Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-05-31
2002-09-03
Cuneo, Kamand (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S261000, C174S265000, C174S255000, C361S777000, C361S774000
Reexamination Certificate
active
06444925
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a press-fit pin connection checking method and system.
2. Description of the Related Art
In recent communications equipment, high-density packaging has proceeded in response to the demands for high performance and multi-functionality to devices to be packaged, so that an increase in number of printed wiring boards layered and a decrease in bonding area and conductor spacing are remarkably proceeding. A component mounting method is also changing from an insert mount technology (IMT) such that a lead is inserted into a through hole and is bonded by flow soldering to a surface mount technology (SMT) such that a component is mounted on a surface pattern and is bonded by reflow soldering, and the SMT is becoming mainstream. At present, the component mounting method is in the shift from the IMT to the SMT, and a printed circuit board (plug-in unit) using both the technologies as mixed is most dominating.
In such a recent trend, a connector component for connecting the printed circuit board to a back wiring board has also changed, and the shift from an insert mount device (IMD) to a surface mount device (SMD) as the connector component has been examined. However, a bonding force for each pin is reduced by adopting the SMT, and the connector component cannot endure a total pressure applied in connecting the printed circuit board and the back wiring board. To cope with this problem, a press-fit connector bonding technique (gastight bonding technique) of press-fitting a press-fit pin into a through hole has risen.
The press-fit connector bonding technique has such merits that the bonding force for each pin is high to ensure a strong holding force of the connector as a whole, that the flow soldering step as a main bonding method in the IMT can be omitted, that the shift to the SMT can be made smoothly, and that the connector is repairable. As seen from the connection between a plug-in unit and a back wiring board, it is considered that the press-fit connector bonding technique will become a dominating technique in the future connector bonding for communications equipment. However, although the IMT is being currently shifted to the SMT, there exist many IMDs that cannot support the SMT, and it is therefore difficult to completely shift the IMT to the SMT in the near future.
In recent communications equipment, not only the high-density packaging has proceeded, but also a signal transmission speed has been increased year by year. Accordingly, increasing a signal transmission speed between a plug-in unit (PIU) and a back wiring board (BWB) is also proceeding. The technique required for high-speed signal transmission includes the suppression of transmission loss, the suppression of reflected waves, and the unification of propagation delay. Accordingly, a connector structure supporting high-speed signal transmission includes a shielding structure, shortening the length of a press-fit pin, and equalizing the lengths of differential signal pair lines. A characteristic impedance is controlled by the shielding structure to suppress the transmission loss. The length of a press-fit pin is shortened to suppress the reflected waves. The lengths of differential signal pair lines are equalized to unify the propagation delay.
While a plug-in unit and a back wiring board are connected by a press-fit connector in general as described above, a plurality of press-fit pins are press-fitted into a plurality of through holes to thereby mount the press-fit connector on the back wiring board or the plug-in unit. Accordingly, it is necessary to check that the press-fit pins are completely press-fitted in the through holes. At present, whether or not the connection of the press-fit pins and the through holes after press-fitting the press-fit pins is acceptable is checked by only visual check for the plug-in unit and by visual check and electrical check in combination for the back wiring board.
FIG. 1
is a schematic sectional view for illustrating a plug-in unit checking method in the prior art. Reference numeral
2
denotes a plug-in unit having a plurality of through holes
4
, and reference numeral
6
denotes a press-fit connector having a plurality of press-fit pins
8
. The press-fit pins
8
of the press-fit connector
6
are press-fitted into the through holes
4
of the plug-in unit
2
to thereby mount the press-fit connector
6
on the plug-in unit
2
. In the conventional visual checking method, whether or not the connection of the press-fit pins
8
and the through holes
4
is acceptable is checked by seeing the through holes
4
from one side (back side) of the plug-in unit
2
opposite to the press-fit connector
6
after press-fitting the press-fit pins
8
into the through holes
4
and by determining whether or not the front ends of the press-fit pins
8
project from the back side of the plug-in unit
2
.
Referring to
FIG. 2
, there is shown a schematic sectional view for illustrating a back wiring board checking method in the prior art. Reference numeral
10
denotes a back wiring board having a plurality of through holes
12
, and reference numeral
14
denotes a press-fit connector having a plurality of press-fit pins
16
. The press-fit pins
16
of the press-fit connector
14
are press-fitted into the through holes
12
of the back wiring board
10
to thereby mount the press-fit connector
14
on the back wiring board
10
. The press-fit connector
6
on the PIU side is preliminarily mounted on a checking printed circuit board
18
. The press-fit connector
6
on the PIU side is engaged into the press-fit connector
14
on the BWB side to thereby electrically connect the checking printed circuit board
18
to the back wiring board
10
. The checking printed circuit board
18
has a plurality of conductor patterns respectively corresponding to the press-fit pins of the press-fit connector
6
and a plurality of output lands respectively formed at the front ends of the conductor patterns.
In the conventional electrical checking method for the press-fit pins
16
on the BWB side as shown in
FIG. 2
, two checking printed circuit boards
18
are electrically connected to the back wiring board
10
, and the output lands of the two checking printed circuit boards
18
are selectively connected to check the electrical continuity, thereby determining whether or not the press-fitted condition of the press-fit pins
16
is acceptable. The wiring in the back wiring board
10
is complicatedly connected to a plurality of plug-in units
2
. Accordingly, to check the connection of all the press-fit pins
16
without omission, a continuity check program is prepared for each design of the back wiring board
10
and the plug-in units
2
in combination, and the continuity check is performed in accordance with this program. The visual check for the back wiring board
10
is similar to that for the plug-in unit
2
as mentioned above with reference to FIG.
1
. That is, whether or not the connection of the press-fit pins
16
and the through holes
12
is acceptable is checked by determining whether or not the front ends of the press-fit pins
16
project from the back side of the back wiring board
10
.
FIGS. 3A
to
3
C are sectional views showing an acceptable mode and a defective mode. More specifically,
FIG. 3A
shows an acceptable mode, and
FIGS. 3B and 3C
show defective modes. The defective modes shown in
FIGS. 3B and 3C
can be detected by the visual check. However, the defective mode shown in
FIG. 3C
cannot be detected by the electrical check, because the press-fit pin
16
is in electrical continuity to the through hole
12
.
Although the visual check is low in efficiency and detection power to defective connection, all kinds of buckling of the press-fit pin
16
as shown in
FIGS. 3B and 3C
can be detected as detectable defective modes by the visual check. on the other hand, although the electrical check is high in efficiency, only the complete buckling of the press-fit pin
16
as shown in
FIG. 3B
s
Fukagawa Kazunari
Matsumoto Hideaki
Teshima Yasuhiro
Dinh Tuan
Katten Muchin Zavis & Rosenman
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