does not require manual soldering. It is an object of the present invention to obtain a printed circuit board, a circuit board, and an electronic component mounting method capable of reducing processing costs.

  In the printed circuit board according to the present invention, a through hole where a lead of an electronic component is soldered and a solid pattern are formed apart from each other on an insulating base material, and the solid pattern electrode has a conductor extending toward the through hole. The tip of the conductor is opposed to at least a part of the through hole and is a soldered part that is soldered together when the lead of the electronic component is soldered to the through hole. It is what.

  According to the present invention, since the through hole and the solid pattern are formed apart from each other, the heat of the solder in the through hole does not escape to the solid pattern, and the solder rise can be improved. In addition, a conductor extending toward the through hole is joined to the electrode of the solid pattern, and the leading end of the conductor is a soldered portion facing and spaced apart from at least a part of the through hole. Since the substrate structure is soldered together when soldering to the through hole, conventional manual soldering is unnecessary. As a result, it is possible to reduce the processing cost when mounting the electronic component, and it is possible to obtain a printed circuit board that can obtain sufficient soldering regardless of the area of the solid pattern.

It is a figure which shows the printed circuit board which concerns on one embodiment of this invention. It is a figure which shows the manufacturing process of the printed circuit board of FIG. It is a figure which shows the state by which the electronic component was soldered to the printed circuit board of FIG. FIG. 5 is a diagram (1/2) illustrating a process of mounting electronic components on the printed circuit board of FIG. 1. FIG. 2B is a diagram (2/2) illustrating the mounting process of the electronic component on the printed board of FIG. 1. It is a figure which shows another soldering construction method. It is a figure which shows the relationship between a through-hole diameter and fillet height. It is a figure which shows a printed circuit board in case an electronic component is a SiC module. FIG. 10 is a diagram (1/2) illustrating a first modification of the printed circuit board of FIG. 1. FIG. 10 is a diagram (2/2) illustrating a first modification of the printed circuit board of FIG. It is a figure which shows the modification 2 of the printed circuit board of FIG. It is BB sectional drawing of FIG. It is a figure which shows the other modification 3 of the printed circuit board of FIG. It is a perspective view of the conductor of FIG. It is a figure which shows the other modification 4 of the printed circuit board of FIG. It is a perspective view of the conductor of FIG. It is a figure which shows the other modification 5 of the printed circuit board of FIG.

1A and 1B are diagrams showing a printed circuit board 1 according to an embodiment of the present invention, in which FIG. 1A is a perspective view and FIG. 1B is a cross-sectional view taken along line AA in FIG. In FIG. 1 and the drawings to be described later, the same reference numerals denote the same or corresponding parts, which are common throughout the entire specification.
The printed circuit board 1 has a through hole 2 for soldering an electronic component 10 (see FIG. 3 described later). The through hole 2 is formed of a hole formed through the insulating base material 1a and a conductive film 3 formed from the inner peripheral surface of the hole to both surfaces of the base material 1a (around the opening of the hole). Moreover, the solid pattern 4 and the pattern 5 which are the wiring patterns formed with metal materials, such as copper, are formed in the surface of the base material 1a. The conductive film 3 and the solid pattern 4 in the through hole 2 are formed so as not to contact each other. Although the entire surface of the base material 1a including the solid pattern 4 is covered with the solder resist 6, the portions shown by hatching in FIG. 1 are peeled off and exposed to the outside.

  The solid pattern 4 is a pattern connected to the power source or the ground, and is a pattern for heat dissipation. A portion of the solid pattern 4 where the solder resist 6 is peeled off is an electrode 7 electrically connected to the electronic component 10, and a conductor 8 is soldered to the electrode 7.

  The conductor 8 has a role of electrically connecting the electronic component 10 soldered to the through hole 2 to the solid pattern 4 and is formed to extend from the electrode 7 toward the through hole 2. The front end portion of the conductor 8 is spaced apart and opposed to at least a part of the through hole 2, and will be described in detail below. When the lead 10a of the electronic component 10 is soldered to the through hole 2, it is soldered together. This is the soldered portion 8a. In the printed circuit board 1 in the state shown in FIG. 1 before the electronic component 10 is soldered to the through hole 2, the conductor 8 is joined to the electrode 7 so as not to contact the through hole 2. The conductor 8 is a metal that gets wet with the solder, and is configured by applying a metal such as Fe, Ni, SUS, or Al, or plating with Ni or the like. As a measure of wetting, it is preferable that the contact angle between the base material and the molten solder is 90 degrees or less.

