Surface mount thermistor packaging method and surface mount thermistor

Abstract

The invention discloses a packaging method of a surface mount thermistor and a surface mount thermistor. The surface mount thermistor comprises a sub-PTC composite board and an encapsulating shell. The sub-PTC composite board comprises a sub-top insulating layer, a sub-PTC core board and a sub-bottom insulating layer. Two sub-top pads are arranged on the top surface of the sub-top insulating layer, and two sub-bottom pads are arranged on the bottom surface of the sub-bottom insulating layer. The encapsulating shell fully encapsulates other areas of the sub-PTC composite board except the top surface of each sub-top pad and the bottom surface of each sub-bottom pad. The sub-top electrode layer of the sub-PTC core board in the sub-PTC composite board is connected to one of the sub-top pads and the corresponding sub-bottom pad through an electrical through hole, and the sub-bottom electrode layer of the sub-PTC core board in the sub-PTC composite board is connected to another sub-top pad and the corresponding sub-bottom pad through an electrical through hole. The invention can realize the simultaneous completion of the preparation and packaging of the surface mount thermistor, simplify the process and improve the efficiency, and can avoid the surface mount thermistor from being affected by the environment to extend the service life.

Description

Technical Field

[0001] The invention belongs to the field of surface mounting technology, and in particular relates to a packaging method of a surface mounting type thermistor and the surface mounting type thermistor. Background Art

[0002] At present, polymer over-current and over-temperature protection elements made of polymer PTC (positive temperature coefficient) composite conductive materials can be used as over-current and over-temperature protection devices for circuits. The over-current and over-temperature protection element is a fuse that can automatically recover and has been widely used in computers, communication equipment, automotive electronics, household and industrial control electrical equipment and other fields.

[0003] Since PTC composite conductive materials are easily affected by the environment and cause resistance degradation, the industry usually applies coatings on the sides of PTC surface mount devices, such as epoxy resin and conformal coating, to isolate the effects of air, water vapor, temperature and other factors on the performance of PTC surface mount devices. However, most PTC surface mount devices are very small, and this additional coating method makes the production efficiency of PTC surface mount devices low.

[0004] Patent CN105869806A discloses a high-stability PTC thermistor component, which requires punching out a concave frame on an FR-4 epoxy board using a punching machine, and placing the PTC chip in the concave frame to form a closed structure; however, due to the small size of the product, the tolerance of the concave frame and the tolerance of the PTC chip are difficult to control to meet the requirements, resulting in very low assembly efficiency, and this packaging structure is not suitable for multi-layer surface mount PTC thermistors. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the present invention provides a packaging method of a surface mount thermistor and a surface mount thermistor, which can achieve simultaneous completion of the preparation and packaging of the surface mount thermistor, simplify the process and improve the efficiency, and can prevent the surface mount thermistor from being affected by the environment to extend the service life.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A method for packaging a surface mount thermistor comprises the following steps:

[0008] S1. Etching a plurality of top isolation holes on the top electrode layer of the PTC core board and etching a plurality of bottom isolation holes staggered with the top isolation holes on the bottom electrode layer; laminating the top pad layer, the top insulating layer, the PTC core board, the bottom insulating layer and the bottom pad layer to obtain a PTC composite board; drilling a plurality of electrical through holes on the PTC composite board, the number of which is equal to the sum of the top isolation holes and the bottom isolation holes, wherein the axis of each electrical through hole coincides with the corresponding top isolation hole or the bottom isolation hole;

[0009] S2, etching the top pad layer to obtain a plurality of top pads and etching the bottom pad layer to obtain a plurality of bottom pads corresponding to the positions of the corresponding top pads, a plurality of electrical through holes are distributed on one side or both sides of each of the top pads, a top end of each of the electrical through holes is connected to the corresponding top pad through a top connecting bar and a bottom end is connected to the corresponding bottom pad through a bottom connecting bar;

[0010] S3, a plurality of grooves are arranged on the PTC composite board to divide each top pad into a plurality of sub-top pads and each bottom pad into a plurality of sub-bottom pads, and the PTC composite board is divided into a plurality of sub-PTC composite boards, two sub-top pads and two sub-bottom pads are distributed on each of the sub-PTC composite boards, the sub-top electrode layer of the sub-PTC composite board is connected to one of the sub-top pads and the sub-bottom pad through an electrical through hole, and the sub-bottom electrode layer is connected to the other sub-top pad and the sub-bottom pad through an electrical through hole;

[0011] S4, after filling the encapsulation glue into each of the grooves and curing by self-leveling, fully encapsulate the other areas of each sub-PTC composite board except the sub-top pad and the sub-bottom pad; cut the PTC composite board along the cutting line corresponding to the position of each groove to obtain a plurality of surface mount thermistors.

