US3409856A

US3409856A - Fixed value coated electrical resistors

Info

Publication number: US3409856A
Application number: US470352A
Authority: US
Inventors: Meoni Angelo
Original assignee: Gerafin S A Soc
Current assignee: Gerafin S A Soc; Gerafin Sa Ste
Priority date: 1964-07-28
Filing date: 1965-07-08
Publication date: 1968-11-05
Anticipated expiration: 1985-11-05
Also published as: FR1411112A; ES315801A1; DE1540488A1; US3478424A; GB1087405A

Description

Nov. 5, 1968 A. MEONI FIXED VALUE COATED ELECTRICAL RESISTORS Filed July 8, 1965 Fly. 7

F/lg. 3

United States Patent 3,409,856 FIXED VALUE COATED ELECTRICAL RESISTORS Angelo Meoni, Paris, France, assignor to Socrete Gerafin S.A., Mesocco, Switzerland Filed July 8, 1965, Ser. No. 470,352 Claims priority, application France, July 28, 1964,

983,258 6 Claims. (Cl. 338--312) ABSTRACT OF THE DISCLOSURE Electrical resistors are formed wherein a metallic band includes a plurality of terminal rods extending along 1ts length from opposite edges of the band. The rods along each edge are attached to insulative bases through aperatures formed therein. One face of each base is coated with spaced layers of conductive meterial, each face electrically coacting with a rod. The opposite face is provided with a layer of resistance material which extends over the edge to electrically coact with the conductive material. The bases are out between adjacent pairs of terminal rods and the rods are severed from the band to form resistors.

The present invention relates to fixed value resistors which are generally utilised in the circuits of radio and television sets, and electronic circuits in general, and more particularly in the technique known as printed circuitry.

At the present time, resistors are generally of cylindrical form although they are sometimes fiat, but in any event they include a terminal connection fixed at each of the ends. The technique of printed circuitry necessitates the provision of parts intended to receive the terminals of the resistors at predetermined distances and fixed in relation to one another, of the order of one-sixth of an inch, that is to say, about two and a half millimetres, or multiples thereof. Also, in order to use the present day resistors it is necessary, before connecting them into a circuit, to bend and to twist at least one of the terminal connections and very often both of them in order to permit these terminals to engage the corresponding connections of the circuit. This operation is time-consuming and inconvenient.

On the other hand, these previously proposed resistors are relatively bulky and are no longer suitable for all the requirements of modern techniques; all of them have one or several classic defects, amongst which it is possible to point out the following:

(a) Uncertainty in the contact between the terminal connection and the semi-conductor constituting the resistance element proper, because of the rigidity of the metallic part intended to effect the connection between the utilisation terminals, which results in a disturbance of the cotnact in question;

(b) Difficulty in obtaining exact values (small tolerance), especially when, in order to obtain the desired values, selection methods are employed;

(c) A relatively high capacitance which is often variable because the susbtantial metallic surfaces opposite to a considerable thickness of the semi-conductor;

(d) A self-inductance which is relatively high and which is variable when methods for the standardisation of resistors is effected by means of a spiral around a cylindrical body.

The term semi-conductor is used herein to mean a material which is suitable for use as a resistance element.

According to the present invention there is provided a method of manufacturing fixed value resistors comprising the steps of coating one face of an insulating support laminate with a thin metallic layer, depositing a layer of a semi-conductor material on a portion of the other face 3,409,856 Patented Nov. 5, 1968 of the support in the longitudinal direction, on one of its longitudinal edges and on a part of the first face, the semi-conductor material being in contact with the said metallic layer, providing a row of holes in the part of the support which is not covered with semi-conductor material, introducing into each hole a conducting rod serving as a terminal connection and disposed substantially normally to the row of holes, setting and soldering the rod on the metallic layer, separating each pair of terminal connections by cutting the support transversely between two terminals of two consecutive pairs of terminals, cutting the metallic layer rigid with the insulating support transversely between the terminals of each pair into two substantially equal parts, and finally standardising each resistors thus formed by comparing its value with the value of a reference resistor and modifying the resistor by removal, in an appropriate zone, of a portion of the semi-conductor material until the value of the resistor reaches that of the reference resistor.

Further according to the present invention there is provided a method of manufacturing resistors comprising the steps of coating one face of an elongate insulating support plate with a conductor material, depositing a layer of resistance material on the other face of the plate and on one longitudinal edge so that there is contact between the conductor and resistance materials, providing a row of holes in the plate in the face coated only with conductor material, inserting a terminal conductor into each hole and making an electrical connection between the conductor layer and each conductor, dividing the plate between alternate terminal conductors, and removing a band of the conductor material from the plate between the terminal conductors of each resistor.

It should be emphasised that the conductor rods forming the terminal connections are preferably obtained by partially cutting through a continuous band of metal, in such a manner that it is easily possible to maintain the predetermined distances between the said connections and above all a large number of operations referred to above can be carried out automatically and continuously without completely separating the resistors from the metallic band carrying the connection rods.

Other complementary characteristics of the invention will become clear from the following description which is given hereafter with reference to the accompanying drawing. It is to be understood that the description and the drawing are only given by way of example and in no way limit the scope of the invention.

FIG. 1 shows a diagrammatic view in elevation of a group of resistances manufactured according to the process which is the subject of the invention, this view showing one of the faces of the resistors;

FIG. 2 shows a view of the other face of a resistor and,

FIG. 3 is a section on the line III-III of FIG. 2.

