GB1583684A

GB1583684A - Electrical layer resistor and a method for its manufacture

Info

Publication number: GB1583684A
Application number: GB2137177A
Authority: GB
Original assignee: Draloric Electronic GmbH
Current assignee: Draloric Electronic GmbH
Priority date: 1976-05-26
Filing date: 1977-05-20
Publication date: 1981-01-28
Also published as: DE2623640A1

Description

(54) AN ELECTRICAL LAYER RESISTOR AND A METHOD FOR ITS MANUFACTURE (71) We, DRALORIC ELECTRONIC GmbH. of Am Plarrer 27, D-8500 Nürnberg, Federal Republic of Germany, a German body corporate, do hereby.declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to an electrical layer resistor comprising a resistance layer applied to a flat carrier body between contact surfaces and a method for its manufacture.

This type of resistor is known as a chip resistor in which the resistance layer is applied, for example by the screen printing method, between two contact surfaces on a main surface and overlapping two narrow opposite sides. In this construction of a resistor, known for example from "Electronic Engineers Master" 1973, Vol. 3, page 1147, the contacting layers extend from the main surface carrying the resistance layer to the opposite main surface in order to ensure safe contacting of the wiring connections of an electronic circuit. This contacting is produced. for example, in the reflowsoldering method wherein the component may begin to float, however. as a result of surface tension of the soldering metal so that accurate location of the component on the circuit is made difficult.Moreover, this type of component takes up a large amount of space in the circuit this amount being determined by its base area.

From US Patent Specification No.

2.777,039 electrical resistors are known for use in printed circuits. These resistors have a circular base area shape and there is arranged between at least two contact surfaces located on a base area. at least one resistance layer. The contact strips may be arranged parallel to each other or concentrically with each other. In this known embodiment, the conductive tracks of the circuit structure of the printed circuit must open into precisely defined tracks in the recesses in the circuit carrier and, with parallel contact surfaces, moreover the discshaped carrier body for the resistors must be used at the correct angular position in order to achieve a contact between the conductive tract and the contact area.

From German Offenlegungsschrift No.

2,413,457 an electrical low value resistance with little induction is known, in which the carrier body has two parallel main areas covered completely by resistive material each of which being separated at the same end solely by the thickness of the insulating carrier body, has a contacting field with electrical connection elements fixed thereto and which are connected together so as to be electrically conductive via a narrow surface located at the other end of the contacting fields, the edges of which have been rounded off.

The invention seeks to provide an electrical layer resistor which may be used simply and directly in a printed circuit, i.e.

which does not have to have any additional connection elements. which does not float on the circuit during a soldering process but is located firmly in the circuit and has a minimum area and space requirement.

According to a first aspect of the invention. there is provided an electrical layer resistor, comprising a resistance layer arranged on a plane. trapezoidal carrier body and connected between two contacts on opposite faces of the carrier body and adjacent the shorter of the two parallel sides thereof.

One or both of the contacts may comprise a contact strip running parallel to the said shorter side from one inclined edge to the other inclined edge.

Thus it is possible to be able to use the resistor in a circuit without having to beware of special orientation thereof. A layer resis tor may be absolutely independent of any orientation when the carrier body has the shape of a double trapezoid.

It is particular advantage in the layer resistance in accordance with the invention that the resistor only requires the space in the circuit which is determined by its crosssection; and that its requirement for space is minimal with respect to conventional electrical resistors used in stacked circuits as it may exploit the thickness of the circuit plate characterized in that a slit corresponding to its cross-section may be cut into the circuit plate in which trapezoidal resistor is placed.

As manufacturing tolerances come into play when manufacturing this type of slot, the layer resistors in accordance with the invention may have shoulders moulded on to the inclined surfaces, these shoulders preventing the resistor from slipping through the slot.

In an embodiment of the invention a contact or contact strip may run along each trapezoidal main surface parallel to the shorter parallel side adjacent thereto from one inclined surface to the other and the resistance layer may cover the two main surfaces and the second, longer, parallel side of the trapezoidal layer resistor or the resistance layers at the two trapezoidal main surfaces may be limited by the contact strip and a connecting strip which covers the large longitudinal side. The contact strips, and the connecting strip which is preferably available may, be of equal width so that the layer resistances in accordance with the invention may be manufactured for example from a fairly long electrically insulated web carrier body wherein it is not important which parallel side is the short and which is the large parallel side of the carrier body of a layer resistance.These metal layers may only be so wide that safe contacting between the contacts and the conductive tracks is possible on the carrier body of a printed circuit. The entire remaining main surface is then available for the resistance layer which may cover the main surface from one inclined surface to the other inclined surface or which may have the shape of a meander.

