JPH0821489B2 - Resistors, resistor elements and resistor-breaking element combinations - Google Patents

Abstract

An apparatus and method by which a flat film-type resistor (10) is intentionally caused to thermal-shock fracture (Figure 1) in response to a predetermined high-voltage overload condition. The resistor includes flat film-type resistor coatings (28, 29) connected to traces (16, 18, 52). Preferably a stressed spring wire (71, 72) is mounted on such film-type resistor and connected in circuit with it. A predetermined solder (76) and temperature gradient are employed to hold the spring wire in bent condition until the solder (76) melts, whereupon the spring (71, 72) flexes and the circuit breaks. Heatsink portions (43-46) are provided in the circuit board for such resistor and receive pins (33-40) thereof. <IMAGE>

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film type resistor, a balanced resistor for a telephone circuit, a resistor such as a telephone resistor, a resistor element, and a resistor-break element combination.

[0002]

BACKGROUND OF THE INVENTION It is important for a balancing resistor used in a line card of a telephone system to have an accurate value. Accurate resistors allow proper line balancing,
Proper balancing results in more faithful voice propagation and better data transmission, improving reliability. However, the exact resistance value is only one of the factors that determines whether or not the balanced resistor is considered good by the telephone company.

Under three specific or standard levels of adverse circumstances, it is crucial that the balancing resistor or line card work well in some way as required by the telephone company. The first level is that there is a line card situation, one of which is blitz, which nevertheless survives and continues to function correctly. The second level is associated with a condition where the balancing resistor is continuously overheated due to overheating of the line card, for example due to incorrect connection by a technician. In connection with this second level, a thermal shutdown operation must be performed to interrupt the current before the line card circuit board begins to burn. The third level is a sudden high voltage, such as when a power line drops into a telephone line. In connection with this third level, the current has to be interrupted virtually instantaneously. Otherwise, the smaller diameter wires of the telephone system may melt.

These demands, which are both accurate balance and the ability to withstand certain types of adverse conditions or the ability to safely interrupt current, make these resistors even smaller than prior art resistors, and It must be filled with a resistor that has only a fraction of the resistance of prior art resistors. A major problem associated with the need for a physically small balanced resistor and a low balanced resistor is when the low resistor is a high resistor during a lightning transient or overload condition. Than introducing more power into it. For example, if the resistance is halved, the power introduced will be doubled. It is very difficult to handle a large amount of electric power generated by a lightning transient current or the like with a physically small resistor. Physically small resistors inherently have less heat dissipation surface area compared to physically large prior art resistors and are therefore difficult to cool.

In short, telephone companies want smaller line cards to fit more cards into a given space. Therefore, they want to miniaturize the components mounted on the card, and also want a minimal number of components to be employed, but still have stringent performance requirements.

In connection with the aforementioned second level adverse situation, it has become common practice to use a fuse or thermal cutoff which is a separately manufactured and separately mounted component. These require separate work steps to assemble on the circuit board, and also require significant space on the board.

In connection with the above-mentioned third-level adverse situation,
Various attempts have been made. These include fuses, voltage control circuits, and the like. These require separate components or individual mounting work steps, as well as additional space on the substrate.

[0008]

SUMMARY OF THE INVENTION In accordance with the present invention, a film type balanced resistor is designed to be thermally shocked and momentarily interrupted when a third level adverse situation occurs. It is configured to That is, the substrate comprises a substrate to which a resistance film can be attached, a resistance film attached to the substrate, and a terminating means connected to the resistance film and connecting the resistance film to an electric circuit. Is configured to momentarily break in response to a thermal shock when a high voltage is applied to the resistance film, the resistance film, the substrate and the terminating means, via the resistor in the thermal shock break through the resistor. The feature is that the electric circuit is cut off. Therefore, no separate components, no extra space on the substrate, etc. is required.

In accordance with the present invention, certain film resistor layouts and very small spring wire structures
It is used in combination with other elements to meet the various requirements of telephone companies for small and precise components. That is, a substrate, a resistance film attached on the substrate, a terminating means attached on the substrate for connecting the resistance film, and a circuit of the substrate mounted with the resistance film in a circuit, In the state of applying, an elongated conductive spring element and solder means for holding one end of the spring on the substrate despite the stressed state, the solder means comprising the resistor and the resistor. It is designed to melt in response to overheating of related elements,
Thereby, one end of the spring is allowed to move away from the substrate, so that the circuit is interrupted and the resistor and other elements of the circuit are protected.

[0010]

1 to 7, a resistor 10 is mounted on a circuit board 11, the latter (circuit board) of which only a small part is shown, that is to say this part. Provides a mounting area for the resistor 10. Not only the resistor 10 but also the telephone line card components are mounted on the circuit board, and all of them constitute a line card of the telephone system. Each line card is
Usually there are two to four telephone lines, each of which is connected to a subscriber line on the ground or in the ground.

4, 5 and 6 show both the front and back sides of the substrate. FIG. 7 shows the bottom and surface of the lower circuit board area.

As shown in FIGS. 2 to 7, the resistor 10 is a film-type resistor, and the film-type resistor has an elongated rectangular substrate 12, which will be described below. It is constructed and associated to rupture in a general manner under set thermal shock conditions.

As shown in FIG. 4, a fixed pattern (metallized) of termination traces 13 is formed on both the front and back surfaces of the substrate 12. The trace 13 is made of, for example, a mixture of palladium-silver and is screen-printed on a substrate and then baked.

As will be described below, there are two resistive films on each side of the substrate 12. For example, two films in one half area on the substrate form one resistor, and two films in the other half area form another resistor. One such resistor and one other resistor are usually balanced in equal proportions (having the same resistance value) so that they are interrelated.