[0012] Furthermore, in step S1: the PTC core board also includes a PTC conductive polymer layer with a positive temperature coefficient, the top electrode layer is located at the top surface of the PTC conductive polymer layer and the bottom electrode layer is located at the bottom surface of the PTC conductive polymer layer; the PTC composite board includes multiple layers of the same PTC core board, an intermediate insulating layer is arranged between the upper and lower adjacent PTC core boards, and each top isolation hole on the upper PTC core board corresponds to the position of the corresponding top isolation hole on the lower adjacent PTC core board; the sum of the number of top isolation holes of the uppermost PTC core board and the number of bottom isolation holes of the lowermost PTC core board in the PTC composite board is equal to the number of electrical through holes.

[0013] Furthermore, in step S1: in the PTC core board, the multiple top isolation holes and the multiple bottom isolation holes are distributed along a rectangular array, and each column of the bottom isolation holes is between two corresponding adjacent columns of top isolation holes, so that the multiple electrical through holes in the PTC composite board are distributed along a rectangular array.

[0014] Further, in step S1: the size of each of the electrical through holes is smaller than the size of the corresponding top isolation hole or bottom isolation hole.

[0015] Furthermore, step S2 is specifically as follows: etching the top pad layer to obtain a plurality of top pads and a plurality of top connecting strips equal to the number of electrical through holes, each of the top pads being arranged horizontally from front to back, a row of electrical through holes being distributed on the inner side of the top pad at the outer edge of the PTC composite board, and a row of electrical through holes being distributed on both sides of the remaining top pads, each of the top connecting strips being located at the top end of one of the electrical through holes; etching the bottom pad layer to obtain a plurality of bottom pads corresponding to the corresponding top pad positions and a plurality of bottom connecting strips equal to the number of electrical through holes, each of the bottom connecting strips being located at the bottom end of one of the electrical through holes; the top end of each electrical through hole is connected to the corresponding top pad through a top connecting strip, and the bottom end is connected to the corresponding bottom pad through a bottom connecting strip.

[0016] Furthermore, the following steps are also included between steps S2 and S3: tinning each of the top solder pads to obtain a tinned top solder pad, the top heights of each of the tinned top solder pads are equal, the top heights of each of the top connecting strips are equal, and the top heights of the tinned top solder pads are higher than the top heights of the top connecting strips; tinning each of the bottom solder pads to obtain a tinned bottom solder pad, the size of each of the tinned bottom solder pads is the same as that of the corresponding tinned top solder pads, and the size of each of the bottom connecting strips is the same as that of the corresponding top connecting strips; the PTC composite panel is adsorbed on a plastic base film, and the plastic base film is adsorbed on a horizontal steel plate.

[0017] Furthermore, in step S3: the plurality of grooves are horizontally distributed in a crisscross pattern, and except for the top solder pad at the outer edge of the PTC composite board, the number of the remaining top solder pads is equal to the number of the longitudinally arranged grooves, and the remaining top solder pads respectively correspond to the positions of the corresponding longitudinally arranged grooves.

[0018] Further,

[0019] In step S1: the top electrode layer, the bottom electrode layer, the top pad layer and the bottom pad layer are all copper foils, the top insulating layer, the middle insulating layer and the bottom insulating layer are all semi-cured resin insulating materials, and the pressing is thermal pressing;

[0020] In step S4: the encapsulating glue is a liquid filling glue, which is cured into a solid insulating material at high temperature.

[0021] A surface mount thermistor is prepared and packaged using the above-mentioned surface mount thermistor packaging method, comprising a sub-PTC composite board and an encapsulation shell, the sub-PTC composite board comprising a sub-top insulating layer, a sub-PTC core board and a sub-bottom insulating layer arranged in sequence from top to bottom, two sub-top pads are provided on the top surface of the sub-top insulating layer, and two sub-bottom pads corresponding to the positions of the corresponding sub-top pads are provided on the bottom surface of the sub-bottom insulating layer, the encapsulation shell fully encapsulates other areas of the sub-PTC composite board except the top surfaces of each sub-top pad and the bottom surfaces of each sub-bottom pad, the sub-top electrode layer of the sub-PTC core board in the sub-PTC composite board is connected to one of the sub-top pads and the corresponding sub-bottom pad through an electrical through hole, and the sub-bottom electrode layer of the sub-PTC core board in the sub-PTC composite board is connected to another sub-top pad and the corresponding sub-bottom pad through an electrical through hole.

