Electrical contact with anti-solder wicking tab

Abstract: An electrical contact (2) has a tab (28) provided in passage (26) which extends through the contact (2). The tab (28) is dimensioned to provide a barrier, past which solder (34) cannot flow. Consequently, as the contact (2) is mounted to a printed circuit board (32), the tab (28) prevents the solder (34) from wicking from the mounting portion (6) to the mating portion (4).

Description: The invention is directed to an electrical contact which has a mounting area for mounting to a substrate or the like. In particular, the electrical contact has anti-solder wicking tabs provided thereon which prevent the flow of solder to the mating area of the contact. A known terminal is disclosed in US-A-2,385,915 which provides for a cylindrical solder terminal that includes a solder blocking portion within the tubular structure. The construction requires some portions of the terminal to have three layers of sheet metal with bent portions along the circumference thereof. The above construction has the advantage of blocking flowing solder from moving up the terminal due to capillary action. However, the above construction has the disadvantages of using much sheet metal material, and it is expensive to make because of the various bends required. Moreover, the terminal's high weight and overall large size make it undesirable in modern applications involving light-weight, compact electronic equipment and components. The present invention provides a hollow electrical terminal according to claim 1. Features of preferred embodiments are defined in the dependent claims. A hollow electrical terminal according to the preamble of Claim 1 is known from DE-A-30 22 428. The present invention has a means to prevent the flow of solder from a mounting portion of the terminal, which cooperates with a substrate, to a mating portion of the terminal, which cooperates with a mating connector. This ensures that the solder will only bond with the mounting portion of the contact, to properly secure the contact to the substrate. As the solder is prevented from flowing or wicking to the mating portion, the mating characteristics of the mating portion will not be adversely effected by the solder. The manufacture of the terminal of a preferred embodiment of the invention accomplishes the task of blocking the solder with a circular tab which is stamped inwardly from the terminal wall for sealing engagement with the inner surface of the terminal. A minimum of sheet metal material is required which is beneficial in that a reduction in overall weight and size of the terminal is advantageously achieved. Reference is now made to the drawings, in which: FIGURE 1 is a perspective view of an electrical contact of the present invention, a portion of the contact has been sectioned to illustrate the anti-solder wicking tab provided therein. FIGURE 2 is a partial cross-sectional view of the contact showing the anti-solder wicking tab in engagement with the wall of the contact. FIGURE 3 is a partial cross-sectional view of the contact, similar to that of Figure 2, showing how the solder flows in the contact. FIGURE 4 is a cross-sectional view of the anti-solder wicking tab, taken along lines 4-4 of Figure 1. A contact or terminal 2, as shown in Figure 1, has a mating portion 4 and a mounting portion 6. The mating portion 4 has a body section 8 with a hollow cylindrical configuration. A tapered section 10 extends from an end of the body section 8. Opposed slots 12 extend from the body section 8 to an opening 14 provided at an end of the tapered section 10. The slots 12 have an increased dimension proximate an end thereof. The slots define a first contact leg 16 and a second contact leg 18 which extend from the body section 8 to the tapered section 10. The slots are positioned to allow the first and second contact legs to have resilient characteristics and to move relative to each other. The opening provided at the end of the tapered section 10, is dimensioned to receive a mating pin (not shown) therein. It is worth noting, that the configuration of the mating portion 2 can be as shown in Figure 1, or can be of any other type of mating portion generally known in the industry. The mounting portion 6 has a main section 20 which has a fixed end which is integral with the body section 8 of the mating portion 4. A lead-in section 22 extends from a free end of the main section 20. The main section 20 has a hollow cylindrical configuration, which has a smaller diameter than the diameter of the body section 8. An opening (not shown) is positioned at the end of the lead-in section 22. Securing barbs 24 are positioned on the outside surface of the main section 20. The securing barbs 24, as best shown in Figure 2, cooperate with a housing 25 when the contacts 2 are inserted into the housing. The cylindrical body section 8 and the cylindrical main section 20 are hollow and form a passage 26 which extends the length of the contact. The openings provided at the end of the lead-in section and the tapered section provided access to the passage 26. An anti-solder wicking tab 28 is positioned in the passage 26 of the mounting portion 6. The anti-solder wicking tab is stamped and formed from a portion of the wall of the main section 20 of the mounting portion 6, and is positioned to extend in a direction which is essentially perpendicular to the wall of the main section 20. An opening 29 is adjacent tab 28. As best shown in Figure 4, the tab 28 is stamped in an essentially circular configuration. A securing section or portion 30 of the tab remains integrally attached to the wall of the main section 20. The tab is dimensioned such that the tab 28 is provided in engagement with the inner wall of the mating portion 20 along the entire circumference of the tab. This ensures that the passage 26 will be completely blocked by the tab 28. As is shown in Figure 2, the cooperation of the inner wall of the mounting section and the tab 28 causes the tab 28 to be deformed within the passage 26. This deformation occurs because the tab is dimensioned to be slightly larger than the passage provided in the mounting portion 6. As the tab 28 is slightly larger than the passage, the entire circumference of the tab will cooperate with the inner walls of the main portion 20 to form a barrier which prevents the flow of material beyond the tab. In order to ensure that the tab is properly positioned, the tab is stamped and formed from the metal stock before the contact is formed. After the tab is formed, the mounting portion, including the hollow main section 20 is formed around the tab 28. This process is controlled such that the inner wall of the main section 20 will engage the entire circumference of the tab 28. In order to ensure that a tight fit is provided, the main section 20 is formed so that the diameter of the passage 26 is slightly less than the diameter of the tab 28. This results in the type of deformation of the tab which is illustrated in Figure 3, which in turn results in an air tight connection between the tab and the inner wall. With the contact properly stamped and formed, the contacts are positioned in a housing and are maintained therein by means of the securing barbs 24. The housing is then positioned on a printed circuit board 32 with the mounting portions 6 of the contacts 2 engaging conductive paths on the printed circuit board. In order to maintain the contacts in electrical and mechanical engagement with the conductive paths, solder 34 (Figure 3) is applied to the mounting portions and conductive paths. The solder is then exposed to energy, by way of conventional means, which causes the solder to flow around the mounting portions 6 of the contacts. The energy is removed, and the solder hardens, thereby ensuring that the contacts and conductive paths will be maintained in engagement. In the prior art contacts, when the solder was exposed to energy, the solder would flow through the hollow mounting portions of the contact to the mating portions, thereby causing the mating portions to become ineffective. However, in the contacts described herein, this problem is eliminated. The anti-solder wicking tabs 28 provide a barrier across which no solder can flow. Consequently, the mating portions 4 remain solder free. As previously discussed, the dimensioning of the tab is important. The entire circumference of the anti-solder wicking tab 28 of the present invention is provided in engagement with the inner wall of the main portion 20 of the mounting portion 6 to form the barrier. If a portion of the circumference of the tab is spaced from the inner wall, a small channel is provided. This channel is significant because as the soldering process occurs, the gases will flow through the channel. As previously discussed, the flow of these gases can form a vacuum which will cause the solder to be pulled through the channel. It is worth noting that although the channel may be small, the force of the vacuum is great. Consequently, even if a small channel is provided between the tab and the inner wall, the flow of solder to the mating portion can be significant. However, the dimensioning of the tab 28 of the present invention eliminates this problem, as no channel is present.

