JP2013030749A - Packaged thermistor and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grant allowable operating characteristics by suppressing the heat conduction of a packaged thermistor.SOLUTION: A temperature dependent thermistor element (2) is placed in an electrically insulating package (1). Heat transfer from the thermistor element (2) generating heat to a substrate through the package (1) is suppressed sufficiently by an upper gap (9), a lower gap (7), a peripheral gap (8) and an air layer held in the upper gap (9).

Description

  The present invention relates to a packaged thermistor that can be soldered onto a substrate by a flow method or a reflow method, and a method for manufacturing the same.

  A positive temperature coefficient thermistor whose resistance value suddenly increases at a predetermined temperature is used in various fields, for example, for overheat protection, overcurrent protection, a temperature detection sensor, or a heater. A positive temperature coefficient thermistor having radial leads includes a disc-shaped thermistor element, a pair of electrodes formed on both end faces of the thermistor element, and electrodes corresponding to each other at an angle of about 120 degrees around the center of the thermistor element. And metal first and second leads electrically connected to the first and second leads. During the mounting, the first and second leads inserted into the through holes of the printed board are soldered to the wiring pattern of the board.

  In recent years, in order to achieve downsizing of the board, omission of through-hole mounting machines, and simplification of the assembly line, it can be mounted on the board by a chip mounter as with other electronic components such as capacitors, resistors or semiconductor elements. There is a need for a packaged thermistor. This packaged thermistor is required to satisfy the same operating characteristics as a conventional packaged thermistor having a radial lead.

Specifically, the first characteristic required for a packaged PTC (positive temperature characteristic) thermistor operates within an allowable time even when used in an external temperature environment that fluctuates in the range of -30 ° C to 80 ° C. It is a point that must be done. For example, as shown in FIG. 20, when a voltage is applied to the PTC thermistor, an inrush current that rapidly increases flows to the PTC thermistor. Then, as the current increases, the PTC thermistor self-heats, the temperature rises, and the resistance value increases. For this reason, after the flowing current reaches the maximum current value I _max , the current rapidly attenuates toward the equilibrium point current value. In this case, by applying a voltage (activation) time T ₀ from the half of the maximum current value I _max by the resistance of the PTC thermistor (I _max × 1/2) time to time T ₁ to be reduced to (T ₁ -T ₀₎ An allowable operating characteristic of the PTC thermistor is determined. For example, Table 1 below shows an example of an allowable operation time when a measurement load resistance is connected in series to a PTC thermistor and a DC voltage is applied to the PTC thermistor in three stages of room temperature, low temperature and high temperature.

  However, when the surface mount type positive temperature coefficient thermistor element shown in FIG. 21, which is currently popular, is directly mounted on the substrate, the amount of heat transferred from the thermistor element to the substrate is large, so that the temperature rise of the element during voltage application becomes slow. However, there is a defect in which the allowable operating characteristics equivalent to those of the non-packaged positive temperature coefficient thermistor having radial leads cannot be obtained. Therefore, in order to give an allowable operating characteristic to the surface mount type thermistor, first, a heat insulating structure capable of suppressing heat conduction between the thermistor element and the case housing the thermistor element and heat conduction between the case and the substrate. It is necessary to form the case with a heat insulating structure that can suppress the above. Second, when mounting a thermistor having a surface mounting structure on a substrate, the case resists the heat and intrusion of molten solder at a contact temperature of 240 ° C. to 270 ° C. and prevents adhesion of the molten solder to the thermistor element. Must. It is necessary to accommodate the thermistor element in the case to avoid the thermal influence and adhesion of the molten solder. There is a risk that the thermistor element may be damaged due to the penetration of molten solder. Therefore, the case that accommodates the thermistor element must have a structure that can sufficiently suppress heat transfer between the thermistor element and the case, and the case and the substrate, and a structure that can sufficiently prevent the molten solder from entering the case. .

  Patent Document 1 below discloses a surface mount type thermistor in which a thermistor body is disposed in an insulating case having an internal cavity, and the internal cavity of the case is closed by an insulating cover. However, in patent document 1, since the terminal of a complicated shape is used, there exists a difficulty that production cost increases. Further, in Patent Document 1, since the thermistor element directly contacts the case or the cover, there is a defect that a sufficient amount of heat is transmitted between the thermistor element and the substrate through the case or the cover. Furthermore, since the elastic contact portion of the lead portion contacts the thermistor element body and the thermistor element body is subjected to mechanical stress that is constantly pressed toward the case or cover, there is a risk that the electrical characteristics of the thermistor element body will fluctuate. is there. Furthermore, this surface-mount type thermistor has a large number of components and requires time and effort to mount terminals having complicated shapes at predetermined positions.

  On the other hand, Patent Document 2 below discloses a surface mount ceramic capacitor that can accommodate an existing through-hole mount electronic component element in a case member. However, in Patent Document 2, since the element main body is in direct contact with the case member, the heat of the element main body is transmitted to the substrate through the case member and the lead terminals, and there is a risk that the operating characteristics of the element main body may fluctuate. Further, it takes skill and considerable time to attach the lead terminal having a complicated shape to the case member. Furthermore, in patent document 2, there exists a possibility that molten solder may penetrate | invade in a case member through the opening part formed in a case member. As described above, the case member of Patent Document 2 that can be used for a ceramic capacitor cannot be used for a package of a temperature sensitive element.

JP-A-8-55703 JP 2009-10116 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a packaged thermistor that can be soldered onto a substrate by a flow method or a reflow method, and a method for manufacturing the same.
Another object of the present invention is to provide a packaged thermistor that can suppress the penetration of molten solder into the package during mounting, and a method for manufacturing the same.