[0022] Furthermore, the sub-PTC core board also includes a sub-PTC conductive polymer layer with a positive temperature coefficient, the sub-top electrode layer is located at the top surface of the sub-PTC conductive polymer layer and the sub-bottom electrode layer is located at the bottom surface of the sub-PTC conductive polymer layer, a top isolation hole is provided on the sub-top electrode layer and a bottom isolation hole is provided on the sub-bottom electrode layer that is staggered with the top isolation hole; the sub-PTC composite board includes multiple layers of the same sub-PTC core board, a sub-middle insulating layer is arranged between the upper and lower adjacent sub-PTC core boards, the top isolation hole on the upper PTC core board corresponds to the position of the top isolation hole on the lower adjacent PTC core board; the sub-PTC composite board includes two electrical through holes, one of which coincides with the axis of each top isolation hole, and the other coincides with the axis of each bottom isolation hole; the sub-top solder pad is a sub-tin-plated top solder pad and the sub-bottom solder pad is a sub-tin-plated bottom solder pad.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The present invention provides a packaging method for a surface mounted thermistor, comprising the following steps: S1, etching a plurality of top isolation holes on a top electrode layer of a PTC core board and etching a plurality of bottom isolation holes staggered with the top isolation holes on a bottom electrode layer; pressing a top pad layer, a top insulating layer, a PTC core board, a bottom insulating layer and a bottom pad layer together to obtain a PTC composite board; drilling a plurality of electrical through holes on the PTC composite board, the number of which is equal to the sum of the top isolation holes and the bottom isolation holes, wherein the axis of each electrical through hole coincides with the axis of the corresponding top isolation hole or the bottom isolation hole; S2, etching a top pad layer to obtain a plurality of top pads and etching a bottom pad layer to obtain a plurality of bottom pads corresponding to the position of the corresponding top pads, wherein a plurality of electrical through holes are distributed on one side or both sides of each top pad, wherein the top end of each electrical through hole is connected to the corresponding top pad through a top connecting strip and the bottom end is connected to the corresponding top pad through a top connecting strip. The bottom connecting strip is connected to the corresponding bottom pad; S3, a plurality of grooves are set on the PTC composite board to divide each top pad into a plurality of sub-top pads and each bottom pad into a plurality of sub-bottom pads and the PTC composite board into a plurality of sub-PTC composite boards, and two sub-top pads and two sub-bottom pads are distributed on each sub-PTC composite board, and the sub-top electrode layer of the sub-PTC composite board is connected to one of the sub-top pads and the sub-bottom pad through an electrical through hole, and the sub-bottom electrode layer is connected to the other sub-top pad and the sub-bottom pad through an electrical through hole; S4, the encapsulation glue is filled in each groove and after self-leveling curing, the other areas of each sub-PTC composite board except the sub-top pad and the sub-bottom pad are fully encapsulated; the PTC composite board is cut along the cutting lines corresponding to the positions of each groove to obtain a plurality of surface mount thermistors. In this way, the method of the present invention can realize the simultaneous completion of the preparation and packaging of multiple surface mount thermistors at one time, thereby simplifying the process and improving the efficiency. Moreover, after the encapsulation glue is self-leveled and cured, the other areas of each sub-PTC composite board except the sub-top pad and the sub-bottom pad can be fully encapsulated, and each cutting line corresponds to the position of the corresponding groove. In this way, the other areas of each surface mount thermistor obtained after cutting except the sub-top pad and the sub-bottom pad are fully encapsulated by the cured encapsulation glue, so that the prepared surface mount thermistor can be prevented from being affected by the environment, thereby extending the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the PTC core board in the present invention;

[0026] Figure 2 for Figure 1 A schematic diagram of the front and back structures of the PTC core board after etching the top isolation holes and the bottom isolation holes;

[0027] Figure 3 for Figure 2 A schematic diagram of the enlarged structure at A in the middle;

[0028] Figure 4A schematic diagram of the structure of a PTC composite board obtained by laminating a top pad layer, a top insulating layer, an upper PTC core board, an intermediate insulating layer, a lower PTC core board, a bottom insulating layer and a bottom pad layer;

[0029] Figure 5 for Figure 4 Exploded view of the PTC composite panel;

[0030] Figure 6 For Figure 4 Schematic diagram of the structure after drilling electrical through holes on the PTC composite board;

[0031] Figure 7 For Figure 6 A schematic diagram of the structure after etching the top pad, the top connecting bar, the bottom pad and the bottom connecting bar on the PTC composite board;

[0032] Figure 8 for Figure 7 Schematic diagram of the structure of the top and bottom pads on the PTC composite board after tinning;

[0033] Fig. 9 For Figure 8 Schematic diagram of the structure after the grooves are milled on the PTC composite plate;

[0034] Fig.10 For Fig. 9 Schematic diagram of the structure of the PTC composite board after the groove is filled with encapsulation glue;

[0035] Fig.11 for Fig.10 A schematic diagram of the structure in which the encapsulation glue in the sub-PTC composite board is self-leveled and cured to fully encapsulate other areas except the sub-tinned top pad and the sub-tinned bottom pad in each sub-PTC composite board;

[0036] Fig.12 For the general Fig.11 A schematic diagram of the front structure of one of the surface mount thermistors obtained after cutting the PTC composite board;

[0037] Fig.13 for Fig.12 Schematic diagram of the reverse structure;

[0038] Fig.14 for Fig.12 Schematic diagram of the cross-sectional structure in the B direction;

[0039] Fig.15 for Fig.13 Schematic diagram of the C-section structure.