In such a resistor network, the trace 13 preferably has the following pattern.
That is, the two lower traces 14 are arranged in the axial direction,
Separated by a central gap 15, the two upper traces 16 are axially aligned, separated by a central gap 17, and the two end traces 18 are connected to the upper trace 16, but the lower trace 14 Not connected to. Each end trace 18 has a relatively short distance between it and the lower trace 14, which makes the length of the substrate as short as possible. Traces 14 and 16 are parallel to each other and parallel to the top and bottom edges of substrate 12,
On the other hand, the end traces 18 are parallel to each other and the substrate 12
Is parallel to the ends of and is perpendicular to the traces 14, 16.

The trace pattern further includes four sets of double pin (solder) pads. For example, the two sets of outer pads 20, 21 are preferably spaced about one third of the distance from the substrate edge to the substrate center. Similarly, the two sets of inner pads 22 and 23 are provided at intervals from the center of the substrate toward the outside. Therefore, the inner ends of the lower traces 14 have inner pads 22, 23.
Are spaced inward from. The two pads 20, 21 and 22, 23 of each set are spaced apart from each other and are connected to each other by a trace area 24. These pads are located close to the horizontal lower edge of the substrate 12.

The outer pads 20, 21 are located in the trace area 2
It is connected to the lower end of the end trace 18 by 6. The inner pads 22 and 23 are connected to the lower trace 14 by a trace area 27.

The two resistance films 28 and 29 are applied to each side of the substrate 12 by screen printing.
As shown in FIG. Therefore, each film 28, 29 is printed with its upper and lower edges overlaid on the traces 16, 14, respectively. The ends of the films 28, 29 are located proximate to the traces 14, 16 but are preferably located so that they do not extend beyond the ends on either side of the traces 14, 16. Film 2
Reference numerals 8 and 29 are glass matrix electrically conductive complex metal oxides.

Referring now to FIG. 6, an arc protection and environmental protection coating 31 is applied on both sides of the substrate 12, on the traces and on the resistive film. This coating is not applied to pads 20-23, and (preferably) to the spaces between adjacent sets of pads 20-21, 22-23. The structure and thickness of the coating 31 will be described below.

The pins 33-40 are all connected to the pads 20-23, respectively, as shown in FIGS. 2 and 3, and to the two pads on the two opposite sides of the substrate 12 (for example, in FIG. 2). There is a pin 40). Each pin has a long extending leg portion, and the leg portion is integrally connected to a jaw portion 41 that grips the lower edge of the base plate 12 by a shoulder portion. For example, there are two jaws on one side of the substrate and one jaw on the other side of the substrate. For example, the front and rear dimensions of the legs of each pin are 0.02
54 cm (0.010 inch) wide with 0.0508 cm (0.020 inch)
Is. The pins are preferably sheeted and stamped phosphor bronze.

Next, the circuit board 11 will be described with reference to FIG.
Although only part of the circuit board is shown in Figure 7 (and Figure 10), the circuit board is a conventional epoxy glass with copper traces on it for connection with numerous components of the circuit (not shown). The substrate. In the preferred embodiment, the substrate 11
Is a copper heat sink area 43 for receiving pins 33-40 on both sides of the board as well as the copper traces on it.
It has -46. Referring to FIGS. 1 and 7, four heat sink regions 4 are provided on each side of the substrate 11 (in this example).
3-46, where each region on the front side of the substrate is (preferably) aligned with the corresponding region on the back side of the substrate. Area 43-46
Eight holes 47 are formed in each area, and there are two holes in each area. Hole 47 is a plated through hole.

The heat sink regions 43-46 are formed by etching at the same time as the copper traces are formed during board fabrication. The solder mask coating 48 is the substrate 11
Are formed on the upper and lower sides.

The pins are inserted into their respective holes 47 until the shoulder at the bottom of the jaw 41 abuts the substrate surface. Then, solder is applied to each hole 47, and the legs of the pin inserted therein are soldered. It is preferred that the heat sink areas 43-46 be covered by a solder mask portion, with no soldering except in the vicinity of the pin legs.

[Description of Method of Using First Embodiment of the Present Invention (FIGS. 1 to 7) and Description of Apparatus] According to the method of using a resistor related to the first embodiment, one of The substrate 12 is used to momentarily rupture due to thermal shock in response to high voltage overloading one resistor, or both resistors on the substrate. Also, according to this method, the termination traces, the resistive film and other elements are
The thermal shock rupture ensures that the circuit is interrupted instantaneously, interrupting all current with little or no arcing.

The resistors just described are each in circuit with the other components of the line card, so that when the circuit is interrupted through one or both resistors, the respective resistors coupled to the resistors. It should be understood that the current in the component also stops.

Therefore, it is possible to overcome the above-mentioned bad situation of the third level by breaking the substrate. For example, even if a high-voltage power supply line drops on a telephone line and a high-voltage overload is momentarily generated, the current is cut off quickly, so that the thin wire of the telephone circuit does not melt.

According to this method, the termination traces and other elements are such that momentary thermal shock failure occurs in a predetermined area of the substrate 12 and not in other areas. Not only does this reduce debris, but as will be explained below in connection with the second embodiment, a considerable length of metal element falls onto other components of the circuit board, causing an arc. Ensure that it does not occur or short circuit.

The substrate 12 is thin enough to momentarily break when a high voltage (high voltage of about 600 volts) is suddenly applied, but thick enough to meet the following two requirements. That is, (1) a considerable amount of heat is generated by the resistance film 2
8 and 29 to effectively conduct heat to the pins 33-40 through the substrate and flow to the heat sink regions 43-46,
(2) The line card shall have sufficient resistance to mechanical damage so as not to be broken.