  The packaged thermistor of the present invention includes an electrically insulating package (1) and a temperature-dependent thermistor element (2) disposed in the package (1). The package (1) includes a bottom wall (31), an inner peripheral wall (32) connected to the periphery of the bottom wall (31), and an inner cavity (11) formed by the bottom wall (31) and the inner peripheral wall (32). A top wall (41) covering the internal cavity (11) of the case (3) and a periphery of the top wall (41) and outside the inner peripheral wall (32) of the case (3). And a cover (4) having an outer peripheral wall (42) to be arranged. Thus, the side surface (26) of the thermistor element (2) is shielded from the surrounding environment by the double wall structure of the inner peripheral wall (32) of the case (3) and the outer peripheral wall (42) of the cover (4). . Further, the surface contact between the inner peripheral wall (32) and the outer peripheral wall (42) reliably blocks the penetration of the molten solder into the package (1). Further, the thermistor element (2) forms a lower gap (7) and a circumferential gap (8) with respect to the bottom wall (31) and the inner circumferential wall (32) of the case (3), respectively, and the top of the cover (4). Since it is arranged to form an upper gap (9) with respect to the wall (41), each air layer and case held in the lower gap (7), the circumferential gap (8) and the upper gap (9) ( The thermistor is composed of the bottom wall (31) of 3), the double wall structure of the inner peripheral wall (32) of the case (3) and the outer peripheral wall (42) of the cover (4) and the top wall (41) of the cover (4). The amount of heat conducted between the element (2) and the outside can be sufficiently suppressed by the package (1).

  The manufacturing method of the packaged thermistor of the present invention is formed by the bottom wall (31), the inner peripheral wall (32) connected to the periphery of the bottom wall (31), and the bottom wall (31) and the inner peripheral wall (32). An electrically insulating package comprising a case (3) having an internal cavity (11) and a cover (4) having a top wall (41) and an outer peripheral wall (42) connected to the periphery of the top wall (41) 1), a lower gap (7) is formed between the bottom wall (31) of the case (3) and the temperature-dependent thermistor element (2) and the inner peripheral wall (32) of the case (3) ) And the thermistor element (2) to form a circumferential gap (8), dispose the thermistor element (2) in the internal cavity (11) of the case (3), and cover (4) to the case Attached to (3), the top wall (41) of the cover (4) covers the internal cavity (11) of the case (3), and the cover (4) outside the inner peripheral wall (32) of the case (3). And arranging the outer peripheral wall (42). By this manufacturing method, a thermistor element (2) having an existing radial lead can be accommodated in the package (1), and a packaged thermistor can be easily manufactured.

  In the present invention, the amount of heat conducted between the thermistor element and the substrate or the outside can be sufficiently suppressed by the package, and allowable operating characteristics can be imparted to the package-enclosed thermistor. In addition, since the package can prevent intrusion of molten solder during mounting, an inexpensive and highly reliable packaged thermistor can be obtained.

The perspective view which shows embodiment of the PTC apparatus which actualized the package enclosure type thermistor by this invention Sectional view of the PTC device along the line II-II in FIG. Sectional view of the PTC device along the line III-III in FIG. Plan view of PTC element Exploded perspective view of PTC device Front view of the case constituting the PTC device Top view of the case Side view of the case Rear view of the case Sectional view of the case along the line XX in FIG. Partial sectional view taken along line XI-XI in FIG. Partial sectional view taken along line XII-XII in FIG. The bottom view of the cover which comprises the PTC apparatus of FIG. Sectional view along line XIV-XIV in FIG. Sectional view along line XV-XV in FIG. The top view which shows the state which mounted | wore the case with the cover shown with a broken line Side view of a PTC device placed on a substrate The perspective view of the PTC device which shows another embodiment of this invention Side view of PTC device fixed on substrate by reflow method Graph showing change in current flowing in thermistor element External view and structural cross-sectional view of surface mount type thermistors that are currently popular

  An embodiment of a PTC device embodying a packaged thermistor according to the present invention and a manufacturing method thereof will be described below with reference to FIGS.

  As shown in FIG. 1, a PTC device (10) according to the present embodiment includes a case (3) and an electrically insulating package (1) having a cover (4) attached to the case (3), and a package ( 1) A thermistor element (2) as a temperature-dependent temperature-sensitive element disposed in the PTC device (10) with only three components: the thermistor element (2), case (3) and cover (4) Can be configured.

  As shown in FIGS. 2 and 3, the thermistor element (2) includes an element body (20) and a pair of electrodes (21, 22) of the element body (20), that is, a lower electrode (21) and an upper electrode (22). ) And a pair of metal leads (5, 6) having a lower inscribed portion (5a) electrically connected to the lower electrode (21), that is, the lower lead (5) and the upper electrode (22) A metal upper lead (6) having an upper inscribed portion (6a) to be electrically connected. The lower lead (5) and the upper lead (6) fixed to each electrode (21, 22) of the thermistor element (2) can be handled integrally as the thermistor element (2). The end of the lower inscribed portion (5a) of the lower lead (5) is fixed to the lower electrode (21) of the element body (20) by solder (28), and the upper inscribed portion (6a) of the upper lead (6) ) Is fixed to the upper electrode (22) of the element body (20) by solder (28). For simplification of illustration, illustration of solder (28) is omitted in drawings other than FIGS.

  The element body (20) formed in a substantially disk shape or disk shape has a flat circular lower surface (23) and an upper surface (24). As shown in FIGS. 4 and 5, the lower inscribed portion (5a) of the lower lead (5) and the upper inscribed portion (6a) of the upper lead (6) are formed on the lower surface (23) of the element body (20). Parallel to the upper surface (24) and extends from the lower electrode (21) and the lower electrode (21) of the element body (20) to the outside of the element body (20). When an inrush current flows to the element body (20) through the lower lead (5) and the upper lead (6), the element body (20) suddenly increases its resistance value at a certain temperature due to self-heating, and the element body (20 ) Reaches a maximum value and then decays.

