BACKGROUND OF THE INVENTION

1 . Field of the invention

This invention relates to an electrical connector for interconnecting electronic components within an electronic system, and more particularly to a bottom entry female electrical connector which can be electrically and mechanically attached to a printed circuit board by a wavesolder operation without being fouled by solder.

2. Related Art

Electrical connectors are widely used for electrically interconnecting one printed circuit board to another, thereby conducting electrical signals from one subsystem to another subsystem within a single system or between distinct systems.

Typically, such connectors consist of a male coupling and a female coupling.

Often, the male coupling consists of an elongated tubular or rectangular coupling, or an elongated solid contact shaft or pin which extends from the body of the male coupling and mates with the female coupling.

Typically, the female coupling of such connectors is designed such that a metallic contact portion can be formed from a single sheet of electrically conductive material, such as copper or copper alloy. The sheet of conductive material is cut by a stamping process to form the contact shape. The stamping is then bent into a shape that will allow the female contact to accept the male contact.

The female contact is usually enclosed in a coupling housing that protects the contact from damage. The housing also electrically insulates the contact from objects with which electrical contact might be undesirable. Such housings are often made of a variety of molded plastics and polymers.

In an attempt to find a means to more rapidly assemble printed circuit boards, and reduce the extensive labor required to install circuit components on printed circuit boards, a process known in the art as "wavesoldering" has been developed. Wavesoldering involves passing a circuit board across a flow of molten solder known as the "wave" while each component which is to be soldered is mounted in plated through-holes associated with that component. Due to the surface tension and adhesion characteristics of the molten solder, the solder is deposited only on metallic surfaces on the printed circuit, such as the plating of the plated through-holes of the printed circuit board and the metallic portions of the components which are exposed to the wave. However, when solder is deposited upon the plating of the through-holes of a printed circuit board, the solder will often times either completely fill or partially block the through-hole. Therefore, when it is desired to keep a particular plated through-hole open, it is typical to mask the hole with a tape fabricated from a plastic or polymer to which the solder will not adhere.

However, it is necessary for solder to flow over the plating of a plated through-hole when electrically interconnecting a device (such as a connector) to the plating of that through-hole. Therefore, a problem exists when it is desirable to utilize a single hole as both an access way and as a point of electrical contact between a mounted device and the printed circuit.

This problem also arises when other means to rapidly assemble printed circuit boards, such as "dip soldering," are used. Dip soldering involves immersing the printed circuit board into a vat of molten solder.

A continuing objective of the electronics industry has been to devise a connector for use in interconnecting printed circuit boards that requires a minimum of labor to install upon a printed circuit board, that is small in size and so consumes minimal surface area on a printed circuit board, that will allow two printed circuit boards to mate in close proximity to one another, and that will remain resilient and durable under adverse mating conditions. In order to reduce the labor required to install an electrical connector on a printed circuit board, many within the industry have attempted to create a connector which can be wavesoldered with little or no fouling of the female coupling.

The prior art discloses a variety of printed circuit board connectors similar to the types shown in FIGURES 1 a-1 c. U.S. Patent No. 4,767,342 entitled "Electrical Connector For Printed Circuit Board," issued August 30, 1988 to Sato., shown in

FIGURE 1 a, is an example of an electrical connector for use with printed circuit boards, in which the objective is to allow mating from either the top side or the

bottom side of the printed circuit board 120. Connectors which allow the male contact pin to enter from the end of the connector in contact with the host printed circuit board are typically known in the art as "bottom entry connectors."

The female coupling 103 of the Sato patent provides a housing 130 surrounding the female contact 140, including a guide opening 134 for guiding a male contact pin 102 into the female contact 140, thereby preventing the male contact 102 from damaging the female contact 140. Because the access hole 122 in the printed circuit board 120 through which the male pin 102 will enter the connector is not the point of electrical contact between the female contact 140 and the host printed circuit 120, there is no need to plate this hole 122. Since the hole 122 is not plated, it will remain free of solder during a wavesolder operation.

To electrically connect the female contact to the host printed circuit 120, the Sato connector provides a lateral conductor 148 and an offset pin 147 which allows the spring contacting tongue 145 which comes in electrical contact with the male pin 102 to be spaced from a plated through-hole 121. The offset pin 147 makes electrical contact with the plated through-hole 121 , thereby electrically connecting the female contact 140 to the host printed circuit 120. Physically displacing the spring contacting tongue 145 away from the plated through-hole 121 by the length of the lateral conductor 148 prevents the spring contacting tongue 145 from being fouled by either solder or flux during a solder operation. Additionally, it is not relevant to the operation of the connector that the plated through-hole 121 fills with solder, since the male mating pin 102 will pass through the unplated hole 122.

