Contact Pin for an Electrical Circuit Board

The present invention relates to a contact pin for an electrical circuit board, which sits in its mounted state in an opening in a connector plate and with a press fit in an opening in a printed circuit board, the press fit portion of the pin sitting in the printed circuit board with at least two peripheral portions in the opening of the printed circuit board, and the contact pin being provided in the press fit portion with a central web-like upset-zone which interconnects the two oppositely arranged outer portions and in which plastical deformation takes place during the pressing-in process.

Contact pins are used in considerable quantities for the production of electronic components, in particular for circuit boards, in the openings of which the contact pins are inserted.

In order to guarantee a firm fit of the contact pins in the corresponding openings in the printed circuit board, it is known to anchor the contact pins with a press fit in the openings of the circuit board. For this purpose, the contact pins have a press fit portion produced by a stamping process, by means of which they are anchored with a press fit in the corresponding opening in the circuit board. A known contact pin with this construction (U.S. Pat. No. 4,274,699) includes a central web-like upset-zone which interconnects two outer portions which are for abutting the edge of the opening of the circuit board. When the contact pin is pressed in, plastic deformation is to be essentially effected in the area of the upset-zone.

For this purpose, the central web has a relatively narrow design. During the deformation due to the pin being pressed into the corresponding opening in the circuit board, the web folds or buckles laterially, involving not a predominantly plastic deformation, however, but a deformation having an essentially elastic portion and thus the build-up of correspondingly large elastic restoring forces. This lateral folding or buckling of the web allows the pin to spring back into its initial position, at least to a certain extent, in case it is removed from the opening in the circuit board again. In the extreme case, the contact pin can, if loaded accordingly, move beyond the shearing limit in the web area, thereby forming two separate arms in the press fit portions which in turn cause the contact pin to be held within the opening in the circuit board by elastic restoring forces. The disadvantage of the known contact pin must thus be considered to be that no definite plastic deformation can take place, but rather an essential portion of elastic restoring forces is present after the pressing-in process and no reliable statements can be made concerning the strength of the press fit due to the lateral buckling or deflection of the web during the pressing-in process.

Due to production errors, in particular tolerance deviations, the connector plate may not be exactly aligned with the printed circuit board. Even a slightly lateral deviation, for example, between the connector plate and the printed circuit board located therebelow forces all contact pins to be on a slant. This also affects the fit of the contact pins in the circuit board since the slanted position may cause damage to the walls of the openings in the printed circuit board and the connector plate which openings are usually coated. If the contact pin deviates from its normal vertical position in its uppermost area on such a slant, this means that the tool (die) for pressing in the contact pin can no longer be directed exactly past the contact pin. All in all, the electrical contact may be impaired by the misalignment of the contact pin.

The invention is based on the problem of providing a contact pin which allows for controlled upsetting without lateral buckling during the pressing-in process and thus for stabilized upsetting.

The invention is further based on the problem of preventing the contact pin, in particular the portions of the contact pin protruding at the top out of the connector plate and protruding at the bottom out of the printed circuit board, from being on a slant due to inexact alignment of the printed circuit board and the connector plate, but also due to thermal extension.

According to the invention, the web is provided with lateral enlargements which rule out that the material deviates or displaces laterally within the upset-zone with the contact pin is being pressed in and during the resulting plastical deformation. Instead, the deformation is confined to the central zone of the contact pin, i.e. into the upset-zone, by displacing the material radially into the center of the contact pin, i.e. into the upset-zone. The outer portions are not deformed but are instead displaced along an axis radial to the longitudinal axis of the contact pin, thus not being subject to any deformation or bending. There is thus essentially a reduction in the radial dimension of the contact pin in the press fit portion perpendicular to the actual longitudinal axis of the contact pin. The material collects essentially within the web area which is compressed into a member of generally spherical cross-sectional shape.