  For example, the element body (20) mainly composed of barium titanate has stable resistance-temperature characteristics, and a small element body (20) can be formed by atomizing the raw material. Since the characteristics and manufacturing method of the PTC element mainly composed of barium titanate are known from, for example, Japanese Patent Application Laid-Open No. 2010-3814 filed by the present applicant, detailed description of the manufacturing method is omitted. In the present invention, a known positive temperature coefficient thermistor such as ceramic PTC, carbon polymer PTC, or metal oxide polymer PTC can be used without limitation.

  As the lower lead (5) and the upper lead (6), external lead wires of general electronic components having a circular cross section or a square cross section such as a copper wire or a tin-plated copper wire can be used. In a commercially available inexpensive disk-type PTC element, the pair of leads are fixed to the element at an angle of 120 degrees with respect to the center of the element. In the present invention, for the miniaturization of the thermistor element (2), As shown in FIG. 4, the lower lead (5) and the upper lead (6) have an angle θ between 80 ° and 100 ° around the center (27) (FIG. 4) of the thermistor element (2), preferably 90 The thermistor element (2) is separated from each other by a certain degree and is horizontally fixed to the thermistor element (2) with the solder (28) and is led out. Can be formed. The lower lead (5) has a lower intermediate part (5b) bent downward at a right angle from the lower inscribed part (5a) and a lower lead bent further at a right angle in the horizontal direction from the lower intermediate part (5b). Part (5c). Similarly, the upper lead (6) is bent at a right angle in the horizontal direction from the upper middle portion (6b) and the upper middle portion (6b) which is bent at a right angle downward from the upper inscribed portion (6a). And an upper deriving unit (6c).

  The package (1) formed by the case (3) and the cover (4) is a known package of electronic components having solder heat resistance such as glass-filled PPS (polyphenylene sulfide resin) or glass-filled LCP (liquid crystal polymer). Material is used. Other known semiconductor or industrial packaging materials having electrical insulation properties such as epoxy resins and silicone resins may be used.

  As shown in FIGS. 6 to 11, the case (3) is connected to the bottom wall (31) formed in a substantially square or rectangular plate shape and at right angles along the periphery of the edge of the bottom wall (31). And formed in the upper part of the inner peripheral wall (32) formed by the inner peripheral wall (32) formed in a substantially square or rectangular cylindrical shape, the inner cavity (11) formed by the bottom wall (31) and the inner peripheral wall (32). And an open portion (37). The inner peripheral wall (32) includes a front wall (16), a rear wall (19) facing the front wall (16), and a pair of side walls disposed between the front wall (16) and the rear wall (19). (17, 18), and a pair of notches (38) are formed at the connection between the front wall (16) and the side walls (17, 18). In the example shown in the figure, a pair of notches (38) are formed at the connection portion between the front wall (16) and each side wall (17, 18), but the present invention is not limited to the connection portion, and an electrical short circuit is prevented. As long as the lower lead (5) and the upper lead (6) can be separated, the pair of notches (38) may be formed anywhere on the front wall (16). Two steps (39) are formed on the front wall (16) and the rear wall (19) at a position higher than the bottom wall (31).

  A claw (50) having an inclined surface (51) and a locking surface (52) formed at the lower end of the inclined surface (51) is provided on each outer surface of the pair of side walls (17, 18). The inclined surface (51) is formed in a tapered shape that extends downward from the side wall (17, 18) toward the lower side of the case (3), and the locking surface (52) is formed with respect to the bottom wall (31). They are formed in parallel. As shown in FIG. 5, the pair of side walls (17, 18) having the claws (50) are formed thicker than the front wall (16) and the rear wall (19). The front wall (16) and the rear wall (19) formed relatively thinly extend from the upper surface (3a) of the case (3) to each step (39) of the front wall (16) and the rear wall (19). A pair of openings (36) is formed, and the case (3) can be reduced in weight and material can be reduced.

  The case (3) has a pair of notches (38) formed downward from the upper surface (3a) of the case (3) at the connection portion between the front wall (16) and each side wall (17, 18), It has a pair of inner dividing grooves (14) formed in a substantially semicircular cross section below them continuously from the notch (38). Since both the lower lead (5) and the upper lead (6) are extended to the outside of the front wall (16) of the case (3) or only the connection portion between the front wall (16) and each side wall (17, 18), The PTC device (10) can be reduced in size. As shown in FIGS. 6, 11 and 12, the inner groove (14a) of the lower notch (38a) in which the inner lower lead (5) of the notch (38) is disposed is the same as the bottom wall (31). The inner groove (14b) of the upper notch (38b) where the inner upper lead (6) of the notch (38) is placed is formed at a position higher than the inner groove (14a). Is done. The lower inscribed portion (5a) of the lower lead (5) is led out from the lower notch (38a) of the inner peripheral wall (32) of the case (3), and the upper inscribed portion (6a of the upper lead (6) ) Is led out from the upper notch (38b) of the inner peripheral wall (32) of the case (3), so the upper middle (6b) of the upper lead (6) is the lower middle of the lower lead (5). It is longer in the vertical direction than the portion (5b). Similarly, the inner groove (14b) in which the upper middle portion (6b) of the upper lead (6) is disposed is perpendicular to the inner groove (14a) in which the lower middle portion (5b) of the lower lead (5) is disposed. Long in the direction.

