GB1566151A - Printed resistance path devices - Google Patents
Printed resistance path devices Download PDFInfo
- Publication number
- GB1566151A GB1566151A GB1098277A GB1098277A GB1566151A GB 1566151 A GB1566151 A GB 1566151A GB 1098277 A GB1098277 A GB 1098277A GB 1098277 A GB1098277 A GB 1098277A GB 1566151 A GB1566151 A GB 1566151A
- Authority
- GB
- United Kingdom
- Prior art keywords
- laser
- resistance
- path
- devices
- sections
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
- H01C7/021—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient formed as one or more layers or coatings
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
- G01K7/183—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer characterised by the use of the resistive element
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/22—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming
- H01C17/23—Apparatus or processes specially adapted for manufacturing resistors adapted for trimming by opening or closing resistor geometric tracks of predetermined resistive values, e.g. snapistors
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- General Physics & Mathematics (AREA)
- Ceramic Engineering (AREA)
- Electromagnetism (AREA)
- Apparatuses And Processes For Manufacturing Resistors (AREA)
- Parts Printed On Printed Circuit Boards (AREA)
Description
(54) iMPROVEMENTS IN OR RELATING TO PRINTED RESISTANCE PATH
DEVICES (711) We, ROSEMOUNT ENGINEERING
COMPANY LIMITED, a British Company, of
Durban Road, Bognor Regis, Sussex, PO22 9QX, 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 present invention relates to printed resistance path devices and also to a method of trimming such devices.
Well known printed resistance path devices comprise an insulating substrate having printed on a surface thereof a path of resistive material. The path usually interconnects a pair of contact pads also printed on the substrate, by which connections can be made to the device. It is known to make such devices with a film of metal and it is also known to make such devices by printing the path on the substrate with an ink formed of a glass fruit containing particles of a metal. The printed substrate is then fired to dry off the ink and vitrify the film. The metal particles in the film can cause it to have properties similar to those of the bulk metal. Printed resistance path devices, formed with either metal films or glass films, printed on insulating substrates, will be referred to hereinafter as printed resistance path devices of the type described.
Printed resistance path devices of the type described may be employed either as resistors or, when formed using a suitable metal having a temperatur ,edependent coefficient of resistance, they may be used as resistance thermometer sensors.
According to a first aspect of the present invention there is privided a printed resistance path device, of the type described, the path of the device having a plurality of links short circuiting sections of the path, the links being disposed to cross a single straight line, the short circuited sections being in two or more groups, the sections of each group having resistances which are similar to each other and different to the resistances of the sections of the or each other group. The links provided in the path of the device of the present invention enable the device to be trimmed in a very advantageous manner.It has proved difficult to print resistance paths in printed resistance path devices of the type described sufficiently accurately and with sufficient consistency in the printed film so that the resistance between the ends of the path of the device is equal to a desired value within a close tolerance. Thus, it has been the practice to trim the device after the path has been printed on the substrate thereof so as to bring the actual resistance of the device closer to the desired value. It will be appreciated that cutting any one of the links provided in the printed resistance path device of the present iivention has the effect of increasing the resistance between the ends of the path.By disposing the links of the device so that they cross a single straight line, successive links can be cut most conveniently by proceeding with a cutting tool along the line until the resistance of the device has been brought closer to the desired value. Because the links all cross a single straight line, successive links can be cut by affecting only a simple linear relative movement, in the direction of the straight line, between the device and the cutting tool.
By the term "similar resistances" used herein, it is meant that the resistances of the short circuited sections are substantially the same within the tolerance made possible by the manufacturing process, i.e. the short circuited sections have a nominal resistance.
Thus, in a typical case, the path is formed with a substantially uniform width and thickness and the short circuited sections having similar resistances are made with substantially the same lengths.
The links short circuiting each group of sections may be disposed to cross said single straight line in a respective region thereof, the regions being arranged along the line in descending order of the resistances of the corresponding groups of sections. With such an arrangement, and in accordance with a further aspect of the invention the device is conveniently trimmed by the steps of initially directing a laser beam from a laser to impinge on said device substantially on said single straight line, and in the region thereof corresponding to the group of sections having the highest resistances, affecting relative movement between the laser and the device so that the beam tracks along the straight line in said region and towards the next adjacent region and cuts through one or more said links in said region turning the laser off when the resistance of the device is increased to within the nominal value of said highest resistances from the desired resistance of the device, continuing the relative movement between the laser and the device and turning the laser beam on again to cut links crossing the next region of the straight line corresponding to the group of sections having the next highest resistance until the resistance of the device is increased to within the nominal value of said next highest resistances from the desired resistance of the device, and repeating the sequence for any further groups of sections.Because all the links cross the single straight line and the regions of the line are arranged in descending order of the resistances of the corresponding groups of sections, the trimming process can proceed with a continuous relative movement between the laser and the device merely switching the laser beam on and off as required until the resistance of the device is within the nominal resistance value of the group of sections having the lowest resistances from the desired resistance of the device.