[0040] Explanation of reference numerals in the figure: 1. PTC core board, 101. top electrode layer, 102. PTC conductive polymer layer, 103. bottom electrode layer, 104. top isolation hole, 105. bottom isolation hole, 2. top pad layer, 3. top insulating layer, 4. bottom insulating layer, 5. bottom pad layer, 6. middle insulating layer, 7. PTC composite board, 701. electrical through hole, 702. top pad, 703. top connecting strip, 704. bottom pad, 705. tinned top pad, 706. tinned bottom pad, 80 1. Groove, 802. Encapsulation glue, 9. Surface mount thermistor, 901. Sub-PTC composite board, 90101. Sub-top insulation layer, 901021. Sub-PTC conductive polymer layer, 901022. Sub-top electrode layer, 901023. Sub-bottom electrode layer, 90103. Sub-bottom insulation layer, 90104. Sub-tinned top pad, 90105. Sub-tinned bottom pad, 90106. Sub-middle insulation layer, 902. Encapsulation shell, 10. Plastic base film, 11. Cutting line. DETAILED DESCRIPTION

[0041] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0042] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or a connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0045] A method for packaging a surface mount thermistor comprises the following steps:

[0046] S1, etching a plurality of top isolation holes 104 on the top electrode layer 101 of the PTC core board 1 and etching a plurality of bottom isolation holes 105 staggered with the top isolation holes 104 on the bottom electrode layer 103, Figure 1-Figure 3 The top pad layer 2, the top insulating layer 3, the PTC core plate 1, the bottom insulating layer 4 and the bottom pad layer 5 are pressed together to obtain a PTC composite plate 7, see Figure 4 and Figure 5 Drill a plurality of electrical through holes 701 on the PTC composite plate 7, the number of which is equal to the sum of the top isolation holes 104 and the bottom isolation holes 105, and each electrical through hole 701 coincides with the axis of the corresponding top isolation hole 104 or bottom isolation hole 105, see Figure 6 ;

[0047] The manufacturing method of the PTC core board 1 is as follows: melt-blending the PTC conductive polymer in a twin-screw extruder, extruding the extruded fusion into a sheet through two high-temperature steel rollers, and obtaining a PTC conductive polymer layer 102; while being extruded by the steel rollers, attaching a top electrode layer 101 to the top surface of the PTC conductive polymer layer 102 and attaching a bottom electrode layer 103 to the bottom surface; and cutting the prepared PTC core board 1 into a required size;

[0048] When drilling the electrical through hole 701, the positions of the top isolation holes 104 and the bottom isolation holes 105 are found according to the target positioning method and the holes are drilled, and metal copper is electroplated in the holes to form the electrical through hole 701;

[0049] S2, etching the top pad layer 2 to obtain a plurality of top pads 702 and etching the bottom pad layer 5 to obtain a plurality of bottom pads 704 corresponding to the positions of the corresponding top pads 702, with a plurality of electrical through holes 701 distributed on one side or both sides of each top pad 702, Figure 7 , the top end of each electrical through hole 701 is connected to the corresponding top pad 702 through a top connecting bar 703 and the bottom end is connected to the corresponding bottom pad 704 through a bottom connecting bar;

[0050] S3, using a milling cutter process to mill a plurality of grooves 801 on the PTC composite board 7, so as to divide each top pad 702 into a plurality of sub-top pads 702, and each bottom pad 704 into a plurality of sub-bottom pads 704, and the PTC composite board 7 is divided into a plurality of sub-PTC composite boards 901, each sub-PTC composite board 901 is provided with two sub-top pads 702 and two sub-bottom pads 704, see Fig. 9 , the sub-top electrode layer 901022 of the sub-PTC composite plate 901 is connected to one of the sub-top pads 702 and the sub-bottom pad 704 through the electrical through hole 701, and the sub-bottom electrode layer 901023 is connected to the other sub-top pad 702 and the sub-bottom pad 704 through the electrical through hole 701;

[0051] S4, using a needle tube glue injection process to fill a certain amount of encapsulation glue 802 into each groove 801 and after self-leveling and curing, fully encapsulate the other areas of each sub-PTC composite board 901 except the sub-top pad 702 and the sub-bottom pad 704, see Fig.10 and Fig.11 ;like Fig.11 As shown, the PTC composite board 7 is cut along the cutting lines 11 corresponding to the positions of the grooves 801 to obtain a plurality of surface mount thermistors 9, one of which is shown in FIG. Fig.12 and Fig.13 .

[0052] In this way, the method of the present invention can realize the simultaneous preparation and packaging of multiple surface mount thermistors 9 at one time, thereby simplifying the process and improving efficiency. Moreover, after the encapsulation glue 802 is self-leveled and cured, it can fully encapsulate the other areas of each sub-PTC composite board 901 except the sub-top pad 702 and the sub-bottom pad 704, and each cutting line 11 corresponds to the position of the corresponding groove 801. In this way, the other areas of each surface mount thermistor 9 obtained after cutting except the sub-top pad 702 and the sub-bottom pad 704 are fully encapsulated by the cured encapsulation glue 802, so that the prepared surface mount thermistor 9 can be prevented from being affected by the environment, thereby extending the service life.

