Chip-scale atomic clock and manufacturing method therefor

Abstract

A chip-scale atomic clock, according to one embodiment of the present invention, comprises: a vapor cell comprising a semiconductor substrate having a cavity for receiving alkali metal vapor therein, an upper transparent substrate disposed on the upper surface of the semiconductor substrate, and a lower transparent substrate disposed on the lower surface of the semiconductor substrate; an upper alignment part disposed on the upper transparent substrate; and a lower alignment part disposed on the lower transparent substrate. The upper alignment part and the lower alignment part are in contact with each other, and the vapor cell is inserted into a recess formed in the upper alignment part and the lower alignment part so as to be aligned.

Description

Chip-scale atomic clock and its manufacturing method

[0001] The present invention relates to a chip-scale atomic clock, and more particularly, to a suspended atomic clock having a vapor cell sandwiched between an alignment part and a flexible substrate.

[0002] A typical atomic clock comprises a physical section containing an atomic vapor cell. The physical section is stacked, labor-intensive, and difficult to manufacture.

[0003] In particular, in order to maximize the advantages of ultra-small atomic devices, it is very difficult to manufacture physical components suspended on flexible substrates, etc., while adopting a suspended structure.

[0004] The physical part of a commercialized atomic clock uses an integrated structure of a light source-vapor cell-detector and a connection method using wire bonding. After vacuum packaging, separate packaging is required to cover it with a magnetic shield and a coil for generating a magnetic field.

[0005] The inventors of the present invention proposed a suspended structure in which vapor cells are arranged on a foldable flexible substrate in Korean Patent No. 10-2289703. The flexible hybrid-based connection process offers the advantages of planar integration followed by foldable assembly, eliminating the need for high-aspect-ratio wire bonding, and enabling magnetic shielding and coil integration as needed. However, the integration process of the light source-vapor cell-detector is labor-intensive, and alignment is challenging.

[0006] In addition, packaging methods using low-temperature co-fired ceramics (LTCC) or printed circuit boards (PCBs) are not easy to achieve in miniaturization and low power consumption, and there are limitations in three-dimensional integration of light source-vapor cell-detector.

[0007] The technical problem to be solved by the present invention is that a vapor cell is suspended by being placed between a pair of flexible printed circuit boards, and can be easily aligned using an alignment part for vertically aligning a light source-vapor cell-photodetector.

[0008] A chip-scale atomic clock according to one embodiment of the present invention comprises a semiconductor substrate having a cavity for accommodating alkali metal vapor, a vapor cell including an upper transparent substrate disposed on an upper surface of the semiconductor substrate, and a lower transparent substrate disposed on a lower surface of the semiconductor substrate; an upper alignment portion disposed on the upper transparent substrate; and a lower alignment portion disposed on the lower transparent substrate. The upper alignment portion and the lower alignment portion contact each other, and the vapor cell is inserted into and aligned with a groove formed in the upper alignment portion and the lower alignment portion.

[0009] In one embodiment of the present invention, the groove of the upper alignment part may be cross-shaped, the groove of the lower alignment part may be cross-shaped, and the shape of the vapor cell may be cross-shaped.

[0010] In one embodiment of the present invention, the upper alignment portion may include an upper through hole, and the lower alignment portion may include a lower through hole.

[0011] In one embodiment of the present invention, the lower alignment portion may further include a lower jaw formed around the lower through hole.

[0012] In one embodiment of the present invention, a 1 / 4 wavelength plate inserted into the lower jaw may be further included.

[0013] In one embodiment of the present invention, the device may further include an upper spacer disposed above the upper alignment portion; and a lower spacer disposed below the lower alignment portion.

[0014] In one embodiment of the present invention, the upper spacer may include an upper spacer alignment portion inserted into an upper alignment groove formed in the upper alignment portion, and the lower spacer may further include a lower spacer alignment portion inserted into a lower alignment groove formed in the lower alignment portion.

[0015] In one embodiment of the present invention, the device may further include an upper printed circuit board disposed above the upper alignment portion; and a lower printed circuit board disposed below the lower alignment portion.

[0016] In one embodiment of the present invention, the device may further include an upper spacer disposed above the upper alignment portion; and a lower spacer disposed below the lower alignment portion. The upper printed circuit board may be disposed between the upper spacer and the upper alignment portion, and the lower printed circuit board may be disposed between the lower spacer and the lower alignment portion.

[0017] In one embodiment of the present invention, the device may further include a photodetector mounted on the upper printed circuit board and facing the vapor cell; and a light source mounted on the lower printed circuit board and facing the vapor cell.

[0018] In one embodiment of the present invention, at least one of an upper heater mounted on the upper printed circuit board and a lower heater mounted on the lower printed circuit board may be further included.

[0019] In one embodiment of the present invention, at least one of an upper heater disposed on the upper alignment surface and a lower heater disposed on the lower alignment surface may be further included.

[0020] In one embodiment of the present invention, at least one of an upper heater disposed on the upper spacer surface and a lower heater disposed on the lower spacer surface may be further included.

[0021] In one embodiment of the present invention, a temperature sensor mounted on the lower printed circuit board may be further included.

[0022] In one embodiment of the present invention, the upper alignment portion and the lower alignment portion can be fixed by an adhesive layer.

[0023] In one embodiment of the present invention, the vapor cell may be cross-shaped, and the vapor cell may include a main chamber disposed at the center of the vapor cell and having the cavity; and four auxiliary chambers connected to the main chamber. The main chamber and the auxiliary chambers may be interconnected by a trench, and at least one of the auxiliary chambers may include an alkali metal.

[0024] In one embodiment of the present invention, a nanostructure performing the function of a 1 / 4 wavelength plate may be further included on the lower transparent substrate surface of the vapor cell.

[0025] In one embodiment of the present invention, the upper alignment portion and the lower alignment portion may be octagonal. Each of the upper alignment portion and the lower alignment portion may include: an octagonal base portion; four protrusions spaced apart from each other and protruding in a triangular prism shape from the sides of the base portion; a through hole formed in the center of the base portion; and a protrusion formed around the through hole.

[0026] In one embodiment of the present invention, a nanostructure may be included on the surface of the lower transparent substrate of the vapor cell.

[0027] In one embodiment of the present invention, the device may further include an upper printed circuit board disposed above the upper alignment portion; a lower printed circuit board disposed below the lower alignment portion; and a magnetic field shield disposed spaced apart from the vapor cell and surrounding the vapor cell to block an external magnetic field.

[0028] In one embodiment of the present invention, the magnetic field shielding part may include an upper shielding part having an upper surface; a lower shielding part having a lower surface; and an intermediate shielding part disposed between the upper shielding part and the lower shielding part.

[0029] In one embodiment of the present invention, the upper printed circuit board can be fitted between the upper shield and the middle shield, and the lower printed circuit board can be fitted between the lower shield and the middle shield.

[0030] In one embodiment of the present invention, the lower shielding portion includes at least one protruding lower protrusion, and the lower protrusion is inserted into and fixed to a through hole formed in the lower printed circuit board, and the middle shielding portion includes at least one protruding middle protrusion, and the middle protrusion is inserted into and fixed to a through hole formed in the upper printed circuit board.

