JPH07142665A - Electronic part provided with lead - Google Patents

Abstract

PURPOSE:To provide an electronic part provided with leads which are free from soldering failures caused by the excessive suck up of molten solder along leads when the leads of an electronic part provided with leads are brought into contact with solder provided to the electrodes of a printed board and soldered to them by heating solder. CONSTITUTION:An electronic part 1a is provided with leads 3 which extent out downward from the side face of its main body 2, wherein the lower end 3a of the lead 3 soldered to an electrode 5 provided to a printed board 4 is set better in wettability than the upper end 3b. Therefore, when solder 6 is fused by heating, the molten solder 6 is prevented from being excessively sucked up along the lead 3 crossing boundary point a between a part excellent in wettability and a part poor in wettability to cause defective soldering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leaded electronic component for soldering a lead extending downward from a main body to an electrode of a printed circuit board.

[0002]

2. Description of the Related Art FIG. 26 is a side view of a conventional leaded electronic component soldered to a printed circuit board. The leaded electronic component 1 has a lead 3 extending downward from the side surface of the main body 2, and the lower end portion 3 a of the lead 3 is soldered to the electrode 5 of the printed board 4 by the solder 6. . In this soldering, the lower end portion 3a of the lead 3 is grounded on the solder 6 formed on the electrode 5 by screen printing means, precoating means, or the like, and then the printed board 4 is sent to a heating furnace and the solder 6 is applied in the heating furnace. Is heated and melted.

When the solder 6 is heated and melted, the melted solder 6 is generally attracted to and attached to the leads 3 so that the surfaces of the leads 3 are generally solder-plated. It improves the wettability of.

[0004]

However, the lead 3
When the wettability is improved by applying solder plating to the solder, the melted solder is excessively attracted to the surface of the lead 3 and sucked up to the upper end portion 3b of the lead 3 as shown by reference numeral 6a in FIG. There is a problem that the soldering state is apt to become defective due to insufficient amount of the solder 6 on the electrode 5 for adhering the lower end portion 3a of the electrode 3 to the electrode 5.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electronic component with leads, which can prevent the molten solder from being excessively sucked up to the upper end side of the leads during soldering so that the soldering state becomes poor. To do.

[0006]

For this reason, in the electronic component with leads of the present invention, the wettability on the lower end side of the leads soldered to the electrodes of the printed circuit board is better than the wettability on the upper end side. Is.

[0007]

In the above structure, when the lower end of the lead is grounded to the solder formed on the electrode of the printed circuit board and the solder is heated and melted, the melted solder is attracted to the lead and sucked along the lead. However, since the wettability on the upper end side of the lead is worse than the wettability on the lower end side, sucking up of the melted solder stops at the boundary of good and bad wettability, and the solder becomes excessive up to the upper end side. Can be sucked up.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a side view showing a state in which an electronic component with leads according to an embodiment of the present invention is soldered to a printed board. This leaded electronic component 1 a has a lead 3 extending downward from the side surface of the main body 2.
The lower end portion 3a of the above is soldered to the electrode 5 of the printed board 4 with the solder 6. In this soldering, after the lower end portion 3a of the lead 3 is grounded on the solder 6 formed on the electrode 5 by screen printing means or precoat means, the printed circuit board 4 is sent to a heating furnace, and the solder 6 is heated in the heating furnace. Is heated and melted.

Solder plating 14 is applied to the lower end 3a side of the lead 3 in order to improve wettability. a is a boundary of the solder plating 14, that is, a boundary of good and bad wettability,
Solder plating 14 on the lower end side 3a below the boundary a
The wettability of the portion to which the mark is applied is better than the wettability of the upper end portion 3b side above the boundary a. As described in the section of the prior art, when the printed board 4 is sent to a heating furnace and the solder 6 is heated and melted in order to solder the lead 3 to the electrode 5, the melted solder 6 is Attempts to wick upwards along 3. However, in this case, the wettability on the lower end 3a side where the solder plating 14 is applied is better than the wettability on the upper end 3b side, so the solder 6 is sufficiently attracted and attached to the lower end 3b side. Since the sucked up of the melted solder 6 stops at the boundary a and does not suck up above the boundary a, as in the conventional example shown in FIG.
The solder 6 does not adhere to the b side. Therefore, a sufficient amount of solder is secured on the electrode 5, and the lower end portion 3a of the lead 3 is sufficiently soldered to the electrode 5 as illustrated.

Next, a method of manufacturing the electronic component with lead 1a will be described with reference to FIG. 2 to 7 show the first method of manufacturing the electronic component with lead 1a in the order of steps. 2 to 7 are plan views of the lead frame 11,
An island 12 on which chips are mounted is formed in the center. Around the island 12, outer leads OL which are the lower end portion 3a and the upper end portion 3b of the lead 3 shown in FIG. 1 and an inner lead IL which is sealed in the inside of the main body 2 with resin are formed by punching means or etching means. Has been done. The material of this lead frame 11 is 4.
It is a 2-alloy and the wettability of solder is poor.

In FIG. 3, plating 13 is partially applied to the tips of the inner leads IL. The plating 13 is applied to improve the wire bondability during wire bonding, which will be described later with reference to FIG. 5, and Ag (silver) is generally frequently used.

Next, as shown in FIG. 4, the outer lead O
Solder plating 14 is partially applied to the tip of L. The solder plating 14 is applied to improve the wettability of the solder 6 when the lower end portion 3a of the lead 3 is soldered to the electrode 5 of the printed board 4 as shown in FIG. The boundary a of the plating 14 becomes the boundary a shown in FIG.

Next, as shown in FIG. 5, after mounting the chip 15 on the island 12, the electrode of the chip 15 and the inner lead IL are connected by the wire 16 by wire bonding. In this case, since the tip portion of the inner lead IL to which the wire 16 is bonded is plated with Ag 13, the wire 16 can be bonded well.