[0053] In one embodiment,

[0054] In step S1: Figure 1 As shown, the PTC core plate 1 further includes a PTC conductive polymer layer 102 with a positive temperature coefficient, a top electrode layer 101 is located at the top surface of the PTC conductive polymer layer 102, and a bottom electrode layer 103 is located at the bottom surface of the PTC conductive polymer layer 102; Figure 4 and Figure 5 As shown, the PTC composite board 7 includes multiple layers of identical PTC core boards 1, an intermediate insulating layer 6 is arranged between the upper and lower adjacent PTC core boards 1, and each top isolation hole 104 on the upper PTC core board 1 corresponds to the position of the corresponding top isolation hole 104 on the lower adjacent PTC core board 1; the sum of the number of top isolation holes 104 of the uppermost PTC core board 1 and the number of bottom isolation holes 105 of the lowermost PTC core board 1 in the PTC composite board 7 is equal to the number of electrical through holes 701.

[0055] In this way, each sub-top electrode layer 901022 of the obtained surface mount thermistor 9 neutron PTC composite board 901 is connected to one of the sub-top pads 702 and the corresponding sub-bottom pad 704 through the corresponding electrical through-hole 701, and each sub-bottom electrode layer 901023 of the surface mount thermistor 9 neutron PTC composite board 901 is connected to another sub-top pad 702 and the corresponding sub-bottom pad 704 through the corresponding electrical through-hole 701, so that each sub-PTC core board of the obtained surface mount thermistor 9 neutron PTC composite board 901 is arranged in parallel.

[0056] Among them, in step S1: in the PTC core board 1, multiple top isolation holes 104 and multiple bottom isolation holes 105 are distributed along a rectangular array, and each column of bottom isolation holes 105 is between two corresponding adjacent columns of top isolation holes 104, so that multiple electrical through holes 701 in the PTC composite board 7 are distributed along a rectangular array.

[0057] Preferably, step S2 is specifically as follows: Figure 7 As shown, the top pad layer 2 is etched to obtain a plurality of top pads 702 and a plurality of top connecting bars 703 equal to the number of electrical through holes 701, each of the top pads 702 is arranged horizontally from front to back, a row of electrical through holes 701 is distributed on the inner side of the top pad 702 at the outer edge of the PTC composite board 7, and a row of electrical through holes 701 are distributed on both sides of the remaining top pads 702, each of the top connecting bars 703 is located at the top of one of the electrical through holes 701; the bottom pad layer 5 is etched to obtain a plurality of bottom pads 704 corresponding to the positions of the corresponding top pads 702 and a plurality of bottom connecting bars equal to the number of electrical through holes 701, each of the bottom connecting bars is located at the bottom end of one of the electrical through holes 701; the top end of each electrical through hole 701 is connected to the corresponding top pad 702 through the top connecting bar 703, and the bottom end is connected to the corresponding bottom pad 704 through the bottom connecting bar.

[0058] Preferably, in step S3: a plurality of grooves 801 are horizontally distributed in a criss-cross pattern, and except for the top solder pad 702 at the outer edge of the PTC composite board 7, the number of the remaining top solder pads 702 is equal to the number of the longitudinally arranged grooves 801, and the remaining top solder pads 702 correspond to the positions of the corresponding longitudinally arranged grooves 801, respectively.

[0059] In this way, except for the top pad 702 at the outer edge of the PTC composite board 7, the other top pads 702 can be divided into two parts by the corresponding grooves 801 arranged longitudinally, thereby relatively reducing the etching workload of the top pad layer 2. In addition, since each bottom pad 704 corresponds to the position of the corresponding top pad 702, the etching workload of the bottom pad layer 5 can also be relatively reduced.

[0060] Wherein, in step S1 : the size of each electrical through hole 701 is smaller than the size of the corresponding top isolation hole 104 or bottom isolation hole 105 .

[0061] In this way, the electrical via 701 coinciding with the axis of the top isolation hole 104 is only electrically connected to the bottom electrode layer 103 of each PTC core board 1, wherein the top isolation hole 104 plays an electrical isolation role to prevent the electrical via 701 from being electrically connected to the top electrode layer 101 of each PTC core board 1, and the electrical via 701 coinciding with the axis of the bottom isolation hole 105 is only electrically connected to the top electrode layer 101 of each PTC core board 1, wherein the bottom isolation hole 105 plays an electrical isolation role to prevent the electrical via 701 from being electrically connected to the bottom electrode layer 103 of each PTC core board 1.

[0062] Among them, in step S1: the top electrode layer 101, the bottom electrode layer 103, the top solder pad layer 2 and the bottom solder pad layer 5 are all copper foils, wherein the copper foils of the top electrode layer 101 and the bottom electrode layer 103 are nickel-plated copper foils; the top insulating layer 3, the middle insulating layer 6 and the bottom insulating layer 4 are all semi-cured resin insulating materials, preferably, the semi-cured resin insulating material is an epoxy resin PP adhesive film, wherein the top insulating layer 3 is used to bond the top solder pad layer 2 and the top electrode layer 101 of the uppermost PTC core board 1, the middle insulating layer 6 is used to bond the bottom electrode layer 103 of the upper PTC core board 1 and the top electrode layer 101 of the lower adjacent PTC core board 1, and the bottom insulating layer 4 is used to bond the bottom electrode layer 103 of the lowermost PTC core board 1 and the bottom solder pad layer 5.