  As shown in FIG. 7, the internal cavity (11) of the case (3) has a substantially cylindrical internal cavity (11) in accordance with the shape of the element body (20) of the thermistor element (2). Each step portion (39) formed on the front wall (16) and the rear wall (19) has a contact surface (47) (FIGS. 5 and 7) formed parallel to the bottom wall (31). And a vertical surface (48) formed perpendicular to the bottom wall (31) and from the contact surface (47) to the bottom wall (31). The contact surface (47) of the step portion (39) is formed at a position lower than the upper surface (3a) of the case (3) and higher than the bottom wall (31). When the thermistor element (2) is arranged in the package (1), the edge (23b) of the lower surface (23) of the element body (20) contacts the contact surface (47) of the stepped part (39), and the bottom wall A lower gap (7) is formed between (31) and the central portion (23a) of the lower surface (23) of the element body (20), and the air layer in the lower gap (7) has a heat insulating effect. That is, only the edge (23b) of the lower surface (23) of the element body (20) is in contact with the case (3) and the element body (20) is supported on the bottom wall (31), and the element body (20) The central portion (23a) of the lower surface (23) is separated from the bottom wall (31) of the case (3), and the majority of the element body (20) in the internal cavity (11) of the case (3) has a lower gap. It is placed on (7). The central portion (23a) shown in FIG. 4 of the lower surface (23) of the element body (20) is a central region forming the lower electrode (21), and the edge portion (23b) is the lower electrode (21) from the outside. An encircling peripheral region that surrounds.

  In the illustrated embodiment, two steps (39) are provided on the front wall (16) and the rear wall (19), but a single step (one on either the front wall (16) or the rear wall (19) ( 39) or a step (39) may be additionally provided on the side walls (17, 18) in addition to the front wall (16) and the rear wall (19). An annular step (39) may be formed along the inner peripheral wall (32) of the case (3). The contact surfaces (47) of the plurality of step portions (39) are formed at the same height, and can hold the element body (20) of the thermistor element (2) horizontally. The front step (39a) formed on the front wall (16) of the case (3) is omitted, and the lower lead (5) and the upper lead (6) and the rear wall (19) of the case (3) are formed. The element body (20) may be held in the internal cavity (11) by the rear stage portion (39b). If the element body (20) is brought into contact with only the rear stage (39b), the contact area between the element body (20) and the case (3) can be further reduced. In some cases, the lower body lead (5) and the upper lead (6) are sandwiched between the case (3) and the cover (4) so that the element body (20) does not come into contact with the stepped portion (39). 20) can also be retained in the internal cavity (11).

  As shown in FIG. 3, the case (3) has two substantially cylindrical leg portions (25) protruding downward from the bottom surface (3b) of the case (3). The rear protrusion (25b) formed close to the rear wall (19) of the case (3) is longer than the front protrusion (25a) formed close to the front wall (16) of the case (3). Is done. Lower the lower lead (5) by projecting the lower middle part (5b) of the lower lead (5) and the upper middle part (6b) of the upper lead (6) downward from the front protrusion (25a). The PTC device (10) can be supported on the substrate (29) by the three points of the portion (5c), the upper lead-out portion (6c) of the upper lead (6), and the rear protrusion (25b) of the case (3). . Since only the rear protrusion (25b) of the case (3) is in contact with the substrate (29), a space for accommodating an external air layer that generates heat insulation between the bottom surface (3b) of the case (3) and the substrate (29). (40) is formed, and heat transmitted from the element (20) to the substrate (29) through the case (3) by the external air layer can be further suppressed. When the thermistor element (2) is mounted in the case (3), the front protrusion (25a) of the case (3) can hold the case (3) almost horizontally together with the rear protrusion (25b). Although not shown, the front protrusion (25a) of the case (3) may be omitted or another protrusion may be provided on the bottom surface (3b) of the case (3).

  As shown in FIGS. 13 to 15, the cover (4) includes a top wall (41), an outer peripheral wall (42) connected at right angles to the periphery of the top wall (41), the top wall (41) and the outer periphery. It has an accommodating part (12) formed by the wall (42) and an open part (46) formed at the lower part of the outer peripheral wall (42). The top wall (41) of the cover (4) is formed in a substantially square or rectangular plate shape that is slightly larger than the bottom wall (31) of the case (3), and the outer peripheral wall (42) is a top wall (41). A substantially square or rectangular cylinder is formed along the edge. The outer peripheral wall (42) of the cover (4) is disposed between the front wall (43), the rear wall (44) facing the front wall (43), and between the front wall (43) and the rear wall (44). And a pair of side walls (45). Further, the cover (4) has four outer dividing grooves (15) formed in the vicinity of the connecting portion between the front wall (43) and the rear wall (44) and each side wall (45). The outer dividing groove (15) of the cover (4) is formed vertically from the outer peripheral wall (42) to the lower part of the outer peripheral wall (42) at a position corresponding to the inner dividing groove (14) of the case (3).

  When assembling the PTC device (10), the thermistor element (2), the case (3) and the cover (4) to which the lead wires are soldered are prepared. The lower lead (5) and the upper lead (6) of the thermistor element (2) are, for example, pre-bent into the predetermined shape shown in the figure, and the lower lead (5) has a lower inscribed portion (5a) and a lower intermediate portion (5b). ) And a lower lead-out portion (5c), and an upper middle portion (6b), an upper middle portion (6b), and an upper lead-out portion (6c) of the upper lead (6). Although not shown or described in detail, the case (3) and the cover (4) are formed by a known manufacturing method such as an injection mold or a transfer mold.

