Circuit module
One object is to prevent electromagnetic wave interference between electronic components with restricted increase of the size of a circuit module. A circuit module according to an embodiment includes a circuit board, a plurality of electronic components provided on the circuit board, a resin mold provided on the circuit board so as to seal the plurality of electronic components in an insulating manner, a conductive shield covering the top surface and the side surfaces of the resin mold, and a plurality of conductive poles having a columnar shape provided in the resin mold and connecting the top surface of the conductive shield and the ground of the circuit board. The resonance caused by frequencies equal to or less than a predetermined maximum usable frequency is restricted.
1. A circuit module, comprising:
a circuit board having a ground;
one or more electronic components provided on the circuit board;
a resin mold provided on the circuit board so as to seal the one or more electronic components in an insulating manner;
a conductive shield covering a top surface and side surfaces of the resin mold; and
a plurality of conductive poles provided in the resin mold, the plurality of conductive poles connecting a top surface of the conductive shield and the ground of the circuit board,
wherein all of a plurality of rectangular regions on the top surface of the conductive shield have two sides with lengths of a and b satisfying Formula (1) expressed as:
f
max
<
c
2
π
ɛ
r
(
m
π
a
)
2
+
(
n
π
b
)
2
(
1
)
where fmax is a predetermined maximum usable frequency, ∈ r is a relative dielectric constant of the resin mold, m and n are any integers, and c is a light speed, each of the plurality of rectangular regions being defined by side surfaces of the conductive shield and one or more of the plurality of conductive poles, each of the plurality of rectangular regions including none of the plurality of conductive poles, and
wherein the plurality of conductive poles are arranged such that a distance between two closest conductive poles is equal to or less than one-fourth of a wavelength at the predetermined maximum usable frequency in the resin mold.
2. The circuit module of claim 1 , wherein the circuit module is a wireless communication module, and the predetermined maximum usable frequency is based on a maximum frequency in wireless communication standards supported by the wireless communication module.
3. The circuit module of claim 1 , wherein the circuit module is a wireless communication module, and the predetermined maximum usable frequency is equivalent to a fourth harmonic of a maximum frequency in wireless communication standards supported by the wireless communication module.
4. The circuit module of claim 1 , wherein a rectangular region having one side with a length corresponding to a length of one side of the circuit board has the other side with a length equal to or greater than half of a maximum length satisfying Formula (1).