Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-03-29
2004-04-06
Talbott, David L. (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S255000, C174S260000, C174S261000, C174S264000, C361S760000, C361S792000, C361S767000, C361S772000, C257S737000, C257S778000, C257S779000
Reexamination Certificate
active
06717069
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a surface-mounting substrate for mounting thereon a part, such as a semiconductor device, and a structure comprising a substrate and a part surface-mounted thereon.
2. Description of the Related Art
As a substrate for mounting thereon a part, such as a semiconductor device, there have been provided a product having a laminate structure of an insulation layer(s) and a patterned wiring line layer(s) on at least a side of a core substrate.
Such a substrate is illustrated in
FIG. 20
, which is a plan view of a substrate for mounting a semiconductor device (not shown) by flip chip bonding, the substrate having connecting terminals
10
arranged on a surface of the substrate so as to be spaced from each other and to form an array of the terminals
10
.
FIG. 21
illustrates a construction of the laminate structure of electrical insulation layers and patterned wiring line layers provided on a core substrate
20
. The laminated structure comprises first and second inner wiring line layers
12
a
,
12
b
, and an outermost wiring line layer
12
, which are formed so as to have certain patterns. The first inner wiring line layer
12
a
is provided on a side of the core substrate
20
, and the second inner layer
12
b
and the outermost wiring layer
12
are separated from the first inner layer
24
a
and the second inner layer
24
b
by insulation layers
22
a
and
22
b
, respectively. The wiring lines in the adjacent layers are connected to each other by vias
12
a
,
12
b
which are formed in the respective insulation layers
22
a
,
22
b
. A through hole
26
is formed in the core substrate
20
, and effectively employed for substrates having connecting terminals arranged at a small pitch of, for instance, 100 micrometers or less.
The connecting terminal
10
is formed in an elongated shape, as clearly seen in FIG.
20
. The site of the terminal
10
, to which an electrode terminal of a semiconductor device (not shown) is to be bonded, is at the end portion of the terminal
10
(i.e., on the line X-X′ in the drawing). The reason why the connection terminal
10
is formed in an elongated shape is that variation in the amount of solder to be coated to the respective connecting terminals
10
must be restrained to reliably bond the electrode terminal of a semiconductor device to the connecting terminal
10
of the substrate.
The coating of the solder
14
to the surface of the connecting terminal
10
is carried out by a method in which a powder of solder is placed on the connecting terminal
10
, and flux is then applied to the solder, after which the solder is coated to the terminal
10
by a reflow process. The method of coating solder to a connecting terminal using a powder of solder is effectively employed for substrates having connecting terminals arranged at a small pitch of, for instance, 100 micrometers or less.
However, when the connecting terminals
10
are arranged with a smaller gap, such as about 30 micrometers, a problem that solder materials on adjacent terminals
10
form bridges when they are fused in a reflow process, resulting in short-circuit between the adjacent terminals
10
, arises.
FIG. 22
illustrates a
mounting substrate having a bridge structure
14
a
of solder materials on the adjacent connecting terminals
10
, which is formed during a reflow process. In conventional surface-mounting substrates, the side faces of the connecting terminal
10
are exposed, and the solder material
14
provided on the top surface of the terminal
10
can be coated not only to the top surface of the terminal
10
but also to the exposed side faces thereof during a reflow process. Short-circuits between the adjacent terminals
10
due to such bridge structures of solder materials tend to occur when the space between adjacent terminals
10
becomes smaller.
In addition, conventional surface-mounting substrates also have a problem that variation in the thicknesses (heights) of the connecting terminals
10
causes variation in the amounts of solder materials on the terminals
10
, which in turn causes variation in the heights of the solder materials after coated to the terminals
10
.
These problems cannot be overlooked in order to provide a miniaturized semiconductor product having an increased number of pins by which the product is to be mounted on a substrate.
Conventional surface-mounting substrates further have a problem that inner layers of patterned wiring lines in a build-up structure are designed based only on wiring schemes, line widths, and line gaps in the respective layers, without considering densities of lines in the respective layers, and, accordingly, the thickness of an insulation layer formed on a layer of wiring lines is varied from a region located on the region of wiring lines at a higher density to a region located on the region of wiring lines at a lower density, which results in poor planarity at the top surface of a product substrate. When flip chip bonding is used to mount a semiconductor device on a substrate, poor planarity at a region of the substrate on which the device is to be mounted gives rise to a problem of unsatisfactory bonding between the semiconductor device and the substrate.
SUMMARY OF THE INVENTION
An object of the invention is to solve the above problems by providing a substrate for surface-mounting a semiconductor device thereon, in which electrical short-circuits between connecting terminals due to bridging of solder materials coated to the terminals can be prevented, even when the connecting terminals are arranged at a very small distance, and variation in thicknesses of the solder materials due to variation in thickness (height) of the terminals can be also prevented, to thereby improve reliability of electrical connections in a structure comprising a substrate and a semiconductor device mounted thereon, and which substrate can also improve reliability of the mounting of semiconductor device by its surface having a good planarity for mounting the device thereon. It is also an object of the invention to provide a structure comprising such a substrate and a semiconductor device or the like mounted thereon.
According to the invention, there is provided a surface-mounting substrate for mounting thereon a part, such as a semiconductor device, which comprises a core substrate, a plurality of layers of patterned wiring lines, which are separated from each other by an insulation layer interposed therebetween, vias piercing through the insulation layer to connect the wiring lines at the layers adjacent to each other, and a layer of connecting terminals to mount a part on the surface-mounting substrate, each of the connecting terminals connecting with the wiring line at the outermost layer of wiring lines, wherein the connecting terminal is filled in an outermost insulation layer provided at the surface of the surface-mounting substrate, and has a surface exposed at substantially the same level as the level of the surface of the outermost insulation layer.
The surface-mounting substrate of the invention may be provided on the surface of each of the connecting terminals with a conductor material, such as a solder material, bonded thereto.
In an embodiment of the surface-mounting substrate according to the invention, the layer of the connecting terminals is separated from the outermost layer of wiring lines by an insulation layer interposed therebetween, and the connecting terminal is connected with the wiring line at the outermost layer of wiring lines through a via piercing through the insulation layer separating the layer of the connecting terminals from the outermost layer of wiring lines.
In another embodiment of the surface-mounting substrate according to the invention, the connecting terminal is directly connected with the wiring line at the outermost layer of wiring lines located under the layer of connecting terminals.
In a further embodiment of the surface-mounting substrate according to the invention, the connecting terminal is directly connected
Patel I B
Paul & Paul
Shinko Electric Industries Co. Ltd.
Talbott David L.
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