Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-10-11
2004-07-27
Cuneo, Kamand (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S261000, C174S267000, C361S760000, C361S767000, C361S772000
Reexamination Certificate
active
06768062
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a connection method, a connection structure, and inspecting methods for the connection state when pad electrodes (component-side pad electrodes) formed on a component and pad electrodes (substrate-side pad electrodes) formed on a substrate are each connected by solder bumps.
2. Description of the Related Art
As an example of connection structure for connecting each of the component-side pad electrodes formed on a component and one of the substrate-side pad electrodes formed on a substrate by means of a solder bump, a connection structure as disclosed in Japanese Unexamined Patent Application Publication 9-82760 (see U.S. Pat. No. 5,914,536, an English language patent family member) is known.
As shown in
FIGS. 7A and 7B
herein, this connection structure is one wherein the semiconductor chip (surface-mount component)
111
, in which a plurality of terminal electrodes (component-side pad electrodes)
112
is provided on the bottom surface thereof, is mounted onto a wiring substrate
113
, and wherein each of the wiring patterns (substrate-side pad electrodes)
114
provided on the wiring substrate
113
and one of the component-side pad electrodes
112
are electrically connected by a bump (solder bump)
115
. In this connection structure, each of bumps
115
is formed of solder
115
a,
and a metallic core
115
b
using Cu or the like. The portion (the outer peripheral portion) formed at the outside of the outer edge of the region corresponding to the plan view of the semiconductor chip
111
, out of the solder
115
a,
makes contact with a solder resist
117
formed on the wiring patterns (substrate-side pad electrodes)
114
.
In this connection structure, the reflow method is used for mounting a semiconductor chip onto the circuit board
113
of the semiconductor chip
111
. Specifically, the connection is performed using the following method.
(1) First, a metallic core
115
b
is formed on each of the terminal electrodes
112
of the semiconductor chip
111
, and a bump
115
is formed by covering the metallic core
115
b
by solder
115
a.
(2) Then, the semiconductor chip
111
is positioned and mounted on the wiring patterns (substrate-side pad electrodes)
114
on the wiring substrate
113
, and after the solder
115
a
of each of the bumps
115
has been melted, the solder
115
a
is cooled down to solidify it.
In this manner, each of the terminal electrodes
112
and one of the wiring patterns (substrate-side pad electrodes)
114
is connected by a bump
115
, and thus the semiconductor chip
111
is mounted onto the wiring substrate
113
. Herein, the melted solder
115
a
flows and spreads over the wiring patterns (substrate-side pad electrodes)
114
, which has a good solder wettability, and is stopped by the solder resist
117
. Hence, by setting the amount of the solder
115
a
of the solder bump
115
and the area of the portion which is not covered with the solder resist
117
of the wiring patterns (substrate-side pad electrodes)
114
to an appropriate value, the contact area between the bumps
115
and the wiring patterns (substrate-side pad electrodes)
114
can be made constant, thereby ensuring a stable connection state.
In the above-described conventional connection structure, however, the substrate-side pad electrodes
114
are formed so as to be extended to the outside of the outer edge of the region corresponding to the plan view of the semiconductor chip
111
. This makes it difficult to apply this connection structure to the case where surface-mount components such as semiconductor chips are mounted at a high density. In addition, this raises a problem in that the miniaturization of the product which is obtained by mounting semiconductor chips and the like is restricted.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-described problems. The object of the present invention to provide a connection method and a connection structure, using solder bumps, for component-side pad electrodes and substrate-side pad electrodes, and inspecting methods for the connection state thereof which are adaptable to high density mounting, and which allow the miniaturization of a product formed by mounting a surface-mount component onto a substrate.
In order to achieve the above-described object, the present invention provides a method for connecting each of component-side pad electrodes and one of substrate-side pad electrodes, when a surface-mount component wherein component-side pad electrodes are formed on the surface thereof opposed to a substrate, and wherein solder bumps are formed on the component-side pad electrodes, is mounted onto a substrate, wherein substrate-side pad electrodes are formed on the surface thereof. This method is characterized by comprising arranging the substrate-side pad electrodes inside the region corresponding to the plan view of the surface-mount component (hereinafter, referred to as the “component-corresponding region”); setting the size of each of the substrate-side pad electrodes, in the direction substantially perpendicular to the outer edge of the component-corresponding region (hereinafter, referred to as the “length of substrate-side pad electrodes”), larger than that of the corresponding component-side pad electrode, in the direction substantially perpendicular to the outer edge of the surface-mount component (hereinafter, referred to as the “length of component-side pad electrode”); and placing the surface-mount component on the substrate so that each of the solder bumps are opposed to a predetermined substrate-side pad electrode, and melting the solder bumps by heating, thereby connecting each of the component-side pad electrodes and one of the substrate-side pad electrodes through the solder.
In the connection method for the pad electrodes in accordance with the present invention, the substrate-side pad electrodes are arranged inside the component-corresponding region; the length of each of the substrate-side pad electrodes is set to be larger than that of the corresponding component-side pad electrode; and the surface-mount component is placed on the substrate so that each of the solder bumps are opposed to a predetermined substrate-side pad electrode, and heated to melt the solder bumping. Therefore, the solder which flows and spreads over each of the substrate-side pad electrodes, allows each of the component-side pad electrodes and one of the substrate-side pad electrodes to be connected with reliability.
Also, since each of the substrate-side pad electrodes is formed inside the component-corresponding region, a high-density mounting can be achieved without risk of generating short-circuiting, as well as the miniaturization of the products can be met. Furthermore, the interconnection between the substrate-side pad electrodes and the substrate side can be achieved by connecting to the wiring formed inside the substrate or on the back surface thereof through, for example, via holes or through holes. Thereby, a configuration wherein the substrate-side pad electrodes or wiring are not formed outside the component-corresponding area, can be obtained.
Moreover, since the length of each of the substrate-side pad electrodes is set to be larger than that of each of the component-side pad electrodes, it is possible to make a pass/fail discrimination, with ease and reliability, of the connection state of the pad electrodes by detecting the shapes of the solder (solder bumps) after they have been melted and have connected the pad electrodes, for example, in a nondestructive inspection by X-ray imaging. Specifically, if the solder bumps still have unchanged shapes, it will be recognized that the solder bumps have not yet been melted and flowed, while if the solder bumps have shapes other than the original shapes thereof, it will be recognized that the solder bumps have been melted and flowed, and consequently that each of the component-side pad electrodes and one of the substrate-side pad electrodes are connected by
Funaki Tatsuya
Hirota Jitsuho
Morimoto Ryoichi
Burns Doane , Swecker, Mathis LLP
Cuneo Kamand
Murata Manufacturing Co. Ltd.
Patel I B
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