[0031] In one embodiment of the present invention, the device may further include an upper coil printed circuit board that is sandwiched between the upper shield and the middle shield and generates a magnetic field; and a lower coil printed circuit board that is sandwiched between the lower shield and the middle shield and generates a magnetic field.

[0032] In one embodiment of the present invention, a printed circuit board disposed on a lower surface of the shielding member may be further included.

[0033] In one embodiment of the present invention, the mounting printed circuit board fixing part may further be included, which is arranged on a lower surface of the mounting printed circuit board and is coupled to the lower shielding part.

[0034] In one embodiment of the present invention, the upper printed circuit board, the lower printed circuit board, and the mounting printed circuit board can be connected continuously.

[0035] In one embodiment of the present invention, the upper alignment portion may further include an upper alignment groove formed on its upper surface, and the lower alignment portion may further include a lower alignment groove formed on its upper surface.

[0036] A method for manufacturing a chip-scale atomic clock according to one embodiment of the present invention may include the steps of: providing a flexible printed circuit board including an upper printed circuit board, a lower printed circuit board connected to the upper printed circuit board, and a mounting printed circuit board connected to the lower printed circuit board; mounting a photodetector on the upper printed circuit board, mounting a light source on the lower printed circuit board, and mounting solder balls on the mounting printed circuit board; and arranging an upper alignment part on the upper transparent substrate in a vapor cell including a semiconductor substrate having a cavity for accommodating alkali metal vapor, an upper transparent substrate disposed on an upper surface of the semiconductor substrate, and a lower transparent substrate disposed on a lower surface of the semiconductor substrate, and arranging a lower alignment part under the lower transparent substrate.

[0037] In one embodiment of the present invention, the method may further include at least one of: arranging the mounted printed circuit board on the lower surface of the lower shielding portion, and fixing the mounted printed circuit board to the lower shielding portion using a mounted printed circuit board fixing portion; coupling the lower printed circuit board to a lower spacer and coupling the lower spacer to the lower alignment portion; coupling the lower printed circuit board to the lower shielding portion; coupling an intermediate shielding portion on the lower shielding portion; coupling an upper printed circuit board to an upper spacer and coupling the upper spacer to the upper alignment portion; coupling the upper printed circuit board to the intermediate shielding portion; and coupling an upper shielding portion on the intermediate shielding portion.

[0038] A magnetic field shielding device of a chip-scale atomic clock according to one embodiment of the present invention comprises: an upper shielding portion having an upper surface; a lower shielding portion having a lower surface; and an intermediate shielding portion arranged between the upper shielding portion and the lower shielding portion. The lower shielding portion includes at least one lower protrusion on its upper surface, the intermediate shielding portion includes at least one intermediate protrusion on its upper surface, the lower protrusion is coupled to a lower printed circuit board, and the intermediate protrusion is coupled to an upper printed circuit board.

[0039] In one embodiment of the present invention, the device may further include at least one lower through hole formed on a lower surface of the lower shield; a mounting printed circuit board arranged on a lower surface of the lower shield; and a mounting printed circuit board fixing part coupled to a lower surface of the mounting printed circuit board and fitted into the lower shield.

[0040] In one embodiment of the present invention, the upper shielding portion may be separated into two or more parts, and the lower shielding portion may be separated into two or more parts.

[0041] A flexible printed circuit board used in a chip-scale atomic clock according to one embodiment of the present invention includes an upper printed circuit board; a lower printed circuit board connected to the upper printed circuit board; and a mounting printed circuit board connected to the lower printed circuit board.

[0042] In one embodiment of the present invention, the upper printed circuit board may include a photodetector, the lower printed circuit board may include a light source, and the mounting printed circuit board may include a protrusion.

[0043] In one embodiment of the present invention, the device may further include an upper coil printed circuit board connected to the mounting printed circuit board; and a lower coil printed circuit board connected to the upper coil printed circuit board.

[0044] In one embodiment of the present invention, the upper coil printed circuit board may include at least two upper coil printed circuit boards that overlap each other, and the lower coil printed circuit board may include at least two upper coil printed circuit boards that overlap each other.

[0045] In one embodiment of the present invention, the upper printed circuit board may include a central region, a peripheral region, and a bridge region connecting the central region and the peripheral region.

[0046] In one embodiment of the present invention, the lower printed circuit board may include a central region, a peripheral region, and a bridge region connecting the central region and the peripheral region.

[0047] In one embodiment of the present invention, the bridge region of the upper printed circuit board may include a straight region and a curved region.

[0048] In one embodiment of the present invention, the central region of the upper printed circuit board may include a first alignment through hole, and the peripheral region of the upper printed circuit board may include a second alignment through hole.

[0049] A chip-scale atomic clock according to one embodiment of the present invention can reduce manufacturing costs and improve operational stability by vertically aligning a light source-vapor cell-photodetector using an alignment unit and an auxiliary alignment unit that align the fittings.

[0050] A chip-scale atomic clock according to one embodiment of the present invention can stably heat an atomic vapor cell by using an upper alignment part and an auxiliary alignment part that are aligned by insertion as heat transfer means.

[0051] In a chip-scale atomic clock according to one embodiment of the present invention, the atomic vapor cell is suspended between an upper flexible substrate and a lower flexible substrate to improve insulation properties and provide resistance to vibration.

[0052] In a chip-scale atomic clock according to one embodiment of the present invention, each of the upper flexible substrate and the lower flexible substrate can be fitted into a magnetic shield to provide a suspended structure of an atomic vapor cell.

[0053] In a chip-scale atomic clock according to one embodiment of the present invention, the upper flexible substrate and the lower flexible substrate are connected to each other by an extension portion so that they can be used in a foldable manner.

[0054] Figure 1 is a conceptual diagram of an atomic clock according to one embodiment of the present invention.

[0055] Figure 2 is a detailed conceptual diagram of the atomic clock of Figure 1.

[0056] Figure 3 is a conceptual diagram showing the vapor cell, upper alignment part, upper spacer, lower alignment part, and upper spacer of Figure 2.

[0057] Fig. 4 is a perspective view showing the magnetic field shield of Fig. 2.

[0058] Figure 5 is an exploded perspective view showing the magnetic field shielding part of Figure 2.

[0059] Fig. 6 is a perspective view showing the vapor cell of Fig. 2.

[0060] Fig. 7 is a plan view showing the vapor cell of Fig. 6.

[0061] Figure 8 is an exploded perspective view showing the vapor cell, upper alignment part, upper spacer, lower alignment part, and upper spacer of Figure 2.

[0062] Figures 9a, 9b, and 9c are plan views showing the upper alignment portion and the lower alignment portion.

[0063] Figures 10a and 10b are cross-sectional views of a vapor cell, an upper alignment portion, and a lower alignment portion.

[0064] Fig. 11 is a plan view showing the upper printed circuit board of Fig. 2.

