Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1999-07-23
2002-09-03
Cuneo, Kamand (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S266000, C174S260000, C361S767000
Reexamination Certificate
active
06444924
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a printed wiring board and its manufacturing method, and particularly relates to joining of the printed wiring board and a mother board.
2. Background Art
For example, as shown in
FIG. 27
, there is conventionally a printed wiring board having a circuit substrate
96
having a mounting portion
97
for mounting an electronic part
970
thereto, a conductor circuit
95
arranged on a surface of the circuit substrate
96
and also arranged within this circuit substrate
96
, and a through hole
93
extending through the circuit substrate
96
.
The electronic part
970
is electrically connected to the conductor circuit
95
by a bonding wire
971
. As shown in
FIGS. 27 and 28
, a pad
92
for mounting a ball thereto is arranged at an end tip of the conductor circuit
95
on a rear face side of the circuit substrate
96
. A soldering ball
91
is joined to a surface of this pad
92
.
The above conventional printed wiring board
9
is joined to an opposite party pad
981
arranged on the surface of a mother board
98
by heating and melting the above soldering ball
91
.
The printed wiring board fulfills a function for transmitting electric information of the electric part to a partner member such as the mother board, etc. by the above structure.
However, the above conventional printed wiring board has the following problems. Namely, as shown in
FIGS. 27 and 28
, the printed wiring board
9
is fixedly joined onto the mother board
98
by the soldering ball
91
. Therefore, the pad
92
for mounting the soldering ball must be arranged in the printed wiring board
9
.
Further, it is necessary to arrange the conductor circuit
95
between the pad
92
for mounting the ball and the through hole
93
and electrically connect the pad
92
and the through hole
92
. Therefore, as shown in
FIG. 28
, the rear face side of the circuit substrate
96
is occupied by the pad
92
for mounting the ball and the conductor circuit
95
connected to the through hole
93
as well as the through hole
93
. Therefore, it is difficult to secure a sufficient space for arranging another conductor circuit on the rear face side of the circuit substrate
96
so that high density wiring is prevented.
When the soldering ball
91
is joined to the opposite party pad
981
, it is difficult to control a melting state of the soldering ball
91
. Namely, the soldering ball
91
is melted and joined by heating this soldering ball
91
to the opposite party pad
981
on the mother board
98
. At this time, the melting state of the soldering ball
91
is different in accordance with elements such as heating temperature, applied pressure, soldering composition, etc. Therefore, as shown in
FIG. 27
, there is a case in which a melting degree of the soldering ball
91
on one side (e.g., a right-hand side of
FIG. 27
) of the printed wiring board
9
is increased and the melting degree of the soldering ball
91
on the other side (e.g., a left-hand side of
FIG. 27
) is decreased. In this case, the printed wiring board
9
is slantingly joined to the mother board
98
. Accordingly, it is difficult to join the conventional printed wiring board
9
to the mother board
98
in parallel with this mother board
98
.
In addition, as shown in
FIG. 29
, the pad
92
for mounting the ball and joining the soldering ball
91
is generally covered with a gold plating film
921
. A gold component of the gold plating film
921
permeates the interior of the soldering ball
91
in heating and melting the soldering ball
91
, and forms an intermediate layer
90
between the metallic plating film
921
and the soldering ball
91
.
This intermediate layer
90
has a property deteriorated by heat. Therefore, when the intermediate layer
90
is formed, joining strength of the pad
92
for mounting the ball and the soldering ball
91
is reduced until 1.0 to 1.4 kg/cm
2
.
Further, the intermediate layer
90
is increased in thickness as the gold plating film
921
covering the pad
92
for mounting ball is increased in thickness. Therefore, w[W]hen the thickness of the gold plating film
921
is increased, the joining strength of the pad
92
for mounting the ball and the soldering ball
91
is further reduced. Accordingly, there is a case in which the joining strength is reduced to a joining strength equal to or smaller than 1.0 kg/cm
2
.
With consideration of such conventional problems, the present invention provides a printed wiring board able to perform high density wiring on a substrate surface and able to be joined to a partner member in parallel with this partner member and having an excellent joining strength, and also provides a manufacturing method of the printed wiring board.
BRIEF SUMMARY OF THE INVENTION
The present invention resides in a printed wiring board having a circuit substrate. The printed wiring board has a conductor circuit and a through hole. A joining pin is inserted and positioned into the through hole. The printed wiring board can be characterized in that the joining pin is manufactured by using a material unmelted at a heating temperature in joining the joining pin to an opposite party pad. The joining pin has a joining head portion which spans a greater diameter than an opening diameter of the through hole. The joining pin also forms and provides a joining portion for joining and connection to the opposite party pad. The joining pin further has a leg portion which extends from the joining head portion. The leg portion has a smaller diameter than the through hole and the joining head portion. Desirably, the leg portion is inserted and positioned into the through hole and is joined to the through hole by a conductive material. The joining head portion can comprise an enlarged end section that provides an enlarged end of the joining portion, while the leg portion can comprise a smaller diameter end section that provides a smaller end of the joining portion.
An operation and effects of the present invention will now be explained.
In the printed wiring board of the present invention, the joining pin is inserted into the through hole. The joining pin has the joining head portion for joining the joining pin to the opposite party pad. Therefore, the through hole and the opposite party pad can be electrically connected to each other by the joining pin by joining the joining head portion to the opposite party pad.
Further, since the through hole and the opposite party pad can be connected to each other by the joining pin in a facing state, as in the conventional case, it is unnecessary to arrange a pad for mounting a soldering ball in addition to the through hole. With this invention, it is also unnecessary to form a conductor circuit for connecting the through hole and the pad for mounting the ball as in the conventional case. Therefore, in the invention a surplus space is formed on a surface of the circuit substrate in a portion except for an opening portion of the through hole. Accordingly, a high density wiring structure can be realized on the substrate surface by forming many other conductor circuits in this space.
The joining pin is manufactured by using a material unmelted at the heating temperature to join the joining pin to the opposite party pad. Therefore, a constant height of the joining head portion is maintained without melting deformation in the above joining. Accordingly, the joining head portion functions as a strut of the printed wiring board at the joining time.
Such a joining head portion functioning as a strut spans a greater diameter than the opening diameter of the through hole. Therefore, when the leg portion of the joining pin is inserted into the through hole, the joining head portion is engaged with the opening portion of the through hole and does not enter the interior of the through hole. Accordingly, the joining head portion can be projected by the same height from a surface of the circuit substrate.
Therefore, when the joining head portion and the opposite party pad are joined to each other, the
Asano Kouji
Ishida Naoto
LandOfFree
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