In a preferred embodiment, the path of the printed resistance path device further has a blank section having a width greater than the width of the rest of the path. This blank section is preferably disposed so that it is traversed by the single straight line. Furthermore, the blank section is most conveniently disposed to be traversed by the single straight line adjacent the region of the line which is crossed by the links short circuiting the group of sections having the lowest resistances. Thus, in the trimming process, the device may be finally trimmed by employing the laser to cut into the blank section along the single straight line until the resistance of the device matches the desired resistance within the required tolerance.It will be appreciated that cutting into the blank section has the effect of lengthening the path of the device and, as a result, increasing the resistance of the device.
In a particularly advantageous embodiment, the path has a tortuous portion extending over a predetermined linear distance and a substantially linear by-pass portion extending along side said tortuous portion, and said links comprise link portions linking said by-pass portion with respective positions at intervals along the length of said tortuous portion.
An example of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 illustrates on an enlarged scale, a printing pattern for a printed resistance path device embodying the present invention and,
Figure 2 is a view in longitudinal cross section of such a device.
Referring to the drawings, a printed resistance path device comprises a printed film 10 of conductive material on an insulating substrate 11, e.g. of a ceramic material.
The printed film 10 has a pattern as illustrated enlarged in Figure 1. In fact, Figure 1 shows the printed film patterns 12, 13 and 14 of three identical devices side by side. In accordance with common practice, tithe patterns for several devices are printed simultaneously on a common sheet of substrate, the substrate being separated after printing to provide the different devices. In the example of Figure 1, only three patterns are illustrated, but in a typical practical arrangement, sixteen printed path patterns may be printed on a single sheet of substrate. The substrate may be scribed prior to printing so that it can readily be broken into the constituent devices.
The printed film 10 of conductive material may be a film of metal. For example, the film may be of platinum metal when the printed resistance film device is to be a resistance thermometer sensor. However, very conveniently the film 10 comprises a vitreous film containing particles of a metal, e.g.
platinum. The printing operation is then preformed by printing the patterns 12 to 14 on the substrate 11 using an ink containing particles of glass and particles of the metal. The printed substrate is then fired to dry the ink and vitrify the glass particles. The resulting vitreous film containing metal particles can have properties similar to those of the bulk metal.
As illustrated in Figure 1, each printed pattern comprises a track or path 'of the conductive film intemlinking a pair of terminal pads 15 and 1.6 at each end of the pattern.
After the conductive film has been printed, and fired if appropriate, the substrate 11 is then printed again with an ink containing particles of glass only. The second printing provides a complete layer 17 of the glass ink over the entire area occupied by the conductive track of the printed pattern, but leaving the terminal pads 15 and 16 uncovered. The printed substrate is then fired again to dry the layer 17 and vitrify it so that it forms a glass protective layer over the conductive track portion of the printed film 10.
The conductive track portion or path of the printed film 10 between the terminal pads 15 and 16 comprises the following elements: a broad tortuous portion, indicated generally by reference numeral 20, a fine tortuous portion, indicated generally by reference numeral 21, and a spiral portion, indicated generally by reference numeral 22.
The portions 20, 21 and 22 of the conductive path are connected in series with one another between the terminal pads 15 and 16. However, the conductive path further comprises a plurality of links 18 and 19 short circuiting sections of the two tortuous portions 2Q and 21. Each of the links 18 and 19 cross a single straight line extending parallel with a longitudinal axis of the discreet printed film of the device. For convenience, the straight line is shown in
Figure 1 as the line 23.
As can be seen in Figure 1, each of links 18 and 19 is effective to short circuit a section of the conductive path. For example, the link 24 nearest to the terminal pad 15 effectively short circuits a section 25 of the tortuous portion 20 of the path. All the links 18 and the links 19 together are effective to short circuit substantially the whole of the broad tortuous portion 20 and the fine tortuous portion 21 of the path.
In the embodiment illustrated in Figure 1 the conductive path further comprises bypass portions 26 and 27 extending alongside the tortuous portions 20 and 21 respectively.
The links 18 are effective to connect the bypass portion 26 with respective positions at intervals along the tortuous portion 20, and correspondingly the links 19 connect bypass portion 27 to positions at intervals along the tortuous portion 21.