  When the printed circuit board 1 configured as described above is manufactured, first, the through hole 2 (including the conductive film 3), the solid pattern 4 and the like are formed, and the electrode 7 is peeled off by removing a part of the solder resist 6. The base material 1a in which is formed is produced. Then, as shown in FIG. 2 (a), a solder paste 11 containing flux is printed and supplied onto the electrode 7, and subsequently, as shown in FIG. 2 (b), the conductor 8 is mounted on a mounting machine such as a mounter. Is mounted on the substrate 1 a so as to pass between the electrode 7 and the through hole 2. Then, in this state, it inserts in soldering apparatuses (not shown), such as a reflow furnace, and is set to the environment more than the melting temperature of the solder paste 11. As a result, as shown in FIG. 2C, the solder paste 11 is in a molten state and then cooled, whereby the conductor 8 and the electrode 7 are soldered, and the printed circuit board 1 is completed. As described above, the conductor 8 and the through hole 2 are not in contact with each other in the completed state of the printed circuit board 1.

  Next, a method for mounting electronic components on the printed circuit board 1 will be described, and a characteristic operation of the printed circuit board 1 according to the present embodiment will be described.

FIG. 3 is a perspective view showing a state in which the soldering of the electronic component to the printed board of FIG. 1 is completed. 4 and 5 are diagrams showing a process of mounting electronic components on the printed circuit board shown in FIG.
First, the lead 10a of the electronic component 10 is inserted into the through hole 2 provided in the printed circuit board 1 (FIG. 4A), and a flux (on the surface opposite to the mounting surface of the electronic component 10 on the printed circuit board 1) (Not shown) is applied and brought into contact with the molten solder 12 (FIG. 4B).

  As a result, the solder 12a wets the inner peripheral surface of the through hole 2 of the printed board 1 and fills the through hole 2 (FIG. 4C). Here, since the conductive film 3 of the through hole 2 is separated from the solid pattern 4, the heat of the solder 12 a can be prevented from escaping to the solid pattern 4 through the conductive film 3, and the solder 12 a is in the middle of getting wet. Can be prevented from solidifying.

  Then, the solder 12a filled in the through hole 2 further wets the lead 10a of the electronic component 10 and comes into contact with the soldered portion 8a of the conductor 8 (FIG. 5D). Thereafter, the printed board 1 is separated from the molten solder 12 and cooled, whereby the lead 10a of the electronic component 10 is held in the through hole 2, and the lead 10a, the conductor 8, and the electrode 7 of the solid pattern 4 are soldered. A circuit is formed (FIG. 5E).

  As a method of bringing the molten solder 12 into contact with the printed circuit board 1, FIG. 4B shows an example of a flow soldering method in which heat is applied to the entire board. However, as shown in FIG. It is good also as a partial soldering method of jetting the solder 12 and soldering only a desired location. In this case, the same effect can be obtained.

Here, the installation height of the soldered portion 8a of the conductor 8 will be described.
FIG. 7 is a diagram showing the relationship between the through-hole diameter and the fillet height. In FIG. 7, the horizontal axis represents the through-hole diameter (mm), and the vertical axis represents the fillet height (mm). The fillet height h is the height of the solder protruding from the end face of the through hole 2 as shown in FIG. As shown in FIG. 6, the fillet height h has a relationship that it is about ½ of the through-hole diameter. Therefore, the installation height of the conductor 8, that is, the distance between the opening of the through hole 2 and the conductor 8 is set to ½ or less of the through hole diameter.

  FIG. 1B shows an example in which the tip of the conductor 8 (the end of the soldered portion 8a) slightly covers a part of the opening of the through hole 2, but it is not necessarily covered. Also good. In short, it is only necessary that the tip of the conductor 8 is located at a position where the solder 12a that has wetted the through hole 2 can come into contact and solder. Therefore, the soldered portion 8a of the conductor 8 refers to a portion in contact with the solder 12a that has wetted the through hole 2, and does not strictly specify the position.

