Connecting terminal for electromagnetic shield

An improved connecting terminal for an electromagnetic shield is provided for use with a printed circuit board. The printed circuit board is contained in a shielded casing having shielding walls to define compartments. The connecting terminal makes an electric connection between the ground pattern, the shielded inside and shielding walls of the shielded casing, thereby preventing an electromagnetic field from interfering with surrounding electric circuits. The connecting terminal comprises an elongated base strip having an undersurface to be soldered to a selected portion of the ground pattern and a pair of inwardly directed contact arms integrally connected to the opposite ends of the elongated base strip. Each contact arm makes contact with the shielded inside and shielding walls of the casing.

BACKGROUND OF THE INVENTION 
The present invention relates generally to electromagnetic shielding for 
preventing interference on surrounding electric circuits or apparatus by 
an electromagnetic field. The present invention is more particularly 
related to a connecting terminal or member for connecting a ground pattern 
formed on a printed circuit board to an electromagnetic shield. 
DESCRIPTION OF THE PRIOR ART 
Electromagnetic fields are generated by a high-frequency oscillator which 
is mounted on a printed circuit board. The printed circuit board and the 
high-frequency oscillator are contained in a shielded casing to contain 
the electromagnetic field. For example, as is well known, portable 
telephones are equipped with means to prevent the electromagnetic field 
generated by the high-frequency oscillator from interfering with 
surrounding electric circuits. 
Specifically, the high-frequency oscillator is formed on the printed 
circuit board and contained in a selected compartment of a casing on the 
printed circuit board. The compartment is defined by surrounding walls. By 
plating the inside of the casing and the walls with nickel or copper and 
electrically connecting them to the ground pattern of the printed circuit 
board, the inside of the casing and the walls function as electromagnetic 
barriers. The casing and the walls are electrically connected to the 
ground pattern by connecting terminals or members which are called 
"connecting terminals for electromagnetic shield." 
One example of such a connecting terminal for an electromagnetic shield is 
shown in FIGS. 14 and 15. A high-frequency oscillator 47 is contained in a 
selected compartment of a casing 41 defined by surrounding walls 43. An 
inside 42 of the casing 41 and surrounding walls 43 are plated with nickel 
or copper. The compartment is electrically connected to the ground pattern 
46 of the printed circuit board 45. Necessary electric connections are 
made by connecting terminals 31. Each terminal 31 comprises a bent-metal 
strip with an extended base 32 and a contact arm 33 integrally connected 
to one end of the extended base 32. The extended base 32 is to be soldered 
to a selected portion of the ground pattern 46, thus allowing the contact 
arm 33 to contact the plated inside 42 of the casing 41. Sufficient-metal 
strips are prepared and soldered to selected portions of the ground 
pattern 46 of the printed circuit board 45. 
Advantageously, this connecting terminal 31 is small, simple in shape and 
structure, and can be used irrespective of the size of the ground pattern. 
However, disadvantageously, the connecting terminal 31 has a contact arm 
on one end. Therefore, the center of gravity is not at the center of the 
elongated base 32 at which the connecting terminal 31 is to be soldered to 
a selected portion of the ground pattern 46. While soldering the 
connecting terminal 31 to the ground pattern 46, it can take an undesired 
or incorrect posture relative to the ground pattern due to the surface 
tension of soldering material. Also, the terminal 31 provides only a small 
space to which negative pressure can be applied for an automatic 
positioning device to suckingly hold the connecting terminal 31. Sometimes 
if the negative pressure is applied to the contact arm 33, it can become 
deformed while the connecting terminal is suckingly held during placement. 
Another example of such a connecting terminal 31' is shown in FIGS. 16 an 
17. The high-frequency oscillator 47 is mounted on the printed circuit 
board 45. The connecting terminal 31' comprises a U-shaped channel to 
receive the edge of the selected shielding wall 43, which stands upright 
form the shielded inside 42 of the casing 41. As seen from FIG. 17, the 
connecting terminal 31' mounts a selected shielding wall 43 with opposite 
sides 32' applied to corresponding opposite sides of the wall 43. The 
connecting terminal 31' has a plurality of contact arms 33' cut and bent 
up from a top surface for contacting selected portions of the ground 
pattern 46 on the printed circuit board 45. When the shielded top cover is 
applied to the casing 41, the contact arms 33' of the connecting terminal 
31' will contact the ground pattern 46 of the printed circuit board 45. 