The conductive path further comprises a blank portion 28. The blank portion 28 has a width greater than the rest of the path and its purpose will be described later. However, as can be seen in Figure 1, the blank portion 28 is disposed so as to be traversed by the straight line 23. A further smaller blank portion 29 is also provided.
The advantages of the arrangement of the conductive path between the terminal pads 15 and 16 arise from the resulting ease of trimming the device. It is a normal re quirement of resistance devices and especially resistance thermometer sensor devices that the devices have to be trimmed to provide desired resistance characteristics. The arrangement of the conductive path as illustraed in Figure 1 provides a very large range through which the resistance of the device can be trimmed. Furthermore, the arrangement enables the trimming process to be carried out with relatively simple movements between the trimming tool and the device.
In a typical trimming operation, the devices are trimmed using a laser to cut through the links 18 and 19. The trimming operation may be preformed after the protective coating 17 of glass has been printed to cover the previously printed conductive path and before the substrate sheet 11 is divided to provide the discreet devices. Initially, the laser and the printed substrate are positioned relative to one another so that the laser beam is directed at a point 30 on the line 23 and next to the terminal pad 15. The laser is then switched on and the substrate is moved relative to the laser so that the laser beam tracks along the line 23 cutting through links 18 starting with the link 24. Simultaneously, connections are made with the terminal pads 15 and 16 and the resistance of the device between the pads is monitored.As successive links 18 are cut by the laser, section 25 and successive further sections of the tortuous portion 20 are connected in series with the spiral portion 22 and the resistance of device is increased. Because the sections of the portion 20 have substantially the same length, their resistances are similar to each other, i.e. have a nominal value, and the resistance of the device increases in substantially equal steps corresponding to this nominal value.
When the measured resistance between the pads 15 and 16 is increased to within this nominal value from the desired resistance value of the device. the laser is switched off. The movement between the substrate and the laser continues, however, and the laser is switched on again when the beam is directed at a point 31 on the line 23 before the first of the links 19. Continued movement of the device then causes successive links 19 to be cut by the laser, further increasing the resistance of the device by nominal amounts corresponding to the resistance of each of the sections of the fine tortuous portion 21.
When the resistance of the device is increased to within the nominal value of the resistances of the sections of the portion 21, which is less than the nominal value of the sections of the portion 20, the laser is again switched off.
However, the movement of the device relative to the laser is continued and the laser is switched on again when the beam is directed at a point 32 immediately before the blank portion 28. Continued movement of the device causes the laser to cut into the blank portion 28, the effect is to increase the length of the conductive path of the device. Thus, as the beam cuts into the portion 28, the resistance d the device is again increased. The laser is switched off when the resistance matches the desired resistance of the device within a predetermined tolerance.
After switching off, the movement of the device relative to the laser is continued along the line 23 until the laser beam is directed at a point 33, whereupon the relative movement between the device and the laser is stopped,
When several devices on a single sheet of substrate are provided, such as illustrated in Figure 1, the operation can proceed immediately to trimming the pattern 13 of the next device by moving the substrate relative to the laser so that the laser beam is directed at a point 34 on pattern 13, corresponding to the point 30 for the pattern 12. The trimming of the pattern 13 is then preformed moving the substrate relative to the laser so that the laser beam tracks along a line 35 corresponding to the line 23.This alternate to and fro movement of the substrate relative to the laser continues, switching the laser on and off as described, until all sixteen devices on a common substrate are trimmed. The devices can then be separated one from another.
If it is necessary to produce devices to a very close tolerance, the blank portions 29 may also be cut into, for example by a laser.
The arrangement of the printed paths of the devices have the particular advantage that the entire sequence of manufacturing the devices, including the trimming process, can be made automatic with relatively little human intervention. The arrangement of all the links 18 and 19, together with the blank portion 28 on the single straight line 23, and also providing several patterns on a single substrate alternately in one orientation and then in the other greatly reduces unnecessary movement between the devices and the laser during the trimming process.
Because each device can be trimmed over a very wide range, the tolerances in the process of printing the conductive pattern on the substrate can be relaxed without the yield of satisfactory devices suffering.
Preferably, the terminal pads 15 and 16 of the devices are over printed with gold, or some other suitable material to provide a low resistance pad to which connections may readily be made. Preferably also, each device is divided with holes 36 and 37 pierced through the substrate 11 through the terminal pads 15 and 16 respectively. The holes 36 and 37 may be made substantially square, as shown in Figure 1. Connections can then readily be made to the completed device by pushing connecting wires through the holes 36 and 37 and soldering them to the gold covered pads 15 and 16, or otherwise bonding the wires to the pads. Alternatively, connections may be made to the device by inserting rivets through the holes 36 and 37. Because the holes are non-circular the rivets are prevented from rotating in the holes which would otherwise tend to break the connections.