The material of substrate 12 is selected to meet the above criteria. Very preferably ceramic.
The preferred ceramic is aluminum oxide. More specifically, it is preferably 96% aluminum oxide (available under the number ADS96R from Cores Ceramics, Inc., Grand Junction, CO).

The preferred thickness of the substrate is 0.1016 cm (0.040 inches).

The upper and outer regions of the substrate and the film thereon are not shown in FIG. These areas have been destroyed by thermal shock fracture. Referring to FIG. 4, the preferred embodiment of the method shows that the traces 18 located at the edges of the substrate 12 conduct current to the upper traces 16. This current passes through pads 20, 21 and trace region 26. Current flows through the films 28, 29 and the trace areas 14, 27 to the remaining pads 22, 23.
Flow through the circuit board in this way.

By providing traces 18 on the outer edge of the substrate, breakage occurs at the upper and outer corners of the substrate,
Is guaranteed to break down and thus interrupt the circuit leading to the components respectively connected to the resistors (as mentioned above, the overload acts only on one resistor and the substrate Only 12 halves are affected, in which case only one trace 18 is destroyed).

Referring again to FIG. 1, the central portion of the substrate and all of the lower edge of the substrate remain. This is a typical aspect as a result of this method and apparatus.

Thermal shock rupture of this resistor requires (1) the purpose of preventing damage to other elements of the telephone system, (2) the need for a separate component or circuit to protect against the instantaneous effects of high voltage. This is done intentionally with the dual purpose of eliminating

Resistors often "burst" for long periods of time due to thermal shock caused by overloading, which is generally viewed as undesirable. On the other hand, the applicant has caused a preset type of "failure",
Creating a controlled situation that produces the desired results. The resistive film and the termination traces are shaped and interrelated to create the required pressure pattern. The resistive film is formed to be protected from the action of voltage and generate sufficient power and heat to break the substrate. In addition, the substrate has such a composition and physical shape that it surely breaks when heated.

The destruction of terminal traces 18 as a result of thermal shock results in a momentary arc and ionization at the location where such traces first rupture. Although the electric arc only occurs for a short period of time, the corners of the substrate 12 are removed,
Ionize the air around it. This greatly increases the arcing tendency in the circuit area where the voltage difference is greatest. It is a further advantageous aspect of this method to provide a coating 31 that prevents arcing in such areas of high voltage differential despite ionizing air.

As shown in FIGS. 4-6, there is a relatively small gap G between the outer end of the lower trace 14 and the lower region of the terminating trace 18. The gap G has a narrow width. This is because the length of the substrate 12 is increased by two increments for each increment in the two resistors. Preferably, the width of each trace 18 facing the trace 14 is slightly less than the width of each trace 18 at a distance above the trace 14. This increases the width of the gap G without increasing the length of the substrate and thus the length of the entire resistor, but this method has severe limitations associated with increasing the gap G.

Further, according to the present invention, a region on the resistor, at least on the gap G and relatively close to the gap G,
Preferably, the arc resistance coating 31 is provided in all areas (FIG. 6) except the areas between the pads 20-23 and the substrate.

In more detail, the coating 31 for arc prevention—and in addition for environmental protection—is a glass layer having a thickness related to the width of the gap G. If the gap G is narrowed to reduce the resistor size, the glass coating is thickened. On the other hand, when the size of the substrate is not small enough to reduce the gap G, the thickness of the glass coating 31 is reduced to reduce the cost.

Explaining a detailed example, the width of the gap is 0.0081.
At 28 cm (0.032 inch), a 0.00254 cm (0.001 inch) thick layer of glass fails (600
It has been found to provide virtually complete protection against V test voltage). The thickness of the coated glass is 0.002032 cm (0.000
8 inch), if the gap width is the same, there is some failure. When the glass deposition thickness is 0.001524 cm (0.0006 inches), there are a significant number of failures with a gap of the specified width. Therefore, in the case of such a gap, the applicant has
A glass coating 31 having a thickness of 01 inches will be adopted.

The glass is screen printed on the traces and resistive film on the substrate as described above. A relatively low melting point glass frit is screen printed in the area shown in FIG. 6 and the portion is subsequently fired to melt the glass particles.

It is important that the glass does not damage the resistance films 28,29. Since the resistive film is fired at temperatures above 800 ° C, the glass frit is designed to have a melting point below 500 ° C. Therefore, the firing temperature is 500 ° C. to melt the layer 31.

The resistor 10 of the first embodiment also satisfies the above-mentioned first level adverse situation. In other words, resistors withstand and operate correctly under adverse conditions such as those caused by transient lightning. This is because it has good heat transfer characteristics from the resistor 10 to the circuit board and from the pins 33-40 to the outside. This will be explained below in connection with the second embodiment.

Second Embodiment of Resistor Combination and Method of the Present Invention, FIGS. 7 to 15 A typical length of the resistor 10 described above is 4.482 cm (1.8 inches). With a resistor length of (for example) 5.08 cm (2 inches), i.e. an additional substrate length of 0.508 cm (0.2 inches), the resistor combination will satisfy all three levels of adverse conditions. This eliminates the need to provide a separate heat blocking element to satisfy the second level adverse situation.

The front side and the back side of the resistors of FIGS. 1 to 6 described above are preferably the same as previously mentioned. In the resistor of the second embodiment, the front surface and the back surface of the substrate are not usually the same as each other, and a certain area will be described separately. The resistor (and circuit board) of the second embodiment is the same as the resistor 10 of the first embodiment, with important exceptions noted below. The elements of the second embodiment substantially corresponding to the elements of the first embodiment have the same numbers except that the letter a is added to the same numbers.

