JP2007324505A - Printed circuit board and electric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board and electric device capable of improving reliability in mounting by sorting parts required for good wettability or parts required for strong bonding strength from mounting components and mounting the parts with a plurality of different kinds of solders so as to satisfy requirements, respectively. <P>SOLUTION: The printed circuit board includes a substrate 1 on which a wiring pattern is formed and a plurality of different kinds of mounting components 3 soldered to the substrate 1. The mounting components 3 are soldered to the substrate 1 by the plurality of different kinds of solders including at least good wettability or strong bonding strength. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a printed wiring board and an electric device using the printed wiring board.

  Conventionally, when electronic components such as resistors, capacitors, transformers, and semiconductors are mounted on a printed wiring board, the soldering is performed by a well-known flow method or reflow method.

  By the way, since the characteristics of solder differ depending on the alloy composition and the like, it is desirable to use the characteristics.

  For this reason, as shown in Patent Document 1, by mounting a different solder paste in accordance with the reflow heating temperature of the electronic component to be mounted, mounting of the electronic component prevents the temperature of the electronic component from being excessively increased during reflow. The method is known.

There is also known an electronic component mounting method that prevents a decrease in bonding reliability by applying a different solder paste according to the type of surface treatment of the terminal of the electronic component to be mounted.
JP 2004-221378 A

  However, in what is shown in Patent Document 1, the first form is to prepare two types of solder having different melting temperatures in accordance with the reflow heating temperature, and the second form is the surface of the terminal of the electronic component. Two different solders are prepared according to the type of treatment.

  Therefore, these are only two types of solder prepared by paying attention to one characteristic such as the melting temperature or the type of surface treatment.

  In the present invention, there are a number of solder characteristic factors such as melting temperature, wettability, joint strength, peelability, and cost. When soldering a mounted component to a printed wiring board, the mounted component has good wettability. Prints that can improve the mounting reliability by selecting the required one and the one that requires high bonding strength and mounting using multiple types of solder to satisfy each requirement It aims at providing a wiring board and an electric equipment.

  The invention of the printed wiring board according to claim 1 includes a board on which a wiring pattern is formed and a plurality of mounting parts soldered to the board, and the mounting parts include at least solder having good wettability; It is characterized in that it is soldered to the substrate by a plurality of kinds of solders with a solder having a strong joint strength.

According to a second aspect of the present invention, there is provided an electric device comprising the main body and the printed wiring board according to the first aspect accommodated in the main body.

In each invention, the definitions and technical meanings of terms are as follows unless otherwise specified.

Soldered to the board with multiple types of solder, at least solder with good wettability and solder with strong joint strength. In addition to solder with good wettability and solder with strong joint strength, for example, mounted components In view of the heat resistance, solder having a low melting temperature, that is, using three or more kinds of solder is also allowed.

Good solder wettability and strong joint strength are different depending on the type of mounted component and the level required by the user, so it is not an absolute standard and is actually used for soldering mounted components. A relative relationship in the type of solder is sufficient.

  According to the present invention, since the mounting component is soldered to the substrate by using a plurality of types of solder, paying attention to the wettability and the bonding strength of the solder, the printed wiring board and the electric device that can improve the mounting reliability Can be provided.

  An embodiment of a printed wiring board and an electric apparatus according to the present invention will be described with reference to the drawings.

1 and 2 show a printed wiring board, FIG. 1 is a schematic diagram of a solder surface (back surface) showing a state in which a mounting component such as an electronic component is not mounted, and FIG. 2 shows a state in which the mounting component is mounted. It is a surface schematic.

In FIG. 1, a wiring pattern is formed on a solder surface of a substrate 1, and a chip component 3c such as an IC which is a surface mounting component is mounted. In addition, a substantially cylindrical through hole 2 is formed in the substrate 1 at an appropriate position corresponding to the inserted mounting component so as to penetrate the front and back surfaces of the substrate 1. A land portion (not shown) is formed on the.

Next, in FIG. 2, a mounting component 3 such as an electronic component is attached to the substrate 1 by soldering. Here, among the mounted components 3, relatively heavy objects 3a such as a transformer are gathered on the right side of the drawing with a broken line A-A as a boundary, and a comparison of chip components such as ICs, semiconductors, resistors, capacitors, etc. Lightweight objects 3b are concentrated on the left side.

In other words, when soldering the mounting component 3 to the substrate 1, a component such as a transformer, which is heavy and requires a bonding strength to the substrate 1 that vibrates during operation, is disposed on the right side, and is lightweight. A chip part such as an IC and a part such as a resistor that are required to have better wettability than the bonding strength are arranged on the left side.

Next, FIGS. 3 and 4 are cross-sectional views schematically showing a soldering process of the substrate 1 using a flow method. In the drawing, parts necessary for the description of the present invention are shown, and detailed illustration of other parts is omitted.

First, in the first step shown in FIG. 3, the printed wiring board 1 is disposed on the opening side of the solder tank 4. For the sake of explanation, only the resistor 5, which is the mounting component 3, is shown, and the lead wire 5 a of the resistor 5 is inserted into the through hole 2.

In the solder tank 4, Sn—Zn lead-free solder material 4a having relatively good wettability is stored in a melted state.