[0065] Fig. 12 is a plan view showing the lower printed circuit board of Fig. 2.

[0066] Fig. 13 is a plan view showing the printed circuit board of Fig. 2.

[0067] Fig. 14 is a plan view showing the upper coil printed circuit board of Fig. 2.

[0068] Fig. 15 is a plan view showing the lower coil printed circuit board of Fig. 2.

[0069] Figures 16 to 18 are plan views showing printed circuit boards according to their mounting status.

[0070] Figures 19 to 24 are drawings explaining a manufacturing process of an atomic clock according to one embodiment of the present invention.

[0071] Figure 25 is a conceptual diagram showing an atomic clock according to another embodiment of the present invention.

[0072] Figure 26 is a conceptual diagram showing an atomic clock according to another embodiment of the present invention.

[0073] Figure 27 is a conceptual diagram showing an atomic clock according to another embodiment of the present invention.

[0074] Figure 28 is a conceptual diagram showing an atomic clock according to another embodiment of the present invention.

[0075] FIGS. 29a and 29b are plan views and exploded perspective views showing a vapor cell block according to another embodiment of the present invention.

[0076] FIGS. 30A and 30B are plan views and exploded perspective views showing a vapor cell block according to another embodiment of the present invention.

[0077] The physical component of an atomic clock device comprises a light source, a vapor cell, and a light detector. The physical component of the atomic clock device may include a coil for controlling the magnetic field of the vapor cell, a heater for controlling the temperature of the vapor cell, a magnetic shield for shielding against external magnetic fields, and a temperature sensor for measuring the temperature of the vapor cell. Vertical alignment of the light source, vapor cell, and light detector is not easy.

[0078] According to the present invention, an atomic clock having a vertical alignment structure of a concave-convex structure or a sandwich structure and a suspended structure in which a vapor cell is placed between a pair of flexible substrates is proposed.

[0079] The present invention offers advantages such as easier manufacturing and alignment compared to conventional assembly processes, the creation of a robust structure, and increased thermal resistance. The suspended structure on a flexible substrate can reduce heater power consumption. The uneven or interlocking structure can provide high-precision optical axis alignment of the light source, vapor cell, and photodetector.

[0080] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosure is thorough and complete and to sufficiently convey the spirit of the present invention to those skilled in the art. In the drawings, components are exaggerated for clarity. Parts denoted by the same reference numerals throughout the specification represent the same components.

[0081] Figure 1 is a conceptual diagram of an atomic clock according to one embodiment of the present invention.

[0082] Figure 2 is a detailed conceptual diagram of the atomic clock of Figure 1.

[0083] Figure 3 is a conceptual diagram showing the vapor cell, upper alignment part, upper spacer, lower alignment part, and upper spacer of Figure 2.

[0084] Fig. 4 is a perspective view showing the magnetic field shield of Fig. 2.

[0085] Figure 5 is an exploded perspective view showing the magnetic field shielding part of Figure 2.

[0086] Fig. 6 is a perspective view showing the vapor cell of Fig. 2.

[0087] Fig. 7 is a plan view showing the vapor cell of Fig. 6.

[0088] Figure 8 is an exploded perspective view showing the vapor cell, upper alignment part, upper spacer, lower alignment part, and upper spacer of Figure 2.

[0089] Figures 9a, 9b, and 9c are plan views showing the upper alignment portion and the lower alignment portion.

[0090] Figures 10a and 10b are cross-sectional views of a vapor cell, an upper alignment portion, and a lower alignment portion.

[0091] Fig. 11 is a plan view showing the upper printed circuit board of Fig. 2.

[0092] Fig. 12 is a plan view showing the lower printed circuit board of Fig. 2.

[0093] Fig. 13 is a plan view showing the printed circuit board of Fig. 2.

[0094] Fig. 14 is a plan view showing the upper coil printed circuit board of Fig. 2.

[0095] Fig. 15 is a plan view showing the lower coil printed circuit board of Fig. 2.

[0096] Referring to FIGS. 1 to 15, an atomic clock (100) according to one embodiment of the present invention includes a vapor cell (120) including a semiconductor substrate (122) having a cavity (121) for storing alkali metal vapor, an upper transparent substrate (124) disposed on an upper surface of the semiconductor substrate (122), and a lower transparent substrate (126) disposed on a lower surface of the semiconductor substrate (122); an upper alignment portion (194) disposed on the upper transparent substrate (124); and a lower alignment portion (196) disposed under the lower transparent substrate (126).

[0097] The upper alignment part (194) and the lower alignment part (196) are in contact with each other and are combined.

[0098] The above vapor cell (120) is inserted into and aligned in the grooves (194c, 196c) formed in the upper alignment part (194) and the lower alignment part (196).

[0099] The vapor cell (120) may be cross-shaped. The vapor cell (120) may include a main chamber (122a) disposed at the center of the vapor cell (120) and having the cavity (121); and four auxiliary chambers (122b) connected to the main chamber (122a). The main chamber (122a) and the auxiliary chambers (122b) may be interconnected by a trench (122c). At least one of the auxiliary chambers (122b) may include an alkali metal (120a). The vapor cell (120) may include a lower transparent substrate (126), a semiconductor substrate (122), and an upper transparent substrate (124) that are sequentially stacked. The shape of the vapor cell (120) may be cross-shaped or may be modified into another shape.

[0100] The semiconductor substrate (122) may be a silicon substrate and may be cross-shaped. The semiconductor substrate (122) may include a cavity (121) penetrating the semiconductor substrate. The semiconductor substrate (122) may further include an auxiliary chamber (122b) for storing an alkali metal. The auxiliary chamber (122b) and the main chamber (122a) may be connected by a channel or a trench. The cavity (121), the main chamber (122a), the auxiliary chamber (122b), and the trench (122c) may be formed through a semiconductor patterning process. The auxiliary chambers (122b) may be arranged on each side of the main chamber (122a) having a square shape.

[0101] The alkali metal (120a) stored in the auxiliary chamber (122b) may be vaporized to fill the cavity (121) of the main chamber (122a). The alkali metal (120a) may be cesium (Cs) or rubidium (Rb). The vapor cell (120) may further include a buffer gas such as Ne. Light from the light source (140) may be transmitted through the cavity (121) and detected by the photodetector (150).

[0102] The upper transparent substrate (124) can cover the upper surface of the semiconductor substrate (122) and seal the cavity (121). The upper transparent substrate (124) can be anodic bonded with the semiconductor substrate (122). The upper transparent substrate (124) can be a cross-shaped glass substrate.

[0103] The lower transparent substrate (126) can cover the lower surface of the semiconductor substrate (122) and seal the cavity (121). The lower transparent substrate (126) can be anodic bonded with the semiconductor substrate (122). The lower transparent substrate (126) can be a cross-shaped glass substrate.

[0104] According to a modified embodiment of the present invention, a nanostructure formed on one side of a lower transparent substrate (126) may be included. The nanostructure may have a width of tens to hundreds of nm and a height of hundreds of nm, and may have a high aspect ratio cylindrical, elliptical, or rod-shaped shape, and may be made of a dielectric material such as silicon, a nitride film, or an oxide film. The nanostructure may function as a 1 / 4 wave plate by controlling the phase velocity along the axis of transmitted light.