A second connector taught in the prior art appears in U.S. Patent No. 3,850,491 entitled "Circuit Board Socket," issued Nov. 26, 1974 to Mouissie. The connector 210, shown in FIGURE 1 b, teaches the use of a plastic body 212 with legs 224 extending outwardly of the body 212. The legs 224 are soldered to the inner sides of a host printed circuit board plated through-hole. A pair of arms 220 lying inside the body 212 make electrical contact with a male mating pin 234. The contact spring 218 is recessed within the plastic body 212. As shown in FIGURE 1 c, due to the poor adhesion to the plastic body 212, and the surface tension of the wave of solder 232, molten solder is prevented from entering the bottom opening of the body 212 and contacting spring 218 during a wavesolder operation. However, because the solder is prone to wicking along metallic surfaces such as the legs 224 of the connector 210, and the plating 233 of the through-hole, solder will be deposited in the crevice 234 between the leg 224 and the plating 233, thereby creating an electrical bond between the connector 210 and the printed circuit board 235.

A third connector, shown in FIGURE 1 d, is taught by U.S. Patent No. 4,750,889, issued on June 14, 1988 to Ignasiak et al. This connector teaches the use of a pin-like solder mask 320 to prevent solder from filling the plated through-hole 318. The mask 320 is held to the connector by a frangible connection or connection material 354 at two sides of each mask 320. The frangible connection is sufficiently strong to retain the mask 320 to the body 330 in a position which will prevent solder from flowing into the plated through-hole in the printed circuit board

(See FIGURE 1 e). However, the frangible connection or material 354 is sufficiently weak to permit the mask 320 to be easily away broken from the connector for purposes of removal, thereby providing a clear access way for a mating pin.

In this device, the plated through-hole 318 serves two purposes. The first purpose is to provide a point of electrical contact between the female contacts 314 and the host printed circuit 312. The second purpose is to provide an access way for the male contact to enter the connector from the bottom.

However, none of the connectors known in the prior art have a single plated through-hole which permits a male mating contact to enter the bottom of a female coupling housing and which also serves as the electrical contact point between the female contact and the conductive traces of the printed circuit board, thereby limiting the amount of surface area required while retaining the ability to be wave- soldered, and which requires no additional labor subsequent to the wavesolder operation and prior to use.

The present invention provides a bottom entry electrical connector which uses a single hole in the host printed circuit board for electrically connecting a female contact to conductive traces on a printed circuit board and for providing access from the bottom of the connector to the female contact by a male contact, and which can be installed upon the host printed circuit board using a single-step wavesolder operation.

SUMMARY OF THE INVENTION

The present invention comprises a bottom entry electrical connector which can be mounted to a printed circuit board by a single step wavesolder operation and which requires minimal area on the surface of a host printed circuit board.

The bottom entry connector of the present invention has a plastic boss which defines a channel containing the female connector contact. The boss is inserted into and substantially fills a printed circuit board plated through-hole. A dual-beam contact portion and a retention portion of the female contact are recessed within a cavity above the channel defined by the boss. The dual-beam contact portion and the retention portion are connected to the printed circuit board via an extension leg which extends from the body of the contact portion along the outer side of the plastic boss, thereby making contact with the plating of the through- hole. Because the contacts and the retention portion are spatially displaced from the surface of the host printed circuit board which will come in contact with a solder wave in a wavesolder operation, no solder fouling of the contact portions will occur. In addition, the boss provides protection against solder flowing into and closing the plated through-hole in the printed circuit board.

Because the invention allows a male mating pin to enter the female connector through the same plated through-hole in the printed circuit board to which the extension leg is electrically connected, the present invention provides a connector which can mate two printed circuit boards in very close proximity, and which requires minimal surface area on the host printed circuit board. Additionally, the

connector can be installed upon the host printed circuit board in a single step process. Further, the connector may be wavesoldered into plated through-holes without the plated through-holes in the host printed circuit being filled with solder.

Further aspects of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings. It should be understood, however, that the detailed description and the specific examples, while representing the preferred embodiment of the invention, are given by way of illustration only.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 a is a perspective view of a prior art electrical connector for printed circuit boards.

FIGURE 1 b is a cross-sectional view of a prior art circuit board socket.

FIGURE 1c is a cross-sectional view of a prior art circuit board socket during a wave soldering process.