  Next, the thermistor element (2) is inserted into the internal cavity (11) through the open part (37) of the case (3) by a mounting machine (not shown), and the element body ( The thermistor element (2) is mounted on the case (3) with the edge (23b) of the lower surface (23) of 20) in contact. At this time, the lower lead (5) and the upper lead (6) of the thermistor element (2) are extended to the outside of the inner peripheral wall (32) through the notch (38) of the inner peripheral wall (32) of the case (3). That is, the lower inscribed portion (5a) of the lower lead (5) is extended to the outside of the case (3) through the lower notch (38a) of the inner peripheral wall (32) of the case (3), and the inner portion of the case (3) The upper middle portion (6b) of the upper lead (6) is extended to the outside of the case (3) through the upper cutout portion (38b) of the peripheral wall (32).

  When the thermistor element (2) is placed in the internal cavity (11) of the case (3), the side surface (26) of the thermistor element (2) is aligned with the inner peripheral wall (32) of the case (3) and the outer periphery of the cover (4). It is shielded from the surrounding environment by the double wall structure with the wall (42). Further, the surface contact between the inner peripheral wall (32) and the outer peripheral wall (42) reliably blocks the penetration of the molten solder into the package (1). Further, the thermistor element (2) forms a lower gap (7) and a peripheral gap (8) with respect to the bottom wall (31) and the inner peripheral wall (32) of the case (3), respectively, and the lower gap (7) and Each air layer held in the circumferential gap (8) can sufficiently suppress heat transfer from the thermistor element (2) to the package (1).

  Subsequently, as shown in FIG. 2, the thermistor element (2) attached to the case (3), the internal cavity (11) of the case (3) and the open part (37) are covered with the case (3) ( 4), the cover (4) is slid along the inclined surface (51) of the nail (50), and then the cover (4) itself is used to open the cover (4). The portion (53) is locked to the locking surface (52) of the claw (50) by snap action, and the cover (4) is attached to the case (3). The cover (4) can be fixed to the outside of the case (3) by using the claw (50) of the case (3) and the opening (53) of the cover (4) without using an adhesive or other fixing members. At this time, the lower middle portion (5b) of the lower lead (5) and the upper middle portion (6b) of the upper lead (6) are arranged between the inner peripheral wall (32) of the case (3) and the cover (4). The lower lead-out part (5c) of the lower lead (5) and the upper lead-out part (6c) of the upper lead (6) lead out from the bottom of the package (1) formed by the case (3) and the cover (4) Thus, the package-enclosed PTC device 10 shown in FIG. 1 can be easily assembled. The thermistor element (2) is arranged so as to form an upper gap (9) with respect to the top wall (41) of the cover (4), so that the air layer and the case held in the upper gap (9) ( The thermistor is composed of the bottom wall (31) of 3), the double wall structure of the inner peripheral wall (32) of the case (3) and the outer peripheral wall (42) of the cover (4) and the top wall (41) of the cover (4). Heat transfer conducted from the element (2) through the package (1) can be sufficiently suppressed. In addition, the lower lead (5) and the upper lead (6) arranged and held between the inner peripheral wall (32) of the case (3) and the cover (4) are provided in the inner cavity (11) of the package (1). The center portion (23a) of the element main body (20) can be prevented from contacting the package (1) and the thermistor element (2) can be prevented from moving.

  When the cover (4) is attached to the case (3), the lower lead-out portion (5c) of the lower lead (5) and the upper lead-out portion (6c) of the upper lead (6) and the bottom surface (3b) of the case (3) Except for this, the cover (4) closes the opening (37) of the case (3) and simultaneously surrounds the inner peripheral wall (32) of the case (3) from the outside. Further, as shown in FIG. 16, a pair of substantially cylindrical passages (14, 14) formed so that the inner dividing groove (14) of the case (3) and the outer dividing groove (15) of the cover (4) are opposed to each other. 15) A lower middle portion (5b) of the lower lead (5) and an upper middle portion (6b) of the upper lead (6) can be arranged in the lower lead (5). When covering the case (3) with the cover (4), the front wall (16) of the case (3) and the front wall (43) of the cover (4) face each other, and the rear wall (19) of the case (3) The rear wall (44) of the cover (4) faces. However, since the outer groove (15) is provided at the four corners of the cover (4), the case (3) can be covered with the cover (4) without increasing the size of the package (1). The inner dividing groove (14) of (3) and the outer dividing groove (15) of the cover (4) face each other to form a pair of passages (14, 15). Further, since the outer dividing grooves (15) are formed at the four corners of the cover (4), the cover (4) can be mounted on the case (3) without considering the mounting direction. Since the inner surface (41a) of the top wall (41) of the cover (4) attached to the case (3) is in close contact with the upper surface (3a) of the case (3), the PTC device (10) is attached to the substrate (29). When soldering is performed, molten solder can be prevented from entering the case (3) from the outer dividing groove (15) of the cover (4) that does not form the passages (14, 15).

  As shown in FIG. 3, since the inner peripheral wall (32) of the case (3) is formed higher than the thermistor element (2), when the cover (4) is attached to the case (3), the cover (4) An upper gap (9) is formed between the top wall (41) and the thermistor element (2). An upper gap (9) is formed between the top wall (41) of the cover (4) and the upper surface (24) of the thermistor element (2) to accommodate an air layer that generates heat insulation. The amount of heat transferred to the external space through the top wall (41) is reduced, and the temperature rise of the thermistor element (2) due to its own heat generation is not hindered.