The connecting terminal 31' assures correct positioning relative to the 
ground pattern 46, and reliable connection between the ground pattern 46 
and the shielded inside 42 and wall 43 of the casing 41. The connecting 
terminal 31', however, must be designed and made to meet individual size 
requirements for customized use, and accordingly the cost involved will 
increase. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a connecting terminal for 
an electromagnetic shield which is free of the defects described above in 
that it facilitates exact soldering to the ground pattern of a printed 
circuit board and permits use with any type or size apparatus. 
To attain this object, the present invention comprises a connecting 
terminal for connecting an electromagnetic shield to a ground pattern 
formed on a printed circuit board. The connecting terminal comprises an 
elongated base strip undersurface to be soldered to a selected portion of 
the ground pattern and a pair of inwardly directed contact arms integrally 
connected to the opposite ends of the elongated base strip. Each contact 
arm has a contact for contacting the electromagnetic shield. 
The connecting terminal is appropriate for use with a printed circuit board 
which mounts a high-frequency oscillator. The printed circuit board is 
contained in a shielded casing having shielding walls to define 
compartments and a shielded inside. The connecting terminal makes electric 
connections between the ground pattern, the shielded inside and the 
shielding walls of the shielded casing, thereby preventing interference of 
the electromagnetic field produced by the high-frequency oscillator with 
surrounding electric circuits. 
The connecting terminal is improved in that the pair of contact arms are 
integrally connected to opposite ends of the elongated base strip and are 
directed inwardly. Preferably, the contact arms are inclined with respect 
to the base strip and converge toward each other. It is also preferable 
that the connecting terminal be symmetrically shaped especially with 
respect to the base strip. Each contact arm makes contact with the 
shielded inside and shielding walls of the shielded casing. 
The center of gravity of the connecting terminal corresponds to the 
geometric or physical center of the connecting terminal. The elongated 
base strip of the connecting terminal and, therefore, the connecting 
terminal can be put in correct position by the self-aligning effect caused 
by the surface tension of the molten solder while the connecting terminal 
is soldered to the ground pattern of the printed circuit board. 
Consequently, the accuracy with which the connecting terminal can be 
soldered to the ground pattern is substantially improved. The necessary 
shielding can be effected by soldering a sufficient number of electric 
connecting terminals to the ground pattern of the printed circuit board. 
The connecting terminal may further comprise a shape retainer filled in the 
space defined by the elongated base strip and the inclined contact arms. A 
negative pressure may be applied to a generally planar top surface of the 
elongated base strip or of the shape retainer to suckingly hold the 
connecting terminal during automatic application of the connecting 
terminal to the selected portion of the ground pattern. The connecting 
terminal is generally symmetrical with respect to the planar surface. 
Other objects and advantages of the present invention will be better 
understood from the following description of electric connecting terminals 
according to preferred embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 show a connecting terminal 1 for an electromagnetic shield 
according to the first embodiment of the present invention. The connecting 
terminal is to be used on a printed circuit board 15 having a ground 
pattern 16 formed thereon as shown in FIG. 12. The connecting terminal 1 
is especially useful with a printed circuit board 15 which mounts a 
high-frequency oscillator 17. The printed circuit board 15 is contained in 
a shielded casing 11 having a shielded inside 12 and shielded walls 13 to 
define compartments. The shielding of the inside 12 and the walls 13 is 
effected by respectively plating the inside and walls of the casing with 
nickel, copper or other suitable material. The connecting terminal 1 for 
the electromagnetic shield is designed to make required electric 
connections between the ground pattern 16, the shielded inside 12 and 
shielded walls 13 of the casing 11, thereby preventing the electromagnetic 
field produced by the high-frequency oscillator 17 from interfering with 
surrounding electric circuits. 
The connecting terminal 1 comprises an elongated base strip 2 having an 
undersurface 7 which is to be soldered to a selected portion of the ground 
pattern 16. A pair of inwardly directed contact arms 3 are integrally 
connected to the opposite ends of the elongated base strip 2. Preferably, 
the shape of the connecting terminal 1 is symmetrical. Most preferably, 
the connecting terminal is shaped symmetrically with respect to the base 
strip 2. The pair of contact arms 3 are preferably inclined with respect 
to the base strip 2 and converge toward each other. Each contact arm 3 has 
a contact 4 to make contact with the shielded inside 12 and/or shielded 
walls 13 of the casing 11. The base strip 2 includes dimples 2a. A 
plurality of connecting terminals 1 are applied as necessary to selected 
portions of the ground pattern 16 to make sufficient electric connections 
between the ground pattern 16, the shielded inside 12 and the walls 13 of 
the casing 11. 
