Electrical connector for printed circuit boards

Contacts fabricated from a thin metal sheet by stamping in the form of a lead frame are used as U-shaped contact assemblies 30 which are straddled over and secured to side walls 22, 23 of the insulating housing 20 or are molded as an integral part thereof. Due to the fact that a gap G is formed between the outer surface 36 of contacts 31 of the contact assembly 30 and outside surface of side walls 22, 23 of the insulating housing 20, the connector 10 can move in a lateral direction relative to the printed circuit board 50.

FIELD OF THE INVENTION 
This invention relates to electrical connectors and more particularly to 
connectors mounted on printed circuit boards. 
BACKGROUND OF THE INVENTION 
Electrical connectors are devices providing for connection between 
conducting objects, and a number of devices of various configurations and 
sizes for this purpose were offered in the art. One type of electrical 
connector is designed specifically for the mounting on printed circuit 
board by soldering. Such connectors usually consist of a plug (male) 
connector and a receptacle (female) connector, and they interconnect 
associated circuits of two parallel printed circuit boards. With a general 
trend toward reduction of electronic devices in size, the space between 
printed circuit boards is being reduced at a fast pace, and in many cases 
it can be as little as a few millimeters. 
Example of connectors for printed circuit boards can be found in U.S. Pat. 
No. 5,224,866; Japanese Utility Model Disclosure Hei 3 (1991)-126389 and 
Japanese Patent Disclosure Hei 4 (1992)-43579. Such conventional 
connectors for printed circuit boards have a number of flat contacts 
intended for the connection by means of surface mounting technology (SMT) 
to contact pads of two parallel printed circuit boards. Contacts of a 
connector mounted on one of the printed circuit boards are designed so 
that they have relatively long effective length in order to be able to 
provide sufficient contact pressure (normal force) developed by the 
spring-loaded design of the contacts against contacts of the mating 
connector. Such an arrangement makes it possible to implement connectors 
for printed circuit boards having a high density of contacts (up to 0.5 mm 
pitch). 
However, elasticity of the contacts made by stamping from a resilient metal 
sheet is rather limited. It is especially difficult to achieve sufficient 
elasticity of contacts in portable communications devices such as personal 
handy phones (PHS) in which the gap between boards can be as little as a 
few millimeters while the component density is very high. In addition, in 
the event of misalignment between two printed circuit boards, when the 
connectors themselves are not exactly aligned with each other, an attempt 
to forcibly join connectors can result in damage of deformation of the 
connectors or their contacts. 
A method to handle misalignment between two boards is offered in U.S. Pat. 
No. 5,501,663 or in Japanese Patent Disclosure No. Hei 4 (1992)-370677. 
This method consists in making at least one housing of two sections 
allowing for certain flexibility due to contacts made in a zigzag 
configuration, thus increasing their effective length. However, in order 
to achieve the flexibility, it is necessary to increase physical 
dimensions of the connector, thus diminishing its suitability for 
small-size high-density applications. 
Another problem observed in high-density electrical connectors is related 
to the edges of the contacts that are fabricated, as mentioned above, by 
stamping from resilient metal sheet material and that become contacting 
surfaces with the mating contacts. The point is that the smoothness of the 
edge surfaces obtained by shearing is inferior to the face surface 
produced by rolling, thus making it difficult to obtain stable and 
reliable electrical connections. 
In order to solve the problem related to poor quality of the contacting 
surfaces, it was offered to cut contacts from a very thin metal sheet, 
bend them to a U-shaped configuration and place them over and around posts 
of the insulating housing so that the rolled surface becomes the 
contacting surface (Japanese Patent Disclosure Hei 3 (1991)-45873). 
Another proposed solution concerned contacts consisting of two arms 
originating from a flat base that are twisted 90.degree., thus providing a 
relatively wide surface of contact (for example, see Japanese Patent 
Disclosure Hei 3 (1991) -70350). 
However, solutions in which such contacts with rolled surfaces as the 
contacting surfaces are used can be offered only for relatively large 
connectors with a low or medium density of contacts (with a pitch over 1 
mm), and can not be applied to small-size high-density connectors. 
SUMMARY OF THE INVENTION 
This invention concerns high reliability electrical connectors for printed 
circuit boards which are arranged a few millimeters apart in high density 
mounting applications which have sufficient flexibility to absorb slight 
misalignment between mating connectors. 
This invention also has a purpose to make it possible to offer miniature 
connectors for printed circuit boards which can be manufactured in 
quantities at a relatively low cost. 