  As described above, according to the present embodiment, since the through hole 2 and the solid pattern 4 are formed apart from each other, the heat of the solder 12 in the through hole 2 is transferred to the solid pattern 4 via the conductive film 3. It is possible to improve the solder finish. Therefore, the printed circuit board 1 with high bonding reliability can be obtained.

  In the printed circuit board 1, the conductor 8 is soldered to the electrode 7 of the solid pattern 4 in advance, and the solder of the soldered portion is a conductor together with soldering the lead of the electronic component 10 to the through hole 2. Therefore, the operation of connecting the electronic component 10 to the solid pattern 4 so as to be electrically conductive can be completed in one soldering process. Therefore, manual soldering in Patent Document 3 is unnecessary, and cost reduction can be achieved. Further, since manual soldering is not required, the conventional inconvenience that the soldering portion is hidden depending on the shape of the electronic component 10 and soldering cannot be performed, and the conductive film 3 of the through hole 2 becomes longer due to a longer soldering time. The problem of peeling off can be solved.

  In addition, the effect that the highly reliable connection between the electronic component 10 and the solid pattern 4 can be completed in one soldering process can be achieved regardless of the area of the solid pattern 4. Therefore, even when the solid pattern 4 has a high heat dissipation property and the conventional printed circuit board as in the above-mentioned Patent Documents 1 to 3 has poor solder rise, the printed circuit board 1 of the present embodiment can be applied. Soldering is possible.

  The electronic component 10 mounted on the printed circuit board 1 according to the present embodiment is arbitrary. However, when an electronic component composed of a wide band gap semiconductor is mounted to form a circuit board, the printed circuit according to the present embodiment is printed. The substrate 1 is particularly effective. The reason is as follows. The wide band gap semiconductor is a general term for semiconductor elements having a larger band gap compared to silicon (Si) elements. In addition to silicon carbide (SiC) elements, for example, gallium nitride (GaN), diamond elements, etc. Is mentioned.

  Since wide band gap semiconductors can operate at high temperatures, they are often used at high temperatures. Therefore, the printed circuit board 1 is required to have high heat dissipation. Therefore, a configuration is adopted in which the solid pattern 4 is formed in a large area, or as shown in FIG. 8, a heat dissipation heat sink 15 is further connected to the solid pattern 4 to enhance the heat dissipation of the solid pattern 4. The In FIG. 8, reference numeral 16 denotes an SiC module.

  Thus, when the heat dissipation of the solid pattern 4 is enhanced from the viewpoint of improving the heat dissipation during product use, in the conventional printed circuit boards such as the above-mentioned Patent Documents 1 to 3, the high heat dissipation is contrary to the electronic component. When mounted, it acts in the direction of releasing the heat of the solder, leading to insufficient solder rise. Therefore, the conventional printed circuit board is not suitable as a substrate for an electronic component capable of operating at a high temperature such as a wide band gap semiconductor. On the other hand, since the printed circuit board 1 of the present embodiment can be bonded with high bonding reliability regardless of the heat dissipation of the solid pattern 4 as described above, an electronic component composed of a wide band gap semiconductor. It is particularly suitable as a substrate.

  Note that the printed circuit board of the present invention is not limited to the structure shown in FIG. 1, and can be variously modified as follows without departing from the gist of the present invention.

(Modification 1)
In the printed circuit board 1 of FIG. 1, the example in which the shape of the conductor 8 is rectangular has been illustrated and described, but the shape of the conductor 8 is arbitrary. For example, it may be substantially U-shaped as shown in FIG. 9 or may be shaped so as to avoid the peripheral component 14 as shown in FIG.

(Modification 2)
11 and 12 are diagrams showing another modification 2 of the printed circuit board 1 of FIG. FIG. 11 is a plan view of a printed circuit board in a state where electronic components are soldered, and FIG. 12 is a cross-sectional view taken along line BB of FIG.
In this example, the entire opening of the through hole 2 is covered with the soldered portion 8a of the conductor 8, and the hole 8b through which the lead 10a of the electronic component 10 passes is provided in the soldered portion 8a. .

  When the conductor 8 is configured in this way, as shown in FIG. 12, the soldering area between the solder 12a that has wetted the through hole 2 and the soldering portion 8a of the conductor 8 can be expanded, and the joining reliability is improved. be able to.