According to the invention, there is thus a controlled and stabilized plastic deformation of the web, whereby the contact pin sits firmly and rigidly within the corresponding opening in the printed circuit board due to this deformation following the pressing-in process. Due to the plastic deformation of material in the upset-zone, tolerance differences may be readily compensated. The upset-zone rules out any considerable recession of the abutting portions of the press fit portion as is the case with contact pins having a larger portion of elastic deformation.

In the following, embodiments of the invention shall be described with reference to the drawing. It shows:

FIG. 1 a cross-section of the pressing-in zone of a contact pin before the pressing-in process,

FIG. 2 a cross-section of the pressing-in zone of the contact pin shown in FIG. 1, following the pressing-in process, and

FIG. 3 a perspective view of the pressing-in zone of a contact pin;

FIG. 4 is a sectional view taken along the plane IV--IV of FIG. 3; and

FIG. 5 is a sectional view taken along the plane V--V of FIG. 3.

FIGS. 1 and 2 show the cross-section of a press fit portion of a contact pin for a circuit board, with which the contact pin is mounted with a press fit in an opening having the circular cross-section indicated by dotted lies in FIG. 2 in a printed circuit board which is not shown. As the cross-sectional view shows, the press fit portion referred to in general as 1 has a web 2 which constitutes a predetermined upset-zone S, disposed in the center and extends along the axis of the contact pin essentially over the axial length of press fit portion 1 or the compression zone. Upset-zone S formed by central web 2 extends between the widened portions 3 which have a trumpet-shaped cross-section forming the outer portions 4 arranged opposite each other radially with respect to the axis of the pin. The outer portions serves the purpose of abutting the edge of the opening of the printed circuit board after the pressing-in process. The outer edges 5 of outer portions 4 are preferably rounded to protect the wall of the opening in the printed circuit board. By means of the rounded outer edges 5 the outer portions are brought in pressing contact with the edges of the opening in the printed circuit board when the contact pin is pressed into the printed circuit board, as indicated in FIG. 2. Outer portions 4 are formed in an essentially rectangular cross-sectional form, which is based on the fact that the press fit portion or the pressing-in zone of the contact pin is molded out of a contact pin with a rectangular, in particular square, cross-section by stamping using two oppositely arranged dies, which are moved toward each other during the stamping process. The width of the die corresponds essentially to the radial dimension of the web of the upset-zone.

As FIG. 1 shows, web 2 of upset-zone S is provided on both sides with generally semi-circular molded enlargements 6, which are more or less of circle-segment shape in the embodiment shown. Enlargements 6 are symmetrical to the radial axis R running through the axis of the pin. In accordance with the view in FIG. 1 the enlargements extend essentially across the entire width of web 2 and run directly via a curve 7 into the trumpet-shaped widened portions 3 of the contact pin.

The view according to FIG. 2 shows that when the pressing-in process is over the plastic deformation of the material has taken place exclusively in the area of upset-zone S, which has become correspondingly thicker. In the embodiment shown, upset-zone S has been deformed more or less spherically. The two outer portions 4, which were essentially spared from deformation, have moved toward each other in the direction of radial axis R, which was effected by a corresponding reduction of the width and a corresponding thickening of upset-zone S. The radial length, i.e. the length perpendicular to the axis of the contact pin, has been reduced from length l.sub.1 of FIG. 1 to length l.sub.2 as in FIG. 2.

In the embodiment according to FIG. 3, the two enlargements 6 do not extend along the entire length of press fit portion 1 but are provided in certain areas or sections along the length of the press fit portion. Between the various enlargements 6, which are in turn formed symmetrically to radial axis R, there are portions free from enlargements, as indicated in the cross-section of FIG. 4. These portions have a uniform web thickness. The web is molded in a straight line, as can also be seen in FIG. 4. The web thickness corresponds approximately to the smallest thickness of enlargements 6. In the embodiment according to FIG. 3, upset-zone S runs into conical widened portions 3 to outer portions 4 not via curves but at an acute angle. In accordance with the embodiment shown, four enlargements 6 are provided on each side of the contact pin, whereby the two outer enlargements taper toward the end of the press fit portion and are also formed so as to be longer than the two enlargements located on the inside.