The connecting terminal 1 can be sucked and held by applying a negative 
pressure to the inner surface 8 of the elongated base strip 2 to 
automatically apply the connecting terminal 1 to a selected portion of the 
ground pattern 16. A sucking area 6 is generally planar and located at the 
center of the elongated base strip 2. The generally planar sucking area 6 
facilitates the exact positioning and soldering of the connecting terminal 
1 to a selected portion of the ground pattern 16. Such exact positioning 
and soldering is permitted by the self-aligning effect, which is caused by 
the preferred symmetrical shape of the connecting terminal 1. The 
connecting terminal 1 is most preferably symmetrical relative to the 
sucking area 6. 
Referring to FIGS. 3, 4 and 5, an electric connecting terminal 1' according 
to a second embodiment has a shape retainer 5' filled in the space S' 
defined by the elongated base strip 2' and the inclined contact arms 3'. 
The shape retainer 5' prevents the deforming of the contact arms 3' during 
application of the connecting terminal 1' to ground pattern 16. The 
connecting terminal 1' can be sucked and held at the generally planar top 
surface 10' of the shape retainer 5' when sucking nozzle (not shown) 
applies a negative pressure to surface 10'. Consequently, connecting 
terminal 1' may be automatically applied to a selected portion of the 
ground pattern 16. 
The shape retainer 5' may be made of nylon, polyalkylene or any other 
suitable insulating material. The elongated base strip 2' has at least one 
and preferably a pair of inverted "V"-shaped retainers 9' integrally 
connected at opposite sides to the base strip 2' for engaging the interior 
of the shape retainer 5' and holding it in the space S defined by the 
elongated base strip 2' and the inclined contact arms 3'. As shown in FIG. 
5, the retainers 9' are integrally connected to a raised portion 2b' of 
the base strip. 
Referring to FIGS. 6, 7 and 8, an electric connecting terminal 1" according 
to a third embodiment is different from the second embodiment of FIGS. 3, 
4 and 5 only in that the contact arms 3" extend straight, thus providing 
unbent contacts 4" at free ends of the contact arms 3". This permits the 
folding of the contact arms 3" on the top surface 10" of the shape 
retainer 5" without leaving any remaining space therebetween. This 
structure reduces the space which the electric terminal 1" occupies. The 
base strip 2" includes a recess 9". 
Referring to FIGS. 9, 10 and 11, an electric connecting terminal 1'" 
according to a fourth embodiment is designed to assure good contact with 
the shielded inside 12 or shielded walls 13 of the casing and, at the same 
time, further minimize the remaining space S'" between the contact arms 
3'" and the top surface 10'" of the shape retainer 5'". The connecting 
terminal 1"" has two inclined contact arms 3'", each having a bent contact 
4'" to assure good contact with the shielded inside 12 or shielded walls 
13 of the casing 11 due to an enlarge contact area. The shape retainer 5'" 
has recesses 18'" notched on the top surface 10'", thereby permitting the 
folding of the contact arms 3'" on the top surface 10'" of the shape 
retainer 5'" without leaving any space S'" remaining therebetween. This 
structure of connecting terminals 1'" accordingly reduces the vertical 
height of the connecting terminal 1'" in use. A generally planar portion 
6'" is provided between recesses 18'" for sucking placement purposes. 
FIG. 12 shows how the electric connecting terminals 1'" of the present 
invention can be used. As seen from FIG. 12, the shielding walls 13 have 
notches 14 intervally spaced from each other. The electric connecting 
terminals 1'", which are soldered to selected portions of the ground 
pattern 16, fit in the notches 14 when the cover plate is put on the 
casing 11, thus shielding surrounding electrical components from the 
electromagnetic field emitted by the high-frequency oscillator 17. 
The connection of the connecting terminal 1'" between the ground pattern 16 
and the shielded wall 13 is shown in FIG. 13. The invasion of the bent 
contacts 4'" into the notched recesses 18'" minimizes the space remaining 
between the ground pattern 16 and the shielded wall 13. The shape retainer 
5'" has the effect of keeping the electric connecting terminal 1'" from 
deforming from its exact, original shape, thereby assuring good contact 
between the ground pattern 16 and the shielded wall 13. 
It will be understood that the invention may be embodied in other specific 
forms without departing from the spirit or central characteristics 
thereof. The present examples and embodiments, therefore, are to be 
considered in all respects as illustrative and not restrictive, and the 
invention is not to be limited to the details given herein.