It is also possible to apply a meander to a main surface and a pocket form flat resistance layer, for example for balancing the resistance, to the opposite main surface.

In a further refinement of layer resistors in accordance with the invention. the contacts or contact strips may be applied by means of the screen printing method. It is also possible that several resistors of any desired structure may be arranged on one or both main surfaces adjacent each other and the contact strips may have interruptions in the vicinity of the short parallel side and the connecting strip on the opposite longer longitudinal side may also have interruptions, said interruptions electrically separating the individual resistors from each other accordingly. These resistor networks have the considerable advantage that no connection conductors, known for example from German Offenlegungsschrift No. 2,316,058, have to be soldered to their connecting surfaces.In fact components with trapezoidal or double trapezoidal outlines are known; in these components, known for example from US Patent Specification No. 2,990,498 or German Gebrauchsmuster No. 7,423,128 it is a question, without exception, of electrical capacitors and not of electrical layer resistors. These known trapezoidal ceramic capacitors are formed in a pressing process at an unfavourable price and are provided with the electrode coatings after sintered burning in of the screen printing method.

According to a second aspect of the invention, there is provided an electrical layer resistor according to claim 1, wherein several resistance layers are arranged one after another on each plane face and the contacts are formed by contact strips which are interrupted to form a plurality of individual contacts.

One or more of the contacts may be formed as a contact strip running parallel to the said shorter side from one inclosed edge to the other inclosed edge.

The trapezoidal layer resistors may be manufactured by applying the contacts or contact strips, any connecting strip and the resistance layers to flat preferably web extruded carrier bodies by means of rotating rollers and the preferably ceramics web is separated after applying and burning-in of the contact and resistance layers by means of a laser beam. This should mean that the web-extruded carrier is only scored by the laser beam and is subsequently broken apart into individual resistors and/or resistor networks. Besides the method of applying the different layers by means of rollers or discs, it is also possible to apply the layers by the screen printing method. by means of dipping, spraying or painting or by combining these methods. The resistor thus manufactured or the resistor network thus manufactured may be enveloped by an electrically insulated protective layer which exposes only the contacts or contact strips. This may take place by means of a dipping process or by means of a screen printing method.

Layer resistances in accordance with the invention may have the advantage that they are placed into the slots in the circuit carrier provided therefor and as a result of the fact that the cut edges along the inclined surfaces do not run absolutely smoothly, they sit firmly in the slots until they are fixed in the circuit by means of a soldering process. A considerable advantage lies in the fact that the measurement tolerances of the slots may be of secondary importance to a large extent as the trapezoidal shape makes it possible to compensate for these tolerances, or shoulders may be formed on to the inclined surfaces running trapezoidally.

A further advantage may lie in the fact that web drawn lengthwise carrier bodies may be provided in the simplest manner in one operation with a plurality of the same or different resistors and/or resistor networks which are separated in a further operation into individual resistors or individual resistor networks and that no additional connection elements are required in order to use the resistors in accordance with the invention in electronic circuits. A considerable advantage lies in minimal space requirement of these resistors.

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which: Figure 1 shows a spatial view of a trapezoidal resistor, Figure 2 shows a side view of a layer resistor in accordance with Figure 1, Figure 3 shows a side view of a layer resistor provided with an envelope and having a dipped resistor layer, Figure 4 shows a sketch and a side view of a trapezoidal layer resistor used in a circuit disc (plate; board; chip), and Figure 5 shows a resistor network on a trapezoidal carrier body, All the drawings are shown on an enlarged scale in order to make the details clearer.