An electrical connector for printed circuit boards according to the present 
invention has a plurality of contacts mounted in a housing each having a 
board-connecting section intended for the soldering to the printed board 
and a contact section intended for the forming of a connection with a 
contact of the mating connector. A characteristic feature thereof is that 
the contacts are formed from a U-shaped thin conductive metal sheet and 
arranged in such a manner that there is a gap between the outer surface of 
the housing and intermediate sections of the contacts, thus allowing the 
connector to move incrementally within certain limits due to such a 
configuration of the contacts. 
Another characteristic feature of the electrical connector according to 
this invention is that the contacts are fixed by insulating strips located 
near both ends, and their middle section is bent in a U-shaped 
configuration. When they are mounted on the housing, they provide for a 
certain degree of movement relative to the printed circuit board. 
In a preferred embodiment, the contacts are made from very thin metal sheet 
material (a thickness of about 0.05 mm) using stamping and other 
manufacturing techniques and arranged at a pitch of 0.5 mm. Contact 
surfaces of the sections forming the connections with mating contacts and 
the surfaces joined to the contact pads of the printed circuit board, are 
smooth rolled surfaces, which assures reliable connections. At the same 
time, due to the fact that the contacts are extremely thin, they can move 
within the space provided in the outer surface of the housing. Therefore, 
connectors can be joined together even if there is a shift-type or 
twist-type misalignment between two printed circuit boards.

Electrical connector 10 of FIG. 1 consists of an insulating housing 20 and 
two rows of contact assemblies 30. A pair of metal fasteners 40 is for the 
attachment of the insulating housing 20 to a printed circuit board 50 
(FIG. 3). Insulating housing 20 has an elongated rectangular 
configuration. In the center, cavity 21 is provided for the insertion of 
the complementary section of the mating connector 100 (FIG. 3). The 
housing has side walls 22, 23 located at both sides and a bottom 24. At 
both ends of the housing, end sections 27, 28 are provided with openings 
25, 26 to accommodate fasteners 40. 
Assemblies 30 of U-shaped contacts are secured in arrays in two rows at 
side walls 22, 23 along the long sides of the insulating housing 20. 
Contact assemblies 30 have contact sections 35 intended for the forming of 
connections with contacts of mating connector 100, that are located inside 
cavity 21 of insulating housing 20, and intermediate sections 36 that 
extend freely along the outer surfaces of side walls 22, 23 of the 
insulating housing. Free ends of intermediate sections 36 are bent 
outwardly at right angles coplanar with the board-mounting face of the 
housing to form board-connecting portions 37 that are soldered to contact 
pads of the board. 
In the preferred embodiment, the contact assemblies are made of gold plated 
copper alloy of the thickness of 0.05 mm and are arranged at a pitch of 
0.5 mm. It is a difficult task to fabricate contacts from extremely thin 
metal sheet material, arrange them at a uniform intervals and prevent them 
from shorting during subsequent handling. 
Therefore, another specific feature of the preferred embodiment of this 
invention is that a number of contacts are arrayed in assemblies 30 in 
order to maintain the alignment of a plurality of highly elastic contacts. 
Below, we will explain the method of fabrication and the design of contact 
assemblies 30 using FIG. 4 for depicting a portion thereof. 
At the beginning, a plurality of contacts 31 constituting contact assembly 
30 are made in the form of a carrier strip in which contacts 31 are 
attached at one end to carrier 32, at a pitch of 0.5 mm for example. 
Across contacts 31 attached to the carrier strip, are formed a first strip 
33 and a second strip 34 made of a thin insulating material preferably by 
the known method of insert molding. First strip 33 is relatively narrow, 
is located near carrier 32 of contacts 31, and is molded so that contacts 
31 are embedded approximately in the center of the strip. Relatively wide 
(for example, about 1.5 mm) second strip 34 is molded at the free ends of 
contacts 31 constituting sections forming connections with contacts of the 
mating connector so that the surface of the contact sections 35 is 
exposed. The middle or intermediate section of the contacts 31 located 
between the first strip 33 and the second strip 34, is bent to form a 
U-shaped configuration which straddles side walls 22, 23 of housing 20 as 
shown in FIG. 1. As one can see from FIGS. 1 and 3, contact assemblies 30 
are mounted in such a manner that the second strip 34 is located inside 
cavity 21 of housing 20, that is, on the inside surfaces of side walls 22, 
23 and the first strip 33 is located on the outer surface, and that the 
exposed contact sections 35 of contacts 31 are facing inside cavity 21 
(that is, away from the internal surfaces of side walls 22, 23). 
The carrier 32 of contacts 31 of contact assemblies 30 is cut off prior to 
the their mounting in housing 20. The cut ends of contacts 31 are bent at 
right angles to form soldering sections 37 which are soldered to the 
contact pads of the printed circuit board 50. As can be seen from FIG. 3, 
the intermediate portions 36 of contacts 31 of contact assemblies 30 
running along the outer surfaces of side walls 22, 23 do not adjoin the 
walls but are spaced a small selected distance outwardly therefrom. 
