Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01C—RESISTORS
  • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
  • H01C17/06—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base
  • H01C17/065—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thick film techniques, e.g. serigraphy
• • 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
  • H01C7/003—Thick film resistors
• • 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
  • H01C7/22—Elongated resistive element being bent or curved, e.g. sinusoidal, helical

Definitions

• High-voltage resistor and high-voltage supply comprising such a high-voltage resistor
• the invention relates to a high-voltage resistor comprising a substantially rectangular substrate of an electrically insulating material which is provided, at two ends, with two electrodes which are connected to each other by means of a meander-shaped resistance layer.
• the invention also relates to a high-voltage supply comprising a transformer or a voltage multiplier as well as a high-voltage resistor, which are cast into an insulating mass.
• High-voltage resistors as well as high-voltage supplies in which such high-voltage resistors are incorporated are used, in particular, in monitors and display tubes.
• a high-voltage resistor of the type mentioned in the opening paragraph is described in the non-prepublished European patent application having publication no. 96203033.4 (PHN 16.059).
• the high-voltage resistor described in said document comprises an electrically insulating substrate of aluminium oxide on which a meander-shaped resistance layer of a sintered thick-film paste is provided by screen printing.
• Two electrodes of sintered AgPd paste are provided at the ends of the resistance layer, also by screen printing.
• the invention more particularly aims at providing a high-voltage resistor which, at the same dimensions and the same construction, can be operated at higher voltages and/or exhibits a longer service life. In addition, the formation of cracks in the epoxy should be reduced.
• a further object of the invention is to provide a high-voltage supply comprising a transformer or a voltage multiplier as well as a high-voltage resistor, which are cast into an insulating mass, which high-voltage supply can be operated at higher voltages and/or has a longer service life.
• a high-voltage resistor comprising a substantially rectangular substrate of an electrically insulating material which is provided, at two ends, with two electrodes which are connected to each other by a meander-shaped resistance layer, which high-voltage resistor is characterized in that one or more recesses are formed in a side face of the substrate.
• the invention is based on the experimentally gained insight that creep between the electrodes occurs to a substantial degree along the side face of the substrate.
• the creep distance along the side face of the substrate is increased substantially by providing one or more recesses.
• the risk of breakdown between the electrodes is reduced and higher voltages can be applied to the resistor.
• the measure in accordance with the invention enables the service life of the resistor to be increased.
• An advantageous embodiment of the high-voltage resistor in accordance with the invention is characterized in that the recesses extend to between the meander-shaped resistance layer. This measure results in a substantial further increase of the creep distance.
• Another interesting embodiment of the high-voltage resistor in accordance with the invention is characterized in that the recesses are provided at two opposite side faces of the substrate. It has been found that this measure results in a substantial reduction of the shortest distance between both side faces, thus causing the mechanical stresses in the insulating mask to be reduced. By virtue thereof, the risk of crack formation in the envelop- ing mass is reduced. This leads to a longer service life of the resistor.
• the invention also relates to a high-voltage supply comprising a transformer or voltage multiplier as well as a high-voltage resistor, which are cast into an insulating mass.
• this high-voltage supply is characterized in that a high-voltage resistor as described hereinabove is employed.
• Fig. 1 shows a plan view of a first embodiment of the high-voltage resistor in accordance with the invention
• Fig. 2 shows a plan view of a second embodiment of the high-voltage resistor in accordance with the invention
• Fig. 3 schematically shows a high-voltage supply in accordance with the invention.
• Fig. 1 shows a high-voltage resistor (1) which comprises a substantially rectangular substrate (2) of an electrically insulating material.
• a substantially rectangular substrate (2) of an electrically insulating material In this case, use was made of aluminium oxide.
• the dimensions of the substrate are 25.4 mm by 12.7 mrr. by 1.0 mm.
• Electrodes (3, 4) are provided at two ends of this substrate by screen printing using an AgPd paste.
• a meander-shaped resistance layer (5) is situated between the electrodes (3, 4). This layer is also provided by screen printing.
• For the resistance material use was made of a lead- ruthenate-containing paste.
• the substrate is also provided with a coating (6) of a synthetic resin, for example a silicon polymer.
• three recesses (7) are formed in a side face of the substrate situated between the ends of the substrate on which the electrodes are provided.
• the recesses can be formed by punching, cutting, etc., after the manufacture of the substrates or, of course, during the manufacture of said substrates.
• the recesses preferably extend to between the meander-shaped resistance layer.
• the formation of these recesses (7) causes the creep distance along the side face of the substrate between the electrodes (3, 4) to be substantially increased. By virtue thereof, the risk of breakdown between these electrodes is reduced and higher voltages can be applied to the resistor.
• Fig. 2 shows a preferred embodiment of the high-voltage resistor in accordance with the invention.
• the recesses are formed at two opposite side faces of the substrate. This measure has the additional advantage that the shortest distance between both side faces is reduced, which leads to a reduction of the mechanical stresses in the insulating mass. By virtue thereof, the risk of crack formation in the enveloping mass is reduced.
• a series of 20 high-voltage resistors of each of the types A, B and C were cast into an insulating mass of an epoxy. Subsequently, at a direct voltage of 20 kV, these resistors were subjected to a temperature cycling test. In this test, the resistors were maintained at a temperature of, successively, 40 °C and 100 °C for 3 hours. The percentage of rejects was determined after 11, 20, 28 and 36 temperature cycles.
• Table 1 shows the results of the experiment. The indicated percentages represent the number of resistors that passed the test after the indicated number of cycles. Table 1 also shows that the presence of the recesses has a favorable effect on the service life of a high-voltage resistor. The greatest effect is achieved if the recesses are formed in two opposite side faces of the substrate.
• Fig. 3 schematically shows a high-voltage supply which, in this case, comprises a transformer 11 as well as a high-voltage resistor 12. Both elements and a screen/focus potentiometer 13, which is known per se, are cast into an insulating mass of an epoxy material.
• the housing of the epoxy material is schematically indicated by means of a dotted line 14.
• a high-voltage resistor as described hereinabove is employed in said housing.
• the transformer 11 steps up the initial voltage via six layers of windings. Across the high-voltage resistor 12, there is applied 4/6 ⁇ s of the total stepped-up voltage.
• the Gl and G2 electrodes of a display tube 15 can be driven via the screen/focus potentiometer.
• the invented high-voltage resistor and high-voltage supply comprising such a high-voltage resistor can be operated at higher voltages and/or demonstrate a longer service life.

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• Engineering & Computer Science (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Manufacturing & Machinery (AREA)
• Non-Adjustable Resistors (AREA)
• Coils Or Transformers For Communication (AREA)
• Adjustable Resistors (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (1)

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• 1998
  • 1998-06-11 EP EP98923010A patent/EP0925592A2/de not_active Withdrawn
  • 1998-06-11 WO PCT/IB1998/000924 patent/WO1999003114A2/en not_active Ceased
  • 1998-06-11 JP JP50835799A patent/JP2001506423A/ja active Pending

Non-Patent Citations (1)

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