Figure 1 shows a trapezoidal ceramics carrier body 1 having resistance layers 2 arranged between contacts or contact strips 3, these covering the main surfaces and the large longitudinal side 4. This type of resistor may be manufactured by applying the contact strips 3 to the opposite main surfaces of the web-drawn elongated carrier body and the connecting strip or layer 7 by means of rollers and by drying them thereon. After forming the resistance layers on to the opposite main surfaces of the carrier body and after sealing in the same. the elongated carrier body 1 is separated along the inclined surfaces 6 and the short longitudinal side 5 is separated from the original metallization. In this method it is advisable to design the contacts or contact strips 3 and connecting strip 7 so as to have the same width so that the entire strand may be used without wastage.

The preferred equal width of the contact or contact strips 3 and the connecting strip 7 covering the large longitudinal side 4 are visible in Figure 2.

A resistance layer 2 may be seen in Figure 3 which has been applied to the carrier body 1 for example bv means of the dipping method and which extends up to the contact strips 3 which are separated from each other by the short longitudinal side 5. An envelope encapsulation 16 which protects the resistance layer from external influences covers the resistance layer and only exposes the contact strips 3. In this embodiment of a layer resistor in accordance with the invention the envelope 16 may also be imprinted so heavily with a shoulder 15 that this shoulder may act to prevent the layer resistor from slipping through any appropriate slot.

Figure 4 shows a layer resistor used in the slot 10 of a circuit board 11. Thus the slot has a length such that the contacts or contact strips 3 project out of the circuit board 11 in the vicinity of the short longitudinal side 5 of the trapezoidal carrier body 1 so that the contacts or contact strips 3 may be connected to the conductive tracks 8 which may be pre-tinned, so as to be electrically conductive by means of a bead of tin 9. In the trapezoidal layer resistor shown in this Figure it is a question of a construction as shown in Figure 1 in which the layer resistors 2 lie between the two contact strips 3 and the connecting strip 7.

Figure 5 shows a resistor network in which a number of resistor layers 2 having a different structure are arranged between contacts 3 on one side 5 and connecting elements or layers 7 on the larger longitudinal side 4, wherein the contacts 3 and the connecting elements or layers 7 are in the form of strips with interruptions 12 and 13.

Thus the structures lying between the two inclined surfaces 6 on both main surfaces are preferably manufactured by means of the screen printing method. However all other known methods of thick film and thin film technology are possible or even combinations of both techniques. The carrier body does not have to comprise ceramics but may for example comprise a plastics material reinforced with glass fibre.

WHAT WE CLAIM IS: 1. An electrical layer resistor. comprising a resistance layer arranged on a plane, trapezoidal carrier body and connected between two contacts on opposite faces of the carrier body and adjacent the shorter of the two parallel sides thereof.

2. An electrical layer resistor according to claim 1 wherein at least one of the contacts comprises a contact strip running parallel to the said shorter side from one inclined edge to the other inclined edge.

3. An electrical layer resistor according to claim 2, wherein a connector strip covers the longer of the two parallel side and its adjacent regions of the plane surface between a contact strip and a connector strip.

