Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Reexamination Certificate
2001-09-13
2002-10-15
Talbott, David L. (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
C174S267000
Reexamination Certificate
active
06465738
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a mounting structure of a grounding terminal on a printed circuit board, wherein the printed circuit board is grounded to a grounding conductor by the grounding terminal, which is mounted on the surface of the printed circuit board by reflow soldering, contacting with and being pressed against the grounding conductor.
BACKGROUND OF THE INVENTION
Conventionally, a mounting structure of a grounding terminal on a printed circuit board for grounding the printed circuit board, in which a grounding terminal is mounted on the surface of the printed circuit board and pressed against a grounding conductor, is known.
FIG. 5
is a plan view of such a conventional grounding structure and
FIG. 6
is a longitudinal sectional view along line VI—VI of FIG.
5
. As shown in
FIG. 6
, the grounding terminal
100
is soldered to the conductive pattern
201
on the printed circuit board
200
with solder
202
. Then, the grounding terminal
100
is pressed against the grounding conductor, thereby grounding the printed circuit board
200
. To illustrate the structure simply, the grounding conductor
300
is not shown in FIG.
5
.
The grounding terminal
100
is formed by bending a strip-like thin sheet metal member with a width of &agr;, for example, 0.8 mm, and has a joint part
101
with a longitudinal length of &bgr;, for example, 3.5 mm. One surface of the joint part
101
is a joint surface
101
a
which is soldered to the conductive pattern
201
on the printed circuit board
200
. Also, the grounding terminal has a contact part
102
which adjoins the joint part
101
and is bent in the upper direction. An outer surface
102
a
of the contact part
102
is pressed against the grounding conductor
300
. As the result of load by the grounding conductor, the contact part
102
is elastically deformed around the bending area &ggr;, and is pressed against the grounding conductor
300
by restoring force caused by the elastic deformation, thereby electrically connecting the printed circuit board
200
and the grounding conductor
300
properly.
When the aforementioned grounding terminal is soldered to the printed circuit board, reflow soldering is usually employed. Reflow soldering comprises the steps of previously applying a suitable amount of solder to the point to be jointed, fixing the grounding terminal to the point temporarily, and melting the solder by using an external heat source, and all these steps are performed automatically. An advantage of reflow soldering is that by allowing a suitable amount of solder to be applied, it prevents solder from being placed at inappropriate points of the printed circuit board, and thus prevents improper soldering such as a defective bridge. Also, there is another advantage that in the case where a relatively small mounting member as aforementioned is to be mounted, self-alignment effect can be expected. That is, even if the temporarily fixed member deviates a little from the conductive pattern of the printed circuit board, the member is moved to the right position by surface tension of the melted solder.
However, there are the following problems in reflow soldering of the above conventional grounding terminal:
(1) The grounding terminal
100
is moved to the right position by self-alignment effect by surface tension of the melted solder, and then is finally positioned by hardening of the melted solder. During the hardening process of the solder, the grounding terminal
100
sometimes deviates from the right position on the printed circuit board
200
because of, for example, vibration. This results from the fact that since the amount of the solder is large, the thermal capacity of the solder is large, and thus it takes time for the solder to harden. If the grounding terminal
100
deviates from the right position, the contact part
102
may not be pressed against the grounding conductor
300
in an appropriate state. Furthermore, the requirements of highly precise mounting performance for allowing high density mounting are not satisfied.
(2) When the temperature of the grounding terminal
100
reaches the melting point of the solder earlier than that of the conductive pattern
201
of the printed circuit board
200
, what is called wicking phenomenon occurs, by which the solder
202
is sucked up along the bending area &ggr; forming the center of elastic deformation of the contact part
102
shown in FIG.
6
. In this case, since the solder
202
adheres around the bending area &ggr;, the elastic deformation performance of the contact part
102
is lowered, and thus it is sometimes impossible to attain elastic deformation enough for the contact part
102
to be pressed against the grounding conductor
300
and conduct electricity to the grounding conductor
300
.
SUMMARY OF THE INVENTION
Wherefore, an object of the invention is to provide a mounting structure of a ground terminal on a printed circuit board formed by soldering, wherein by solving the problems caused by reflow soldering of the grounding terminal to the printed circuit board, the printed circuit board is properly grounded to a grounding conductor.
Another object of the invention is to provide a grounding terminal used for the above mounting structure.
In order to achieve the above objects, there is provided a grounding terminal mounted on a printed circuit board which is able to have contact with a grounding conductor, the grounding terminal comprising: a joint part having a plurality of joint surfaces which are to be soldered to a conductive pattern on the printed circuit board; a contact part extending from the joint part through a bending area bent in the opposite direction of the joint surfaces, and arranged to be able to have contact with the grounding conductor, which is elastically deformed upon being pressed by the grounding conductor; and at least one of the contact surfaces of the joint part having a smaller surface area than those of the other contact surfaces.
Also, there is provided a mounting structure in which a grounding terminal able to have contact with a grounding conductor is mounted on a printed circuit board, the grounding terminal comprising: a joint part having a plurality of joint surfaces which are to be soldered to a conductive pattern on the printed circuit board; a contact part extending from the joint part through a bending area bent in the opposite direction of the joint surfaces, and arranged to be able to have contact with the grounding conductor, which is elastically deformed upon being pressed by the grounding conductor; at least one of the contact surfaces of the joint part having a smaller surface area than those of the other contact surfaces; and the grounding terminal being mounted on the printed circuit board by reflow soldering, using an amount of solder corresponding to the surface area of each joint surface.
REFERENCES:
patent: 3504095 (1970-03-01), Roberson et al.
patent: 4422128 (1983-12-01), Zurlinden et al.
patent: 4679889 (1987-07-01), Seidler
patent: 5029254 (1991-07-01), Stickney
patent: 5441429 (1995-08-01), Seidler
patent: 5749741 (1998-05-01), Bellas et al.
patent: 6300579 (2001-10-01), Yumi
patent: 6303874 (2001-10-01), Muramatsu
patent: 58-53372 (1983-04-01), None
patent: 62-195978 (1987-12-01), None
Davis & Bujold P.L.L.C.
Kitigawa Industries Co., Ltd.
Norris Jeremy
Talbott David L.
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