The resistor combination of the second embodiment is numbered 51 (FIG. 10). 8 (front view) and FIG.
Referring to the (rear view), the substrate 12a has a lower trace 1
In addition to 4a, it has an upper trace 16a and an end trace 18a. The inner ends of the traces 16a, 14a on each half of the resistor are farther apart than in the first embodiment. On each side of the resistor, the trace section 52 has a lower trace 14
a and connects to the inner end of a and extends upward inward
Has reached. The pads 53 on each side of the substrate are spaced apart and are close to the top edge of the substrate 12a. Only the front side of the resistor has a pad 54 close to the bottom edge of the substrate (FIG. 8).
The pads 54 are the pads 5 on the front surface of the substrate, respectively.
Right under 3.

Pads 56-63 (FIG. 8) are on substrate 12a.
The pads 56-59 arranged along the bottom edge of the substrate 12a in the half region of the substrate 12a are in a mirror image relationship (symmetrical positions) with the pads 60-63 in the other half region.
Pads 56 and 60 are connected to trace region 26a, respectively, and to upper trace 16a via end trace 18a. Trace portions 64 and 65 are
The pads 56 and 57 and the pads 60 and 61 are connected to each other.

The pad 56 is connected to the end of the substrate and the adjacent pad 5.
It is located at a sufficient distance from 7. Correspondingly, the pad 60 is arranged at a sufficient distance from the end of the resistor and the pad 61. On the other hand, pads 58 and 59 are close to each other, and pads 62 and 63 are also close to each other. The pair of pads 58, 59 are close to the inner end portion of the trace 14a, which inner end portion is relatively wide as shown. Correspondingly, the pad pair 62, 63 is located on the trace 14 on the right side.
It is relatively close to the inner end portion of a and is relatively wide as shown.

Trace area 66 connects pads 58, 59 to each other and trace area 67 connects pads 62, 63 to each other. Trace area 68 connects pads 59 and 54, while trace area 69 connects pads 63 and 54.

No pads 54 or trace areas 68, 69 are provided on the back surface of the substrate (FIG. 11). Components 56, 64, 57, 58, 66, 59, 63, 67, 6
Reference numerals 2, 61, 65, and 60 have components corresponding to the back surface of the substrate, and these components have the same numbers except that the letter b is added to the same numbers.

The resistance films 28a and 29a are shown in FIGS.
As shown in FIG. 2, the upper and lower end pieces 16a and 14
It is provided between a and. The overcoat layer 31a of FIGS. 10 and 13 includes various pads and pads 57-58 and 61-6.
2 (and 57a-58a, 61a-62a) but on each resistor on each side.

[Spring Wire Interruption] The conductive spring wire 71 is connected to the pad 5 on the front surface of the resistor on the left side.
Soldered between 3 and 54. The electrically conductive spring wire 72 is attached to the pad 5 on the front of the resistor on the right side.
Soldered between 3 and 54. Each wire 71, 7
2 is in a stressed or flexed condition, rather than in a free condition, with the lower end of each wire jumping from pad 54 in response to melting of the pad. (The solder is not shown in FIGS. 10 and 13, but
It is shown in FIGS. 14 and 15. ) The upper ends of the spring wires 71 and 72 are bent into a U-shape like a hairpin, engage with the periphery of the upper edge of the substrate 12a, and are soldered to the pad 53 on the back surface of the substrate (FIGS. 13 and 14). .
Therefore, the current is flowing in both resistive films 28a-substrate 12a.
Through the traces 52 from the front and back resistive films to the spring wires 71 and to the pads 54.
It has a relationship that flows to the pin connected to it. The same current pattern occurs with respect to film 29a-in a mirror image of the case described above-current flows in series through spring wire 72.

Each wire 71, 72 connected to the pad 54
The lower end of is bent by being bent by a semicircle so as to increase the amount of wire metal bonded to the solder as shown in FIG.

Referring now to FIGS. 14 and 15, it should be understood that these figures show two positions of spring 71, and that the same applies to spring 72 and its associated attachments. The spring 71 has a U-shaped upper end 71a whose arm is fixed (by a spring bias) to the pad 53 on the back side of the substrate 12a. This arm is firmly fixed to the pad by solders 74 and 75.

The spring 71 below the solder 74 on the front side of the substrate 12a is curved along the flexible portion 71b, and this portion is stressed so as to jump to the position shown in FIG. When there is a regular position in FIG. 14,
The lower end of the portion 71b is fixed to the pad 54 by the solder 76, and the solder 76 is joined to the twisted portion 73 as shown in FIG.

The jaws of the eight pins 77-84 are connected to the respective pads 56-59, 63, 62, 61, 60. As explained in connection with the first embodiment,
These pins pass through the plated through holes of the circuit board 11a and are soldered (FIG. 10). Around the through holes on both sides of the substrate, there is a heat sink area corresponding to those other than the above-mentioned positions. With the exception of the space between the pinholes corresponding to and receiving the pins shown in FIG. 10, there are two heatsinks directly opposite each pin or pair of pins as shown in FIG.

Spring wire 71 adopted by the applicant,
The material for 72 is 17-7 PH, state C stainless steel. The diameter of each wire is 0.0304 cm (0.012 inches). The preferable diameter range of the springs 71 and 72 is 0.0127.
cm (0.005 inches) to 0.0508 cm (0.020 inches).

Each spring wire is silver-plated. The solder used for the pads 54 on the front side of the substrate 12a, and preferably for all pads on the substrate, is 96.5% tin and 3.5% silver. The melting point of this eutectic is 221 ° C.

