JPS5828115A - Method of producing contact for lead switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a contact for a reed switch, and particularly to an improvement for eliminating variations in contact resistance.

A reed switch has a pair of reed pieces sealed inside a glass tube, and the ends of the pair of reed pieces are brought into contact or separated by manipulation of a magnetic field from around the glass tube to turn on the switch.
This is to turn it off.

Therefore, the lead piece is made of a magnetic material, and the contact part at the end is made of Au, rhodium, or copper.
A contact metal layer made of a non-magnetic material such as Cu) is usually provided by a plating process.

When such a reed switch is used under a high load with a high current flowing through it, or when it is desired to keep the contact area before opening and closing particularly small, the thickness of the contact metal layer must be increased. When a thick metal layer is plated, the plated metal itself becomes an electrode, so once irregularities are formed on the surface of the metal, those irregularities are increased during the plating process. Therefore, reed switches with thickly plated contact metal layers do not have smooth surfaces and are noticeably uneven, resulting in high contact resistance.The contact resistance value is not constant for each switch, and there is large variation between products. There was a lot of stuff.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a method for manufacturing a reed switch having a thickly plated contact metal layer with a smooth contact surface and less variation in contact resistance between products. purpose. For this reason, in the present invention, after the plating process for forming the contact metal layer, an electrolytic polishing process is performed to electrolytically polish the plated metal.

FIG. 1 shows the plating process.

The lead piece 1 is a 5270 mm (52 mm Ni, 48 mm Fe) round bar that is press-formed and cut, and has been subjected to a cleaning process and a magnetic annealing process. Lead piece 1 is immersed in plating solution 2 and plated metal 3 (contact metal), for example Au, Rh.
+ or Cu is formed on the surface of the lead piece 1. At this time, unevenness is formed on the surface of the plated metal 3. Next, the lead piece 1 on which the plated metal 3 has been formed is immersed in an electrolytic solution 4 as shown in FIG. 2, and the surface of the plated metal 3 is electrolytically polished.

In such an electrolytic polishing process, due to the characteristics of electrolytic polishing, thicker parts of the plated metal 3 receive a larger amount of electrolytic polishing than thinner parts, so the unevenness of the optical surface of the plated metal 3 is averaged out as shown in Figure 2. A substantially uniform and smooth surface can be obtained. FIG. 3 is a graph showing variations in contact resistance between a reed switch subjected to the electrolytic polishing process according to the present invention and a reed switch manufactured using the conventional method. The horizontal axis is the initial contact resistance (m10
, and the vertical axis is the number of products expressed as a percentage. The solid line graph shows a reed switch using the method of the present invention, and the dotted line graph 27 shows a reed switch using the conventional method without electrolytic polishing. The plating thickness of both products is 6μ.As you can see from Figure 0, the solid line is higher)'? -Centage products concentrate on low contact resistance values within a narrow range. In other words, a reed switch using the method of the present invention has a lower contact resistance and less friction than conventional switches.

As explained above, in the present invention, the surface of a contact metal layer whose surface is particularly uneven due to thick plating is easily and reliably smoothed by electrolytic polishing. Therefore, the contact resistance of the reed switch is low and stable, and a product with less variation in contact resistance is obtained, which improves the reliability of the switch.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 show methods related to the method of the present invention, respectively. FIG. 3 is a cross-sectional view of one end of the lead during the process and electrolytic polishing process, and FIG. 3 is a graph showing variation in contact resistance of the reed switch. 1... Lead piece, 2... Plating solution, 3... Plating metal, 4... Electrolyte solution. Patent applicant Fujitsu Limited Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney 1) Yukio Patent attorney Akira Yamaguchi Figure 1 Illustration 2

Claims (1)

[Claims] 1. A method for manufacturing a reed switch contact including a contact plating step of plating a contact metal on the end of a lead made of a magnetic material, characterized by performing an electrolytic polishing step of electrolytically polishing the plated metal after the plating step. A method for manufacturing contacts for reed switches.