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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone unit incorporating a load resistance and the like. Prior Art FIG. 3 is a cross-sectional
view showing a microphone unit of a conventional electret condenser microphone. The
configuration of this conventional example will be described below with reference to FIG. In FIG.
3, 1 is a drawing cloth, 2 is a cylindrical metal case having a sound hole 2a on the top surface, 3
is a film ring formed by uniformly stretching a vibrating film 4 having a metal surface by metal
deposition or the like, 5 is A gap spacer, 6 is a fixed electrode, 7 is an insulator, and the fixed
electrode 6 is supported on the upper side thereof. The reference numeral 8 denotes a printed
circuit board provided at the bottom of the insulator 19 at the FET 19, the reference numeral 10
denotes a load resistance, and the reference numeral 11 denotes a capacitor capsule. In this
description, a wheel electret type using an electret material for the vibrating membrane 4 is
taken as an example, but the same applies to a pack electret type where an electret material is
provided on the fixed electrode 6 side. The fixed electrode 6, the insulator 7, the FET 8, the
printed circuit board 9, and the load resistor IO can be considered as one amplifier block, and the
above-described components are fixed to the metal case 2 by the caulking portion 2b. In the
electret condenser microphone configured as described above, it is necessary to use a small-sized
resistor in order to incorporate the load resistor 10, or the number of parts increases with I?, so
the load resistive portion It can not be avoided that the degree of assembly difficulty increases
compared to the attached electret condenser microphones. Therefore, the cost will increase. In
addition, since the size of the load resistor IO physically determines the size of the electret
condenser microphone, there is a disadvantage that it is not suitable for miniaturization. It is an
object of the present invention to provide an inexpensive built-in microphone unit such as a load
resistor which has the above-mentioned drawbacks eliminated and which is easy to assemble and
has a possibility of downsizing. Means for Solving the Problems In order to achieve the above
object, the present invention is configured such that a load resistor is formed on a printed circuit
board provided on the bottom of an insulator by a print resistor. Therefore, according to the
present invention, the number of parts can be reduced, the assembly can be facilitated, and the
load resistance can be made thin, so that the effect of downsizing, in particular, thinning can be
obtained. Embodiment The configuration of an embodiment of the present invention will be
described below with reference to the drawings. FIG. 1 is a sectional view, and the same parts as
FIG. 3 are indicated by the same reference numerals.
In FIG. 1, the difference from FIG. 3 is that the load resistor 10 is formed on the printed circuit
board 9 by the printed resistor 12. 2 is a partial enlarged cross-sectional view of the printed
resistance 12 part in FIG. 1. In FIG. 2, 9a is a copper foil pattern on a printed circuit board, 12a is
a printed resistance by carbon etc., 12b is a copper foil pattern 9a and Electrode terminals made
of gold, silver or the like for improving the continuity of the printing resistor 12a, and 12c an
overcoat made of an epoxy resin or the like for preventing the printing resistor 12a or the like
from deteriorating due to environmental conditions. As described above, according to the present
invention, since the load resistance is formed on the printed circuit board by the printing
resistance, the number of parts and the configuration are the same as the electret condenser
microphone with the load resistance portion, and assembly is easy. While being able to provide
an inexpensive load resistance built-in microphone unit, the printing resistance can be made thin,
and there is no physical restriction on the load resistance, so that it has the advantages of being
able to be made smaller, particularly thin.
Brief description of the drawings
FIG. 1 is a cross-sectional view of a microphone unit in an embodiment of the present invention,
FIG. 2 is an enlarged view of an essential part in FIG. 1, and FIG. 3 is a cross-sectional view
showing a conventional microphone unit.
ииииииииииииииииииииииииииииииииииии ? и и и и и и и и и и и и и и и и и и и и и и и и и Printed circuit board, 12 и и и и и и и и и и printing
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