[0105] According to a modified embodiment of the present invention, the other side of the lower transparent substrate (126) may include an ND (neutral density) filter film for reducing the amount of light incident on the vapor cell. The ND filter film may include a thin rapid film of several nm for absorbing light and an anti-reflection film using at least one layer of dielectric material for preventing reflection.

[0106] The upper alignment portion (194) may be positioned on the upper transparent substrate (124). The upper alignment portion (194) may include an upper through hole (194d). Light may pass through the upper through hole (194d). The upper through hole (194d) may have a rectangular shape. The upper alignment portion (194) may have an octagonal shape.

[0107] The upper alignment portion (194) may include an octagonal base portion (194a); four protrusions (194b) spaced apart from each other and protruding in a triangular prism shape from the sides of the base portion; an upper through hole (194d) formed at the center of the base portion (194a); and a protrusion formed around the upper through hole (194d). The four protrusions (194b) provide a groove (194c) in the upper alignment portion (194) to align and accommodate the vapor cell (120).

[0108] The upper alignment portion (194) may further include an upper alignment groove (194e) formed on its upper surface. The upper alignment groove (194e) may be formed at an edge of the upper surface. The upper alignment groove (194e) may be coupled with the upper spacer (192). The upper alignment portion (194) may provide heat from the upper heater (180) to the vapor cell (120).

[0109] The lower alignment portion (196) may be positioned at the bottom of the lower transparent substrate (126). The lower alignment portion (196) may include a lower through hole (196d). Light may travel through the lower through hole (196d). The lower alignment portion (196) may include a lower ledge (196f) formed around the lower through hole (196d). A quarter wavelength plate (130) may be inserted into and aligned with the lower ledge (196f). The lower alignment portion (196) may be octagonal.

[0110] The lower alignment portion (196) may include an octagonal base portion (196a); four protrusions (196b) spaced apart from each other and protruding in a triangular prism shape from the sides of the base portion (196a); a lower through hole (196d) formed at the center of the base portion (196a); and a protrusion (196f) formed around the lower through hole (196d). The four protrusions (196b) provide a groove (196c) in the lower alignment portion (196) to align and accommodate the vapor cell (120). The groove (196c) formed by the four protrusions (196b) has the same shape as the vapor cell (120).

[0111] The lower alignment portion (196) may further include a lower alignment groove (196e) formed on its lower surface. The lower alignment groove (196e) may be coupled with a lower spacer (198).

[0112] The upper alignment part (194) and the lower alignment part (196) can be fixed by an adhesive layer (191). Accordingly, the upper alignment part (194) and the lower alignment part (196) can easily align the vapor cell (120) and the 1 / 4 wave plate (130). The material of the upper alignment part (194) and the lower alignment part (196) can be a semiconductor, metal, or plastic.

[0113] The upper spacer (192) is positioned above the upper alignment portion (194). The upper spacer (192) may have the same octagonal shape as the upper alignment portion (194). The upper spacer (192) may include an upper spacer alignment portion (192a) that is inserted into an upper alignment groove (194e) formed in the upper alignment portion (194). The upper spacer (192) may be an octagonal plate. The lower surface of the upper spacer (192) may be coupled to the upper printed circuit board (16) to align the upper printed circuit board (16) with the vapor cell. The upper printed circuit board (16) may include a photodetector (150) and an upper heater (180).

[0114] A lower spacer (198) is disposed below the lower alignment portion (196). The lower spacer (198) may include a lower spacer alignment portion (198a) inserted into a lower alignment groove (196e) formed in the lower alignment portion (196). The lower spacer (198) may be an octagonal plate. An upper surface of the lower spacer (198) may be coupled to a lower printed circuit board (14) to align the lower printed circuit board with the vapor cell (120). The lower printed circuit board (14) may include a light source (140), a temperature sensor (160), and a lower heater (170). The light source (140), a quarter wavelength plate (130), the vapor cell (120), and the photodetector (150) may be aligned vertically.

[0115] An upper printed circuit board (16) is placed on top of the upper alignment member (194). The upper printed circuit board (16) may be placed between the upper spacer (192) and the upper alignment member (194). A photodetector (150) is mounted on the upper printed circuit board (16) and is placed to face the vapor cell (120).

[0116] The upper heater (180) is mounted on the upper printed circuit board (16). The upper heater (180) is embedded in the upper printed circuit board (16) to heat the upper spacer (192) and the upper alignment portion (194), and can heat the vapor cell (120). The resistance of the upper heater (120) may be at the level of 40 ohms. The upper heater (120) may provide a pair of current paths that flow in opposite directions to minimize the generation of a magnetic field.

[0117] The temperature of the upper spacer (192), the upper alignment part (194), and the lower alignment part (196) may be 80 to 130 degrees Celsius.

[0118] The lower printed circuit board (14) is placed below the lower alignment portion (196). The lower printed circuit board (14) may be placed between the lower spacer (198) and the lower alignment portion (196).

[0119] The upper printed circuit board (16), the lower printed circuit board (14), and the mounting printed circuit board (12) can be connected in series. The upper printed circuit board (16), the lower printed circuit board (14), and the mounting printed circuit board (12) can be made of a flexible material, and can be, for example, a double-sided or single-sided substrate made of polyimide material. Accordingly, the atomic clock can be manufactured precisely and easily.

[0120] The above vapor cell block (190) is supported and suspended by the upper circuit board (16) and the lower circuit board (14). The vapor cell block (190) is suspended by the legs of the printed circuit board, thereby providing insulation and reducing external vibration.

[0121] The light source (140) is mounted on the lower printed circuit board and may be a VCSEL (Vertical Cavity Surface Emitting Laser). The wiring connected to the light source (140) may be connected to the outside through the lower printed circuit board. The light source (140) is mounted on the lower printed circuit board (14) and positioned to face the vapor cell. The light source (140) may be a laser light source.

[0122] The photodetector (150) may be a silicon photodetector. The wavelength of the detector may be selected based on the wavelength of the light source.

[0123] A quarter-wave plate (130) may be placed between the light source and the lower transparent substrate. The light source may be a laser diode such as a VCSEL (Vertical Cavity Surface Emitting Laser). The light source outputs linearly polarized light, and the quarter-wave plate may convert the linearly polarized light into circularly polarized light and provide it to the cavity.

[0124] A temperature sensor (160) may be placed and fixed on the lower printed circuit board (14). The temperature sensor (160) may be electrically connected to the lower printed circuit board (14) by wire bonding or the like. The temperature sensor (160) is mounted on the lower printed circuit board (14) and detects the temperature of the lower printed circuit board (14).

[0125] The upper heater (180) heats the upper spacer (192), and the upper spacer (192) can heat the vapor cell (120) through thermal contact with the upper alignment part (194).

