# Patent

## Title
Communication module

## Abstract

A communication module includes a circuit board having electronic components thereon, an insulative molded member encapsulating the electronic components on the circuit board, and an antenna unit on the molded member. The circuit board is electrically connected to the antenna unit through a post terminal. The antenna unit and the molded member define a cavity therebetween.

## Background
CLAIM OF PRIORITY
This application claims benefit of priority to Japanese Patent Application No. 2014-240334 filed on Nov. 27, 2014, which is hereby incorporated by reference.
BACKGROUND
1. Field of the Disclosure
The present disclosure relates to a wireless communication module for data communication.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2009-290553 discloses a high-frequency module including an antenna suitable for radio communication equipment. This high-frequency module includes a circuit board having a plurality of circuit components thereon, a molded resin member covering the circuit components on the circuit board, and the antenna, which is flat, on the molded resin member.
In the above-described related-art module, the molded resin member, which is insulative, is placed under the planar antenna. The antenna is capacitively coupled to the molded resin member. In other words, the characteristics of the antenna are affected by the dielectric constant of the molded resin member. This restricts selection of a material for the molded resin member and circuit design. Furthermore, the circuit board, the planar antenna, and the molded resin member have different coefficients of thermal expansion. The circuit board or the planar antenna may be strained upon molding or depending on the environment, leading to a degradation in performance.
SUMMARY
A communication module includes a circuit board having a plurality of electronic components thereon, an insulative encapsulating member covering the electronic components on the circuit board, and a plate-shaped antenna unit on the encapsulating member. The circuit board is electrically connected to the antenna unit through a connecting member. The antenna unit and the encapsulating member define a cavity therebetween.
In this communication module, the cavity between the antenna unit and the encapsulating member allows a reduction in capacitive coupling between the antenna unit and the encapsulating member, made of resin, as compared with that in the related art, resulting in reduction of electrical effects of the encapsulating member on the antenna unit. Furthermore, the above-described configuration can minimize strain caused by thermal expansion of the encapsulating member made of resin.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a communication module according to a first embodiment of the present invention;
FIG. 2 is an exploded perspective view of the communication module of FIG. 1;
FIG. 3 is a cross-sectional view of the communication module taken along the line III-III in FIG. 1;
FIG. 4 is a cross-sectional view illustrating a molding die for the communication module taken along the line III-III in FIG. 1 before formation of a molded member of the communication module.
FIG. 5 is a cross-sectional view illustrating the molded member of the communication module taken along the line III-III in FIG. 1 before attachment of an antenna unit;
FIG. 6 is a cross-sectional view of a communication module according to a second embodiment of the present invention taken along a line corresponding to the line III-III in FIG. 1;
FIG. 7 is a cross-sectional view of a communication module according to a third embodiment of the present invention taken along a line corresponding to the line III-III in FIG. 1;
FIG. 8 is an exploded perspective view of a communication module according to a fourth embodiment of the present invention;
FIG. 9 is a perspective view of the communication module of FIG. 8 when viewed in a direction opposite to the direction in FIG. 8;
FIG. 10 is an exploded perspective view of a communication module according to a fifth embodiment of the present invention; and
FIG. 11 is a perspective view of the communication module of FIG. 10.



DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
Communication modules according to embodiments of the present invention will be described with reference to the drawings. The drawings are for illustration purposes only and are not drawn to scale.
As illustrated in FIGS. 1 to 3, a communication module 1 according to a first embodiment of the present invention includes a circuit board 2 having electronic components 2a and 2b thereon, a molded member 3, serving as an encapsulating member, and a plate-shaped antenna unit 5 including an antenna pattern 4.
In the present embodiment, the electronic component 2a may be an electronic component having a relatively high height, for example, a coil or an oscillator. The electronic component 2b may be an integrated circuit having a lower height than the electronic component 2a. The electronic components 2a and 2b are electrically connected through solder 2d to a circuit pattern 2c formed of copper foil on the circuit board 2. The circuit board 2 has a lower surface having thereon a circuit pattern 2e, serving as an external connection terminal of the communication module 1. The circuit pattern 2e is electrically connected to the above-described circuit pattern 2c via a through-hole 2f. 
The molded member 3 is made of insulating resin, such as epoxy resin or silicone resin. The molded member 3 covers and encapsulates the electronic components 2a and 2b on the circuit board 2. The molded member 3 may include a wall portion 3a extending along an outer edge of the circuit board 2, a recess 3b having a depth associated with the height of the electronic component 2a on the circuit board 2, and a recess 3c having a depth associated with the height of the electronic component 2b on the circuit board 2. The wall portion 3a has an upper edge 3a1 on which the antenna unit 5 is mounted, with an adhesive 6 therebetween. As is seen from FIG. 3, the recess 3c is deeper than the recess 3b in the present embodiment.
A cylindrical post terminal 7, serving as a connecting member for electrically connecting the circuit board 2 to the antenna unit 5, is placed in the wall portion 3a of the molded member 3. The post terminal 7 is connected at a point adjacent to its lower end to the circuit pattern 2c of the circuit board 2 through the solder 2d. The post terminal 7 having an upper end face 7a is placed such that the upper end face 7a is flush with the upper edge 3a1 of the molded member 3.
The antenna unit 5 including an insulating substrate has an upper surface 5a on which the antenna pattern 4 including linear parts and having a length appropriate for a transmitting and receiving frequency is formed of copper foil. The antenna pattern 4 has two ends. One end of the two ends serves as a connection end 4a connected to the post terminal 7. The antenna pattern 4 extends to a connection recess 5b in a side surface of the antenna unit 5. The other end of the antenna pattern 4 is a free end 4b. The upper end face 7a of the post terminal 7 is electrically connected to the connection end 4a of the antenna pattern 4 through solder 8 in the connection recess 5b. 
Referring to FIG. 3, the communication module 1 with the above-described configuration has a hermetically closed cavity 9 defined by the antenna unit 5 and the molded member 3 having the recesses 3b and 3c. The cavity 9 results in an increased distance between the molded member 3, which is a dielectric, and the antenna pattern 4, thus reducing electrical effects of the molded member 3 on antenna characteristics.
The antenna pattern 4 in the present embodiment has a monopole structure having a first end that is free. The free end 4b of the antenna pattern 4 is electrically more unstable than the connection end 4a. In the present embodiment, the height of a portion of the cavity 9 (or the depth of the recess 3c) adjacent to the free end 4b of the antenna pattern 4 may be made greater than the height of another portion of the cavity 9 (or the depth of the recess 3b) adjacent to the connection end 4a to form steps. This achieves further reduction of electrical effects of the molded member 3 on the free end 4b. 
A method of making the communication module 1 will now be described. The solder 2d in paste form is applied to an upper surface of the circuit board 2 having the circuit patterns 2c and 2e thereon. The circuit board 2 is then allowed to pass through a reflow oven, thus fixing the electronic components 2a and 2b and the post terminal 7 to the circuit board 2. After that, the method proceeds to a molding step.
As illustrated in FIG. 4, a molding die includes a plate-shaped lower die segment 10 and an upper die segment 11. The upper die segment 11 is in contact with the upper surface of the circuit board 2 such that the circuit board 2 is sandwiched between the lower die segment 10 and the upper die segment 11. The upper die segment 11 has a protrusion 11a and a protrusion 11b formed so that each of the protrusions 11a and 11b is at a predetermined distance from the upper surface of the corresponding one of the electronic components 2a and 2b. The upper die segment 11 further has injection ports 11c, through which mold resin is injected, such that the injection ports 11c open at a level corresponding to the upper edge 3a1 of the wall portion 3a of the molded member 3. Each of the protrusions 11a and 11b of the upper die segment 11 has a sloping side surface to enhance the flowability of the mold resin in the die and to enable the upper die segment 11 to be easily removed after the mold resin is hardened. The mold resin is poured into the die through the injection ports 11c under pressure while the circuit board 2 is sandwiched between the upper die segment 11 and the lower die segment 10. Since each of the protrusions 11a and 11b of the upper die segment 11 is at a predetermined distance from the corresponding one of the electronic components 2a and 2b, the protrusion 11b of the upper die segment 11 is at a minimum distance from the circuit board 2. This allows the pressure under which the mold resin is poured to be increased, so that spacing between the electronic component 2b and the circuit board 2 is filled with the mold resin with no clearances. Thus, the electronic component 2b is firmly encapsulated in the molded member 3.
After the mold resin is hardened, the upper die segment 11 is removed. At this time, the upper edge 3a1 of the wall portion 3a of the molded member 3 may have unnecessary mold resin parts like burrs. The mold resin may be left on the upper end face 7a of the post terminal 7. After the upper die segment 11 is removed, therefore, the upper edge 3a1 of the wall portion 3a of the molded member 3 is polished to eliminate the unnecessary mold resin parts and flatten the upper edge 3a1 and the upper end face 7a of the post terminal 7. After that, the adhesive 6 is applied to the upper edge 3a1 and the antenna unit 5 is attached to the upper edge 3a1 to hermetically seal the communication module 1, thus forming the cavity 9.
Then, the connection end 4a of the antenna pattern 4 is electrically connected to the upper end face 7a of the post terminal 7 with the solder 8 in the connection recess 5b of the antenna unit 5. Thus, the communication module 1 is completed.