  In the present embodiment, the lower middle portion (5b) of the lower lead (5) and the upper middle portion (6b) of the upper lead (6) are sandwiched between the inner peripheral wall (32) of the case (3) and the cover (4). The edge (23b) of the lower surface (23) of the element body (20) abuts on the step (39) of the inner peripheral wall (32) of the case (3), and the bottom wall (31) of the case (3) The element body (20) is held above. The lower lead (5) and the upper lead (6) and the step (39) of the inner peripheral wall (32) of the case (3) substantially assemble the element body (20) within the inner cavity (11) of the case (3). It can be supported horizontally. When the cover (4) is attached to the case (3), the lower middle part (5b) and the upper lead (6) of the lower lead (5) are covered by the inner peripheral wall (32) of the case (3) and the cover (4). The upper intermediate part (6b) is firmly held, the element body (20) is held almost horizontally only by the lower lead (5) and the upper lead (6), and the step of the inner peripheral wall (32) of the case (3) The portion (39) and the edge portion (23b) of the lower surface (23) of the element body (20) may be spaced apart from each other. In this case, the step (39) of the inner peripheral wall (32) of the case (3) may be omitted. Since the element body (20) does not contact the case (3) at all, the amount of heat transferred from the element body (20) to the substrate (29) through the case (3) can be further reduced.

  As shown in FIG. 17, when the PTC device (10) is attached to the substrate (29) by the flow type soldering method, the lower surface (29) of the substrate (29) is used by using a known adhesive application device such as a dispenser. An adhesive is applied to the soldering surface. Next, the PTC device (10) is placed on the substrate (29) by a known chip mounter (surface mounter), and the bottom surface of the substrate (29) and the bottom surface (3b) or leg (25) of the case (3). ) And are fixed. Subsequently, although not shown in the drawings, the board (29) is transported onto a solder tank in which liquefied solder is stored with the mounting surface of the board (29) facing downward. In the solder bath, liquid solder is ejected upward from the nozzle by the pump to form a solder jet, and the solder jet is formed by allowing the mounting surface of the substrate (29) to contact the top of the solder jet and passing the substrate (29). Solder is attached to the mounting surface of the substrate (29) that has passed through, and the lower lead (5) and upper lead (6) of the PTC device (10) are electrically connected to the circuit pattern of the substrate (29). Can do.

  18 and 19 show another embodiment of the present invention in which the PTC device (10) is soldered to the substrate (29) by the reflow method. In the PTC device (10) shown in FIG. 18, the lower lead (5) includes a lower inscribed portion (5a) electrically connected to the lower electrode (21) of the element body (20), and a lower inscribed portion ( A lower intermediate portion (5b) bent at a right angle downward from 5a) and a lower lead-out portion (5c) extending further downward from the lower intermediate portion (5b) and led out of the package (1) Prepare. Similarly, the upper lead (6) includes an upper inscribed portion (6a) electrically connected to the upper electrode (22) and an upper intermediate portion bent at a right angle downward from the upper inscribed portion (6a). (6b) and an upper lead-out portion (6c) that extends further downward from the upper middle portion (6b) and is led out of the package (1). At the time of mounting, the solder paste (34) is printed on the land portion on the mounting surface side of the double-sided substrate (29), and the lower lead (5) and the upper lead (6) of the PTC device (10) are attached by the chip mounter. The PTC device (10) is placed on the substrate (29) by being inserted into the through hole (30) of the substrate (29). Next, the substrate (29) and the PTC device (10) are heated in a well-known reflow furnace, and as shown in FIG. 19, the molten solder paste (34) is used to pass through holes (30 The lower lead-out portion (5c) of the lower lead (5) and the upper lead-out portion (6c) of the upper lead (6) to be inserted into the wiring pattern (29a) of the substrate (29) are soldered. Thereby, the lower lead (5) and upper lead (6) of the PTC device (10) and the circuit pattern (29a) of the substrate (29) can be electrically connected. Instead of the reflow method, a PTC device (10) shown in FIG. 18 may be applied to a flow method soldering method.

In the PTC device (10) of the present embodiment, the step (39) in the case (3) causes the bottom wall (31) of the case (3) and the center portion (23) of the lower surface (23) of the element body (20) ( 23a), a lower gap (7) is formed, the cover (4) is attached to the inner peripheral wall (32) of the case (3), and the top wall (41) of the cover (4) and the element body (20 ) Between the bottom surface (3b) of the case (3) and the substrate (29) by the legs (25) protruding from the bottom surface (3b) of the case (3). A space (40) can be formed. As a result, the amount of heat transmitted from the element body (20) to the substrate (29) through the package (1) can be reduced, and fluctuations in the allowable operating characteristics of the thermistor element (2) can be suppressed. The lower lead (5) and the upper lead (6) are bent downward from the outside of the case (3) and pass between the inner peripheral wall (32) of the case (3) and the cover (4). Since it is led out of the package (1), the creepage distance between the internal cavity (11) of the case (3) and the outside is extended, and the molten solder enters the internal cavity (11) of the case (3). Can be suppressed, and the thermal influence from the substrate (29) can be reduced. In this way, it is possible to form a package-enclosed PTC device (10) that exhibits an allowable operating characteristic equivalent to that of an existing non-packaged thermistor having radial leads.

Table 2 shows the time (T from time T ₀ when voltage is applied (start-up) to time point T ₁ when the PTC samples A, B and C drop to half the maximum current value I _max (I _max × 1/2). ₁ -T ₀ ) is measured data. PTC samples A, B and C all have an element resistance value of 1.8Ω, but A is a book in which an internal gap including a lower gap (7), a circumferential gap (8) and an upper gap (9) is formed. The operation time of the package-enclosed PTC according to the invention, B is the operation of the package-enclosed PTC in which the thermistor element is surrounded by the epoxy resin filled in the lower gap (7), the circumferential gap (8) and the upper gap (9) of the package Time and C indicate the operation time of a packageless PTC having a conventional radial lead. PTC sample A exhibits an operating time equivalent to C, but B increases the heat capacity in the package and increases the amount of heat conducted to the outside, so that the allowable operating time at room temperature (1.0-3. 0 seconds) and the allowable operating time at low temperatures (within 40 seconds).