4. An electrical layer resistor according to claim 1, 2 or 3. wherein the resistance

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the measurement tolerances of the slots may be of secondary importance to a large extent as the trapezoidal shape makes it possible to compensate for these tolerances, or shoulders may be formed on to the inclined surfaces running trapezoidally. A further advantage may lie in the fact that web drawn lengthwise carrier bodies may be provided in the simplest manner in one operation with a plurality of the same or different resistors and/or resistor networks which are separated in a further operation into individual resistors or individual resistor networks and that no additional connection elements are required in order to use the resistors in accordance with the invention in electronic circuits. A considerable advantage lies in minimal space requirement of these resistors. The invention will now be described in greater detail, by way of example, with reference to the drawings, in which: Figure 1 shows a spatial view of a trapezoidal resistor, Figure 2 shows a side view of a layer resistor in accordance with Figure 1, Figure 3 shows a side view of a layer resistor provided with an envelope and having a dipped resistor layer, Figure 4 shows a sketch and a side view of a trapezoidal layer resistor used in a circuit disc (plate; board; chip), and Figure 5 shows a resistor network on a trapezoidal carrier body, All the drawings are shown on an enlarged scale in order to make the details clearer. Figure 1 shows a trapezoidal ceramics carrier body 1 having resistance layers 2 arranged between contacts or contact strips 3, these covering the main surfaces and the large longitudinal side 4. This type of resistor may be manufactured by applying the contact strips 3 to the opposite main surfaces of the web-drawn elongated carrier body and the connecting strip or layer 7 by means of rollers and by drying them thereon. After forming the resistance layers on to the opposite main surfaces of the carrier body and after sealing in the same. the elongated carrier body 1 is separated along the inclined surfaces 6 and the short longitudinal side 5 is separated from the original metallization. In this method it is advisable to design the contacts or contact strips 3 and connecting strip 7 so as to have the same width so that the entire strand may be used without wastage. The preferred equal width of the contact or contact strips 3 and the connecting strip 7 covering the large longitudinal side 4 are visible in Figure 2. A resistance layer 2 may be seen in Figure 3 which has been applied to the carrier body 1 for example bv means of the dipping method and which extends up to the contact strips 3 which are separated from each other by the short longitudinal side 5. An envelope encapsulation 16 which protects the resistance layer from external influences covers the resistance layer and only exposes the contact strips 3. In this embodiment of a layer resistor in accordance with the invention the envelope 16 may also be imprinted so heavily with a shoulder 15 that this shoulder may act to prevent the layer resistor from slipping through any appropriate slot. Figure 4 shows a layer resistor used in the slot 10 of a circuit board 11. Thus the slot has a length such that the contacts or contact strips 3 project out of the circuit board 11 in the vicinity of the short longitudinal side 5 of the trapezoidal carrier body 1 so that the contacts or contact strips 3 may be connected to the conductive tracks 8 which may be pre-tinned, so as to be electrically conductive by means of a bead of tin 9. In the trapezoidal layer resistor shown in this Figure it is a question of a construction as shown in Figure 1 in which the layer resistors 2 lie between the two contact strips 3 and the connecting strip 7. Figure 5 shows a resistor network in which a number of resistor layers 2 having a different structure are arranged between contacts 3 on one side 5 and connecting elements or layers 7 on the larger longitudinal side 4, wherein the contacts 3 and the connecting elements or layers 7 are in the form of strips with interruptions 12 and 13. Thus the structures lying between the two inclined surfaces 6 on both main surfaces are preferably manufactured by means of the screen printing method. However all other known methods of thick film and thin film technology are possible or even combinations of both techniques. The carrier body does not have to comprise ceramics but may for example comprise a plastics material reinforced with glass fibre. WHAT WE CLAIM IS:

1. An electrical layer resistor. comprising a resistance layer arranged on a plane, trapezoidal carrier body and connected between two contacts on opposite faces of the carrier body and adjacent the shorter of the two parallel sides thereof.

layer covers the plane faces from one inclined edge to the other inclined edge.

5. An electrical layer resistor according to claim 2 or 3, wherein the resistance layer is a meandering resistance path.

6. An electrical layer reistor according to claim 1, wherein several resistance layers are arranged one after another on each plane face and the contacts are formed by contact strips which are interrupted to form a plurality of individual contacts.

7. A method of producing an electrical layer resistor comprising forming a carrier body of trapezoidal shape, applying a resistance layer and contacts to the carrier body with the resistance layers connected between two contacts on opposite faces of the carrier body and adjacent to the shorter of the two parallel sides thereof.

8. A method according to claim 7, wherein at least one of the contacts is formed as a contact strip running parallel to the said shorter side from one inclined edge to the other inclined edge.

9. A method according to claim 7 or 8, wherein the contacts or contact strips and resistance layers are applied to the plane carrier bodies by means of rotating rolls.

10. A method according to claim 9, wherein the carrier bodies are cut by a laser beam from a drawn ceramic strand after sintering and after applying and burning in the contacts or contact strips and the resistance layers.

11. A method according to claim 10, wherein the elongate strand drawn carrier body is scratched by a laser and broken apart.

12. A method according to claim 7 or 8.

wherein the contacts or contact strips and the resistance layers are applied by screen printing.

13. A method according to any one of claims 7 to 12. wherein the resistor is surrounded by an electrically insulating casing which only exposes the contacts or contact strips.

14. A method according to claim 13.

wherein the casing is applied by screen printing.

15. An electrical layer resistance arrangement substantially as described herein with reference to the drawings.

16. A method of producing an electrical layer resistance arrangement substantiallv as described herein with reference to the drawings.