The communication module 1 has the cavity 9 on the molded member 3. The dielectric loss tangent of part including the molded member 3 (particularly, the recesses 3b and 3c), serving as a dielectric, and the antenna unit 5 (particularly, the antenna pattern 4) is accordingly smaller than that in the related art. Consequently, the antenna pattern 4 is little affected by the dielectric constant of the molded member 3, thus enabling the antenna unit 5 to have stable electrical characteristics. In addition, the cavity 9 allows the strain of the entire communication module 1 caused by the difference in coefficient of thermal expansion among the molded member 3, the circuit board 2, and the antenna unit 5 to be reduced as compared with that in the related art, and also allows a reduction in amount of mold resin used, leading to a reduction in cost. In the present invention, the antenna pattern 4 has a monopole structure and the free end 4b of the antenna pattern 4 is accordingly electrically more unstable than the connection end 4a thereof. In the present embodiment, the recess 3c of the molded member 3 adjacent to the free end 4b of the antenna pattern 4 is made deeper than the recess 3b adjacent to the connection end 4a, thus further reducing the electrical effects of the molded member 3 on the antenna characteristics. This facilitates designing the circuitry of the entire communication module 1.
FIG. 6 illustrates a communication module 100 according to a second embodiment of the present invention. FIG. 6 is a cross-sectional view of the communication module 100 taken along a line corresponding to the line III-III in FIG. 1 in the first embodiment. The same components as those in the first embodiment are designated by the same reference numerals and a detailed description of these components is omitted.
The communication module 100 according to the present embodiment further includes an electronic component 2g in addition to the components of the communication module 1 according to the first embodiment. The electronic component 2g is a small component, such as a resistor or a capacitor, and has a lower height than the electronic component 2b. In this case, the electronic components 2a, 2b, and 2g are arranged in order of decreasing height in a direction from the connection end 4a of the antenna pattern 4 to the free end 4b. A molded member 30 includes a wall portion 30a and has recesses 30b, 30c, and 30d surrounded by the wall portion 30a. The recesses 30b, 30c, and 30d have different depths associated with the heights of the electronic components 2a, 2b, and 2g. In the communication module 100, a cavity 90 can accordingly be maximized in association with the shapes of the electronic components mounted on the circuit board 2.
FIG. 7 illustrates a communication module 110 according to a third embodiment of the present invention. FIG. 7 is a cross-sectional view of the communication module 110 taken along a line corresponding to the line III-III in FIG. 1 in the first embodiment. The same components as those in the first and second embodiments are designated by the same reference numerals and a detailed description of these components is omitted.
The third embodiment differs from the second embodiment in that a recess 31b surrounded by a wall portion 31a of a molded member 31 has a surface sloping down in the direction from the connection end 4a of the antenna pattern 4 to the free end 4b. This facilitates simplification of a die for forming the molded member 31 in addition to achieving the same advantages offered by the second embodiment.
FIG. 8 is an exploded perspective view of a communication module according to a fourth embodiment of the present invention. FIG. 9 is a perspective view of the communication module according to the fourth embodiment. The same components as those in the first embodiment are designated by the same reference numerals and an explanation of these components is omitted.
The communication module, indicated at 120, according to the present embodiment includes the circuit board 2 and a molded member 32 on the circuit board 2 as in the first embodiment. The molded member 32 may include a wall portion 32a and have recesses 32b and 32c and a gap 32f that is under the free end 4b of the antenna pattern 4. The adhesive 6 is applied to an upper edge 32a of the wall portion 32a and the antenna unit 5 is attached to the molded member 32, thus forming a cavity 92 between the molded member 32 and the antenna unit 5. As described above, the free end 4b of the antenna pattern 4 is electrically the most unstable and is accordingly most affected by the molded member 30, serving as a dielectric. The above-described configuration, however, has the gap 32f under the free end 4b in addition to the cavity 92, thus enabling the antenna pattern 4 to have more stable electrical characteristics. Furthermore, the cavity 92 opens through the gap 32f. This eliminates an adverse effect on the communication module 120 caused by expansion or contraction of air in the cavity 92 in response to a change in environment.
FIG. 10 is an exploded perspective view of a communication module according to a fifth embodiment of the present invention. FIG. 11 is a perspective view of the communication module according to the fifth embodiment. The same components as those in the first embodiment are designated by the same reference numerals and an explanation of these components is omitted.
The communication module, indicated at 130, according to the fifth embodiment includes the circuit board 2 and a molded member 33 covering the circuit board 2. The molded member 33 includes two wall portions 33a each having an upper edge 33a1, and has a U-shaped recess 33b. The upper end face 7a of the cylindrical post terminal 7 electrically connected to the circuit board 2 is exposed at the upper edge 33a1 of one of the wall portions 33a of the molded member 33. The communication module 130 further includes an antenna unit 50 including a film member made of, for example, polyethylene terephthalate (PET). The antenna unit 50 has an upper surface 50a having an antenna pattern 40 thereon. The antenna pattern 40 has a connection end 40a having a through-hole 50b, a free end 40b, and short linear parts 40c. The antenna unit 50 is attached to the upper edges 33a1 of the wall portions 33a of the molded member 33 with the adhesive 6 such that the short linear parts 40c extend along the upper edges 33a1 of the molded member 33. After that, the solder 8 is applied to the through-hole 50b of the antenna unit 50, thus electrically connecting the connection end 40a of the antenna pattern 40 to the upper end face 7a of the post terminal 7.
In the fifth embodiment, the recess 33b of the molded member 33 and the antenna unit 50 define a space that serves as a cavity 93. A space under one end of the antenna unit 50 in which the free end 40b is placed may serve as a gap 33f. 
The fifth embodiment achieves further reduction in amount of mold resin used and facilitates simplification of the structure of a die, leading to a reduction in cost. Additionally, the amount of the mold resin under the antenna pattern 40 can be further reduced, thus further reducing the effects of the mold resin on the antenna unit 50.
The present invention is not limited to the above-described embodiments. The present invention may be appropriately modified without departing from the scope of the present invention.