[0063] In one embodiment,

[0064] The following steps are also included between step S2 and step S3: Figure 8 As shown, tin is plated on each top pad 702 to obtain a tinned top pad 705, the top heights of each tinned top pad 705 are equal, and the top heights of each top connecting bar 703 are equal, and the top heights of the tinned top pads 705 are higher than the top heights of the top connecting bars 703. Preferably, the thickness of the tinned top pad 705 is greater than 40 μm, and the thickness of the top pad layer 2 is 12-18 μm; tin is plated on each bottom pad 704 to obtain a tinned bottom pad 706, each tinned bottom pad 706 is the same size as the corresponding tinned top pad 705, each bottom connecting bar is the same size as the corresponding top connecting bar 703, and in addition, the size of each bottom pad 704 is the same as the size of the corresponding top pad 702; the PTC composite board 7 is adsorbed on the plastic base film 10, and the plastic base film 10 is adsorbed on the horizontal steel plate, and a protective film is attached to each tinned top pad 705.

[0065] In this way, by plating tin on each top pad 702 and plating tin on each bottom pad 704, the sub-tinned top pad 90104 or the sub-tinned bottom pad 90105 in the manufactured surface mount thermistor 9 can be conveniently soldered to the circuit board.

[0066] In step S4, the encapsulating glue 802 is a liquid filling glue, which is cured into a solid insulating material at high temperature, wherein the self-leveling is specifically performed in a vacuum oven, and then the temperature is raised to 150°C and kept warm for 10 minutes until the liquid filling glue is cured. Preferably, the encapsulating glue 802 is epoxy resin or polyurethane; wherein the thickness of the encapsulating glue 802 filled in each groove 801 is greater than 100 μm, and the top height of the encapsulating glue 802 is not higher than the top height of the tin-plated top pad 705 and is higher than the top height of the top connecting strip 703.

[0067] In one embodiment:

[0068] In step S1:

[0069] The etching process conditions of the top isolation hole 104 and the bottom isolation hole 105 are: after 3-5wt% H 2 SO4 pickling and degreasing, 80℃ drying, 100-120℃ photosensitive film pasting, 6-8 / 21class exposure, 50-60% development, etching completed;

[0070] The pressing is specifically carried out under a vacuum hot press machine, wherein the vacuum hot pressing process conditions are: first set the vacuum condition to 0.5-0.8Mpa, then maintain the hot pressing pressure at 220Psi and the hot pressing temperature at 160°C for 10 minutes, then maintain the hot pressing pressure at 280Psi and the hot pressing temperature at 170°C for 120 minutes, and finally maintain the cold pressing pressure at 100Psi and the cold pressing temperature at 30°C for 30 minutes, and the pressing is completed.

[0071] In step S2 , the etching process conditions of the top pad layer 2 and the bottom pad layer 5 are the same, and are completely the same as the etching process conditions of the top isolation hole 104 and the bottom isolation hole 105 in step S1 .

[0072] like Figure 12-Figure 15As shown, a surface mount thermistor is prepared and packaged using the above-mentioned surface mount thermistor packaging method, including a sub-PTC composite board 901 and an encapsulation shell 902, the sub-PTC composite board 901 includes a sub-top insulating layer 90101, a sub-PTC core board and a sub-bottom insulating layer 90103 arranged in sequence from top to bottom, two sub-top pads 702 are provided on the top surface of the sub-top insulating layer 90101, and two sub-bottom pads 704 corresponding to the positions of the corresponding sub-top pads 702 are provided on the bottom surface of the sub-bottom insulating layer 90103. The encapsulating shell 902 completely encapsulates the other areas of the sub-PTC composite board 901 except the top surfaces of each sub-top pad 702 and the bottom surfaces of each sub-bottom pad 704. The sub-top electrode layer 901022 of the sub-PTC core board in the sub-PTC composite board 901 is connected to one of the sub-top pads 702 and the corresponding sub-bottom pad 704 through the electrical through hole 701, and the sub-bottom electrode layer 901023 of the sub-PTC core board in the sub-PTC composite board 901 is connected to the other sub-top pad 702 and the corresponding sub-bottom pad 704 through the electrical through hole 701.

[0073] Among them, Fig.15 As shown, the sub-PTC core plate also includes a sub-PTC conductive polymer layer 901021 with a positive temperature coefficient, a sub-top electrode layer 901022 is located at the top surface of the sub-PTC conductive polymer layer 901021, and a sub-bottom electrode layer 901023 is located at the bottom surface of the sub-PTC conductive polymer layer 901021, a top isolation hole 104 is provided on the sub-top electrode layer 901022, and a bottom isolation hole 105 staggered with the top isolation hole 104 is provided on the sub-bottom electrode layer 901023; the sub-PTC composite plate 901 includes multiple layers of the same sub-PTC core The board has a sub-middle insulating layer 90106 arranged between the upper and lower adjacent sub-PTC core boards, and the top isolation hole 104 on the upper PTC core board 1 corresponds to the top isolation hole 104 on the lower adjacent PTC core board 1; the sub-PTC composite board 901 includes two electrical through holes 701, one of which coincides with the axis of each top isolation hole 104, and the other electrical through hole 701 coincides with the axis of each bottom isolation hole 105; the sub-top pad 702 is a sub-tin-plated top pad 90104 and the sub-bottom pad 704 is a sub-tin-plated bottom pad 90105.