[0126] The lower heater (170) can control the temperature of the light source. The lower heater (170) is mounted on the lower printed circuit board (14) and can control the temperature of the light source (140). The lower heater (170) can simultaneously heat the vapor cell (120).

[0127] According to a modified embodiment of the present invention, the upper heater (180) may be disposed on the surface of the upper alignment portion (194). The lower heater (170) may be disposed on the surface of the lower alignment portion (196).

[0128] According to a modified embodiment of the present invention, the upper heater (180) may be disposed on the surface of the upper spacer (192). The lower heater (170) may be disposed on the surface of the lower spacer (198).

[0129] The magnetic field shield (110) is arranged to surround the vapor cell block (190) and is spaced apart from the vapor cell block (190) to block an external magnetic field. The magnetic field shield (110) may have a hollow rectangular cylinder shape.

[0130] The magnetic field shielding member (110) may include an upper shielding member (112) having an upper surface; a lower shielding member (116) having a lower surface; and an intermediate shielding member (114) disposed between the upper shielding member (112) and the lower shielding member (114).

[0131] The upper printed circuit board (16) can be fitted between the upper shield (112) and the intermediate shield (114). The lower printed circuit board (14) can be fitted between the lower shield (116) and the intermediate shield (114). The magnetic field shield (110) is separated into a plurality of parts and can be easily aligned by fitting. The material of the magnetic field shield (110) can be a mu metal or a ferromagnetic substance.

[0132] The above intermediate shielding portion (114) may include at least one protruding intermediate protrusion (114a). The intermediate protrusion (114a) may be inserted into and fixed to a through hole (16a) formed in the upper printed circuit board. The upper shielding portion (112) has a groove that engages with the intermediate protrusion (114a), and the groove of the upper shielding portion (112) may be fit-fitted with the intermediate protrusion (114a) formed on the upper surface of the intermediate shielding portion (114).

[0133] The lower shielding portion (116) may include at least one protruding lower protrusion (116a). The lower protrusion (116a) may be inserted into and fixed in a through hole (14a) formed in the lower printed circuit board (14). The intermediate shielding portion (114) has a groove on its lower surface that engages with the lower protrusion (116a), and the groove of the intermediate shielding portion (114) may be fit-fitted with the lower protrusion (116a) formed on the upper surface of the lower shielding portion (116).

[0134] The magnetic field generating coil (22c, 24c) may include a coil pattern (22c) formed on an upper coil printed circuit board (22) and a coil pattern (24c) formed on a lower coil printed circuit board (24). A current flowing in the coil pattern (22c, 24c) may form a magnetic field in the direction of the central axis. The magnetic field generating coil (22c, 24c) may be arranged inside the magnetic shield (110).

[0135] The upper coil printed circuit board (22) may include a first upper coil printed circuit board (22a) having a coil pattern (22c) and a second upper coil printed circuit board (22b) having a coil pattern (22c). The first upper coil printed circuit board (22a) and the second upper coil printed circuit board (22b) may be folded and bonded to each other to provide one upper coil. The upper coil printed circuit board (22) may be fitted between the upper shield and the lower shield. For the fitting, the upper coil printed circuit board (22) may have a through hole (22d). The upper coil printed circuit board (22) may be fitted between the upper shield and the middle shield and may generate a magnetic field.

[0136] The lower coil printed circuit board (24) may include a first lower coil printed circuit board (24a) having a coil pattern (24c) and a second lower coil printed circuit board (24b) having a coil pattern (24c). The first lower coil printed circuit board (24a) and the second lower coil printed circuit board (24b) may be folded and bonded to each other to provide one lower coil. The lower coil printed circuit board (24) may be fitted between the upper shield and the lower shield. For the fitting, the lower coil printed circuit board (24) may have a through hole (24d). The lower coil printed circuit board (24) may be fitted between the lower shield and the middle shield and may generate a magnetic field.

[0137] A printed circuit board (12) may be placed on the lower surface of the shielding portion (110). The printed circuit board (12) may be provided with solder balls or connection pads (12b) and may be electrically connected to an external circuit. The printed circuit board (12) may be provided with a through hole (12a).

[0138] The above-mentioned mounting printed circuit board fixing portion (32) may include a flat portion and a protruding portion (32a). The above-mentioned mounting printed circuit board fixing portion (32) is arranged on the lower surface of the above-mentioned mounting printed circuit board (12) and may be fitted into the through-hole (116b) of the lower shielding portion (116) through the through-hole (12a) of the above-mentioned mounting printed circuit board.

[0139] A magnetic shield (110) of a chip-scale atomic clock includes an upper shield (112) having an upper surface; a lower shield (116) having a lower surface; and an intermediate shield (114) disposed between the upper shield and the lower shield. The lower shield (116) includes at least one lower protrusion on its upper surface. The intermediate shield (114) includes at least one intermediate protrusion on its upper surface. The lower protrusion (116a) is coupled to a lower printed circuit board, and the intermediate protrusion (116a) is coupled to an upper printed circuit board.

[0140] The lower shielding portion (116) includes at least one through hole (116b) formed on the lower surface of the lower shielding portion (116).

[0141] The mounting printed circuit board fixing part (32) is coupled to the lower surface of the mounting printed circuit board (12) and is fitted into the lower shielding part (116).

[0142] According to a modified embodiment of the present invention, the upper shielding portion may be divided into two or more parts. The lower shielding portion may be divided into two or more parts. An upper coil may be placed between the divided upper shielding portions, and a lower coil may be placed between the divided lower shielding portions. Accordingly, the position of the coil for generating a magnetic field may be changed.

[0143] A flexible printed circuit board according to one embodiment of the present invention is used in a chip-scale atomic clock. The printed circuit board (10) includes an upper printed circuit board (16); a lower printed circuit board (14) connected to the upper printed circuit board (16); and a mounting printed circuit board (12) connected to the lower printed circuit board (14).

[0144] The upper printed circuit board (16) includes a light detector (150). The lower printed circuit board (14) includes a light source (140). The mounting printed circuit board (12) includes a solder ball (12b).

[0145] The printed circuit board (10) includes a first upper coil printed circuit board (24a) connected to the mounting printed circuit board (12); a second upper coil printed circuit board (24b) connected to the first upper coil printed circuit board (24a); a first lower coil printed circuit board (22a) connected to the second upper coil printed circuit board (24b); and a second lower coil printed circuit board (22b) connected to the first lower coil printed circuit board (22a).

[0146] The upper printed circuit board (16) includes a central region (17a), a peripheral region (17b), and a bridge region (17c) connecting the central region and the peripheral region. The bridge region (17c) of the upper printed circuit board may include a straight region and a curved region. The straight region may extend in a diagonal direction, and the curved region may extend in a lateral direction.

[0147] The first alignment through hole (16b) can be formed at the vertex of the central region (17a) of the upper printed circuit board (16). The first alignment through hole (16b) can be combined with the upper spacer alignment portion (192a) of the upper spacer (192).

[0148] The second alignment through hole (16a) may be positioned at the vertex of the peripheral region (17b) of the upper printed circuit board. The second alignment through hole (16a) may be coupled to the intermediate protrusion (114a) formed on the upper surface of the intermediate shielding portion.

