Contact element for edge connectors

Abstract: An electrical contact element (2,102) for an edge connector (1,101) is disclosed. The contact element (2,102) includes a C-shaped second contact device (30,130) connected to a resilient support part (20,120) and having opposing contact (20a,30a,120a,130a) for receiving a daughter card (6,106) therebetween.

Description: The present invention refers to an edge connector which receives the edge of a daughter card on which is loaded, for example, a memory module, and is used to connect electrically the memory module to the circuits on a motherboard to which the connector is attached. A variety of electric contact elements for edge connectors have been used thus far. However, there have been no proposals for electric contact elements for edge connectors which are versatile enough to handle the wide variations in thickness of daughter cards. U.S. standards for the thickness of daughter cards are 1.27 + 0.1/- 0.08 (mm) and Japanese standards are 1.2 + 0.15/-0.12 (mm). An electric contact which could handle differences in thickness of approximately 0.3 mm would be required to conform to these two sets of standards. Conventional electric contact elements, however, have not been able to handle this difference in thickness sufficiently. An example of this type of connector is the electric contact element used for the low insertion input connector as described in U.S. Patent No. 4,737,120. In this connector, the edge of the daughter card were clamped by two electric contact surfaces which faced-each other. However there was practically no leeway for one of the electric contact surfaces to deform. The contact part of the other electric contact part which made contact with the root part (which was deformed) was close by so that no significant resilient deformation was possible. When this was significantly deformed, there were problems in that the base part was subjected to plastic deformation or was damaged so that it could not handle the wide variations in thickness of the daughter card. The electrical contact element which is used in the connector disclosed in Laid-Open Japanese Patent No. 60-230378 and in Laid-Open Japanese Patent No. 63-193473 features a support part between (a) the C-shaped contact member which accepts the edge of the daughter card and (b) the base part which supports the C-shaped contact member which is short. As a result, there is the likelihood that stress will concentrate on the support part and plastic deformation will take place. The elastic deformation of the electric contact element relies only on the C-shaped contact member so that (a) there are limitations on the amount of plastic deformation and (b) the electric contact element cannot handle the wide variations in thickness of the daughter card. Next, Laid-Open Japanese Patent No. 63-193473 discloses an electric contact element for a connector which is soldered onto the surface of the motherboard to which the edge connector is attached (the "surface mounting type" of connector, hereafter referred to as "SMT"). In this connector, the bottom surface of the base part of the electric contact element is soldered directly to the motherboard. However, there are problems with this when there are variations in temperature. There is the possibility that temperature cracks will appear on the soldered part which is interposed between the motherboard and the base part of the electric contact part caused either by the difference in the thermal expansion coefficient of the electric element and the motherboard or due to the fact that the external force when the motherboard is mounted onto the connector is applied directly to the base part of the electric contact element thus breaking the connection. Document EP-A2-0,407,864 of the elder European application 90 112 700.1 discloses an edge connector for receiving an edge of a circuit board. The contacts positioned in the housing of the connector include a resilient stand-up section having a tip defining a first contact point and a C-shaped section having a tip defining a second contact point with the circuit board being received between the first and second contact point. The circuit board is received in a first angular position and then rotated to a second angular position. From document US-A-3,732,531, an electrical connector has come to be known. The contacts comprise a C- or U-shaped outer contact member and a U-shaped inner contact member. An edge of a circuit board is simply slid from top downwards into an opening rather than rotation after insertion. Therefore, it is an object of the present invention to take into consideration the above-mentioned problems and provide an electric contact element for edge connectors which can handle the wide variation in thickness of the daughter card by increasing the amount of resilient deformation. This object is solved according to the invention by an electrical edge connector according to the features of independent patent claim 1. Dependent claims 2 and 3 exhibit advantageous, non-trivial improvements of the subject-matter of claim 1. The electric contact element for edge connectors is equipped with a C-shaped first contact device which comprises a first part and a second part which extend upward from both ends of the base part which is fixed to the bottom part of the cavity of the housing; a C-shaped second contact device which is coupled to the front end of the elastic or resilient support part which extends from the side of the above-mentioned base part of the first contact device at a sharp angle to the above-mentioned base part and a connection device which protrudes onto the bottom wall of the above-mentioned housing from the above-mentioned base part of the above-mentioned first contact device and connects to the motherboard. It uses either of the above-mentioned first and second contact devices or both as a contact with the daughter card. The invention shall now be described with reference to the following drawings: FIGURE 1 is a side cross-section of the first embodiment of the invention; FIGURE 2 is a side cross-section of the second embodiment of the invention. Figure 1 gives an overview of the electric contact element and the housing of the invention. Electric contact element 2 is pressed into housing 4 from the top at the position of arrow P and is forced into housing 4 and is retained on the bottom part of cavity 5 of housing 4 when convex part 2a (which is formed on the outside of both side surfaces of electric contact point 2) locks into the wall 4a of housing 4. Electric contact element 2 is made up of (a) a C-shaped first connection device which comprises a second support column (second part) whose front end first extends upward from the first support column 12 (first part) which itself extends upward from one end of base part 11, then extends inside the electric contact element; (b) a resilient support part 20 which extends in a direct line from near the base part of the above-mentioned second support column 14 at a sharp angle to base part 11; and (c) a second contact device 30 which first extends to the front end of the above-mentioned second support column 14 from the front end of the part 20, then makes a U-turn, and then curves in a C-shape along the inside of the above-mentioned part 20 and the second support column 14. Front end 20a of the above-mentioned part 20 faces the above-mentioned second support column 14 and forms the first contact. Front end 30a of the above-mentioned second contact device 30 faces the above-mentioned first contact 20a and extends to form the second contact. The inside 14a of front end of the above-mentioned second support column 14 faces the above-mentioned first contact 20a and forms a protrusion which serves as a reserve contact. Daughter card 6 is inserted between the above-mentioned first contact 20a and the second contact 30a. These are connected to daughter card 6 by turning in the direction indicated by arrow Q. When the sheet of the above-mentioned daughter card 6 is thin, the surfaces of the first contact 20a and the second contact 30a as well as the reserve contact 14a inside the front end of the above-mentioned second support column 14 are connected to the surface of the daughter card 6. The reserve contact 14a acts as an anti-overstress device which regulates the amount of deformation so that the above-mentioned second contact device 30 is not deformed excessively especially when a daughter card with a thick sheet is inserted. Part 20 extends at a sharp angle to base part 11. The length of part 20 being long so that the amount of potential elastic deformation increases. Further, the electric contact element has a low profile and the connector can accordingly be of a low profile. Electric contact element 2 is equipped with sliding surface 14b which is inclined toward part of the above-mentioned second support column 14 and which is opposite front end 30a of the above-mentioned second contact device 30. When this sliding surface 14b is deformed as the above-mentioned second contact device is mounted onto daughter card 6, it makes contact with the above-mentioned outside surface 30b and functions to slide front end 30a of the second contact device 30 along surface 6a of daughter card 6. Daughter card 6 is inserted between the above-mentioned first contact 20a and the second contact 30a of electric contact element 2. The C-shaped second contact device 30 and part 20 deform elastically upon the daughter card being turned to the position indicating by 6'. The amount of deformation and the stress involved are dispersed to the above-mentioned second contact device 30 and to the rising part 20 so that (a) the amount of resilient deformation can be increased; (b) the wide variations in sheet thickness of daughter card 6 can be handled; and (c) an electric contact point can be realized which has reliable electric contact characteristics and which makes contact with both sides of daughter card 6 with great contact pressure. The above-mentioned reserve contact 14a acts as an anti-overstress device for the above-mentioned second contact device 30. It prevents plastic deformation from extreme deformation by controlling the amount of deformation of the second contact device 30. The end 30b of the second contact device 30 makes contact with the sliding surface 14b and slides along surface 6a of daughter card 6. This makes it possible for daughter card 6 to be mounted smoothly even when there are scratches and other surface irregularities on surface 6a of daughter card 6 and prevents the above-mentioned second contact device 30 from excessive deforming and from plastic deformation. Protrusions (not shown) are located on the inside surface 12a of the first support column 12 or on plane 20b of the front end of rising part 20. These make contact with each other and are used as anti-overstress devices to prevent the above-mentioned rising part from deforming excessively. Reference number 16 in Figure 1 indicates the tine part of electric element 2 which is soldered to motherboard 8. The figure also indicates tine part 17 (arrayed in zigzag fashion with tine part 16) on the electric contact element (not shown) adjacent electric contact element 2. Figure 2 indicates a second embodiment. It indicates daughter card 106 which is clamped between first contact 120a and second contact 130a and which fits in last of all at position 106' which is parallel to the bottom surface of the housing. Since electric contact element 102 is configured exactly as element 2 except that the rising part 120 extends from the root part (near the base part) of the second support column 114 so that it is parallel to base part 111, we shall not go into detail about how it works since this is clear from the drawing. The same reference numbers used for the contacts and other parts used with respect to element 2 correspond to the same parts in Figure 2.

