JPH04293297A - Printed wiring board and soldering method - Google Patents

Abstract

PURPOSE:To improve productivity and to prevent a decrease in quality by soldering a surface mounting component to a component with leads by solders to be supplied to pads and through holes. CONSTITUTION:Pads 23 and through holes 22 are coated from an upper surface A of a wiring board 21 with cream solders 24, 25. Then, a chip component 26 and a component 30 with leads are mounted as surface mounting components on the surface A. The board 21 mounted with the components 26, 30 is heated by a heater 32. Thus, the solders 24, 25 are melted, and sucked between the electrodes of the component 26 and the pads 23. In this case, flux in the solder 25 adhered to the end of the lead 31 is volatilized by the heat of the heater 32 to reduce its volume, and satisfactorily sucked into the hole 22 by a capillary phenomenon.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board on which surface mount components and leaded components are mounted together, and a soldering method used in manufacturing this printed wiring board.

0002

BACKGROUND OF THE INVENTION Flow soldering and reflow soldering are widely known methods for soldering components to printed wiring boards. The flow soldering method is
Soldering is performed by pouring molten solder into the soldering area. When applying this method to parts with leads (discrete parts, hereinafter referred to as leaded parts), the leads are inserted from the top into through-holes formed in advance on the printed wiring board, and preheated with a preheating heater. Molten solder is sprayed onto the rear lower surface (jet soldering method) or immersed in a molten solder bath (immersion soldering method).

[0003] The reflow soldering method is usually applied to chip components, flat pack ICs, LSIs, and other surface mount components without leads, in which cream solder is applied to the pads (soldering points) in advance, and the cream solder is applied to the pads (soldering points) in advance. After the components are fixed using viscosity, cream solder is heated and melted using a heater to perform soldering.

On the other hand, in recent years, printed wiring boards on which leaded components and surface-mounted components are mounted together have come to be used in order to increase the packaging density. In this case, conventionally, a flow soldering method and a reflow soldering method have been used in combination.

FIGS. 2A to 2D are process diagrams of this conventional soldering process. In this figure, a printed wiring board 1 is provided with through holes 2, 2 and pads 3, 3 in advance. Cream solder 4, 4 is applied to the pads 3, 3 by printing using a metal mask or the like (FIG. 2A). A chip component 5 as a surface mount component is placed on the upper surface a of the wiring board 1 on the cream solder 4 of the pads 3, 3, and is held by the viscosity of the cream solder 4 itself (FIG. 2B). The cream solder 4 is then melted by heating with a heater 6. That is, the chip component 5 is soldered by reflow soldering (FIG. 2C).

[0006] This wiring board 1 is then transferred from the upper surface a onto the molten solder bath 9 after the leads 8, 8 are inserted into the through holes 2, 2 of the component 7 with leads. The solder tank 9 may be a jet solder tank on the surface of which a jet of molten solder is generated by a pump, or an immersion solder tank that holds stationary molten solder. When this molten solder comes into contact with the lower surface b of the wiring board 1, the molten solder is transferred to the through holes 2 and 2.
It gets sucked up inside. As a result, soldering with the leaded component 7 using the flow soldering method is completed (Fig. 2D
).

As described above, in the conventional method, the surface mount component 5
After fixing with cream solder 4, melting this cream solder 4 with heater 6 and performing reflow soldering,
Furthermore, the leaded component 7 was flow soldered. Therefore, two soldering steps are required, which not only causes poor productivity, but also causes the chip component 5 to be reflow soldered to be heated to a high temperature twice. This may lead to deterioration in quality or reliability of the parts.

[0008]

[Purpose of the Invention] The present invention was made in view of the above circumstances, and is intended to increase productivity and eliminate the risk of deterioration in quality and reliability when surface mount components and components with leads are mixedly mounted. The purpose is to provide a printed wiring board that is free of Another object of the present invention is to provide a soldering method for use in manufacturing this printed wiring board.

[0009]

According to the present invention, this object is achieved in a printed wiring board on which surface mount components and leaded components are mounted together, in which the surface mount components are bonded to the pads by cream solder, and the leaded components are This is achieved by a printed wiring board characterized in that soldering is performed by reflow soldering using cream solder supplied to the through holes.

Another object is achieved by a soldering method for a printed wiring board in which surface mount components and leaded components are mounted together, which is characterized by comprising the following steps. That is: ■ Supplying cream solder to the pad to which the surface mount component is soldered and the through hole to which the lead of the leaded component is soldered; a step of fixing the mounted component; ■ a step of inserting the lead of the leaded component from the top surface of the printed wiring board into the through hole to which the cream solder has been supplied; ■ reflow soldering of the surface mount component and the leaded component The process of doing.