[0149] The above lower printed circuit board (14) may include a central region (15a), a peripheral region (15b), and a bridge region (15c) connecting the central region and the peripheral region. The straight region may extend in a diagonal direction, and the curved region may extend in a lateral direction.

[0150] The first alignment through hole (14b) can be formed at the vertex of the central region (15a) of the lower printed circuit board (14). The first alignment through hole (14b) can be combined with the lower spacer alignment portion (198a) of the lower spacer (198).

[0151] The second alignment through hole (14a) may be positioned at the vertex of the peripheral region (15b) of the lower printed circuit board. The second alignment through hole (14a) may be coupled to the lower protrusion (116a) formed on the upper surface of the lower shielding portion.

[0152] Figures 16 to 18 are plan views showing printed circuit boards according to their mounting status.

[0153] Figures 19 to 24 are drawings explaining a manufacturing process of an atomic clock according to one embodiment of the present invention.

[0154] Referring to FIGS. 16 to 24, a method for manufacturing a chip-scale atomic clock is as follows:

[0155] A step of providing a flexible printed circuit board (10) including an upper printed circuit board (16), a lower printed circuit board (14) connected to the upper printed circuit board (16), and a mounting printed circuit board (12) connected to the lower printed circuit board (14);

[0156] A step of mounting a light detector (150) on the upper printed circuit board (16), mounting a light source (140) and a temperature sensor (160) on the lower printed circuit board (14), and mounting a solder ball (12b) on the mounting printed circuit board (12); and

[0157] A vapor cell (120) including a semiconductor substrate (122) having a cavity (121) for storing alkaline metal vapor, an upper transparent substrate (124) disposed on an upper surface of the semiconductor substrate (122), and a lower transparent substrate (126) disposed on a lower surface of the semiconductor substrate (122), comprises the steps of: arranging an upper alignment part (194) on the upper transparent substrate (124) and arranging a lower alignment part (196) under the lower transparent substrate (126);

[0158] Referring to FIG. 16, a flexible printed circuit board (10) is prepared, which includes an upper printed circuit board (16), a lower printed circuit board (14) connected to the upper printed circuit board (16), and a mounting printed circuit board (12) connected to the lower printed circuit board (14).

[0159] The flexible printed circuit board (10) may further include a first upper coil printed circuit board (24a) connected to the mounting printed circuit board (12); a second upper coil printed circuit board (24b) connected to the first upper coil printed circuit board (24a); a first lower coil printed circuit board (22a) connected to the second upper coil printed circuit board (24b); and a second lower coil printed circuit board (22b) connected to the first lower coil printed circuit board (22a).

[0160] The upper coil printed circuit board (22) includes the first upper coil printed circuit board (22a) and the second upper coil printed circuit board (22b).

[0161] The lower coil printed circuit board (24) includes the first lower coil printed circuit board (24a) and the second lower coil printed circuit board (24b).

[0162] Referring to Fig. 17, a light detector (150) is mounted on the upper printed circuit board (16), a light source (140) is mounted on the lower printed circuit board (14), and a solder ball (12b) is mounted on the mounting printed circuit board (12). The lower printed circuit board (14) may further have a temperature sensor.

[0163] Again, referring to FIG. 8, a vapor cell (120) including a semiconductor substrate (122) having a cavity (121) for storing alkaline metal vapor, an upper transparent substrate (124) disposed on an upper surface of the semiconductor substrate, and a lower transparent substrate (126) disposed on a lower surface of the semiconductor substrate is provided, wherein an upper alignment part (194) is disposed on the upper transparent substrate (124), and a lower alignment part (196) is disposed on a lower portion of the lower transparent substrate (126).

[0164] Referring to FIGS. 18 and 19, the printed circuit board (12) is placed on the lower surface of the lower shielding portion (116), and the printed circuit board fixing portion (32) is used to fix the printed circuit board (12) to the lower shielding portion (116).

[0165] Referring to FIG. 20, the lower printed circuit board (14) is coupled to the lower spacer (198), and the lower spacer (198) is coupled to the lower alignment portion (196).

[0166] Referring to Fig. 21, the lower printed circuit board (14) is coupled to the lower shielding portion (116). The lower coil printed circuit board (24) can be coupled to the lower alignment portion (196).

[0167] Referring to Fig. 22, the middle shield (114) is attached to the lower shield (116).

[0168] Referring to Fig. 23, the upper coil printed circuit board (22) can be coupled to the lower alignment portion (196). The upper printed circuit board (16) is coupled to the upper spacer (192), and the upper spacer (192) is coupled to the upper alignment portion (194).

[0169] Next, the upper printed circuit board (16) is bonded to the intermediate shield (114).

[0170] Referring to Fig. 24, the upper shield (112) is attached to the intermediate shield (114).

[0171] Figure 25 is a conceptual diagram showing an atomic clock according to another embodiment of the present invention.

[0172] Referring to FIG. 25, the atomic clock may include a vapor cell block (290). The vapor cell block (290) includes a vapor cell (120), an upper alignment portion (194), and a lower alignment portion (196). The upper alignment portion (194) may be aligned and coupled to an upper printed circuit board (16) via a protrusion. In addition, the lower alignment portion (196) may be aligned and coupled to a lower printed circuit board (14) via a protrusion.

[0173] Figure 26 is a conceptual diagram showing an atomic clock according to another embodiment of the present invention.

[0174] Referring to FIG. 26, the atomic clock may include a magnetic shield (310). The magnetic shield (310) may include an upper shield (112, 112'), a middle shield (114), and a lower shield (116, 116').

[0175] The upper shielding portion (112, 112') may be separated into two or more pieces. The lower shielding portion (116, 116') may be separated into two or more pieces. An upper coil may be placed between the separated upper shielding portions, and a lower coil may be placed between the separated lower shielding portions. Accordingly, the position of the coil for generating a magnetic field may be changed.

[0176] Figure 27 is a conceptual diagram showing an atomic clock according to another embodiment of the present invention.

[0177] Referring to FIG. 27, the atomic clock may include a vapor cell block (490). The vapor cell block (490) includes a vapor cell, an upper alignment portion (194), and a lower alignment portion (196). The upper alignment portion (194) may be bonded to an upper printed circuit board (16) by an adhesive. In addition, the lower alignment portion (196) may be bonded to a lower printed circuit board (14) by an adhesive.

[0178] Figure 28 is a conceptual diagram showing an atomic clock according to another embodiment of the present invention.

[0179] Referring to FIG. 28, the atomic clock may include a vapor cell block (590). The vapor cell block (590) includes a vapor cell (120), an upper alignment portion (194), and a lower alignment portion (196). The upper alignment portion (194) may be aligned and coupled to a recessed portion of the upper alignment portion (194) by a protrusion (16') of the upper printed circuit board (16). In addition, the lower alignment portion (196) may be aligned and coupled to a recessed portion of the lower alignment portion (196) by a protrusion (14') of the lower printed circuit board (14).