[0074] In summary, the present invention introduces encapsulation glue 802 and encapsulation process in the preparation process of surface mount thermistor 9, which can fully encapsulate the surface mount thermistor 9 while preparing it; for surface mount devices, the present invention is an alternative to the traditional end surface coating method. The traditional production method is to first cut the PTC composite board 7 into independent chip components, and then brush protective glue on the four end surfaces of the chip components one by one, while the method of the present invention is to cut the whole board into chip components after filling the glue, and achieve the purpose of encapsulating all six surfaces of the surface mount thermistor 9. The surface mount thermistor 9 has better waterproof and oxidation resistance, good environmental resistance, and high feasibility of mass production.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A method for packaging a surface mount thermistor, characterized in that: The following steps are involved: S1. Etching a plurality of top isolation holes (104) on the top electrode layer (101) of the PTC core plate (1) and etching a plurality of bottom isolation holes (105) on the bottom electrode layer (103); pressing the top pad layer (2), the top insulating layer (3), the PTC core plate (1), the bottom insulating layer (4) and the bottom pad layer (5) together to obtain a PTC composite plate (7); drilling a plurality of electrical through holes (701) on the PTC composite plate (7) equal in number to the sum of the top isolation holes (104) and the bottom isolation holes (105), wherein the electrical through holes (701) coincide with the axis of the top isolation holes (104) or the bottom isolation holes (105); S2, etching the top pad layer (2) to obtain a plurality of top pads (702) and etching the bottom pad layer (5) to obtain a plurality of bottom pads (704) corresponding to the positions of the corresponding top pads (702); S3, a plurality of grooves (801) are provided on the PTC composite plate (7) to divide each of the top pads (702) into a plurality of sub-top pads (702) and each of the bottom pads (704) into a plurality of sub-bottom pads (704) and to divide the PTC composite plate (7) into a plurality of sub-PTC composite plates (901), two sub-top pads (702) and two sub-bottom pads (704) are distributed on the sub-PTC composite plates (901), a sub-top electrode layer (901022) of the sub-PTC composite plate (901) is connected to one of the sub-top pads (702) and the sub-bottom pad (704) through an electrical through hole (701), and a sub-bottom electrode layer (901023) is connected to another sub-top pad (702) and the sub-bottom pad (704) through an electrical through hole (701); S4, filling the encapsulating glue (802) into each of the grooves (801) and after self-leveling and curing, completely encapsulating the other areas of each sub-PTC composite board (901) except the sub-top pad (702) and the sub-bottom pad (704); cutting the PTC composite board (7) along the cutting line (11) corresponding to the position of each of the grooves (801) to obtain a plurality of surface mount thermistors (9).

2. A method for packaging a surface mount thermistor according to claim 1, characterized in that: In step S1: the PTC core board (1) further comprises a PTC conductive polymer layer (102) with a positive temperature coefficient, the top electrode layer (101) is located at the top surface of the PTC conductive polymer layer (102) and the bottom electrode layer (103) is located at the bottom surface of the PTC conductive polymer layer (102); the PTC composite board (7) comprises multiple identical PTC core boards (1), an intermediate insulating layer (6) is arranged between the upper and lower adjacent PTC core boards (1), and each top isolation hole (104) on the upper PTC core board (1) corresponds to the position of the corresponding top isolation hole (104) on the lower adjacent PTC core board (1); the sum of the number of the top isolation holes (104) of the uppermost PTC core board (1) and the number of the bottom isolation holes (105) of the lowermost PTC core board (1) in the PTC composite board (7) is equal to the number of electrical through holes (701).

3. A method for packaging a surface mount thermistor according to claim 2, characterized in that: In step S1: in the PTC core board (1), the plurality of top isolation holes (104) and the plurality of bottom isolation holes (105) are distributed along a rectangular array, and each column of the bottom isolation holes (105) is located between two corresponding columns of adjacent top isolation holes (104), so that the plurality of electrical through holes (701) in the PTC composite board (7) are distributed along a rectangular array.

4. A method for packaging a surface mount thermistor according to claim 2, characterized in that: In step S1: the size of each of the electrical through holes (701) is smaller than the size of the corresponding top isolation hole (104) or bottom isolation hole (105).