## Claims

1. A communication module comprising:
a circuit board having a plurality of electronic components thereon;
an insulative encapsulating member covering the electronic components on the circuit board, the encapsulating member including a wall portion provided in an outer peripheral area of a top portion of the encapsulating member, and a recess portion provided in the residual area of the top portion of the encapsulating member so as to be surrounded by the wall portion;

a plate-shaped antenna unit on the encapsulating member, the antenna unit including an insulating substrate provided on the wall portion of the encapsulating member, and an antenna pattern on a top surface of the insulating substrate so as to be located on the opposite side of the encapsulating member through the insulating substrate;
the circuit board being electrically connected to the antenna unit through a connecting member; and
a bottom surface of the insulating substrate and the recess portion of the encapsulating member defining a cavity therebetween.

2. The module according to claim 1, wherein the encapsulating member has steps in the cavity such that the steps correspond to heights of the electronic components on the circuit board.

3. The module according to claim 1, wherein the electronic components include at least one integrated circuit and the encapsulating member on the integrated circuit is at a maximum distance from the antenna unit in the cavity.

4. The module according to claim 1, wherein the wall portion extends along an outer edge of a bottom surface of the antenna unit.

5. The module according to claim 1, wherein the encapsulating member has a gap extending through a side portion of the encapsulating member.

6. The module according to claim 5, wherein the antenna pattern has a monopole structure having a first end that serves as a free end and a second end that serves as a connection end electrically connected to the circuit board, and the gap is under the free end of the antenna pattern.

7. The module according to claim 1, wherein the bottom surface of the insulating substrate is fixed on the wall portion of the encapsulating member with an adhesive.