[0180] FIGS. 29a and 29b are plan views and exploded perspective views showing a vapor cell block according to another embodiment of the present invention.

[0181] Referring to FIGS. 29a and 29b, an upper alignment portion (194) may be disposed on the upper transparent substrate (124). The upper alignment portion (194) may include an upper through hole (194d). Light may propagate through the upper through hole (194d). The upper through hole (194d) may have a rectangular shape. The upper alignment portion (194) may have a square shape.

[0182] The upper alignment portion (194) may include a base portion (194a) having a square shape; four protrusions (194b) spaced apart from each other and protruding in a square pillar shape from the vertices of the base portion; an upper through hole (194d) formed at the center of the base portion (194a); and a protrusion formed around the upper through hole (194d). The four protrusions (194b) provide a groove (194c) in the upper alignment portion (194) to align and accommodate the vapor cell (120).

[0183] The upper alignment portion (194) may further include an upper alignment groove (194e) formed on its upper surface. The upper alignment groove (194e) may be formed at the edge of the upper surface. The upper alignment groove (194e) may be coupled with the upper spacer (192).

[0184] The lower alignment portion (196) may include a base portion (196a) having a square shape; four protrusions (196b) spaced apart from each other and protruding in a square pillar shape from the vertices of the base portion; a lower through hole (196d) formed at the center of the base portion (196a); and a protrusion formed around the lower through hole (196d). The four protrusions (196b) provide a groove (196c) in the lower alignment portion (196) to align and accommodate the vapor cell (120).

[0185] The above lower alignment portion (196) may further include a lower alignment groove formed on its lower surface.

[0186] FIGS. 30A and 30B are plan views and exploded perspective views showing a vapor cell block according to another embodiment of the present invention.

[0187] Referring to FIGS. 30A and 30B, an upper alignment portion (194) may be disposed on the upper transparent substrate (124). The upper alignment portion (194) may include an upper through hole (194d). Light may propagate through the upper through hole (194d). The upper through hole (194d) may have a rectangular shape. The upper alignment portion (194) may have a square shape.

[0188] The upper alignment portion (194) may include a base portion (194a) having a square shape; four protrusions (194b) spaced apart from each other and protruding in a square pillar shape from the vertices of the base portion; an upper through hole (194d) formed at the center of the base portion (194a); and a protrusion formed around the upper through hole (194d). The four protrusions (194b) provide a groove (194c) in the upper alignment portion (194) to align and accommodate the vapor cell (120).

[0189] The upper alignment portion (194) may further include an upper alignment groove (194e) formed on its upper surface. The upper alignment groove (194e) may be formed at an edge of the upper surface. The upper alignment groove (194e) may be coupled with the upper spacer (192). Adjacent protrusions (194b) may be connected to each other by a partition wall to form a groove (194c) inside the upper alignment portion.

[0190] The lower alignment portion (196) may include a base portion (196a) having a square shape; four protrusions (196b) spaced apart from each other and protruding in a square pillar shape from the vertices of the base portion; a lower through hole (196d) formed at the center of the base portion (196a); and a protrusion formed around the lower through hole (196d). The four protrusions (196b) provide a groove (196c) in the lower alignment portion (196) to align and accommodate the vapor cell (120).

[0191] The lower alignment portion (196) may further include a lower alignment groove formed on its lower surface. The lower alignment groove may be formed at an edge of the lower surface. The lower alignment groove may be coupled with a lower spacer (198). Adjacent protrusions (196b) may be connected to each other by a partition wall to form a groove (196c) within the lower alignment portion.

[0192] Although the present invention has been illustrated and described with respect to specific preferred embodiments, the present invention is not limited to these embodiments, and includes various forms of embodiments that can be implemented by a person having ordinary skill in the art to which the invention pertains without departing from the technical spirit of the present invention claimed in the claims.

Claims

1. A vapor cell including a semiconductor substrate having a cavity for storing alkali metal vapor, an upper transparent substrate disposed on an upper surface of the semiconductor substrate, and a lower transparent substrate disposed on a lower surface of the semiconductor substrate; An upper alignment portion disposed on the upper transparent substrate; and Including a lower alignment part arranged on the lower transparent substrate, The upper alignment part and the lower alignment part are in contact with each other, A chip-scale atomic clock, characterized in that the vapor cell is inserted into and aligned in a groove formed in the upper alignment portion and the lower alignment portion.

2. In paragraph 1, The groove of the upper alignment part is cross-shaped, The groove of the lower alignment part is cross-shaped, A chip-scale atomic clock characterized in that the shape of the vapor cell is cross-shaped.

3. In paragraph 1, The upper alignment portion includes an upper through hole, A chip-scale atomic clock, characterized in that the lower alignment portion includes a lower through hole.

4. In paragraph 3, A chip-scale atomic clock, characterized in that the lower alignment portion further includes a lower jaw formed around the lower through hole.

5. In paragraph 4, A chip-scale atomic clock further characterized by comprising a quarter-wave plate inserted into the lower jaw.

6. In paragraph 1, an upper spacer positioned above the upper alignment portion; and A chip-scale atomic clock further characterized by comprising a lower spacer disposed below the lower alignment portion.

7. In paragraph 6, The upper spacer includes an upper spacer alignment portion that is inserted into an upper alignment groove formed in the upper alignment portion, A chip-scale atomic clock, characterized in that the lower spacer further includes a lower spacer alignment portion inserted into a lower alignment groove formed in the lower alignment portion.

8. In paragraph 1, An upper printed circuit board positioned above the upper alignment portion; and A chip-scale atomic clock further comprising a lower printed circuit board disposed below the lower alignment portion.

9. In paragraph 8, an upper spacer positioned above the upper alignment portion; and Further comprising a lower spacer positioned below the lower alignment portion, The upper printed circuit board is positioned between the upper spacer and the upper alignment portion, A chip-scale atomic clock, characterized in that the lower printed circuit board is positioned between the lower spacer and the lower alignment member.

10. In paragraph 8, a photodetector mounted on the upper printed circuit board and facing the vapor cell; and A chip-scale atomic clock further characterized by comprising a light source mounted on the lower printed circuit board and facing the vapor cell.

11. In paragraph 8, an upper heater mounted on the upper printed circuit board; and A chip-scale atomic clock characterized by further comprising at least one lower heater mounted on the lower printed circuit board.

12. In paragraph 8, an upper heater disposed on the upper alignment surface; and A chip-scale atomic clock characterized by further comprising at least one lower heater disposed on the lower alignment surface.

13. In paragraph 8, an upper heater arranged on the upper spacer surface; and A chip-scale atomic clock characterized by further comprising at least one lower heater disposed on the lower spacer surface.

14. In paragraph 8, A chip-scale atomic clock further comprising a temperature sensor mounted on the lower printed circuit board.

15. In paragraph 1, A chip-scale atomic clock, characterized in that the upper alignment part and the lower alignment part are fixed by an adhesive layer.

