JP2002171053A - Soldering method and method for manufacturing electronic circuit device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder connecting part of high connection reliability, wherein generation of lift-offs is restrained, when lead-free solder is used as fused solder. SOLUTION: Solder 6, having composition which will not extend to the solid- liquid coexisting region of solder material constituting a solder bath 10, is previously supplied to land electrodes 3 of a double-sided printed wiring board 1. After that, insertion components are mounted, and subjected to flow soldering. Thereby the concentration of elements, which extend the solid-liquid coexisting region of the lead-free solder, is reduced in fillet parts 11 formed on the land electrodes 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering method for inserting an electric component having leads into a wiring board having through holes and mounting the component, and an electric circuit device using the soldering method. And, more particularly, to a method using lead-free solder.

[0002]

2. Description of the Related Art When manufacturing an electric circuit device in which a wiring board and an electric component are electrically connected and integrated, a lead of the electric component is inserted into a through hole provided in the wiring board and soldered. As a method, a flow soldering method in which the lower surface of a wiring board is brought into contact with a solder bath to spread solder through a through hole to a land provided on the upper surface of the wiring board and solder the land and the lead is widely used. It is used. This is because the flow soldering method is considered to have high productivity when many electronic components are connected together. Regarding such soldering, see, for example, Japanese Patent Application Laid-Open No. 7-22750.
As in the process disclosed in Japanese Unexamined Patent Publication, a method using soldering in a reflow furnace is also proposed.

[0003]

As a solder material used for flow soldering, a solder containing Pb (Sn-Pb eutectic solder) is generally used. Is becoming a problem, and Pb is an obstacle to the recycling of electronic devices.Therefore, many companies, universities and research institutes are actively researching and developing Pb-free solder (lead-free solder). Application of Pb-free solder to electronic devices has also begun. In 1998, it was applied to players of magneto-optical disk drives, and later to refrigerators and videos. However, when flow soldering is performed using lead-free solder as molten solder, the solder solidifies and leads of the inserted component and land portions of the electrodes provided in through holes of the wiring board into which the inserted component is inserted. A defect caused by “lift-off (also referred to as fillet lifting)” occurs in which a fillet formed over the land is pulled away from the land portion and floats, making it difficult to increase the manufacturing yield. Especially in soldering in the flow soldering method,
Impurities are easily mixed in the solder bath, and almost all of the connection portions may be lifted from the lands immediately after soldering, so that it is difficult to repair and the productivity is significantly deteriorated.

The present invention has been proposed in order to solve the above-mentioned problems, and an electric circuit device which suppresses the occurrence of lift-off even when lead-free solder is used and has excellent connection reliability is manufactured. It is an object of the present invention to provide a mounting method by flow soldering.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a method of soldering a wiring board having a through hole provided with a land portion and an electric component having a lead inserted into the through hole. In the solder mounting method for connecting to each other, a step of supplying a material for reducing the concentration of impurities mixed into the solder with respect to the solder is provided to at least one of the wiring board and the electric component. Provide a soldering method. The effect on the solder is lead, or the effect is particularly great when the solder is applied to a material substantially free of lead in the composition. Further, the present invention provides a method of manufacturing an electric circuit device for soldering an electric component having a lead to a double-sided printed wiring board having a through hole using a solder bath, the method comprising: Manufacturing the electric circuit device, comprising: supplying a material for lowering at least onto a land portion of an electrode included in the through hole before inserting the lead into the through hole of the electric component. Provide a way. The present invention also provides a step of printing solder on a land portion of a plurality of electrodes and through holes provided on one main surface of a wiring board by printing, and a step of mounting a surface-mounted component on the electrode supplied with the solder. Mounting, and heating the wiring board by a reflow furnace, inserting a lead having an electrical component into a through hole provided in the wiring board, and dipping the wiring board in a solder bath, A method for manufacturing an electric circuit device, comprising:

[0006]

