Package for integrated devices

Abstract: This package for integrated devices, to be fixed on supporting plates, in particular on printed circuits, comprises contact pins (5a,5b) to be inserted in holes (2) of the supporting plates (1) and to be soldered thereto. To prevent overturning of the package, which may lead to short circuits among the components, at least some (5a) of the contact pins are provided with protruding portions (10) defining abutments cooperating with the supporting plate to limit the inclination of the package with respect to the plate.

Description: The present invention relates to a combination including a package for integrated devices and a printed circuit board. As is known, packages for integrated devices which must be fixed to printed circuits are initially placed in position on the printed circuit by inserting the pins of the package in the appropriate holes provided in the plate having the printed circuit thereon, and then finally soldered or welded. Accordingly, until the final soldering, the packages, not being fixed to the supporting plate, may be subject to oscillations or movements which move them away from the position which they should assume and in some cases can even cause a short circuit among adjacent components. This risk is more present in packages in which the center of gravity of the system is not arranged centrally with respect to the supporting pins, for example in the so-called single-in-line packages. In fact this type of package generally comprises two or more integrated devices mounted on a common substrate and provided with pins for connection to the printed circuit. In this case, the center of gravity may be greatly displaced with respect to the vertical plane passing through the center of the pins or of the rows of pins constituting the terminals of the device or devices. This situation is also due to the fact that usually the pins of the packages have a cross section considerably smaller than that of the holes, to facilitate their insertion in said holes even in case of not perfect centering with respect to the required position. Typically, therefore, for pins 0.7 mm wide, holes with a diameter comprised between 1 and 1.2 mm are provided. A circuital element with pins including leaf type springs is known from DE-A-1 916 410. The pins form a system for securing the circuital element on a circuit carrier plate (cf. page 1, bottom paragraph or last two lines of page 2). According to DE-A-1 916 410 the leaf spring elements only press against the wall of the hole and, due to the spring force exerted by the leaf springs, the circuital element is held in its position on the carrier plate. The Publication RADIO FERNSEHEN ELEKTRONIK, Vol. 30, No. 12, December 1981, pages 771-774, Berlin, DD; Schreier et al.: "Fixieren steckbarer Bauteile auf Leiterplatten" basically also relates to a system for fixing electronic packages on a carrier plate, as indicated by the title. In one embodiment of said publication (cf. Figure 3b) the pins are provided with lugs which work as spacing elements. G. Leonida "Handbook of Printed Circuit Design, Manufacture, Components and Assembly", 2nd edition, 1982, Electrochemical Publications Limited, 8 Barns Street, Ayr, Scotland, page 74-90, teaches (see in particular page 75, Section 2.4.1) various pin shapes which are intended for locking the components to a PCB after component insertion on the board. Thus, the "Handbook of Printed Circuit Design, Manufacture, Components and Assembly" is directed toward a snap type mounting (or flush mounting) of the components to the board. Moreover, as explained in the "Handbook of Printed Circuit Design, Manufacture, Components and Assembly" at page 75, Section 2.4.1, the various shapes of the pins are intended for vertically spacing the components from the board. Given this situation, the aim of the present invention is to provide a package of the indicated type in combination with a printed circuit board, capable of solving the above described problem, and in particular of eliminating or at least considerably reducing the possibility of inclination of the package of the integrated device with respect to the desired vertical position, so as to reliably prevent the occurrence of undesired short circuits among the different components to be fixed to a printed circuit. Within this aim, a particular object of the present invention is to provide a package which has a simple and cheap structure and does not alter the criteria currently used for fixing the package to said printed circuit. This aim, the objects mentioned and others which will become apparent hereinafter, are achieved by a combination including a package for integrated devices and a printed circuit board as defined in the accompanying claims. The features and advantages of the invention will become apparent from the description of some preferred but not exclusive embodiments, illustrated only by way of non-example in the accompanying drawings, wherein: figures 1a and 1b illustrate the behaviour of a known package; figures 2a to 2c illustrate the behaviour of a similar package, produced however according to the invention; figure 3 shows another variated aspect for packages of a different type; and figures 4a to 4c illustrate possible embodiments of the abutment elements according to the invention. Reference should initially be made to figures 1a and 1b, illustrating the structure and the behaviour of an exemplifying package produced according to the prior art. In the figure, 1 indicates the supporting plate defining a printed circuit, having holes 2 for the insertion of the pins, indicated here at 5a and 5b, of a package of a known type. In the specific case a package, generally indicated at 3, with seven pins and identified by the name HEPTAWATT (registered trade-mark), has been illustrated. Said package comprises a body 4 and a plurality of pins arranged along two parallel rows, of which only the pin 5a of the front row and the pin 5b of the rear row are visible. In the shown example, three other front pins 5a and two other rear pins 5b, conveniently offset, are however present. In the figure the center of gravity of the complete device has been indicated at B and, as is apparent in the figure, is arranged greatly behind the vertical plane (indicated by the dot-and-dash line 6) defined by the midline between the rows of pins. A further device 7, which may be constituted by a component of any type, has also been indicated schematically on the plate 1. As illustrated in figure 1b, due to the eccentric position of the center of gravity B, a force F acting on the package 3 (though with a very small value) causes the inclination or the overturning of the package 3 which, in the illustrated case, leads to the formation of a short circuit in the point indicated at 8. This situation is clearly to be avoided so that the overall circuit may reliably operate. Figures 2a to 2c illustrate instead a first