FIGURE 1 d is a perspective view of a prior art through-board electrical component header having an integral solder mask.

FIGURE 1 e is a fragmentary side elevation view of a prior art through-board electrical component header having an integral solder mask, partly broken away in section.

FIGURE 2a is a front cross-sectional view of the inventive bottom entry connector.

FIGURE 2b is a side cross-sectional view of the inventive bottom entry connector.

FIGURE 2c is a top plan view of the inventive bottom entry connector.

FIGURE 3 is a top plan view of the contact used in the preferred embodiment.

Like reference numbers in the drawings refer to like elements.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best presently contemplated modes of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense.

FIGURES 2a, 2b, and 2c show the present invention in three cross-sectional views.

An elongated hollow boss 1 extends from a housing 2 of the connector 3, shown best in FIGURES 2a and 2c. The boss 1 is intended to penetrate a host printed circuit board 4 from the top through a plated through-hole 10, as shown in FIGURE 2c. The hollow boss 1 defines a central opening 7 along a longitudinal axis 14 of the boss 1 through which a male mating pin (not shown), affixed to a subsystem such as a printed circuit board or an electronic component, may enter to make electrical contact with a female contact 6.

The boss 1 is fabricated from a non-wetting material, such as plastic, to which solder will not adhere. When the boss 1 is inserted into the plated through-hole 10 of the host printed circuit board 4, the boss 1 extends past the bottom surface

15 of the printed circuit board 4. Due to the surface tension of a wave of solder which passes over the bottom of the printed circuit board 4 during a typical wavesolder operation, and the non-wetting property of the boss 1 , solder will not enter the opening 7 at the bottom of the boss 1 . In addition, the extension of the boss 1 past the bottom surface of the printed circuit board is such that the boss will sufficiently interfere with formation of a film of solder which would otherwise

bridge the plated through-hole 10. The extension of the boss also prevents solder from entering or blocking the plated through-hole when the printed circuit board is subjected to a "dip solder" operation in which the printed circuit board is immersed in a vat of molten solder.

The female contact 6 is enclosed in a cavity 5 within the housing 2, the cavity preferably being contiguous with the top of the opening 7. In the embodiment shown, the female contact 6 is a cantilevered dual mating beam style contact similar to that described in pending U.S. Patent application Ser. No. 7/677,778, filed on Mar. 29, 1991 and assigned to the assignee of the present invention, Elco Corporation. The contact shown in the preferred embodiment of the present invention is adapted for use as a very low profile connector. Even so, any contact may be used in this invention, and the female contact 6 shown is depicted only for the purpose of clarity and ease of understanding.

In FIGURE 3, the female contact 6 is shown as it appears before being formed by a bending process into the shape which it assumes when placed in the coupling housing 2. An extension leg 8 extends from the body 9 of the contact 6. When formed and placed in the housing 2, the leg 8 extends down the outside of the boss 1 such that the leg 8 makes electrical contact with the plating of the through- hole 10 in the host printed circuit board 4 when the boss 1 is inserted into the through hole 10. The length of the leg 8 is slightly greater than the length of the boss 1 , such that contact beams 1 1 of the contact 6 are disposed sufficiently high above the bottom of the opening 7 to prevent solder, flux or other contaminants from fouling the contact beams 1 1 during a solder operation, such as a wave-

soldering operation. During the wavesolder operation, a bond will form between the leg 8 and the plating of the plated through-hole 10 which will serve to mechanically and electrically connect the coupling 3 to the plating of the plated through-hole 10.

Protruding from the body of the contact 6 are two retention members 12. The retention members fit into recesses in the housing and prevent the contact 6 from being dislodged from the housing 2. Three contact dimples 13 are shown which provide proper contact force, as described in the prior application Serial No. 07/677,778 referred to above.

Because the boss 1 substantially fills the plated through-hole 10, which also serves as the access hole through the host printed circuit board 4 for a male mating pin, solder cannot fill the hole 10. Additionally, since the boss 1 is slightly elongated, it serves to guide the male mating pin into the contact beams 11 , and prevents the male mating pin from entering the coupling 3 on an acute angle and thereby causing damage to the contact beams 1 1.

It will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, the female contact 6 may be constructed in a variety of ways that are well known in the art, and which differ from that shown in the preferred embodiment, providing that an extension leg 8 extends from the body of the contact within the cavity 5 to the a point along the

outside of the boss 1 which to allow the leg to make electrical contact with the plating of the plated through-hole 10 in the printed circuit board 4. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiment, but only by the scope of the appended claims.