JPH0220863Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to an electromagnetic interference countermeasure capacitor mounted on a hybrid integrated circuit board.

Prior Art and Problems Transistors may turn on when noise voltage is mixed in with them. That is, FIG. 1 shows an example of a lamp drive circuit for automobile equipment, in which Q1 is a transistor that turns on and off the lamp, R1 and R2 are resistors inserted in the base circuit, D1 and D2 are diodes, and input terminals T1 and Alternatively, when a positive voltage is applied to T2, transistor Q1 turns on, turning on a lamp (not shown) connected to its collector, and when the input voltage at terminals T1 and T2 disappears, Q1
is turned off and the lamp is extinguished, but if an electromagnetic noise voltage is applied to terminals T1 and/or T2, the noise voltage is rectified by diode D1 and/or D2, and as a result, the base of transistor Q1 becomes positive. The transistor Q1 may be biased to a potential, a base current may flow, and the transistor Q1 may be turned on.

Countermeasures against such malfunctions (referred to as EMi countermeasures)
, the capacitors C1 and C2 are connected to the diode D
1 and D2 in parallel. That is, when the capacitors C1 and C2 are present, the diodes D1 and D2 are short-circuited in an alternating current manner, and the direct current potential of the base of the transistor Q1 is 0, so that Q1 is no longer turned on.

EMi countermeasure capacitors are sometimes installed in parallel to the base and emitter of the transistor. Figure 2 is an example of this, where Q3 is the output transistor, Q2 is its driver transistor, R3 to R6 are resistors, and C
3 is an EMi countermeasure capacitor connected in parallel to the base and emitter of the transistor. Without capacitor C3, the electromagnetic noise voltage input to input terminal T3 would be rectified by the base and emitter junction of transistor Q2, that is, by the diode, and as a result, Q
2 is on, so Q3 is also on. When the capacitor C3 is present, the base and emitter junctions of the transistor Q2 are short-circuited in an alternating current manner, and the rectification effect is substantially eliminated.

Integrated circuits use a large number of transistors and diodes, which also requires a large number of capacitors for EMi countermeasures. If such a capacitor is mounted as individual parts, there are disadvantages such as the number of parts increases, the mounting space becomes large, making it impossible to achieve miniaturization, and the mounting work is complicated, leading to increased costs. Particularly in hybrid ICs, the substrate is made of ceramic and various integrated circuits and individual parts are attached to it, but the dimensions are usually not that large, so it is a problem to attach a large number of capacitors with individual parts.

Purpose of the invention The present invention is an attempt to form a capacitor for EMi countermeasures using extremely simple means and to improve the above-mentioned problems associated with mounting individual parts.

Structure of the invention The present invention relates to a capacitor for preventing electromagnetic interference that is connected in parallel to a diode part of a hybrid integrated circuit, and a capacitor that is connected in parallel to a diode part of a wiring pattern on a board of the hybrid integrated circuit to which one end of the diode part is connected. A dielectric film is deposited, a wiring pattern to which the other end of the diode part is connected is extended over the dielectric film, and static electricity is removed at the crossover portion of both wiring patterns facing each other through the dielectric film. The feature is that a capacitance is formed, which will be explained next with reference to Examples.

Embodiment of the invention FIG. 3 shows an embodiment of the invention, 10, 12,
14 is a wiring pattern on the hybrid IC board SUB, and 16 is a chip diode attached to these wiring patterns. A dielectric film 18 is deposited on the wiring patterns 10 and 14 to form a capacitor, and an enlarged portion 12 of the wiring pattern 12 is formed on the dielectric film 18.
a, 12b are formed. The wiring on the ceramic substrate of a hybrid IC is formed by, for example, printing a conductive paste with a screen and heating and sintering it, so the pattern shown in the figure is first formed by wiring patterns 10, 1
4, print the dielectric film 18 thereon, and then print the wiring pattern 12.

Since the conductor patterns 10 and 12a and 14 and 12b face each other with the dielectric film 18 in between, these crossover portions form a capacitor, and the chip diode 16 connects the terminals 16a, 16b, 1
Since there are two diodes connected to 6a and 16c, the device of FIG. 3a is finally represented by the equivalent circuit of FIG. 3b. This is the transistor Q in Figure 1.
Diode D inserted into the base input circuit of 1
1, D2, and capacitors C1 and C2. In this way, according to the present device, EMi countermeasures can be applied to the diodes D1 and D2 without the need for connection work using the capacitors C1 and C2 made of individual parts.

When the dielectric film 18 is made of glass ceramic, the dielectric constant εs is 9 to 15. Therefore patterns 10 and 12
If the opposing area of a or 14 and 12b is S, and the spacing and the thickness of the dielectric film d are 0.04 mm, the capacitance C [PF] of capacitors C1 and C2 is C=εs・εo・
S/d=(1.86~15)×Smm ² (εo=8.854×
10 ^-12 [F/m]). Using this formula, the facing area Smm ² may be determined so as to obtain the required capacitance value.
The capacitance value of the EMi capacitor is small, about 20 pF or less, and the width of the wiring pattern is several mm, so it is necessary to simply cross over both wiring patterns, or slightly expand the width or length at the crossover part. That's fine.

Effects of the invention As is clear from the above explanation, this invention does not require mounting space for the EMi capacitor, making it possible to downsize the hybrid IC.
This eliminates the need to attach individual parts such as chip capacitors, resulting in reductions in manufacturing time and costs.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams illustrating a capacitor for EMi countermeasures, and FIG. 3 is a diagram showing an embodiment of the present invention, in which a is a plan view and b is an equivalent circuit diagram. In the drawing, C1 to C3 are EMi countermeasure capacitors,
SUB is the hybrid IC board, 10, 12, 1
4 is a wiring pattern, D1 and D2 are diodes, 1
6 is its individual component, 18 is a dielectric film, 12a, 1
2b is the wiring pattern 10,1 of the wiring pattern 12
4. It is an extension part above 4.

Claims (1)

[Claims for Utility Model Registration] In a capacitor for electromagnetic interference prevention that is connected in parallel to a diode section of a hybrid integrated circuit, the wiring to which one end of the diode section of the wiring pattern on the substrate of the hybrid integrated circuit is connected. A dielectric film is applied to the pattern, a wiring pattern to which the other end of the diode section is connected is extended over the dielectric film, and a crossover portion of both wiring patterns facing each other with the dielectric film interposed therebetween is formed. A capacitor for a hybrid integrated circuit characterized by forming a capacitance.