GB2284948A - Surface mount connector and method of making same - Google Patents

Abstract

An SMT connector (30) comprises contacts (40) disposed in one or more rows. Each contact (40) has a solder connection section (41) reflow soldered to a solder pad (50) on a circuit board and a contact section (41) to be mated with a complementary contact of a matable connector. To produce the connection, the contacts (40) have their contact sections (42) inserted into contact retention holes (61) in a housing (60) which maintains proper alignment between the contacts (40) and the solder pads (50) and which is removed from the contacts (40) after reflow soldering to the solder pads (50). <IMAGE>

Description

SURFACE MOUNT CONNECTOR AND METHOD OF MAKING SAME The present invention relates to an electrical connector and more specifically to a surface mount connector to be surface mounted to solder pads on a (printed) circuit board and a method of making such surface mount connector.

Surface mount technology (SMT) has been utilized widely to implement electrical circuits for primarily high performance, high density and compact electronic machines and equipment. The SMT uses active devices such as transistors and ICs and passive devices such as resistors, capacitors and diodes comprising such electronic circuitries and attaches such devices to solder (or conductive) pads on one surface or both surfaces on a c c--zuSit it board or a substrate (collectively referred to as circuit board hereunder) on which cream solder Is applied. Subsequently, an infrared beam or a laser beam is directed to melt the cream solder for soldering.

Advantages of se SMT include the capability of implementing hitch density electronic circuits for intended perfo=ance on a surface of a circuit board by directly soldering qMT devices and components without drilling holes i the circuit board for receiving soldering leads of such devices. Also, electronic circuits built cn cne surface of such circuit board is easy to trace an tus improves serviceability.

Elimination cf icing soldering leads of electronic devices and components helps to miniaturize such devices, thereby miniaturizing the electronic machines and equipment using such electronic circuits.

Now, most modern electronic machines and equipment use more than one circuit board and/or electronic component or unit to be interconnected using most generally electrical connectors (referred to simply as connectors hereunder). In order to miniaturize the overall electronic machines and equipment, there are strong needs for developing not only miniature SMT electronic devices but also electromechanical parts and components such as connectors. As G result, various types of SMT connectors have been proposed and developed and some of them are in commercial use.

Generally, connectors comprise insulating housings and one or more contacts (or terminals) to be retained in the housings. The housings are usually used for integrally retaining a plurality of contacts with predetermined spacing or isolated from one another or from other electrically conductive parts. One example of conventional ST connectors is disclosed in Japanese Utility Model Publication No. 92-3432. Such a conventional SMT connector 1 is illustrated in the accompanying FIG.6 and Includes a generally box-shaped housing 10 comprising a bottom wall 11 and sidewalls 12 open at the top t provide a recess 13 and, for example, two rows of contact receiving passageways 14 formed in the bottom wall 11. Fixedly Inserted into the contact receiving passageways 14 i the housing 10 are generally L-shaped contacts 20 each comprising a generally straight contact section 21 received in the respective contact receiving passageway 14 with the end portion thereof extending into recess 13 of 10 and a solder connection section or solder tail 22 extending outwardly along the bottom wall 11 of the housing 10.

Such conventional SMT connector 1 is positioned on a circuit board 25 having solder pads 26 on one surface thereof in correspondence with the solder connection sections 22 of the contacts 20. The solder connection sections 22 of the contacts 20 are reflow soldered to the solder pads 2 on the circuit board 25 by the above mentioned SMT technique. In order to increase the retention force between the connector 1 and the circuit board 25, it is possible to fixedly mount one or more mounting tab 28 on the outer surface of the bottom wall 11 of the housing 10. The mounting tab 28 is soldered to corresponding mounting pad 29 on the circuit board 25.

The above mentioned conventional SMT connector 1 includes the contacts 20 to be fixedly retained in the contact receiving passageways 14 in the bottom wall 11 of the housing 10 by conventional means such as frictional engagement by deforming or coining the contacts 20. This means that about one half of the post-like vertical section of each contact 20 is buried in the bottom wall 11 of the housing 10 and the remaining halfAextending into the recess 13 of the housing 10, is available for mating with a matable connector not shown1 thereby limiting the effective contact length. n other words, the conventional SMT connect or 1 requires relatively large height in order to provide a required effective contact length. This is a bottleneck in designing low profile SMT connectors for compact electronic machines and equipment such as hard disc drives ('EDDs).

It is therefore an object of the present invention to provide a low profile SMT connector having a large number of SMT contacts to be reflow soldered properly in alignment with solder pads on a circuit board.