5. The method for packaging a surface mount thermistor according to claim 3, characterized in that: Step S2 specifically comprises: etching the top pad layer (2) to obtain a plurality of top pads (702) and a plurality of top connecting strips (703) equal in number to the number of electrical through holes (701), wherein each of the top pads (702) is horizontally arranged from front to back, a row of electrical through holes (701) is distributed on the inner side of the top pad (702) at the outer edge of the PTC composite board (7), and a row of electrical through holes (701) is distributed on both sides of the remaining top pads (702), and each of the top connecting strips (703) is located at one of the top pads (702). The bottom pad layer (5) is etched to obtain a plurality of bottom pads (704) corresponding to the positions of the corresponding top pads (702) and a plurality of bottom connecting bars equal in number to the number of the electrical through holes (701), each of the bottom connecting bars being located at the bottom end of one of the electrical through holes (701); the top end of each electrical through hole (701) is connected to the corresponding top pad (702) via a top connecting bar (703) and the bottom end is connected to the corresponding bottom pad (704) via a bottom connecting bar.

6. A method for packaging a surface mount thermistor according to claim 1, characterized in that: The steps between step S2 and step S3 also include the following steps: plating tin on each of the top solder pads (702) to obtain a tinned top solder pad (705), wherein the top heights of each of the tinned top solder pads (705) are equal, and the top heights of each of the top connecting strips (703) are equal, and the top heights of the tinned top solder pads (705) are higher than the top heights of the top connecting strips (703); plating tin on each of the bottom solder pads (704) to obtain a tinned bottom solder pad (706), wherein each of the tinned bottom solder pads (706) has the same size as the corresponding tinned top solder pad (705), and each of the bottom connecting strips has the same size as the corresponding top connecting strips (703); and adsorbing the PTC composite board (7) onto a plastic base film (10), and adsorbing the plastic base film (10) onto a horizontal steel plate.

7. A method for packaging a surface mount thermistor according to claim 5, characterized in that: In step S3: the plurality of grooves (801) are horizontally distributed in a crisscross manner, and except for the top solder pad (702) located at the outer edge of the PTC composite board (7), the number of the remaining top solder pads (702) is equal to the number of the longitudinally arranged grooves (801), and the remaining top solder pads (702) respectively correspond to the positions of the corresponding longitudinally arranged grooves (801).

8. The method for packaging a surface mount thermistor according to claim 2, wherein: In step S1: the top electrode layer (101), the bottom electrode layer (103), the top pad layer (2) and the bottom pad layer (5) are all copper foils, the top insulating layer (3), the middle insulating layer (6) and the bottom insulating layer (4) are all semi-cured resin insulating materials, and the pressing is thermal pressing; In step S4: the encapsulation glue (802) is a liquid filling glue, which is cured into a solid insulating material at high temperature.

9. A surface mount thermistor, prepared and packaged using the surface mount thermistor (9) packaging method according to any one of claims 1 to 8, characterized in that: The invention comprises a sub-PTC composite plate (901) and an encapsulating shell (902), wherein the sub-PTC composite plate (901) comprises a sub-top insulating layer (90101), a sub-PTC core plate and a sub-bottom insulating layer (90103) arranged in sequence from top to bottom, two sub-top welding pads (702) are arranged on the top surface of the sub-top insulating layer (90101), and two sub-bottom welding pads (704) corresponding to the positions of the corresponding sub-top welding pads (702) are arranged on the bottom surface of the sub-bottom insulating layer (90103), and the encapsulating shell (902) encapsulates the sub-PTC composite plate (901) and the sub-PTC core plate (903). The other areas except the top surface of each sub-top pad (702) and the bottom surface of each sub-bottom pad (704) are fully encapsulated, and the sub-top electrode layer (901022) of the sub-PTC core plate in the sub-PTC composite plate (901) is connected to one of the sub-top pads (702) and the corresponding sub-bottom pad (704) through the electrical through hole (701), and the sub-bottom electrode layer (901023) of the sub-PTC core plate in the sub-PTC composite plate (901) is connected to another sub-top pad (702) and the corresponding sub-bottom pad (704) through the electrical through hole (701).

10. A surface mount thermistor according to claim 9, characterized in that: The sub-PTC core plate also includes a sub-PTC conductive polymer layer (901021) with a positive temperature coefficient, the sub-top electrode layer (901022) is located at the top surface of the sub-PTC conductive polymer layer (901021) and the sub-bottom electrode layer (901023) is located at the bottom surface of the sub-PTC conductive polymer layer (901021), a top isolation hole (104) is provided on the sub-top electrode layer (901022) and a bottom isolation hole (105) is provided on the sub-bottom electrode layer (901023) and is staggered with the top isolation hole (104); the sub-PTC composite plate (901) includes multiple layers of the same sub-PTC core plate, the upper and lower layers are adjacent to each other. A sub-middle insulating layer (90106) is arranged between the sub-PTC core plates, and the top isolation hole (104) on the upper PTC core plate (1) corresponds to the position of the top isolation hole (104) on the lower adjacent PTC core plate (1); the sub-PTC composite plate (901) includes two electrical through holes (701), one of which coincides with the axis of each top isolation hole (104), and the other of which coincides with the axis of each bottom isolation hole (105); the sub-top pad (702) is a sub-tin-plated top pad (90104) and the sub-bottom pad (704) is a sub-tin-plated bottom pad (90105).

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