Next, as shown in FIG. 6, the main body 2 is formed by a resin molding device in order to protect the chip 15, the wire 16 and the inner lead IL. Next lead frame 1
Predetermined part of 1 is punched with a die, and the punched lead 3
By bending forming, the leaded electronic component 1a is completed as shown in FIG. The lower end portion 3 of the lead 3 of the electronic component with lead 1a manufactured in this manner
Solder plating 14 for improving the wettability is applied to the a side, and therefore, as described with reference to FIGS. 1 and 26, the melted solder 6 is excessively sucked up to the upper end 3b side. It is possible to solve the problem that the soldering state becomes poor and to perform good soldering.

Next, a second method of manufacturing the electronic component with leads of the present invention will be described with reference to FIGS. Figure 8
9 and FIG. 9 are the same as FIGS. 2 and 3, and the description thereof will be omitted. As shown in FIG. 10, chips 15 are formed on the island 12.
After mounting and connecting the electrode of the chip 15 and the tip of the inner lead IL with the wire 16, the main body 2 is formed as shown in FIG. Thereafter, as shown in FIG. 12, solder plating 14 is applied to the tips of the outer leads OL, and then the lead frame 11 is punched to complete the leaded electronic component 1b shown in FIG.

Next, a third method of manufacturing an electronic component with leads of the present invention will be described with reference to FIGS. Figure 1
4 is a plan view of the same lead frame 11 as in FIG. As shown in FIG. 15, the outer leads OL and the inner leads IL are simultaneously plated with plating 13a and 14a. The material of the platings 13a and 14a is Au (gold) or Pd (palladium).

Next, as shown in FIG. 16, the chip 15 is mounted on the island 12 and connected by the wire 16, and then, as shown in FIG.
As shown in FIG. 18, the main body 2 is formed by a resin molding apparatus, and the lead frame 11 is punched out to complete the leaded electronic component 1b shown in FIG. The lower end 3a side of the lead 3 is plated with Au or Pd 14a, and the same effect as the electronic component with lead 1a of the first embodiment can be obtained.

Next, a fourth method of manufacturing the electronic component with leads of the present invention will be described with reference to FIGS. The material of the lead frame 11 shown in FIG. 19 is copper, and the wettability of the solder is very good as compared with the lead frame of 4.2 alloy described above. Now, as shown in FIG. 20, after plating 13 of Ag on the tip of the inner lead IL, a chip 15 is mounted on the island 12 and connected by wires 16 as shown in FIG.

Next, after forming the main body 2 as shown in FIG. 22, a solder wettability reducing process is applied to the main body 2 side of the outer lead OL exposed to the outside of the main body 2 as shown in FIG. In this embodiment, the heat-resistant organic thin film 17 is coated to reduce the wettability of the solder.
However, the heat-resistant organic thin film 17 is not coated on the tip of the outer lead OL. As a material for the heat resistant organic thin film 17, for example, polyimide or Teflon is used. Of course, the specific means for the wettability reduction processing is not limited to this embodiment. Next, as shown in FIG. 24, the lead frame 11 is punched to complete the leaded electronic component 1d.

FIG. 25 shows a state in which the electronic component with lead 1d manufactured as described above is soldered to the printed board 4. Since the material of the lead frame 11 is copper having good wettability, and the lower end portion 3a of the lead 3 is not coated with the heat-resistant organic thin film 17, the tip end portion has good wettability, but the upper end portion of the lead 3c has The wettability is reduced by coating the heat-resistant organic thin film 17. Therefore, also in this case, the same operational effect as in the case of the first to third embodiments can be obtained. As is clear from each of the above embodiments, the leaded electronic component of the present invention can be manufactured by various methods.

[0021]

As described above, in the electronic component with leads of the present invention, the wettability on the lower end side of the leads soldered to the electrodes of the printed circuit board is better than the wettability on the upper end side. , When the solder is heated and melted for soldering, sucking up of the melted solder stops at the boundary of good and bad wettability, eliminating excessive sucking up of the solder to the upper end side, which is good. Can be soldered to.

[Brief description of drawings]

FIG. 1 is a side view showing a state in which an electronic component with leads according to an embodiment of the present invention is soldered to a printed circuit board.

FIG. 2 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 3 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 4 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 5 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 6 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 7 is a perspective view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 8 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 9 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 10 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 11 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 12 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 13 is a perspective view of a method for manufacturing a leaded electronic component according to an embodiment of the present invention.

FIG. 14 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 15 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 16 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 17 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 18 is a perspective view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 19 is a plan view of the method for manufacturing the electronic component with leads according to the embodiment of the present invention.

FIG. 20 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 21 is a plan view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 22 is a plan view of the method for manufacturing the electronic component with leads according to the embodiment of the present invention.

FIG. 23 is a plan view of the method for manufacturing the electronic component with leads according to the embodiment of the present invention.

FIG. 24 is a perspective view of a method for manufacturing an electronic component with leads according to an embodiment of the present invention.

FIG. 25 is a side view showing a state in which a leaded electronic component according to an embodiment of the present invention is soldered to a printed board.

FIG. 26 is a side view of a state in which a conventional electronic component with leads is soldered to a printed circuit board.

[Explanation of symbols]

 1a, 1b, 1c, 1d electronic component with lead 2 main body 3 lead 3a lower end of lead 3 3b upper end of lead 3

Claims (1)

[Claims] 1. In a leaded electronic component in which a lead extends downward from the side surface of a main body, the wettability of the solder on the lower end side of the lead soldered to an electrode of a printed circuit board to the solder on the upper end side. Electronic components with leads, which are characterized by better wettability.