DETAILED DESCRIPTION OF THE INVENTION The inventors of the present invention have found that an element which increases the difference between the solidus temperature and the liquidus temperature (solid-liquid coexistence region) of lead-free solder is a cause of the lift-off, and it is the substrate electrode or the insertion with lead. It was clarified that this is due to the fact that it may be mixed into the solder bath holding the solder bath via lead plating of parts. In many cases, the medium that mixes impurities into the solder is an electric component mounted on a wiring board, in addition to foreign substances adhering to the surface thereof, as well as a metal previously attached to a lead of the electric component. As the components of the film elute and diffuse into the solder, the solid-liquid coexistence region of the solder material in the solder bath is changed. Lead is a typical impurity that easily alters the properties of the lead-free solder. In addition, Sn-Ag-
Even when using Cu-based solder and Sn-Bi-based solder for lead plating, even if the solders do not contain lead, Bi diffuses into the solder bath and the solidus temperature and liquid Increase the difference in phase line temperature. Therefore, in the present invention,
In order to prevent the solid-liquid coexistence region of the solder material from expanding, lift-off is eliminated by lowering the concentration of impurities mixed in at least the solder connecting the lead portion of the insertion component and the land portion of the wiring board.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic view showing a manufacturing process of an electric circuit device using the flow soldering method according to the present invention. The double-sided printed wiring board 1 shown in FIG. 1 (a) is a wiring board on which electrodes for fixing electric components are arranged on both main surfaces. A through hole 2 having a hole diameter of 0.8 mm is formed so as to communicate between the main surfaces.
A land portion 3 of 7 mm is formed. First, Fig. 1 (b)
As shown in (1), a metal mask 5 having an opening at a portion corresponding to the land portion 3 of the surface electrode 4 and the through hole 2 is placed on one main surface of the double-sided printed wiring board 1. A paste-like solder (lead-free solder) not containing lead is arranged on the metal mask 5, and the opening of the metal mask 5 is filled with a solder paste using a squeegee. In the present embodiment, Sn-3.5
Ag-0.5Cu (a solder material having a composition of 3.5 wt% silver, 0.5 wt% copper, and the balance tin) was used. Next, the metal mask 5 is retracted from the double-sided printed wiring board 1 so that the solder 6 is printed on the surface electrodes 4 and the lands 3. The composition of the solder supplied to the surface electrode is not particularly limited as long as the effect of the present invention can be obtained. Further, as long as the effects of the present invention can be obtained, the method of supplying the solder is not particularly limited to printing, and the solder may be supplied by disposing a solder sheet or the like.

Next, as shown in FIG. 1C, chip components 7 such as capacitors and resistors, which are surface-mounted electric components, are mounted on predetermined surface electrodes 4 and heated by a reflow furnace. And solder each. At this time, the solder 6 supplied on the land 3 also melts and adheres to the land 3. Thereby, when the double-sided printed wiring board 1 is transported to a subsequent step, it becomes easy to prevent the supplied solder 6 from falling off. Further, even if the amount of solder is uneven on the land during the filling of the solder paste, the unevenness is eliminated by once wet and spreading over the entire land portion 3 and solidifying again. Therefore, the soldering quality at the time of flow soldering may be improved. Therefore, it is preferable to include a step of melting the solder on the land before supplying the insertion component.

Next, as shown in FIG. 1 (d), for the electric component 8 provided with a lead such as an electrolytic capacitor which is an electric component to be inserted and mounted, the lead is supplied from the main surface on the side to which the solder material is supplied. Are inserted into the through holes XXXX, thereby mounting each electric component 8 on the double-sided printed wiring board 1. Here, a plating film of Sn-10Pb is formed on the leads of the mounted electric component 8. Lead is Cu
In many cases, the material is made of Fe, Fe, an alloy thereof, 42 alloy, or the like. The plating film is provided on at least the surface of the outer lead by a method such as electroplating in order to prevent oxidation of the lead made of such a material and to improve the wettability of the solder to the lead.

Next, as shown in FIG. 1E, a Sn-3.5Ag-0.5Cu solder bath 10 stored in a stationary bath 9 is
By immersing the double-sided printed wiring board 1, the solder material creeps up in the through-hole, and the solder material of the solder bath 10 reaches the solder 6 of the land portion 3 printed in advance. At this time, the solder 6 supplied in advance is re-melted by the heat generated by the solder material of the solder bath 10 and solidified by the progress of heat radiation, so that the electric component 8 is soldered. As a result, as shown in FIG.
An electric circuit device on which the solder fillet 11 is formed is manufactured.

