JPH06333620A - Surface mounted parts and parts mounting substrate - Google Patents

Abstract

PURPOSE:To dispense with manual soldering for reinforcement so as to enhance connection strength by using a lead, to the surface of which palladium plating is applied, and fixing the lead to a land of a substrate by solder including bismuth. CONSTITUTION:Palladium plating 11 is applied to the surface of a conductive base member 4 of a reinforcing lead 3 of a connector 10, and is not applied to other leads for electric connection. A part disposing substrate 20 is automatically fixed onto a substrate 8, where the connector 10 is printed-wired, by a machine with cream solder 21 including 8% of bismuth. In a land 9 on the substrate 8, solder plating 9B is applied onto a copper foil 9A. The solder 21 for connecting the lead 3 to the land 9 shows high connection strength owing to the application of the plating 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mount component and a component mount board, and more particularly, to a solder bond strength when a lead of the surface mount component to which external force is applied during use is attached to the substrate with solder containing 8% bismuth (solder). Related to improvements to improve.

[0002]

2. Description of the Related Art In recent years, a large number of surface mount components are attached to printed wiring boards. Usually, the lead interval (pitch) of surface mount components is extremely narrow. As shown in FIG. 2, surface mount components to which external force is applied during use such as the connector 1 are provided with leads 3 for reinforcing mechanical connection in addition to the leads 2 for electrical connection. In these leads 2 and 3, as shown in FIG. 3A, a nickel plating layer 5 is usually formed on a conductive base material 4 for preventing oxidation,
Furthermore, a solder plating layer 6 is formed on top of this in order to compensate for the extremely poor solderability of nickel. Alternatively, as shown in FIG. 3B, a copper plating layer 7 may be formed as a base of the nickel plating layer 5. Although not shown, the land of the printed wiring board is usually a copper foil plated with solder.

When a surface mount component having a narrow lead pitch as described above is mounted on a substrate, a solder bridge is likely to occur. Therefore, in order to prevent solder bridging, cream solder containing 8% bismuth, which has good solderability, is used, and surface mounting components are automatically soldered to the lands of the board by a machine.

However, although the solder containing 8% bismuth is excellent in solder breakability, it is inferior in solder drawability as compared with ordinary 60-40 solder (eutectic solder). That is, the force of alloying with the other party is weak, and the solder bond strength is insufficient. Therefore, when the connector 1 receives an external force at the time of use, the reinforcing lead 3 causes the land 9 of the board 8 to move as shown by a broken line in FIG.
The connector 1 may be detached from the substrate 8 by peeling off.

Therefore, conventionally, in order to prevent the parts such as the connector 1 from coming off, after the automatic soldering using the cream solder containing 8% bismuth, the reinforcing lead 3 is reinforced by the eutectic solder by hand. Soldering is used to compensate for the lack of bond strength. That is, conventionally, manual work was required to improve the solder bond strength.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems of the prior art, so that surface mounting components and component mounting boards which do not require manual soldering for reinforcement and have high solder joint strength are provided. Is to provide.

[0007]

To achieve the above object, the surface mount component according to the invention of claim 1 is characterized in that it has a lead whose surface is plated with palladium. The leads of the surface-mounted component are not basically limited to those for electrical connection or those for reinforcing mechanical connection, but normally, at least on the substrate as in the invention of claim 2. It is preferable that the lead is a lead that receives an external force in the mounted state.

A component mounting board according to a third aspect of the present invention which achieves the above object, has the surface mounting component according to the above-mentioned first or second aspect on the substrate, and the leads of the surface mounting component are mounted on the land of the substrate. % It is characterized by being attached with solder containing bismuth.

[0009]

When the conventional surface mount type connector is closely observed from the board, solder is not left on the leads of the connector in many cases, and solder is left on the land of the board. Therefore, it was judged that there was a cause on the lead side, various plating was applied to the lead surface, and soldering was performed on the land of the board with solder containing 8% bismuth. It has been found that the bonding strength can be obtained and that manual soldering for reinforcement is unnecessary.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to an embodiment shown in the drawings. FIG. 1 is a partially cutaway view showing a surface mount component and a component mount board to which the present invention is applied. In FIG.
The surface mount type connector 10 is the same in appearance as the connector 1 shown in FIG. 2, but the plating structure of the reinforcing lead 3 is different. That is, the reinforcing lead 3 of the connector 10 of this embodiment
Is a conductive base material 4 whose surface is plated with palladium. The other leads for electrical connection (see reference numeral 2 in FIG. 2) are not plated with palladium, and the same as in the conventional case.
It has the plating structure shown in (a) or (b).

The component mounting board 20 is the connector 1 described above.
0 is automatically attached to the printed wiring board 8 by a machine using 8% bismuth-containing cream solder. The land 9 on the substrate 8 is obtained by applying solder plating 9B on the copper foil 9A.

The solder 21 containing 8% bismuth that connects the lead 3 and the land 9 hardly spreads from the state of the solder when printed, but the high solder bond due to the interposition of the palladium plating layer 11 formed on the lead 3. The strength was obtained and the parts did not come off.

Although the palladium-based plating layer 11 is formed only on the reinforcing lead 3 of the connector 10 in the above embodiment, the contact type connection portion of the connector 10 (the broken line portion in FIG. 2).
The lead for electrical connection may be plated with palladium as long as it does not adversely affect the performance. Further, not only the connector 10 but also a surface-mounted component that receives an external force during use can be prevented from coming off by forming a palladium plating layer on the lead.

[0014]

According to the present invention, the lead of the surface mount component, particularly the lead of the surface mount component which receives an external force during use, such as a lead for reinforcing the mechanical connection of the connector, is plated with palladium. Therefore, when the surface mount component is attached to the substrate with the solder containing 8% bismuth, a high solder bond strength can be obtained without manually performing reinforcing soldering.

[Brief description of drawings]

FIG. 1 is a partially cutaway view showing an embodiment of a surface mount component and a component mount board of the present invention.

FIG. 2 is a diagram showing a surface mount type connector.

FIG. 3 is a cross-sectional view showing a lead of a conventional surface mount component.

FIG. 4 is an explanatory diagram of conventional problems.

[Explanation of symbols]

 2 Electrical connection lead 3 Reinforcing lead 4 Lead conductive base material 8 Printed wiring board 9 Land 9A Copper foil 9B Solder plating layer 10 Surface mounting type connector 11 Palladium plating layer 20 Component mounting board 21 8% Bismuth-containing solder

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location H05K 3/34 H 7128-4E // H01G 1/14 F 9174-5E H01L 23/50 D

Claims (3)

[Claims] 1. A surface-mounted component having a lead whose surface is plated with palladium. 2. The surface mount component according to claim 1, wherein the lead is a lead that receives an external force when mounted on a substrate. 3. A component mounting, comprising the surface mounting component according to claim 1 or 2 on a substrate, and the lead of the surface mounting component is attached to a land of the substrate with solder containing 8% bismuth. substrate.