The manufacture of the devices can be substantially completely automated, allowing a significant reduction in costs. Furthermore, the devices may be sold without leadout wires, also reducing the cost of each unit.
The resulting device is both cheap and convenient to customers used to handling electronic components since the device can be soldered into place in a circuit.
WHAT WE CLAIM IS:- 1. A printed resistance path device of the type described, the path of the device having a plurality of links short circuiting sections of the path, the links being disposed to cross a single straight line the short circuited sections being in two or more groups, the sections of each group having resistances which are similar to each other and different to the resistances of the sections of the or each other group.
2. A device as claimed in claim 1 wherein the links short circuiting each group of sections are disposed to cross said single straight line in a respective region thereof, the regions being arranged along the line in descending order of the resistances of the corresponding groups of sections.
3. A device as claimed in claim 1 or claim 2 wherein the path of the printed resistance path device further has a blank section having a width greater than the width of the rest of the path.
4. A device as claimed in claim 3, wherein the blank section is disposed so that it is traversed by the single straight line.
5. A device as claimed in claim 4, as appendant to claim 2, wherein the blank section is disposed to be traversed by the single straight line adjacent the region of the line which is crossed by the links short circuiting the group 'of sections having the lowest resistances.
6. A device as claimed in any preceding claim wherein the path has a tortuous portion extending over a predetermined linear distance and a substantially linear by-pass portion extending along side said tortuous portion, and said links comprise link portions linking said by-pass portion with respective positions at intervals along the length of said tortuous portion.
7. A method of trimming the printed resistance path device claimed in claim 2 or any of claims 3 to 6 as appendant to claim 2, comprising the steps of initially directing a laser beam from a laser to impinge on said device substantially on said single straight line and in the region thereof cor
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (11)
1. A printed resistance path device of the type described, the path of the device having a plurality of links short circuiting sections of the path, the links being disposed to cross a single straight line the short circuited sections being in two or more groups, the sections of each group having resistances which are similar to each other and different to the resistances of the sections of the or each other group.
2. A device as claimed in claim 1 wherein the links short circuiting each group of sections are disposed to cross said single straight line in a respective region thereof, the regions being arranged along the line in descending order of the resistances of the corresponding groups of sections.
3. A device as claimed in claim 1 or claim 2 wherein the path of the printed resistance path device further has a blank section having a width greater than the width of the rest of the path.
4. A device as claimed in claim 3, wherein the blank section is disposed so that it is traversed by the single straight line.
5. A device as claimed in claim 4, as appendant to claim 2, wherein the blank section is disposed to be traversed by the single straight line adjacent the region of the line which is crossed by the links short circuiting the group 'of sections having the lowest resistances.
6. A device as claimed in any preceding claim wherein the path has a tortuous portion extending over a predetermined linear distance and a substantially linear by-pass portion extending along side said tortuous portion, and said links comprise link portions linking said by-pass portion with respective positions at intervals along the length of said tortuous portion.
7. A method of trimming the printed resistance path device claimed in claim 2 or any of claims 3 to 6 as appendant to claim 2, comprising the steps of initially directing a laser beam from a laser to impinge on said device substantially on said single straight line and in the region thereof cor
responding to the group of sections having the highest resistances, affecting relative movement between the laser and the device so that the beam tracks along the straight line in said region and towards the next adjacent region and cuts through one or more said links in said region turning the laser off when the resistance of the device is increased to within the nominal value of said highest resistances from the desired resistance of the device, continuing the relative movement between the laser and the device and turning the laser beam on again to cut links crossing the next region d the straight line corresponding to the group of sections having the next highest resistances until the resistance of the device is increased to within the nominal value of said next highest resistances from the desired resistance of the device, and repeating the sequence for any further groups of sections.
8. A method as claimed in claim 7 and for trimming the device claimed in claim 5, wherein the device is finally trimmed by employing the laser to cut into the blank section along the single straight line until the resistance of the device matches the desired resistance within the required tolerance.
9. A printed resistance path device sub stantially as hereinbefore described with reference to and as illustrated in the drawings.
10. A method of trimming the device claimed in claim 9, substantially as hereinbefore described with reference to the drawings.