In the embodiment, stable soldering is realized by using a solder having the same composition as the solder material previously printed on the double-sided printed wiring board 1 as a solder material of the solder bath. As long as the quality is assured, the impurity concentration may be reduced by supplying another material in advance. That is, a process of supplying a material for reducing the concentration of impurities mixed into the solder may be performed.

The amount and composition of the solder material supplied in advance can be appropriately changed according to the solder material used for the solder bath, the size of the land portion, the composition of the plating applied to the leads, and the like. . Further, in the embodiment, the heating is performed by the reflow furnace before the flow soldering is performed by the solder bath, but it is not necessary to perform the reflow heating as long as no trouble occurs in the transportation, the flow soldering, and the like. Further, in the embodiment, the solder bath held by the stationary bath is used, but a solder bath provided with a jet may be used.

In the embodiment, a double-sided printed wiring board is used as a wiring board, but the present invention is not limited to this, and a multilayer wiring board may be used, for example. Further, in the embodiment, the electric circuit device in which the surface mounting component and the insertion mounting component are mixed is described. However, it is needless to say that the present invention is applicable to an electric circuit device including only the insertion mounting component. It is.

[0014]

As described above in detail, by applying the soldering method and the method for manufacturing an electric circuit device according to the present invention, the occurrence of lift-off is suppressed, and even when lead-free solder is used, An electric circuit device with high connection reliability can be provided with high productivity.

[Brief description of the drawings]

FIGS. 1A to 1E are schematic diagrams showing a manufacturing process of an electric circuit device according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Double-sided printed wiring board, 2 ... Through hole, 3 ... Land part, 4 ... Surface electrode, 5 ... Metal mask, 6 ... Solder,
7 ... electric parts (surface mount parts), 8 ... electric parts (insertion mount parts), 9 ... stationary bath, 10 ... solder bath, 11 ... solder fillet

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B23K 1/20 B23K 1/20 J // B23K 101: 42 101: 42 (72) Inventor Tatsuya Tatsuya Shinmachi, Ome-shi, Tokyo 3-3-3 Toshiba Digital Media Engineering Corporation In-house F-term (reference) 4E080 AA01 AB02 5E319 AA02 AC01 BB01 BB05 CC23 CC28 CC36 CD28 CD29 CD31 GG03

Claims (9)

[Claims] 1. A solder mounting method for connecting a wiring board having a through hole provided with a land portion and an electric component having a lead inserted into the through hole to each other by soldering. A soldering method, comprising a step of supplying a material for reducing the concentration of impurities mixed in the solder with respect to the solder for at least one of the solders. 2. A wiring board having a through-hole provided with a land portion, wherein a lead of an electric component is inserted into the through-hole, and solder flows into the through-hole, whereby the wiring is formed. In a solder mounting method for connecting a substrate and the electric component to each other, the method further includes a step of performing a process for reducing the concentration of impurities mixed in the solder with respect to the solder on at least one of the wiring board and the electric component Soldering method characterized by performing. 3. The solder mounting method according to claim 1, wherein the impurity for the solder is lead. 4. The solder mounting method according to claim 1, wherein the solder is a material substantially free of lead in the composition. 5. A method for manufacturing an electric circuit device for soldering an electric component having a lead to a double-sided printed wiring board having a through hole using a solder bath, wherein the concentration of impurities mixed into the solder material of the solder bath is determined. Manufacturing the electric circuit device, comprising: supplying a material for lowering at least onto a land portion of an electrode included in the through hole before inserting the lead into the through hole of the electric component. Method. 6. The method for manufacturing an electric circuit device according to claim 5, wherein the composition of the solder supplied in advance is the same as the solder composition of the solder bath. 7. The electric device according to claim 5, wherein the solder is supplied by printing solder on at least a land portion of an electrode of the wiring substrate and supplying the wiring substrate to a reflow furnace. A method for manufacturing a circuit device. 8. A step of supplying solder by printing onto a plurality of electrodes disposed on one main surface of the wiring board and a land portion of a through hole, and a surface mount component to the electrode supplied with the solder. Mounting the wiring board with a reflow oven, inserting a lead of an electric component into a through hole provided in the wiring board, and immersing the wiring board in a solder bath. A method for manufacturing an electric circuit device, comprising: 9. The method for manufacturing an electric circuit device according to claim 5, wherein the solder is a material substantially free of lead in the composition.