The solder for connecting the pins to the circuit board 11a is 63% tin and 37% lead and melts at a temperature of 183 ° C. In other words, the temperature is 38 ° C. lower than the melting point of tin-silver solder. To melt.

According to the method and apparatus of the present invention, the melting point of the solder on the board is certainly higher than that of the solder that connects the pins to the circuit board, while the latter solder is the former solder 76 (FIGS. 14 and 15). It will not melt until it has melted (if all melted) until the springs 71, 72 are released from the position shown in FIG. 14 to the open circuit position shown in FIG.

Pads 58, 59 and 54 and pad 62,
Since 63 and 54 are close to each other and are close to the inner corners of the lower ends of the resistive films 28a and 29a, respectively, these pads and the solder thereon are relatively hot. This is especially true because the substrate 12a conducts heat relatively well as a ceramic and conducts heat from the corner regions of the resistive film to the pads. Most of this heat is not only dissipated into the circulating air in the container containing the line card, but also drops to the pins 79 and 80 and the pins 81 and 82 of the circuit board 11a and the copper heat sinks on both sides of the board. Come on.

The transfer of heat to the pins and the transfer of heat from the pin area of the circuit board through the heat sink is accomplished by the spring 7
1 and / or spring 72 is released, that is, the conventional solder of the circuit board is not melted before spring 71 and / or spring 72 is disengaged.

The same heat transfer action in which the heat is reduced by descending from the pads of the circuit board to the pins may be the case in the first embodiment described above. Can withstand the bad situation of the level.

This second embodiment can also withstand a second level of adverse conditions. Because (one or both)
This is because the springs in the board disengage and interrupt the current, protecting the board and ensuring that it does not burn. To be used again on the line card for operation, a technician can replace the existing resistor assembly with the same.

In the event of a momentary high voltage overload associated with the third level of adverse conditions, the springs 71, 72 will not disengage, but instead the upper region of the substrate 12a will shatter due to thermal shock. . The fracture mode is the same as that shown in FIG. 1, for example. The central part of the substrate 12a does not break, so that the springs 71, 72 and the elements coupled thereto do not fall onto other parts of the substrate and there is no possibility of an electric arc.

To make the resistor of this embodiment, pins 71-8, all connected to tie bars (not shown).
4 jaws are mounted on each pad on the bottom edge of the substrate 12a. The lower parts of the spring wires 71, 72 are initially longer than shown and project downwards from the substrate towards the backside area of the tie bars. Therefore, the tie bar holds the portion of the spring in contact with the pad 54, which spring is in the flexing relationship of FIG.

The assembly is then dipped into the melt bath of the particular solder described above or (but not desirably) of the other solder while simultaneously securing the jaws of all pins to their respective pads and springs to pad 54. Fixed to. The portion of the spring near the upper pad 53 is either soldered by a separate dipping operation to be performed later, or at the same time by dipping the entire resistor in a solder bath. Then, the spring portion protruding from the tie bar is cut off.

A typical resistor embodying the invention is 5
It has a resistance of 0 ohms, i.e. the total value of each face in the center of the substrate is 50 ohms. This 50 ohm resistor produces 3.125 watts by applying a voltage of 12.5 V and an ambient temperature of 85 in the container holding the line card.
Operates continuously up to ° C. When the temperature exceeds 85 ° C, the ambient temperature and the temperature due to the heat generated by the resistors at the lower ends of the springs 71 and 72 are combined, and the springs 71 and 72 come off to interrupt the current.

For film resistors of constant resistance, the film may be provided only on one side of the substrate instead of having resistors on both sides of the substrate.

The detailed description set forth above is clearly understood by the drawings and examples, and the spirit and scope of the present invention are limited only by the claims.

In the first embodiment (FIGS. 1 to 7), the substrate on which the resistance film is provided is preferably flat.

Here, the substrate is made of ceramic and is thin enough to break in response to a high voltage overload applied to the resistance film and thick enough to withstand mechanical pressure. It is preferable to set.

The ceramic substrate has a thickness of 0.1016.
It is preferably about cm (0.040 inch).

The terminating means also includes conductive traces mounted on the substrate and connected to the resistive film, and mounted on the substrate and soldered to the traces for connection to a circuit board. It is preferable to include a pin.

The high voltage overload is 600 volts.

Further, it is preferable to provide a molten glass layer on at least a region of the trace where an electric arc is likely to occur.

It may also be a film resistor with the built-in ability to break the circuit in response to a sudden overload.

That is, a flat ceramic substrate, resistance film means provided on the substrate, terminal traces provided on the substrate and connected to the resistance film means, and mounted on the substrate and connected to the traces. The resistive film means, the substrate and the trace are subject to thermal shock rupture when a sudden high voltage overload is applied to the pin, thereby interrupting the trace and also the resistor. It may be characterized in that the circuit is cut off through a film means.

Here, the resistance film means is formed by thick film screen printing, and the trace is formed by screen printing, and an arc prevention coating means is screen printed on the resistance film means and on the trace, respectively. Is preferably formed by.

The coating means is preferably a glass layer.

Also, the substrate is elongated, and the termination trace includes a trace region disposed between an end of the resistive film and an end of the substrate, the substrate and the termination trace of the substrate. The corners and traces are preferably associated such that they break due to high voltage overload.

