Resin substrate

Details Resin substrate Resin substrate

2000-01-04

2003-02-11

Paladini, Albert W. (Department: 2827)

Electricity: conductors and insulators

Conduits, cables or conductors

Preformed panel circuit arrangement

C361S772000

Reexamination Certificate

active

06518518

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin substrate, which has a substrate body and a pin serving as an input/output terminal, and more particularly to a resin substrate having a pin which can reliably be connected to a socket or another substrate.
2. Description of the Related Art
Conventionally, a structure has been known in which a pin serving as an input/output terminal is secured and stood erect on a substrate body made of an insulating material, such as resin, for example, epoxy resin, or composite material of the resin and glass fibers, the pin being secured and stood erect by using a lead and tin (hereafter “Pb—Sn”) soldering material, such as Pb—Sn eutectic solder.
As the foregoing resin substrate, a resin substrate
101
structured, for example, as shown in
FIG. 6
is exemplified. A substrate body
102
of the resin substrate
101
has a resin insulating layer
103
and a circuit layer (not shown). A first main surface
102
A of the resin substrate
101
has a connection pad
104
formed thereon. A solder resist layer
105
is formed to reach the edge of the connection pad
104
.
The pin
11
has a large-diameter portion
111
A and a shaft portion
111
b
and having a structure that the overall surface is applied with nickel (hereafter “Ni”) plating or gold (hereafter “Au”) plating (not shown). The large-diameter portion
111
A of the pin
111
is secured with a soldering material
115
to be opposite to the connection pad
104
allowed to expose over the solder resist layer
105
. The soldering material
115
for establishing the connection between the pin
111
and the substrate body
102
is welded to substantially the overall surface of the exposed connection pad
104
and portions of the large-diameter portion
111
A and the shaft portion
111
b
such that the soldering material
115
forms substantially a truncated-cone fillet shape.
When the resin substrate
101
has been joined to the socket, a large gap DSA is formed between the first main surface
102
A of the substrate body
102
and the upper surface SKA of the socket SK, for example, as shown in FIG.
7
. When the resin substrate
101
is mounted on another substrate or the like, also a large gap is formed. The reason for this lies in that the soldering material
115
upwards moved and welded to the shaft portion
111
b
of the pin
111
when the pin
111
is soldered to the substrate body
102
substantially enlarges the diameter of the shaft portion
111
b
of the pin
111
. Thus, the shaft portion
111
B cannot sufficiently deeply be inserted into the socket SK or a through hole of the other substrate.
If the large gap is formed, the overall height realized after the resin substrate
101
has been joined to the socket SK or the like is enlarged excessively. Thus, a requirement for reducing the height cannot be met. The pin
111
of a type which projects over the first main surface
102
A by a short length sometimes suffers from unsatisfactory reliability of the connection with the socket SK or the like. Moreover, a requirement for connecting the substrate made of the resin
101
and the socket SK or the other substrate to each other for a shortest distance cannot be met.
As the wettability between the soldering material
115
and the Au-plated layer on the surface of the pin
111
is improved, the height HSA of the soldering material
115
which upwards moves when the pin
111
is secured is enlarged. When the wettability is adjusted to reduce the height HSA of the soldering material
115
which upwards moves, it can be considered that the overall height realized after the resin substrate
101
has been joined to the socket SK or the like can be reduced.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a resin substrate with which the gap between the substrate body and another substrate or the like can be reduced when the resin substrate having a multiplicity of pins serving as input/output terminals and stood erect is joined to a socket or another substrate.
According to the present invention, there is provided a resin substrate, comprising: a substrate body made of resin or a composite material containing resin and formed into a plate-like shape which has a first main surface; and a pin having a surface on which an Au-plated layer is formed, wherein the pin is soldered to the substrate body with a soldering material mainly composed of Sn and Sb so as to be projected over the first main surface of the substrate body.
The present invention has the structure that the soldering material for securing the pin and the substrate body to each other is the soldering material mainly composed of Sn and Sb. The foregoing soldering material becomes wet with Au plating on the surface of the pin. The wettability is inferior to the Pb—Sn soldering material. Therefore, the foregoing soldering material, which is capable of soldering the pin to the substrate body, does not considerably upwards move along the pin.
Therefore, the portions to which the solder is welded and, the diameter of each of which is enlarged can be decreased. Hence it follows that the pin can sufficiently deeply be inserted into the socket or the through hole of another substrate. Therefore, the gap between the first main surface of the substrate body and the socket or the other substrate can be reduced. As a result, the overall height realized after the resin substrate has been joined to the socket or the like can be reduced.
The substrate body may be made of resin, such as epoxy resin, or an insulating material made of a composite material of the foregoing resin and glass fibers. The substrate body includes a laminated circuit substrate having a core substrate, on either side or two sides of which insulating layers and circuit layers are alternately laminated. As an alternative to this, a laminated circuit substrate having no core substrate and having the foregoing laminated structure is included.
The pin must have the surface on which the Au-plated layer is formed. The bonding strength of the substrate body or the like must be considered to arbitrary select the pin. The pin may be a pin in the form of the head of a nail or a pin having a large-diameter portion in an intermediate portion thereof. The material of the pin is exemplified by metal, such as covar, a 42NI—Fe alloy or a copper alloy. It is preferable that a Ni-plated layer is formed as the base layer for the Au-plated layer.
The soldering material must mainly be made of tin (hereafter “Sn”) and antimony (hereafter “Sb”). In consideration of the melting point and the bonding strength, the quantity of the foregoing elements must be determined. In addition to the elements, such as Sn and Sb, silver (hereafter “Ag”), bismuth (hereafter “Bi”), Au, Pb, indium (hereafter “In”), aluminum (hereafter “Al”), arsenic (hereafter “As”) or the like may be added in a small quantity.
In the present invention, it is preferable that the height of the pin projecting over the first main surface is 2 mm or smaller.
If the length of the pin projecting over the first main surface of the substrate body is too short, that is, if the length is 2 mm or smaller, the portion of the pin which can be inserted into the socket or the through hole of the substrate is too short to reliably connect the resin substrate to the socket or the like when upward movement of the soldering material takes place greatly. If the connector of the socket is brought into contact with the soldering material which covers the pin, the reliability of the connection sometimes deteriorates as compared with the reliability realized when the contact with the Au-plated layer is made.
The present invention, which is arranged to use the soldering material mainly composed of Sn and Sb having a poor wettability with the pin as compared with the lead-tin (hereafter “Pb—Sn”) soldering material, is able to prevent upward movement of the soldering material which occurs when the pin is secured. Although the portion of the pin which projects over the substrate body is short,

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