Claims: An electrical edge connector (1,101) having: a) a dielectric housing (4,104) and a plurality of electrical contact members (2,102) each including an outer C-shaped contact member (10,110) for securing the electrical contact member (2,102) in said dielectric housing (4,104) and b) an inner C-shaped contact member (30,130) positioned within the outer C-shaped contact member (10,110) for receiving a daughter card (6,106) in a first angular position and then rotating to a second angular position, characterized in that c) the inner C-shaped contact member (30,130) is connected to the free end of a relatively long spring member (20,120) d) extending from the outer C-shaped contact member (10,110) in substantially parallel or enclosing an acute angle to the base of the outer C-shaped contact member (10, 110), e) so that the daughter card (6,106) is substantially parallel or enclosing an acute angle to the bottom of the housing (4,104) in the second angular position. An electrical edge ccnnector (1,101) according to claim 1, characterised in that a free end of the outer C-shaped contact member (10,110) covers the free end (30a,130a) of the inner C-shaped contact member (30,130) to protect the inner C-shaped member (30,130). An electrical edge connector (1,101) according to claim 1, characterized in that a free end (30b,130b) of the inner C-shaped contact member (30,130) is extending to abut an inner surface (14b,114b) of the outer C-shape contact member (10,110) when the daughter card (6,106) is inserted or extracted.

Inventors: JUN SAITO, KASHIWA YOUICHI, YOSHIKAZU TANIKAWA, JUN, SAITO, KASHIWA, YOUICHI, YOSHIKAZU, TANIKAWA
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1990
Main classification: H01R23
IPC codes: H01R12, H01R24