Further, a thermal response circuit breaking means is provided on the substrate in circuit with the resistance film means, and the thermal response circuit breaking means is distinguished from a high voltage overload acting on the resistance film means. Preferably, the excess current melts in response to the continuous flow through the resistive film means and interrupts the circuit through the resistive film means. Incorporating a thermal response circuit breaker device in a balanced resistor in this manner results in only a slight increase in resistor size as compared to the absence of such a device. By incorporating the circuit breaker in the resistor, no additional assembly steps are required when mounting the resistor on the substrate.

Further, it is preferable that the resistance film means is mounted on the circuit board, the terminal pin is inserted into the board, and the circuit board has a heat sink element at the position of the pin. In this way, precision resistor balancing resistors are placed on a relatively small board, which, combined with the relatively small heat sink area of the circuit board, allows very low resistance as the telephone company desires. Above, it can handle the relatively large power introduced.

It is preferable that the pins are soldered to the board with solder having a relatively high melting point, and the pins are soldered to the circuit board with solder having a relatively low melting point.

A balanced resistor for a telephone circuit may be constructed as follows.

That is, an elongated flat substrate having a front surface and a back surface, resistance films respectively provided on the front surface and the back surface which are each half of the substrate, and 4 arranged along the lower edge of the substrate. Number of pins and termination traces on the substrate that connect between the pins and the resistor film, the resistor films on each of the front and back sides of each half of the substrate having a gap between them. Separated from each other by regions, the resistance film on each side of the gap region forms one of two resistors, the resistors on each side of the gap region being relative to resistors on the other side. The resistance values are balanced, and the pins are 2 with respect to the front and back resistive films of the substrate on both sides of the gap area.
Two pins on one side of the termination trace and the gap region are connected in parallel with each other to the resistive film on the front and back sides of the substrate on the one side, and the termination trace and the gap region are connected. The two pins on the other side of
Connected in parallel with each other to the resistive films on the front and back sides of the substrate on the other side, the substrate, the resistive film and the termination traces being connected to the substrate by a high voltage overload acting on the pins, A sudden thermal shock rupture occurred in the termination trace, causing at least one resistor to rupture,
The telephone circuit may be configured to be cut off.

Here, it is preferable to melt and coat a glass film on the substrate, the resistance film and the trace.

Also, the substrate is substantially rectangular and the termination traces extend along each end of the substrate and include trace regions connecting the pins and termination traces at the upper edge of the film. The high voltage acting on the pins causes a thermal shock rupture in the substrate and the trace region at the edge of the substrate, the rupture occurring in only a small portion of the substrate, including the gap region and the lower edge of the substrate. It is preferable to have a relationship that does not exist.

Further, a spring wire in a stressed state is soldered to the substrate and circuit-connected to at least one trace region of the resistor, and a solder for the spring wire is melted by a solder at one end of the spring wire. Therefore, it is preferable that the spring is flipped up from the substrate to interrupt the circuit.

In addition, at least one of the gap regions has two
Preferably, a plurality of spring wires are arranged, and one end of each spring wire is connected to the resistance film on both sides of the substrate.

Also, the substrate is substantially rectangular and the termination traces include trace regions extending along the edge of the substrate to connect the pins to the termination traces at the upper edge of the film. A high voltage acting on the substrate causes a thermal shock rupture in the substrate and in the trace region at the edge of the substrate, which rupture occurs in only a small portion of the substrate and does not include the gap region or the lower edge of the substrate. In such a relationship, the spring wire under stress is soldered to the substrate, circuit connected to at least one trace region of the resistor, the solder for the spring wire is melted by the solder at one end of the spring wire. So that a wire is flipped up from the substrate to break the circuit, and at least one of the gap regions is
Preferably, a plurality of spring wires are arranged, and one end of each spring wire is connected to the resistance film on both sides of the substrate.

The second embodiment (FIGS. 8 to 15)
In, the substrate is preferably flat and made of ceramic.

Here, it is preferable that the spring element is a spring wire, the other end of which is bent so as to be folded back around one end edge of the substrate, and the other end thereof is separated from one end fixed by solder means.

Further, a second resistance film is provided on the side of the substrate remote from the spring wire, and the second resistance film is connected to the folded back bent end of the spring wire on the remote side. Preferably, in response to the melting of the soldering means, a circuit is connected via both resistance films to break the circuit.

Also, the resistance film and the ceramic cause thermal shock rupture of the ceramic in response to a sudden high voltage applied to the terminals of the resistor, thereby breaking the circuit through the resistance film. It is preferably configured to.

Further, the resistance film and the termination means of the resistance film are arranged so that the thermal shock breakage does not damage the region of the ceramic below the spring wire, whereby the spring wire is subjected to the thermal shock. Preferably, it does not fall from the resistor in response to a break.

Wherein said terminating means includes a pin soldered to said board and adapted for soldering to a circuit board, said pin protruding from a through hole in the circuit board and soldered thereto. It is preferable that the solder means on the substrate has a melting point substantially higher than that of the solder that fixes the pins to the circuit board.

Further, it is preferable to provide a heat sink pad in the through hole of the circuit board in order to dissipate heat from the pin.

Further, the resistance film is formed on the substrate by thick film screen printing, the terminating means includes a termination trace on the substrate, and an arc prevention overcoat layer is screen-printed on the resistance film and the termination trace. Preferably.

It may also be a telephone resistor configured as follows to shut off the circuit in response to two types of overload situations.

That is, it comprises a ceramic substrate, a resistance film provided on the ceramic substrate, a terminal means for the resistance film, and a thermal response blocking means mounted on the substrate. Thermal shock rupture in response to sudden high voltage overload on the film,
The thermal response interrupting means is configured to interrupt the circuit via the resistance film, and the thermal response interrupting means is configured to interrupt the circuit via the resistance film in response to a prolonged current overload. It may be a feature.