Instead, they form a gap G therewith, and since contacts 31 are made of a 
very thin metal sheet, connector 10 can slightly move in the right-to-left 
direction relative to printed circuit board 50. 
Contact assemblies 30 can be fixed to housing 20 by pressing the second 
strips 34 of contact assemblies 30 into grooves 29 formed on both sides of 
cavity 21 of housing 20. If necessary, it is possible to form grooves 
corresponding to positions of each contact on the end surface of side 
walls 22, 23 of housing 20 (the upper surface in FIG. 1), and contacts 31 
with formed barbs can be pressed into such grooves. 
The purpose of fasteners 40 is to secure connector 10 to printed circuit 
board 50 after the soldering sections 37 were joined to the contact pads 
of the printed circuit board by means of SMT (reflow technique) in order 
to reinforce its attachment thereto against repetitive insertions and 
removals. When plug section 112 of mating connector 100 is inserted in 
cavity 21 of the housing of connector 10 with an excessive force applied 
to soldering sections 37 of contacts 31 of contact assembly 30, there is 
danger that the soldering sections 37 become separated from the contact 
pads of the printed circuit board 50. The function of fasteners 40 is to 
eliminate or reduce the force generated by the pulling of mating connector 
100 from connector 10 to the soldering sections 37 of contacts 31. 
Fasteners 40 are fabricated by stamping and bending. As shown in FIG. 1, 
each fastener 40 consists of a main body 41 extending perpendicularly to 
the printed circuit board having at the lower end a soldering shoulder 42 
which is fixed by soldering to a metal pad made on the printed circuit 
board. At the upper end is a retaining shoulder 43 holding the housing by 
pressing on the upper surfaces of mounting openings 27, 28, and a pair of 
L-shaped arms 44, 45 whose purpose is to secure the fasteners in mounting 
openings 27, 28. 
Due to the above described design, when electrical connector 10 is mounted 
on the printed circuit board, its housing 20 can move parallel to the 
printed circuit board but it is prevented from being lifted off the board 
by fasteners 40. In this embodiment, the lower ends of fasteners 40 are 
soldered to the pads made on the printed circuit board 50; however, it is 
not the only method of the mounting. Instead, openings can be made in the 
printed circuit board 50 and instead of the soldering shoulder 42, a pair 
of spring-loaded legs can be made similar to the device described in the 
Japanese Utility Model Disclosure Hei 1 (1989)-42645 that will be pressed 
in such rectangular openings. 
Next, we will provide explanations concerning the mating connector 100 used 
with electrical connector 10 for printed circuit boards with reference to 
FIG. 2. Connector 100 has an insulating housing 110 consisting of a 
rectangular base 111 and a plug portion 112 extending upward. At both ends 
of insulating housing 110, a pair of metal fasteners 150 are pressed in. 
On both side surfaces 113 of plug portion 112 of housing 110, a number of 
slots 114 are formed. In slots 114 are arranged two rows of L-shaped 
contacts 120 each consisting of a contacting section 121 and a soldering 
section 122. Free ends of contacting sections 121 of contacts 120 are 
extended outside through the outside surfaces 113 near the front end of 
plug portion 112 of housing 110. 
Fasteners 150 of mating connector 100 shown in FIG. 2 each have a retaining 
section 151 which is pressed in the groove 115 of housing 110, and a 
soldering section 152 that is secured on printed circuit board 200 (FIG. 
3) by soldering to a pad. Unlike connector 10 shown in FIG. 1, connector 
100 is fixed to printed circuit board 200 so that it can not move relative 
to the board. 
FIG. 3 depicts connector 10 shown in FIG. 1 and connector 100 shown in FIG. 
2 in a mated state. Contact sections 121 of contacts 120 of mating 
connector 100 soldered to printed circuit board 200, form a spring-loaded 
connection with the contact sections 35 of contacts 31 of contact 
assemblies 30 of connector 10 soldered to printed circuit board 50. As can 
be seen from FIG. 3, contact sections 112 of two rows of contacts 120 of 
mating connector 100 are retained in housing 110 so that their backs face 
the central partition 116. That is, the bases of the contact sections 121 
of contacts 120 are against central partition 116, and the cantilevered 
portions with the contacting point located on the free ends, extend 
outside away from central partition 116. Resultingly, contact sections 121 
of contacts 120 are spring loaded providing contacting pressure necessary 
for reliable connection between contacts 31 and 121 of connectors 10 and 
100. 