An insulating support 1 in the form of a laminate of, for example, Bakelite-coated cardboard, is employed and is covered on one face (that shown in FIG. 1) by a thin metallic layer 2, for example, of copper. On a portion of the other face (that shown in FIG. 2) of the support 1, there is deposited along the length a thin layer 3 of a semiconductor material, for example, graphite. This deposit is effected by any known means or process, for example, by spattering or by dipping. With the latter method of operation, the two faces of the support are equally covered with semi-conductor material. The deposit is effected from one of the edges of the insulating support and also covers the corresponding longitudinal edge 4 in such a manner that the semi-conductor material is in contact .with the metallic layer 2. It is also possible to effect, between the layer 2 and the semi-conductor, a supplementary short circuit, for example by deposit of a varnish with a silver base. A row of holes 5 in even numbers, preferably eqiui-distant from one another, is drilled in the part 1a of the support which is not covered with semi-conductor material. The distance between two consecutive holes is appropriate to the use intended for the resistor and generally is equal to the spacing between the axes of two consecutive terminals of a printed circuit. This distance is generally equal to one-sixth of an inch, or about two and a half millimetres.

A conducting rod 6 is introduced into each hole 5 which forms a terminal connection and is arranged perpendicularly to the row of holes. It is set into and firmly connected to the copper face of the support by solder 7. In order to obtain the desired spacing between two consecuti-ve terminal connections, these are preferably obtained by cutting from a metallic band 8, the other side of the band carrying in the same manner a second series of conducting rods 6 symmetrical to the first in order to permit simultaneous manufacture of a second series of resistors.

Each pair of the terminal connections 6 is then separated corresponding to one of the resistors, by cutting the sup port' transversely along slits 1b between two terminals belonging to two consecutive pairs, as is shown in FIG. 1. In order to insulate electrically in each resistor the two terminal connections, the metallic layer 2 rigid with the insulating support 1, is cut transversely into two parts 211 and 2b, which are substantially equal, between the terminals 6 of each pair, the

parts

2a and 2b remaining in contact with the semi-conductor material. This operation is effected by any means or process which is known and, for example, by chemical etching, or mechanically by means of a milling cutter or a fraising operation.

There is thus obtained for each pair of terminal connections 6, a resistor of an indefinite value. In order to obtain resistors of more exact value, it is necessary to standardise them. Standardisation is effected by com.- parison of the value of each of the resistors with the value of a predetermined reference, after having separated the two terminals from the band.

For this operation, the means generally employed for the separation of the metallic layer into two substantially equal parts is utilised and a slit in the edge and in the face seen in FIG. 2 of the semi-conductor which is transverse to the length of the resistor and which prolongs the line of separation of the

parts

2a and 2b of the metallic layer, the length of the slit depending on the difference between the value of the part-formed resistor and that of the reference. Thus, the standardisation of the resistors is effected by extending the resistance circuit.

As is effected for all resistors of the miniature type, it is then possible to provide a coating of the resistor which serves as a protection against humidity with the aid of an appropriate varnish and also to mark the value of each resistor according to the codes normally employed, such as the colour code. The latter operations can be effected, for example, by dipping.

The resistor thus obtained has all the desired characteristics: small bulk, exact spacing between the terminal connections, standardised value, etc. It remains however to emphasise that in a resistance of this type, the metallic layer has several functions. It forms a radiator for the dis sipation of heat because of its substantial surface. Furthermore, it ensures contact with the semi-conductor and enables easy soldering of the connection rods at a distance spaced relatively to the contact between the metallic layer and the semi-conductor layer, which allows for a certain deformation between these two zones. Moreover, the relative dispositions of the semi-conductor, the metallic layer and of the connection rods permit standardisation of the resistor from the side opposed to the latter.

Finally, in order to ensure continuous contact under best conditions, between the semi-conductor layer 3 and the

parts

2a and 2b the conductor layer, these can be rounded or chamfered at the edge 2c adjacent to the longitudinal edge 4 of the insulating support 1, as is shown in FIG. 3.

The invention is not limited to the single method for carrying it out which has been described and shown, but covers moreover any modifications with regard, in particular, to the dimensions of the insulating support, the coverings of conducting and semi-conducting material, the thickness, the nature of the materials used and the methods of manufacture and standardisation which are employed.

I claim:

1. An electrical resistor comprising:

an elongate insulating base strip having two faces and two longitudinal edges,

a layer of conductive material on one face divided into two electrically separate parts,

a layer of resistance material on the other face, along at least one of the longitudinal edges and on a part of the conductive layer,

a terminal connection rod in electrical contact with one part of the conductor layer, and

slot means, said slot means being in alignment with a line which divides said two parts of the conductive layer, each of said two parts of the conductive layer intersecting the resistance material along the surface extending from the slot to the outer edge of the resistance material.

2. An electrical resistor according to claim 1, wherein the insulating base plate is made of synthetic-resin coated cardboard.

3. An electrical resistor according to claim 1, wherein the said two parts of the conductor layer are of equal area.

4. An electrical resistor according to claim 1, wherein the conductive layer is rounded at the intersection zone with the resistance layer.

5. An electrical resistor according to claim 1, wherein the conductive layer is chamfered at the intersection zone with the resistance layer.

6. The resistor of claim 1, wherein said slot is variable in length to thereby vary the resistance of the resistor.

References Cited UNITED STATES PATENTS 1,416,036 5/1922 Kempton l74l67 X 2,978,364 4/1961 Blaustein 338-308 X 3,067,310 12/1962 Waltz et al 338-308 X 3,161,457 12/ 1964 Schroeder et al.

RICHARD M. WOOD, Primary Examiner.

I. G. SMITH, Assistant Examiner.