In addition, a disconnection method for disconnecting the telephone circuit including the resistor in response to a sudden high voltage overload,
(A) providing the resistor in the form of a resistance film on a substrate configured to be subjected to thermal shock rupture, and (b) intending the thermal shock rupture characteristic peculiar to the substrate on which the resistance film is provided. Selectively, causing the substrate to momentarily break in response to a high voltage overload as a result of a power line dropping onto the telephone line, and interrupting the circuit through the resistive film. And (c) connecting the resistor to a telephone circuit adapted to be exposed to a high voltage overload when a power line drops on the telephone line.
The blocking method may be characterized by including the following.

In the method of manufacturing the combination of the resistor element and the circuit breaker element according to the second embodiment, the resistor is a film resistor having a terminal pin, and the pin is soldered on the substrate of the resistor. It is preferable to fix the same solder with the same dipping operation.

[0104]

As described above, according to the present invention, it is possible to withstand the bad situations of the first, second and third levels. For example, when a third level bad situation occurs, the circuit is momentarily broken by thermal shock destruction. Therefore, no separate components, no extra space on the substrate, etc. is required.

Further, according to the present invention, the film resistor layout and the very small spring wire structure are adopted in combination with other elements so as to meet various requirements of the telephone company for small and precise components. Has been done.

[Brief description of drawings]

FIG. 1 is an isometric view showing a fractured substrate bonded to the bottom of a circuit board.

FIG. 2 is a front plan view of the resistor (network) of FIG. 1, but without showing the substrate, but before breakage occurs.

FIG. 3 is an end elevational view of the resistor shown in FIG.

FIG. 4 is a plan view of the resistor substrate of FIGS. 1-3, showing both front and rear termination traces of the resistor substrate.

FIG. 5 is a front and back plan view of a resistor after applying a resistive film (represented schematically by hatching) to a substrate.

FIG. 6 is a front and back plan view of a resistor after overcoating (illustrated with alternate hatching).

FIG. 7 is a plan view showing the top and bottom surfaces of the circuit board depicted in FIG. 1 in the lower region (pins not shown) of the balancing resistor.

FIG. 8 is a front plan view showing a balancing resistor according to a second embodiment having means for interrupting current when a second level adverse situation occurs.

FIG. 9 is a front plan view similar to FIG. 8, showing a resistive film.

FIG. 10 is a front plan view similar to FIG. 9, showing in cross section the overcoating and circuit breaker spring means, as well as the pins and lower area of the circuit board, the heat sink and solder not shown.

FIG. 11 is a rear plan view of the resistor of FIGS. 8-10, showing termination traces at the rear of the resistor.

FIG. 12 is a rear plan view of a resistor provided with a resistance film at the rear.

FIG. 13 is a rear plan view of a resistor overlaid on the rear, which corresponds to the rear view of FIG. 10 with pins and circuit board portions not shown and solder not shown.

14 is an enlarged view showing a partial cross-section and a partial side elevational view taken along line 14-14 of FIG.

FIG. 15 is a view similar to FIG. 14, showing the position of the springs after the circuit break.

[Explanation of symbols]

 10 resistor 11 circuit board 12, 12a substrate 13 trace 14, 14a lower trace 16, 16a upper trace 18 end trace 20-23, 53, 54, 56-63 pad 28, 29, 28a, 29a resistive film 31 environment Protective coating 33-40, 77-84 Pin 43-46 Heat sink area 71, 72 Spring wire 74, 75, 76 Solder

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01H 85/048

Claims (17)