Due to such a design, it is possible to implement a very narrow spacing of 
approximately 4 mm between printed circuit boards 50 and 200 joined 
together by means of connectors 10 and 100, that is, to implement a low 
profile structure. In addition, since electrical connector 10 can to some 
degree move in lateral direction relative to printed circuit board 50, 
printed circuit boards 50 and 200 can be joined together even when there 
exists some misalignment. The contacts 31, 121 provide for a reliable 
connection even with this low-profile structure, the mating length can be 
as short as 1.2 mm. 
FIG. 5 depicts another embodiment of an electrical connector for printed 
circuit boards according to this invention. In this cross sectional 
drawing (similar to the cross section illustrated in FIG. 3), connector 
10' is shown mated with mating connector 100 shown in FIG. 2. 
Electrical connector 10' is similar to connector 10 described above, and 
here we will explain only the features that are different. Insulating 
housing 20' has side walls 22',23' and bottom 24' forming a box-like 
structure or a structure with a U-shaped cross section, and in this 
respect is similar to insulating housing 20. However, the difference is 
that cavities are made in the lower portions located near the bottom 24' 
of the outer surfaces of side walls 22',23'. 
Contact assemblies 30' are bent to a U-shaped configuration and arranged in 
two rows, after which they can be secured in insulating housing 20' 
preferably by insert molding. That is, if in connector 10, the contact 
assemblies 30 were bent and then mounted to the insulating housing 20, in 
connector 10' they are molded as an integral part of insulating housing 
20'. Contact assemblies 30' are made as a plurality of contacts 31' 
connected to a carrier (forming a comb-like configuration), placed in the 
mold and insert molded to form the housing. The carrier is cut off after 
the molding is accomplished. 
The front ends of contacting section 35' of contacts 31' are embedded in 
the bottom 24' of insulating housing 20' so that the inside surfaces of 
the contacting sections 35' are exposed to cavity 21'. However, unlike in 
the contact assembly 30, the contact sections 35' of the contact assembly 
30' do not have an insulating strip, but rather they are insert molded in 
the inside surfaces of side walls 22' and 23' of the insulating housing 
20' by inside surfaces of contacts 31'. Soldering sections 37' of contacts 
31' are secured at a desired pitch, for example, at 0.5 mm, by a plastic 
strip 33' made of the same plastic material as the insulating housing 20'. 
As it was mentioned above, contacts 31' are fabricated from, for example, 
0.05 mm metal sheet and bent to a U-shaped configuration, and cavities are 
provided on the outer surfaces of side walls 22', 23' of the insulating 
housing 20'. Therefore, a gap G exists between the outside surface 36' of 
contact 31' and the outer surfaces of side walls 22', 23' of insulating 
housing 20'. Resultingly, when electrical connector 10' is secured on 
printed circuit board 50' by soldering, it can move relative to the board 
within limits corresponding to the size of gap G. 
Strip 33' of contact assembly 30' can be formed by molding before it is 
molded in insulating housing 20' as its integral part. The size of gap G 
between the outer surfaces of side walls 22', 23' of insulating housing 
20' and the outside surface 36' of contact 31' can be selected freely 
depending on the degree of movement the designer wants to impart to 
connector 10'. 
Above, we have provided explanations concerning embodiments of the 
electrical connector for printed circuit boards according to this 
invention. However, this invention is not limited only to the embodiments 
described above and various modifications can be made depending on 
specific applications. For example, necessary strips 33, 33' used for the 
alignment of contacts in contact assemblies, may be replaced with adhesive 
tape. Contacting sections of the mating connector contacts can be of a 
J-shaped configuration to increase their elasticity. 
Contacts of the electrical connectors according to this invention are 
fabricated from extremely thin metal sheet by stamping and bending and are 
arranged in the insulating housing in such a manner that there is a gap 
between the contacts and housing side walls making it possible for the 
connector to move laterally relative to the printed circuit board. This 
feature compensates for some misalignment with a mating connector and to 
provide for a reliable engagement. Therefore, these connectors are 
excellent for joining together two printed circuit boards in small-size 
high-density electronic equipment. 
Another advantage of the electrical connector is that the contacting 
surface of the contacts is the smooth rolled surface of the metal sheet 
and the same is true for the contacts of the mating connector, thus 
providing for a stable highly reliable electrical connection. This also 
helps to prevent abrasion of gold plating off the contacting sections due 
to repetitive engagements and disengagements of the connectors. 
Another advantage consists in the fact that the contact assembly may be 
made in the form of a lead frame and can be either fixed to the insulating 
housing or molded as an integral part thereof, thus making it possible to 
simplify the manufacturing process and to reduce its cost. Therefore, 
these connectors are excellent for the use in inexpensive small-size 
high-density electronic applications such as portable telecommunications 
devices.