[0011]

Embodiment FIGS. 1A to 1D are process diagrams of an embodiment of the present invention. In this figure, numeral 21 is a printed wiring board,
Through holes 22, 22 and pads 23, 23 are formed (FIG. 1A).

Cream solder 24, 25 is applied to pads 23, 23 and through holes 22, 22 from the upper surface (mounting surface) A of this wiring board 21, for example, by printing using a metal mask (FIG. 1B).

Next, a chip component 26 as a surface mount component and a component with leads 30 are mounted on this upper surface A (FIG. 1C). That is, the chip component 26 is fixed by pressing the electrode portions at both ends against the cream solder 24 and by the viscosity of the cream solder 24 itself. Further, the leads 31, 31 of the leaded component 30 are inserted into the through holes 22, 22 from above.

The upper surface A of the wiring board 21 with the components 26 and 30 attached thereto is heated by the heater 32. Therefore, the cream solders 24 and 25 are melted. Cream solder 24 is sucked between the electrode portion of chip component 26 and pad 23. A considerable amount of the cream solder 25 is pushed out from the through hole 22 when the lead 31 is inserted into the through hole 22 and adheres to the protruding end of the lead 31, but the flux in the cream solder 25 is volatilized by heating by the heater 32. As the volume decreases, the material is sucked into the through hole 22 due to capillary action. Therefore, the solder does not hang down like an icicle at the tip of the lead 31 and harden. According to experiments, even when the through holes 22 were filled with cream solder, there were no problems such as the cream solder melting and dripping or hanging down on the tips of the leads 31.

Furthermore, in supplying cream solder by printing as in this embodiment, if the amount supplied to the through holes 22 is insufficient, it is desirable to repeat printing using a metal mask two or more times. In this case, since the amount of supply to pad 23 is determined by the thickness of the metal mask, this pad 23
There will be no excess supply. Furthermore, instead of printing, the cream solder 24, 25 may be supplied using a dispenser or the like that moves a supply nozzle to a supply position and supplies a predetermined amount.

In this embodiment, the thickness of the wiring board 21 is 1.6 m.
m, the diameter of the through hole 22 is 0.8 to 1.0 mm, and the lead diameter is 0.6 to 0.8 mm, an appropriate amount of cream solder 25 is supplied to the through hole 22 by one printing, and a good Soldering was possible.

[0017]

Effects of the Invention As described above, the first aspect of the invention is that the surface mount components and the leaded components are soldered by the reflow soldering method using cream solder supplied to the pads and through holes. It has high properties and does not require preheating as is the case with flow soldering, so there is no risk of deterioration in quality or reliability due to repeated heating.

Further, the invention according to claim 2 provides a method for supplying cream solder from the top surface of the printed wiring board to the pads of the surface mount component and through holes for inserting leads, while fixing the surface mount component to the pads from the top surface. Since the leads of leaded components are inserted into through holes and the printed wiring board is reflow soldered, surface mount components and leaded components can be reflow soldered in one process, greatly improving productivity. It becomes possible to do so. In addition, since soldering can be performed by heating once, the number of times the product is heated is reduced, and there is no risk of deterioration in quality or reliability due to heat.

Further, according to the third aspect of the invention, since cream solder is supplied to the pads and through holes in one printing, it is possible to further improve productivity.

[Brief explanation of drawings]

FIGS. 1A to 1D are process explanatory diagrams of an embodiment of the present invention.

[Figure 2
A to 2D] Diagrams showing conventional processes

[Explanation of symbols]

21 Printed wiring board 22 Through hole 23 Pad 24, 25 Cream solder 26 Chip parts 30 Parts with leads 31 Lead 32 Heater

Claims (3)

[Claims] 1. In a printed wiring board on which surface mount components and leaded components are mounted together, the surface mount components are mounted with cream solder supplied to pads, and the leaded components are mounted with cream solder supplied to through holes. , a printed wiring board characterized in that each is soldered using a reflow soldering method. 2. A method for soldering a printed wiring board in which a surface mount component and a component with leads are mounted together, the method comprising the following steps: ■ The surface mount component is A step of supplying cream solder to a pad to be soldered and a through hole to which a lead of the leaded component is soldered; ■ A step of fixing the surface mount component to the pad to which the cream solder has been supplied; a step of inserting the lead of the leaded component from the top surface of the printed wiring board into the through hole to which the cream solder has been supplied; (2) a step of reflow soldering the surface mount component and the leaded component; 3. The soldering method according to claim 2, wherein in step (3), the cream solder is supplied to the pads and through holes by one printing.