In order to overcome the above problems and to achieve the above object, the SMT connector according to the present invention comprises a plurality of SMT contacts removably retained in contact retention holes in a housing. Subsequent to reflow soldering of the SMT contacts to the solder pads on a circuit board, the housing is removed from the contacts, thereby leaving only SMT contacts reflow soldered to the solder pads for mating with a matable (complementary) connector.

The SMT connector and the method of making such SMT connector according to the present invention will be described in more detail hereunder by reference to the accompanying drawings, in which: FIG. 1 is an exploded perspective view to explain one preferred embodiment of the SMT connector.

FIG. 2 is a cross sectional view of a contact pair inserted into the contact retention holes in the housing as shown in FIG. 1.

FIG. 3 is a drawing to explain the steps of making the contacts to be used for the SMT connector in FIG. 1.

FIG. 4 is a perspective view of the contacts inserted in the contact retention holes in the housing.

FIG. 5 is an illustration to remove the housing from the contacts reflow soldered to the solder pads on the circuit board.

FIG. 6 is a cross sectional view of one example of the conventional SMT connector.

Illustrated in FIG. 1 is a perspective view cf the SMT connector 30 and the method of making such SMT connector according to the present invention. In FIG.

1, generally --shaped contacts 40 are disposed in two rows. Each contact 40 comprises a solder connection section 41 to be soldered to a solder pad 50 on a circuit board inot shown) and a contact section (or contact post) 42 substantially normal to the solder connection section 41 and the solder pad 50, A pair of contacts 40 in the two rows are disposed in a backto-back relationship, thereby outwardly extending the solder connect-on sections 41 from the respective contact sections 42 The contacts 40 and also the solder pads 50 are disposed in a igh density, for example, about 1.27-mm centerline pitch. In order to obtain proper alignment of these contacts 40 with the solder pads 50 on the circuit board, the contact sections g2 of the contact 40 are inserted and retained in the respective contact retention holes 61 in the housing 60 Also, there are formed notches (or slots) 63 at the bottom surfaces of both sidewalls 62 of the housing 60 for receiving or positioning the solder connection sections 41 of the contacts 40 inserted into the contact retention holes 61, A pair of ribs (or protrusions) 65 are formed at both upper sides of the housing 60s.

Illustrated in FIG. 2 is a cross sectional view of a pair of contacts 40 inserted and retained in the contact retention holes 61 in the housing 60 in FIG.

1. As understood from FIG. 2, the post-like contact sections 42 of the pair of contacts *10 are inserted into the contact retention holes 61 in the housing 60 in such a manner that the solder connection sections 41 of the contacts 50 are received in the notches 63 to extend outwardly, thereby maintaining proper alignment between adjacent contacts 40 for reflow soldering to the respective solder pads 50 Illustrated in FIG. 3 is the contacts 40 for the SMT connector 30 in order to describe how the contacts 40 are made. The contacts 40 are made by stamping for example O.;O-mm thick brass plate. That is, a pair of contacts 40a, 40b are stamped out of such brass plate in a bacx-to-bact relationship with for example 1.27-mm centerline pitch equal to the centerline pitch of the two rows of the contact retention holes 61 in the housing -0. Such contact pairs 40a, 40b are coupled to each other by a bridge section 48 at the free end of about 0.5-mm wide arm 47 coupled to a carrier strip 45 at a constant spacing (for example 6.0-mm) equal to the locations of pilot holes 46 There are proved slots (or slits) 49 at both sides of each bridge section 48. A large number of such contact paIrs 40a, 40b are wound around a large reel (not shown) along with che carrier strip 45 for storage.

Now, description will be made of the method of making the SMT connector 30 according to the present invention. Firstly, the housing 60 having two rows of contact retentIon holes 61 is made by molding an appropriate plastic material and a series of contact pairs 40a, GOb are made by stamping a metal plate, such as brass, and plating the surface of such contact pairs, as illustrated in FIG. 3. Subsequently, the contact pairs iota, 40b are fed from a reel (see FIG. 3) to be inserted into the contact retention holes 61. in the housing 60 as illustrated in FIGs. 1 and 2. Since the contact pairs 40a, 40b are disposed at the same pitch as that of the rows of the contact retention holes (61) in the housing 60, it is to be noted that the contact pairs 40a, 40b, carried by the carrier strip 45,. can be inserted into two rows of the contact retention holes 61 at one time in the proper back-to-back relationship. Note that the slots 49 are formed at both sides of the bridge section 46 of the contact pairs 40a, 40b; thereby separating the contact pairs 40a, 40b into independent or separated contacts at the bridge section 48 by simply pushing the contacts at the solder connection sections 41 to insert the contact pairs Oa, 40b into the contact retention holes 61, Such contact pairs dOa, 40b are repeatedly inserted into the contact retention holes 61 in the housing 60 to reach the desired number.