11. A resistance thermometer sensor comprising a printed resistance path device as claimed in any of claims 1 to 6 or claim 9 wherein the path has a temperature dependent coefficient of resistance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1098277A GB1566151A (en) | 1978-03-13 | 1978-03-13 | Printed resistance path devices |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1098277A GB1566151A (en) | 1978-03-13 | 1978-03-13 | Printed resistance path devices |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1566151A true GB1566151A (en) | 1980-04-30 |
Family
ID=9977876
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1098277A Expired GB1566151A (en) | 1978-03-13 | 1978-03-13 | Printed resistance path devices |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB1566151A (en) |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0092406A2 (en) * | 1982-04-16 | 1983-10-26 | RAYCHEM CORPORATION (a Delaware corporation) | Elongate electrical heating device and a system comprising such devices |
| EP0150784A2 (en) * | 1984-02-01 | 1985-08-07 | Koch Elektronik AG | Trimming method for a temperature sensor |
| US4574188A (en) * | 1982-04-16 | 1986-03-04 | Raychem Corporation | Elongate electrical assemblies |
| US4582983A (en) * | 1982-04-16 | 1986-04-15 | Raychem Corporation | Elongate electrical assemblies |
| US4659913A (en) * | 1982-04-16 | 1987-04-21 | Raychem Corporation | Elongate electrical assemblies |
| GB2184893A (en) * | 1985-12-19 | 1987-07-01 | Marconi Electronic Devices | Circuit arrangement |
| US4791276A (en) * | 1982-04-16 | 1988-12-13 | Raychem Corporation | Elongate electrical assemblies |
| US4999731A (en) * | 1986-08-22 | 1991-03-12 | Northern Telecom Limited | Surge protector for telecommunications systems |
| US5057964A (en) * | 1986-12-17 | 1991-10-15 | Northern Telecom Limited | Surge protector for telecommunications terminals |
| GB2243956A (en) * | 1990-05-09 | 1991-11-13 | Sfernice S A | Electrical resistors presenting selectable resistance values and methods of making same |
-
1978
- 1978-03-13 GB GB1098277A patent/GB1566151A/en not_active Expired
Cited By (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0092406A3 (en) * | 1982-04-16 | 1984-02-29 | Raychem Corporation | Elongate electrical assemblies |
| US4574188A (en) * | 1982-04-16 | 1986-03-04 | Raychem Corporation | Elongate electrical assemblies |
| US4582983A (en) * | 1982-04-16 | 1986-04-15 | Raychem Corporation | Elongate electrical assemblies |
| US4659913A (en) * | 1982-04-16 | 1987-04-21 | Raychem Corporation | Elongate electrical assemblies |
| EP0092406A2 (en) * | 1982-04-16 | 1983-10-26 | RAYCHEM CORPORATION (a Delaware corporation) | Elongate electrical heating device and a system comprising such devices |
| US4791276A (en) * | 1982-04-16 | 1988-12-13 | Raychem Corporation | Elongate electrical assemblies |
| US4840494A (en) * | 1984-02-01 | 1989-06-20 | Albert Koch | Calibrated temperature sensor and method of calibrating same |
| EP0150784A2 (en) * | 1984-02-01 | 1985-08-07 | Koch Elektronik AG | Trimming method for a temperature sensor |
| WO1985003570A1 (en) * | 1984-02-01 | 1985-08-15 | Tz Winterthur Ag | Method for adjusting a temperature probe, and temperature probe manufactured according to said method |
| EP0150784A3 (en) * | 1984-02-01 | 1985-09-25 | Tz Winterthur Ag | Trimming method for a temperature sensor, and temperature sensor produced by this method |
| GB2184893A (en) * | 1985-12-19 | 1987-07-01 | Marconi Electronic Devices | Circuit arrangement |
| US4794367A (en) * | 1985-12-19 | 1988-12-27 | Marconi Electronic Devices Limited | Circuit arrangement |
| GB2184893B (en) * | 1985-12-19 | 1989-10-18 | Marconi Electronic Devices | Circuit arrangement |
| US4999731A (en) * | 1986-08-22 | 1991-03-12 | Northern Telecom Limited | Surge protector for telecommunications systems |
| US5057964A (en) * | 1986-12-17 | 1991-10-15 | Northern Telecom Limited | Surge protector for telecommunications terminals |
| GB2243956A (en) * | 1990-05-09 | 1991-11-13 | Sfernice S A | Electrical resistors presenting selectable resistance values and methods of making same |
| US5206623A (en) * | 1990-05-09 | 1993-04-27 | Vishay Intertechnology, Inc. | Electrical resistors and methods of making same |
| GB2243956B (en) * | 1990-05-09 | 1994-10-05 | Sfernice S A | Electrical resistors and methods of making same |
| DE4115328C2 (en) * | 1990-05-09 | 2002-10-31 | Sfernice S A | Electrical resistors and methods of making them |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PE20 | Patent expired after termination of 20 years |
Effective date: 19980312 |