It is as follows if the effect by this Embodiment is enumerated.
[1] The thermistor element (2) can be accommodated in the package (1) to form a packaged thermistor having the same dynamic characteristics as the non-package type having radial leads.
[2] The thermistor element (2) forms a lower gap (7) and a circumferential gap (8) with respect to the bottom wall (31) and the inner circumferential wall (32) of the case (3), respectively. Since it is arranged to form an upper gap (9) with respect to the top wall (41), each air layer and case held in the lower gap (7), the circumferential gap (8) and the upper gap (9) Due to the double wall structure of the bottom wall (31) of (3), the inner peripheral wall (32) of the case (3) and the outer peripheral wall (42) of the cover (4) and the top wall (41) of the cover (4), Heat transfer conducted from the thermistor element (2) to the package (1) and the substrate can be sufficiently suppressed.
[3] The lower middle portion (5b) of the lower lead (5) and the upper middle portion (6b) of the upper lead (6) are bent downward from the outside of the case (3), and the inner peripheral wall of the case (3) Since (32) and the cover (4) are passed through and led out of the package (1), the creepage distance between the internal cavity (11) of the case (3) and the outside is extended, and the case ( Intrusion of molten solder into the internal cavity (11) of 3) can be suppressed, and thermal influence from the substrate can be reduced.
[4] The side surface (26) of the thermistor element (2) can be shielded from the surrounding environment by the double wall structure of the inner peripheral wall (32) of the case (3) and the outer peripheral wall (42) of the cover (4).
[5] By the surface contact between the inner peripheral wall (32) and the outer peripheral wall (42), the penetration of the molten solder into the package (1) can be surely blocked.

Embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made. Although the present invention has been described in detail for purposes of illustration with respect to embodiments that are presently considered to be optimal and preferred, the embodiments of the present invention are subject to various modifications and changes that fall within the spirit of the invention and the scope of the claims. Since this is possible, the present invention should not be construed as being limited to the above-described embodiment.
The temperature-dependent semiconductor device to which the present invention is applied is not limited to a positive temperature coefficient thermistor. For example, the temperature-dependent semiconductor device is an NTC thermistor whose resistance decreases with increasing temperature or a CTR thermistor whose resistance decreases rapidly when a predetermined temperature is exceeded. The invention may be applied. Further, the present invention may be applied to other thermistors such as a ceramic PTC obtained by adding an additive to barium titanate or a polymer PTC in which conductive particles such as carbon black are dispersed in a polymer or a temperature-dependent element. Although not shown, a case and a cover other than a square, such as a circle or an ellipse, may be formed.
In the illustrated embodiment, an example is shown in which the bottom wall (31) and the inner peripheral wall (32) of the case (3) and the top wall (41) and the outer peripheral wall (42) of the cover (4) are connected at right angles. The inner peripheral wall (32) and the cover (4) including a bottom wall (31) and a pair of side walls (17, 18) of the case (3) at an angle other than a right angle, in a range of 90 degrees to 60 degrees, for example, an angle of 85 degrees. ) Top wall (41) and outer peripheral wall (42) may be connected in whole or in part at substantially the same inclination angle.
Further, the thickness of the inner peripheral wall (32) of the case (3) and / or the outer peripheral wall (42) of the cover (4) may be changed. For example, the inner peripheral wall (32) is gradually thinned upward from the bottom wall (31) of the case (3), and the outer peripheral wall (42) is gradually decreased downward from the top wall (41) of the cover (4). The cover (4) can be easily attached to and detached from the case (3).

  The present invention relates to a vehicle-mounted door mirror control device, a heating temperature control device for a heater, a resettable fuse for a secondary battery such as a lithium ion battery, a temperature detection sensor, an inrush current reduction device for a power supply circuit, a current limiting device or a circuit. The present invention can be applied to various package-encapsulated temperature-dependent resistors such as a protection device.

  (1) ・ ・ Package, (2) ・ Thermistor element (PTC element), (3) ・ Case, (3b) ・ ・ Bottom, (4) ・ Cover, (5) ・ Lower lead, (5a ) ・ ・ Lower inscribed part, (5b) ・ ・ Lower middle part, (5c) ・ ・ Lower lead-out part, (6) ・ ・ Upper lead, (6a) ・ ・ Upper inscribed part, (6b) ・ ・ Upper Middle part, (6c) ・ ・ Upper lead part, (7) ・ ・ Lower gap, (8) ・ ・ Gap, (9) ・ ・ Upper gap, (10) ・ ・ Package enclosed thermistor (PTC device), (11) ・ ・ Internal cavity, (14) ・ ・ Inner split groove, (15) ・ ・ Outer split groove, (20) ・ ・ Element body, (21) ・ ・ Lower electrode, (22) ・ ・ Upper electrode, (23b) ・ ・ Edge, (25) ・ ・ Leg, (31) ・ ・ Bottom wall, (32) ・ ・ Inner wall, (37) ・ ・ Open part, (38) ・ ・ Notch, (38a ) ・ ・ Lower cutout, (38b) ・ ・ Upper cutout, (39) ・ ・ Step, (41) ・ ・ Top wall, (42) ・ ・ Outer wall, (50) ・ Claw, (51) ..Inclined surface, (52) ... Locking surface, (53) Part,

Claims (18)