[Claims] 1. A substrate having a front surface and a back surface, into which a resistance film can be attached, a resistance film attached to the front surface of the substrate, and a resistance film attached to the back surface of the substrate. And a terminating means connected to the both resistance films and connecting these resistance films to an electric circuit, wherein the substrate has a high voltage applied to the resistance film on its front surface and the resistance film on its back surface. Is configured to momentarily substantially rupture in response to a thermal shock when the front termination means has electrically conductive termination traces at the edge regions at the front ends of the substrate and the edge regions at the rear ends of the substrate. Then
The termination traces are each configured to separate from an outer edge portion of the resistive film and to be substantially ruptured momentarily when the region of the substrate ruptures in response to a high voltage applied to the resistive film, A resistor, wherein the both resistance films, the substrate and the terminating means are arranged to interrupt the electric circuit by the thermal shock breakage. 2. The resistor according to claim 1, wherein the substrate is a ceramic that is continuous and resistant to mechanical breakdown, and when a high voltage overload is applied to the resistive film, Thin enough to break in response to
A resistor characterized by being set thick enough to withstand mechanical pressure. 3. The resistor according to claim 1, wherein the two resistance films are formed so as to substantially coincide with each other, and are arranged so as not to be substantially displaced from each other. Resistor. 4. The resistor according to claim 1, wherein a resistance film on the front surface of the substrate is connected in parallel with a resistance film on the back surface of the substrate. 5. The resistor according to claim 2, wherein electrically conductive termination traces provided on a front surface and a back surface of the substrate are respectively connected to the resistance film, and the both resistance films and the conductive film are connected to each other. A resistor having a glass coating on the terminal trace. 6. The resistor according to claim 1, wherein the high voltage is 600 volts. 7. A film-type resistor having a built-in ability to cut off a circuit in response to a sudden overload, a flat ceramic substrate, a resistance film means provided on the ceramic substrate, and A plurality of termination traces provided on the ceramic substrate and connected to the resistance film means; a plurality of termination pins mounted on the ceramic substrate and connected to the termination trace; and the resistance film means and a circuit to form the ceramic substrate. A thermal response circuit interrupting means provided in the ceramic substrate and the resistance film means, the ceramic substrate and the termination trace when the high voltage overload suddenly acts on the termination pin, and The end traces are subjected to thermal shock, thereby breaking the end traces and interrupting the electrical circuit. The thermal response circuit breaking means melts in response to an excess current, which is distinguished from a high voltage overload acting on the resistance film means, continuously flowing through the resistance film means, A film-type resistor characterized in that it is configured so as to cut off. 8. A balanced resistor for a telephone circuit, comprising an elongated flat substrate having a front surface and a back surface, and a resistance film provided on each of the front surface and the back surface, which is each half of the board. Four pins arranged along the lower edge of the substrate, and termination traces provided on the substrate for connecting between the pins and the resistive film, the front surface being each half of the substrate and the The resistor films on both sides of the back surface are each separated from each other by a gap region, the resistor films on each side of the gap region forming one of two resistors, the resistor films on each side of the gap region. Are balanced in resistance with respect to the resistors on the other side, and there are two pins on both sides of the gap region for the front and back resistive films of the substrate, the termination trace and the gap region. Two pins on one side are connected in parallel with each other to the resistive film on the front and back sides of the substrate on the one side, and the termination trace and the two pins on the other side of the gap region are , Parallel to each other and connected to the resistive films on the front and back surfaces of the substrate on the other side, wherein the substrate, the resistive film and the termination trace are connected to the substrate by a high voltage overload acting on the pins, A balanced resistor in a telephone circuit, characterized in that a sudden thermal shock rupture occurs in said termination trace, causing at least one resistor to rupture and interrupt said telephone circuit. 9. A balanced resistor for a telephone circuit as claimed in claim 8, wherein a spring wire under stress is soldered to the substrate, and at least one of the resistors comprises the termination trace and Circuit connection, wherein the solder for the spring wire is configured such that when overheating occurs, the solder portion at one end of the spring wire melts and flips one end of the spring wire away from the substrate to interrupt the telephone circuit. A balanced resistor for a telephone circuit, which is characterized in that 10. A telephone resistor configured to interrupt a circuit in response to two types of overload conditions, a thin substrate having a flat front surface and a back surface, and a resistor provided on the substrate. Resistance film means, terminal means for connecting the resistance film means to an electric circuit, and thermal response blocking means mounted on the substrate and connected to the electric circuit, wherein the substrate is the terminal means. The circuit is configured to break the circuit by thermal shock rupture in response to a sudden action of a 600 volt overload, and the thermal responsive breaking means breaks the circuit in response to a prominent current overload. A resistor for a telephone, which is configured as described above. 11. A film-type resistor element, a thin substrate having a front surface and a back surface, a resistance film provided on the front surface of the substrate, a resistance film provided on the back surface of the substrate, and the substrate. First and second pads respectively provided on the back surface and the front surface of the pad so as not to be substantially displaced from each other, a conductive spring wire having an engaging end portion, and an engaging end portion of the conductive spring wire. A tip of the conductive spring wire connected to the first pad, and a region of the conductive spring wire adjacent to the tip of the engaging end connected to the second pad; and a body of the conductive spring wire of the substrate. A third pad provided on the same side as, a solder for connecting the free end of the conductive spring wire away from the engaging end to the third pad, and one of the resistors of the resistor film. A means for connecting one edge of the film to the first pad; and a means for connecting a corresponding edge of the other resistance film of the resistance film to the second pad. The engagement end extends around an edge of the substrate near the first and second pads, and the conductive spring wire springs up from the substrate when the engagement end is connected to the pad. A film type resistor characterized in that the corresponding edges of the other resistance film are connected to each other by a portion of the conductive spring wire engaging around the edge of the substrate. element. 12. The film type resistor element according to claim 11, wherein the resistance film and the substrate are formed of the conductive spring wire in response to a sudden voltage of 600 volts applied to the resistance film. A film type resistor element, characterized in that the substrates are configured to be broken in a region away from, and are related to each other. 13. A resistor-breaking element combination, a substrate having a front surface and a back surface, a resistance film provided on the front surface and a back surface of the substrate, and a resistance film provided on the substrate and connected to the both resistance films. And an elongated conductive spring element mounted on the substrate and forming a circuit with the both resistance films, the conductive member placed in a stressed state such that one end thereof is constantly directed so as to jump up from the substrate. Elastic spring element, and solder means for holding one end of the conductive spring element at a predetermined position of the substrate against the stressed state, the solder means preventing overheating of the resistance film and related elements. In response, it melts and separates one end of the conductive spring element from the substrate to shut off the circuit and protect the resistive film and other elements of the circuit. Ri Na configured to so that, also, the resistive film and said substrate, said termination means
Thermal shock rupture in response to high voltage acting on
A resistor-breaking element combination, characterized in that it is constructed and arranged to break a circuit. 14. The resistor-breaking element combination according to claim 13, wherein the substrate is flat and made of ceramic. 15. The resistor-breaking element combination according to claim 14, wherein the conductive spring element is a spring wire,
The resistor-breaking element combination, wherein the other end is bent so as to be folded back around one edge of the substrate. 16. The resistor-blocking element combination according to claim 15, wherein one of the resistance films and the spring wire are on one side of the substrate, and one of the resistance films. The other resistor film is on the other side of the substrate and is connected to the folded end of the spring wire on the other side of the substrate. 17. The resistor-breaking element combination according to claim 13 , wherein the resistance film and the terminating means are configured to prevent the area portion of the substrate supporting the spring wire from being broken by the thermal shock breakage. A resistor-breaking element combination, wherein the spring wire is configured not to drop from the substrate in response to the thermal shock rupture.