Upon completing the insertion of the required number of contact pairs 40a; 40b into the contact retention holes 61 in the housing 60, the housing 60 is loaded with a large number of contacts 40a, 40b as illustrated in FIG. 4. The housing 60 having the contacts 40 retained in the contact retention holes 61 is disposed on the solder pads 50 on a circuit board or reflow soldering between the solder connection sections 41 of the contacts 40 and the solder pads 50 in the manner hereinbefore described. It should be noted that the slots 49 not only make the contact pairs 40a, 40b easy to separate but also provide the plated edges for improved reflow soldering. When completing the reflow soldering, the housing 60 is removed from the contacts 40 with the fingers 70 or a robot arm, as illustrated in FIG. 5.

The ribs 65 of the housing 60. are used for this purpose. The angle of the bottom surface of the rib 65 and the sidewall 62 is chosen to be about 91 degrees for ease of removal of the housing 60P.

The SMT connector and the method of making such connector according to the present invention has been Hereinbefore described in detail based on one preferred embodiment. Siowever, it should be appreciated that the present invention is not limited only to such embodiment and various modifications to meet particular applications can be made without departing from the scope of this invention. For example, the contacts for the SMT connector may be disposed in a single row rather than dual rows as in the shown embodiment. Plural rows of such contacts may be disposed in a staggered relationship or higher density. The contacts are not limited to the -shaped post contacts but may be low insertion force contacts for SIMM (single in-line memory module) connectors having generally C-shaped contact sections in 0-shaped outer retention sections as disclosed in .S. Patent No. 4,984,996 or Japanese Patent Publication No. 63-193473. Also, the housing may be provided with alignment posts and/or resilient retention leas at both ends thereof for retention of the contacts on the circuit board during reflow soldering of the contacts to the solder pads as disclosed in, for example, Japanese Utility Model Publication No. 9034774, Japanese Utility Model Publication No. 91-37764 and Japanese Patent Publication No. 92-291196. The resilient retention legs are resiliently latched to openings in te circuit board and thus can be unlatched using fingers or simple tools for removal after reflow soldering.

The SMT connector according to the present invention ensures proper reflow soldering of the contacts to the solder pads on the circuit board by simply retaining such contacts in the contact retention holes in the housing only during the reflow soldering operation. n other words, the housing is removed after reflow soldering, thereby shortening the length of the contacts to provide a low profile SMT connector. Also, the contact sections of the contacts are effectively kept clean from adhering flux or other foreign materials during reflow soldering because the contact sections are protected in the contact retention holes in the housing.

On the other hand, according to the method of making the SMT connector of the present invention, the contact pairs Integrally coupled to the carrier strip are effectivelv inserted into the contact retention holes in the housings in a pair. Accordingly, SMT connectors having any desired number of contacts can be made very easy and in a less expensive manner. Again, the housing can be removed from the contacts after reflow soldering.

Claims (13)

1. A surface mount connector device comprising a plurality of connector contacts having first sections for electrical connection to contacts on a circuit board and second sections for electrically connecting with a matable connector, and a removable aligning housing having contact retention holes for receiving the second sections and for aligning the first sections with the circuit board contacts, said connector contacts being loaded in said housing for connection to the circuit board contacts, whereafter said housing is removable from said contacts.

2. The device of claim 1, wherein the connector contacts are disposed in two rows in said housing.

3. The device of claim 1 or 2, wherein the connector contacts are L-shaped.

4. The device of claim 1, 2 or 3, wherein the connector and circuit board contacts are disposed in a high density.

5. The device of any preceding claim, wherein the housing includes slots for engaging the first sections of the connector contacts and for disposing the first sections in correct alignment with the circuit board contacts.

6. The device of claim 5, wherein the housing has a bottom and the slots are disposed along the bottom of said housing.

7. The device of any preceding claim, wherein the connector contacts are stamped from brass plate.

8. The device of any preceding claim, wherein the housing is configured to facilitate removal of the housing from the connector contacts.

9. The device of claim 8, wherein the housing has ribs disposed therealong.

10. A surface mount connector device constructed, arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.

11. A method of making a surface mount connector comprising mounting connector contacts in contact retention holes of a removable housing, placing the housing on a circuit board to align sections of the connector contacts with contacts on the circuit board, securing said sections to the circuit board contacts, and removing the housing leaving the contacts secured to the circuit board.

12. The method of claim 11, wherein said sections of the connector contacts are solder tails which are soldered to circuit board contacts in the form of solder pads.

13. A method of making a surface mount connector substantially as hereinbefore described with reference to the accompanying drawings.