embodiment according to the invention. Here the package 3, for example of the same type shown in figures 1a and 1b, again comprises a body 4 and a plurality of front pins 5a and a plurality of rear pins 5b which are inserted in the holes 2 of a plate 1. According to this first embodiment, however, the pins indicated at 5b (that is those arranged closest to the vertical plane passing through the center of gravity) are provided with protruding portions indicated at 10. In the specific case, the projection 10 of the illustrated pin 5b is constituted by a region of said pin which has been folded outwardly, for example stamped by means of a punch, on the already formed pin. Said protruding portion defines an abutment cooperating with an edge of the hole 2 to prevent or at least limit the inclination of the pins and of the entire package with respect to the plane perpendicular to the plate. This behaviour is illustrated in figure 2b and in the enlarged detail of figure 2c. In fact, under the action of a force F acting on the upper part of the package, due to the eccentric position of the center of gravity, the package still tends to overturn backwards, but in this case this rotation is severely limited by the presence of the projection 10. In fact, as can be seen in figure 2c, the inclination of the pin 5b causes the pin to rest against the edges of the plate 1 at the point 11 on the front side of said pin and at the point 12 at the projection 10. The projection 10 therefore behaves like an abutment which prevents a further inclination of the pin and therefore of the package with respect to the plate 1. As can be seen from the comparison of figures 1b and 2c (in which the effect has been in any case emphasized for exemplifying reasons) in practice the pin 5b provided with the projection 10 inclines itself with respect to the vertical to the plate 1 by a much smaller angle than that possible with a package of the conventional type. Said reduced inclination prevents therefore the contact of the package 3 with further components of the circuit, reliably avoiding thereby the onset of short circuits. Figure 3 illustrates another solution, possible in the case of a package of a different type, having a body 4' provided with a plurality of pins arranged along a single row. In this case the pins, indicated at 15a and 15b, have been provided with projections 14 alternately facing one side or the other of the row of said pins. In this manner swinging of the package in one direction or the other is prevented. However, if the center of gravity of the system is greatly displaced towards one of the two sides thereof, also in this case, the pins may be exclusively provided with projections extending all in the same direction. Figures 4a 4c illustrate different configurations of the projections which may be formed on the pins according to the invention. In particular, 16 indicates a solution having a triangular profile and having an undercut, while the projection indicated at 17 and illustrated in figure 5b has a rectangular configuration. The solution illustrated in figure 4c, instead, has a curved projection indicated at 18, substantially free from discontinuity surfaces. As is apparent from the preceding description, the invention fully achieves the intended objects. In fact, by virtue of the provision of a protruding surface on at least some of the pins for fixing packages to a perforated plate, any possible inclination of the package is reduced or completely eliminated, thereby effectively preventing an overturning thereof and its resting against adjacent components of the same circuit, with the possibility of short circuit. Moreover, said projections may be simply obtained by stamping or drawing formed pins, with production costs which are generally modest and in any case much smaller than the costs required for the search of the defectively soldered components according to the prior art. The invention thus conceived is susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept. In particular the protruding portions provided on the pins may be directed towards one side or the other, as illustrated, may be formed at different heights of said pins, according to the requirements. Furthermore, though according to the preferred embodiment, due to cost reasons, the projections according to the invention are provided preferably by stamping on already formed pins, the projections may be simultaneously formed with the pins. Furthermore, the materials employed, the shapes and dimensions may be any according to the requirements. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: A combination including a package for integrated devices and a printed circuit board (1), said package being adapted to be fixed on said printed circuit board (1), said package comprising contact pins (5a, 5b; 15a, 15b) to be loosely inserted in holes (2) of said printed circuit board (1) and to be soldered thereto, at least some (5b; 15a, 15b) of said contact pins comprising protruding portions (10; 14; 16-18) defining abutments, wherein each abutment is configured to rest against a first respective upper edge (12) of one of said holes (2), each respective contact pin resting against a second respective lower edge (11) of one of said holes (2), opposite to said first one (12), such as to allow only limited inclination of the package (3) with respect to said printed circuit board (1). A combination according to claim 1, characterized in that A combination according to one or more of the preceding claims, characterized in that said protruding portions (10; 14; 16-18) comprise outwardly folded regions of the pins. A combination according to one or more of the preceding claims, characterized in that said folded regions are obtained by stamping. A combination according to one or more of the preceding claims, comprising two parallel rows of pins (5a, 5b) and having center of gravity (B) arranged eccentrically with respect to the two rows of pins, characterized in that said protruding portions (10) are formed on at least part of the pins (5b) of a first row closest to the center of gravity of the package. A combination according to claim 5, characterized in that said protruding portions (10) are arranged on the pins (5b) of the first row on a side thereof opposite to the other row. A combination according to claim 6, characterized in that said pins (5b) provided with protruding portions (13) define, at the latter, a width greater than the width of the holes (2) of the printed circuit board (1). A combination according to one or more of claims 1 to 4, comprising a single row of pins, characterized in that said protruding portions (14) are provided at least in part alternately on opposite sides of the row of pins (15a, 15b).

Inventors: MASSIRONI ANGELO, MASSIRONI, ANGELO
Applicants: SGS THOMSON MICROELECTRONICS, SGS-THOMSON MICROELECTRONICS S.R.L.
Application year: 1988
Main classification: H05K3
IPC codes: H01L23, H05K3