16. In paragraph 1, The above vapor cell is cross-shaped, The above vapor cell: a main chamber disposed at the center of the vapor cell and having the cavity; and Containing four auxiliary chambers connected to the main chamber, The above main chamber and the above auxiliary chamber are interconnected by a trench, A chip-scale atomic clock, characterized in that at least one of the auxiliary chambers comprises an alkali metal.

17. In paragraph 1, A chip-scale atomic clock further characterized by including a nanostructure performing the function of a quarter-wave plate on the lower transparent substrate surface of the vapor cell.

18. In paragraph 1, The upper alignment portion and the lower alignment portion are octagonal, Each of the upper alignment portion and the lower alignment portion: Octagonal shaped base; Four protrusions spaced apart from each other and protruding in the shape of triangular prisms from the edge of the base portion; a through hole formed in the center of the above base portion; and A chip-scale atomic clock characterized by including a ledge formed around the through hole.

19. In paragraph 1, A chip-scale atomic clock characterized by including nanostructures on the lower transparent substrate surface of the vapor cell 20. In paragraph 1, An upper printed circuit board positioned above the upper alignment portion; A lower printed circuit board arranged below the lower alignment portion; A chip-scale atomic clock, characterized in that it further includes a magnetic shield arranged to surround the vapor cell and to block an external magnetic field while being spaced apart from the vapor cell.

21. In paragraph 20, The above magnetic shielding: Upper shield having an upper surface; A lower shield having a lower surface; and A chip-scale atomic clock, characterized by including an intermediate shield positioned between the upper shield and the lower shield.

22. In paragraph 21, The above upper printed circuit board is sandwiched between the upper shield and the middle shield, A chip-scale atomic clock, characterized in that the lower printed circuit board is sandwiched between the lower shield and the middle shield.

23. In paragraph 21, The lower shielding portion comprises at least one protruding lower protrusion, The above lower protrusion is inserted and fixed into a through hole formed in the lower printed circuit board, The above intermediate shielding portion comprises at least one protruding intermediate protrusion, A chip-scale atomic clock, characterized in that the intermediate protrusion is inserted into and fixed in a through hole formed in the upper printed circuit board.

24. In paragraph 21, An upper coil printed circuit board sandwiched between the upper shield and the middle shield and generating a magnetic field; and A chip-scale atomic clock further comprising a lower coil printed circuit board sandwiched between the lower shield and the middle shield and generating a magnetic field.

25. In paragraph 21, A chip-scale atomic clock further comprising a printed circuit board arranged on a lower surface of the shielding portion.

26. In paragraph 25, A chip-scale atomic clock, characterized in that it further includes a mounting printed circuit board fixing part arranged on a lower surface of the mounting printed circuit board and coupled with the lower shielding part.

27. In paragraph 25, A chip-scale atomic clock, characterized in that the upper printed circuit board, the lower printed circuit board, and the mounting printed circuit board are connected continuously.

28. In paragraph 1, The upper alignment portion further includes an upper alignment groove formed on its upper surface, A chip-scale atomic clock, characterized in that the lower alignment portion further includes a lower alignment groove formed on its upper surface.

29. A step of providing a flexible printed circuit board including an upper printed circuit board, a lower printed circuit board connected to the upper printed circuit board, and a mounting printed circuit board connected to the lower printed circuit board; A step of mounting a photodetector on the upper printed circuit board, mounting a light source on the lower printed circuit board, and mounting a solder ball on the mounting printed circuit board; and A method for manufacturing a chip-scale atomic clock, comprising: a semiconductor substrate having a cavity for accommodating alkaline metal vapor; an upper transparent substrate disposed on an upper surface of the semiconductor substrate; and a lower transparent substrate disposed on a lower surface of the semiconductor substrate; the step of disposing an upper alignment part on the upper transparent substrate and disposing a lower alignment part under the lower transparent substrate in a vapor cell.

30. In paragraph 29, A step of placing the above-mentioned printed circuit board on the lower surface of the lower shielding portion and fixing the above-mentioned printed circuit board to the lower shielding portion using a mounting printed circuit board fixing portion; A step of bonding a lower printed circuit board to a lower spacer and bonding the lower spacer to the lower alignment portion; A step of bonding the lower printed circuit board to the lower shielding portion; A step of bonding an intermediate shield part on the lower shield part; A step of bonding an upper printed circuit board to an upper spacer and bonding the upper spacer to the upper alignment portion; A step of bonding the upper printed circuit board to the intermediate shield; and A method for manufacturing a chip-scale atomic clock, characterized by further comprising at least one step of bonding an upper shield on the intermediate shield.

31. In the magnetic shielding device of a chip-scale atomic clock, Upper shield having an upper surface; A lower shield having a lower surface; and Including an intermediate shield positioned between the upper shield and the lower shield, The lower shielding portion includes at least one lower protrusion on its upper surface, The above intermediate shielding portion includes at least one intermediate protrusion on its upper surface, The above lower protrusion is bonded to the lower printed circuit board, A magnetic shielding device characterized in that the above intermediate protrusion is bonded to an upper printed circuit board.

32. In paragraph 31, At least one lower through hole formed in the lower surface of the lower shield; A printed circuit board arranged on the lower surface of the lower shielding portion; and A magnetic shielding device characterized by further including a mounting printed circuit board fixing part coupled to a lower surface of the mounting printed circuit board and fittedly coupled with the lower shielding part.

33. In paragraph 31, The above upper shield is divided into two or more parts, A magnetic field shielding device characterized in that the lower shielding part is separated into two or more parts.

34. In a flexible printed circuit board used in a chip-scale atomic clock, The above printed circuit board: upper printed circuit board; a lower printed circuit board connected to the upper printed circuit board; and A flexible printed circuit board comprising a mounting printed circuit board connected to the lower printed circuit board.

35. In paragraph 34, The upper printed circuit board includes a photodetector, The above lower printed circuit board includes a light source, A flexible printed circuit board characterized in that the above-mentioned printed circuit board includes a protrusion.

36. In paragraph 34, An upper coil printed circuit board connected to the above-mentioned printed circuit board; and A flexible printed circuit board further comprising a lower coil printed circuit board connected to the upper coil printed circuit board.

37. In paragraph 36, The upper coil printed circuit board includes at least two upper coil printed circuit boards that overlap each other, A flexible printed circuit board, characterized in that the lower coil printed circuit board includes at least two upper coil printed circuit boards that overlap each other.

38. In paragraph 34, A flexible printed circuit board, characterized in that the upper printed circuit board includes a central region, a peripheral region, and a bridge region connecting the central region and the peripheral region.

39. In paragraph 34, A flexible printed circuit board, characterized in that the lower printed circuit board includes a central region, a peripheral region, and a bridge region connecting the central region and the peripheral region.

40. In paragraph 38, A flexible printed circuit board, characterized in that the bridge region of the upper printed circuit board includes a straight region and a curved region.

41. In paragraph 38, The central region of the upper printed circuit board includes a first alignment through hole, A flexible printed circuit board, characterized in that a peripheral area of ​​the upper printed circuit board includes a second alignment through hole.

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