Here, a mask sheet 10 is attached to the right side of the solder surface of the substrate 1, that is, in a region where a mounting component such as a heavy transformer is disposed, so that the solder bath of the solder bath 4 does not act. Yes.

On the other hand, the left side of the solder surface of the substrate 1, that is, a region where a mounted component such as a lightweight resistor is disposed, is immersed in the solder bath, and the resistance 5 inserted into the through hole 2 The lead wire 5a is soldered.

Next, in the first process shown in FIG. 3 to the second process shown in FIG. 4, the printed wiring board 1 is disposed on the opening side of the solder bath 4 as described above. For the sake of explanation, only the resistor 5 soldered in the above-described process and the transformer 6 to be soldered from now on are shown. Similarly, the lead wire 6 a of the transformer 6 is inserted into the through hole 2.

In the solder tank 4, the Sn—Ag—Cu-based lead-free solder material 4b, which meets the requirements for the bonding strength and is considered to have a relatively high bonding strength, is stored in a melted state.

Here, a mask sheet 11 is attached to the left side of the solder surface of the substrate 1, that is, in a region where a chip component such as an IC, which is a lightweight object, and a mounting component such as a resistor are disposed, and a solder bath in the solder bath 4 is provided. It does not work.

On the other hand, the right side of the solder surface of the substrate 1, that is, a region where a mounting component such as a heavy transformer is disposed is immersed in a solder bath, and the transformer 6 inserted into the through hole 2 The lead wire 6a is soldered.

The Sn—Ag—Cu-based lead-free solder material and the Sn—Zn-based lead-free solder material described above have a good wettability in the relative comparison between the Sn—Zn-based lead-free solder material and the Sn—Zn-based lead-free solder material. The Ag—Cu-based lead-free solder material is selected from the viewpoint of high bonding strength.

As described above, in the first step shown in FIG. 3, soldering of a mounting component that is relatively lightweight and requires wettability to solder is performed, and in the second step shown in FIG. Solder mounting components that require solder joint strength.

Therefore, the reliability of soldering can be improved by selecting the solder having the characteristics that meet the requirements of the mounted component.

In this embodiment, Sn—Zn-based lead-free solder material is used as the solder with emphasis on wettability, and Sn—Ag—Cu-based lead-free solder material is used as the solder with emphasis on joint strength. There is no limitation, and materials attached with Bi, In, etc. may be used with emphasis on the respective characteristics of wettability and bonding strength, and the wettability required for mounting parts by considering various alloy compositions. The solder material may be selected by paying attention to the property and bonding strength.

Further, in this embodiment, the flow method has been described as a soldering method, but any of a reflow method and a method using a solder application device that discharges solder paste from a discharge nozzle may be used, and the method is not limited to the soldering method. .

Furthermore, with regard to the placement of the mounting components on the board, the mounting components that use a relatively heavy object, that is, solder that has a strong bonding strength, are gathered on the right side, and are relatively light, that is, have good wettability. We explained the case where the mounting parts using solder are gathered on the left side, but this is not limited to this arrangement, and mounting parts using solder with strong joint strength and mounting parts using solder with good wettability are mixed on the board It may be.

In this case, each part is selected from the viewpoint of wettability and bonding strength, and correspondingly, the mask pattern is changed in the flow method, or two types of solder corresponding to each part in the method using the coating apparatus. You can use different materials.

In addition, the mounting component can be applied to either a lead type insertion mounting component or a surface mounting component.

Next, an embodiment of the electric device of the present invention will be described.

FIG. 5 is a perspective view showing a lighting fixture 20 as an electric device. This luminaire 20 includes a box-shaped main body 21 and a fluorescent lamp 23 as a discharge lamp attached via a lamp socket 22. The upper surface side of the main body 21 forms a mounting surface 21 a that is attached to a ceiling or the like, and the lower surface side forms a reflecting surface 21 b that reflects light from the fluorescent lamp 23.

A discharge lamp lighting device 24 is accommodated in the main body 21, and the above-described printed wiring board is accommodated in the discharge lamp lighting device 24.

According to this lighting fixture, the improvement of the reliability of mounting of the mounting components on the printed wiring board and the improvement of the reliability of the lighting fixture can be expected.

Note that the electrical equipment includes office equipment such as a copying machine and household equipment such as a microwave oven.

It is the surface schematic which shows embodiment of the printed wiring board of this invention, and shows the state in which the mounting components are not mounted. It is the surface schematic which shows the state in which the same mounting component was mounted. It is sectional drawing which shows typically the 1st soldering process of the printed wiring board of this invention. It is sectional drawing which shows the said 2nd soldering process typically. It is a perspective view which shows embodiment of a lighting fixture as an electric equipment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 3 Mounting component 4 Solder tank 20 Lighting fixture

Claims (2)

A substrate on which a wiring pattern is formed;
A plurality of mounted components soldered to the board;
The printed wiring board is characterized in that the mounting component is soldered to the board with a plurality of types of solder, at least a solder with good wettability and a solder with high bonding strength. With the body;
The printed wiring board according to claim 1 housed in a main body;
An electrical apparatus comprising:

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