(Modification 3)
FIG. 13 is a view showing another modified example 3 of the printed circuit board of FIG. FIG. 14 is a perspective view of the conductor of FIG.
FIG. 1 shows a configuration example in which the conductor 8 is a flat plate and the entire conductor 8 is close to the base 1a. However, a space is formed between the conductor 8 and the base 1a when the conductor 8 is soldered to the electrode 7. It is good also as a shape to do. When comprised in this way, the heat dissipation from the conductor 8 to ambient air can be improved at the time of product use after soldering.

(Modification 4)
FIG. 15 is a view showing another modification 4 of the printed circuit board of FIG. FIG. 16 is a perspective view of the conductor of FIG.
In this example, a part of the part to be soldered 8a of the conductor 8 is shaped to enter the through hole 2 so as not to contact the conductive film 3 of the through hole 2. With this configuration, the contact with the solder can be made more reliable, and the joining reliability can be improved. Note that the configuration for allowing a part of the conductor 8 to enter the inside of the through hole 2 is not limited to the configuration illustrated in FIGS. 15 and 16 and can be appropriately modified according to the ease of processing.

(Modification 5)
FIG. 17 is a view showing another modified example 5 of the printed circuit board shown in FIG.
In the modification of FIG. 17, the shape of the joint between the electrode 7 and the conductor 8 is a shape that takes into account the self-alignment (self-correction) effect. The self-alignment effect is a phenomenon in which the positional deviation of the conductor 8 is corrected by the surface tension of the solder when the solder paste 11 (see FIG. 2A) printed on the electrode 7 is heated and melted. With such a configuration, it is possible to improve the mounting position accuracy of the conductor 8 when the printed circuit board 1 is manufactured. Note that the shape illustrated in FIG. 17 is an example, and the shape of the joint portion in consideration of the self-alignment effect is not limited to this shape.

  In addition, although it demonstrated as an independent modification each in said modification 1-5, it is also possible to use combining each modification suitably. Thereby, the printed circuit board 1 provided with each effect can be obtained.

  DESCRIPTION OF SYMBOLS 1 Printed circuit board, 1a base material, 2 Through hole, 3 Conductive film, 4 Solid pattern, 5 Pattern, 6 Solder resist, 7 Electrode, 8 Conductor, 8a Soldering part, 8b Hole, 10 Electronic component, 10a Lead, 11 Paste, 12 Molten solder, 13 Nozzle, 14 Peripheral parts, 15 Heat sink.

Claims (11)

  A through hole where a lead of an electronic component is soldered and a solid pattern are formed apart from each other on an insulating substrate, and a conductor extending toward the through hole is joined to the electrode of the solid pattern, and the conductor The front end portion of the electronic device is spaced apart from at least a part of the through hole and is a soldered portion that is soldered together when the lead of the electronic component is soldered to the through hole. Printed circuit board characterized by   The printed circuit board according to claim 1, wherein an opening of the through hole is covered with the soldered portion of the conductor, and a hole through which the lead of the electronic component passes is provided in the soldered portion.    The printed circuit board according to claim 1, wherein the conductor has a shape that forms a space with the base material.   4. The distance between the soldered portion of the conductor and the opening of the through hole is equal to or less than ½ of the diameter of the through hole. 5. Printed circuit board as described in 1.   5. The printed circuit board according to claim 1, wherein a part of the part to be soldered of the conductor is configured to enter the inside of the through hole.   The printed circuit board according to claim 1, wherein the solid pattern is a heat dissipation pattern.   The printed circuit board according to claim 1, wherein the solid pattern is a pattern connected to a power source or a ground.   A circuit board in which a circuit is formed by soldering electronic component leads to the through holes and the conductor of the printed circuit board according to claim 1.   9. The circuit board according to claim 8, wherein the electronic component includes a wide band gap semiconductor.   The circuit board according to claim 9, wherein the wide band gap semiconductor is one of SiC, GaN, and diamond. A method for mounting an electronic component on a printed circuit board according to any one of claims 1 to 7,
Inserting electronic component leads into the through holes of the printed circuit board;
In the printed circuit board, the molten solder is brought into contact with the surface opposite to the lead insertion side of the electronic component, the molten solder is filled in the through hole, and then the molten solder filled in the through hole is used. A method of mounting an electronic component, comprising: soldering the lead and the soldered portion of the conductor.

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