Claims: A hollow electrical terminal (2) having a mounting portion (6) comprising main section (20) and a lead in section (22), and a mating portion (4) comprising a body section (8), wherein the main section (20) has a solder stop (28) therein, wherein the solder stop (28) comprises a tab which is stamped from a wall of the main section (20) thereby forming a hole (29) in the main section (20), characterized in that the circumferential edges of tab (28) sealingly engage the inner surface of main section (20) between said hole (29) and the lead in section (22). The electrical terminal (2) of claim 1, wherein the body section (8) includes a pair of slots (12) each having an opening (14) so that the slots (12) form resilient contact legs (16, 18) on the body section (8). The electrical terminal (2) of claim 1 or 2, wherein the body section (8) includes a tapered section (10) at one end thereof. The electrical terminal (2) of claims 1, 2 or 3, wherein the main section (20) includes barbs (24) for engaging a housing (25) and a printed circuit board (32). The electrical terminal (2) of claim 4, wherein the main section (20) includes a tapered section (22) at an end thereof. The electrical terminal (2) of any of claims 1 to 5, wherein the hole (29) is essentially a circular hole.

Inventors: BROWN GARRY LEE, BROWN, GARRY LEE
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1993
Main classification: H01R13
IPC codes: H01R13, H01R9, H01R4, H05K3