An electrically insulating package and a temperature-dependent thermistor element disposed in the package;
The package is connected to the bottom wall, a case having an inner peripheral wall connected to the periphery of the bottom wall and an inner cavity formed by the bottom wall and the inner peripheral wall, and a top wall covering the inner cavity of the case and the periphery of the top wall. And a cover having an outer peripheral wall disposed outside the inner peripheral wall of the case,
The thermistor element is arranged so as to form a lower gap and a circumferential gap with respect to the bottom wall and the inner peripheral wall of the case, respectively, and an upper gap with respect to the top wall of the cover. . The thermistor element includes a pair of electrodes and a pair of leads fixed to each electrode,
The package-enclosed thermistor according to claim 1, wherein a pair of leads are led out from a pair of notches formed on an inner peripheral wall of the case, and the pair of leads are further sandwiched between the case and the cover. The thermistor element includes an element body having a pair of electrodes,
The pair of electrodes has a lower electrode and an upper electrode,
The pair of leads is made of a metal lower lead having a lower inscribed part electrically connected to the lower electrode of the element body, and a metal having an upper inscribed part electrically connected to the upper electrode of the element body. With an upper lead,
The package-enclosed thermistor according to claim 2, wherein the lower inscribed portion of the lower lead and the upper inscribed portion of the upper lead are extended to the outside of the inner peripheral wall through a cutout portion of the inner peripheral wall of the case. The lower lead has a lower intermediate portion that bends downward from the lower inscribed portion,
The upper lead has an upper intermediate portion that bends downward from the upper inscribed portion,
The lower intermediate portion and the upper intermediate portion pass between the inner peripheral wall of the case and the cover and are led out of the package.
The package-enclosed thermistor according to claim 3, wherein the cover attached to the case surrounds the inner peripheral wall of the case from the outside and covers the thermistor element, the internal cavity of the case, and the open portion.   The package encapsulation according to claim 4, wherein the lower middle portion of the lower lead and the upper middle portion of the upper lead held between the inner peripheral wall of the case and the cover hold the element body above the bottom wall of the case via the lower gap. Type thermistor. Forming at least one step on the inner peripheral wall at a position higher than the bottom wall of the case;
The packaged thermistor according to claim 2, wherein the edge of the element body is brought into contact with the stepped part. The lower lead has a lower lead-out portion bent at a right angle from the lower middle portion,
The upper lead has an upper lead-out portion bent at a right angle from the upper middle portion,
The case has an inner dividing groove formed on the outer side of the inner peripheral wall,
The cover has an outer groove formed inside at a position corresponding to the inner groove of the case,
A lower middle portion of the lower lead and an upper middle portion of the upper lead are disposed in a pair of passages formed by arranging the inner and outer grooves facing each other, and the lower lead-out portion and the upper lead of the lower lead The packaged thermistor according to claim 4, wherein the upper lead-out part is led out from the package. The notch formed on the inner peripheral wall of the case includes a lower notch formed on the inner peripheral wall at a position higher than the bottom wall, and an upper notch formed on the inner peripheral wall at a position higher than the lower notch,
The lower inscribed part of the lower lead extends to the outside of the case through the lower notch of the inner peripheral wall of the case,
The upper middle part of the upper lead extends to the outside of the case through the upper notch on the inner peripheral wall of the case,
3. The packaged thermistor according to claim 2, wherein the upper middle portion of the upper lead is longer in the vertical direction than the lower middle portion of the lower lead.   The package-enclosed thermistor according to claim 7, wherein a lower lead-out portion of the lower lead and an upper lead-out portion of the upper lead protrude below the at least one leg portion provided on the bottom surface of the case. Providing at least one claw having an inclined surface and a locking surface formed at the lower end of the inclined surface outside the inner peripheral wall of the case;
When attaching the cover to the case, after sliding the cover along the slanted surface of the nail, use the elasticity of the cover itself to lock the opening formed in the cover to the nail locking surface by snap action The packaged thermistor according to claim 2, wherein A bottom wall, an inner peripheral wall connected to the periphery of the bottom wall, a case having an inner cavity formed by the bottom wall and the inner peripheral wall, and a cover having an outer peripheral wall connected to the periphery of the top wall and the top wall Preparing an electrically insulating package; and
A thermistor element is disposed in the internal cavity of the case by forming a lower gap between the bottom wall of the case and the temperature-dependent thermistor element and a circumferential gap between the inner peripheral wall of the case and the thermistor element. Process,
A method of manufacturing a package-enclosed thermistor, comprising: attaching a cover to the case; covering the inner cavity of the case with a top wall of the cover; and disposing the outer peripheral wall of the cover outside the inner peripheral wall of the case. . The thermistor element includes a pair of electrodes and a pair of leads fixed to each electrode,
The method for producing a package-enclosed thermistor according to claim 11, further comprising a step of disposing a thermistor element in the case in a state in which the pair of leads are led out from the pair of notches formed in the inner peripheral wall of the case.   The method for producing a package-enclosed thermistor according to claim 12, comprising a step of attaching the cover to the case in a state where a pair of leads is sandwiched between the case and the cover. The thermistor element includes an element body having a pair of electrodes,
The pair of electrodes has a lower electrode and an upper electrode,
The pair of leads is made of a metal lower lead having a lower inscribed part electrically connected to the lower electrode of the element body, and a metal having an upper inscribed part electrically connected to the upper electrode of the element body. With an upper lead,
The method for producing a packaged thermistor according to claim 12 or 13, comprising a step of extending a lower inscribed portion of the lower lead and an upper inscribed portion of the upper lead to the outside of the inner peripheral wall through a cutout portion of the inner peripheral wall of the case. Providing the lower lead with a lower intermediate portion bent downward from the lower inscribed portion of the lower lead, and providing the upper intermediate portion bent upward from the upper inscribed portion of the upper lead with the upper lead;
The lower intermediate part and the upper intermediate part that pass between the inner peripheral wall of the case and the cover are led out of the package, the cover surrounds the inner peripheral wall of the case from the outside, the thermistor element, the internal cavity of the case, and the open part The method for producing a package-enclosed thermistor according to claim 14, further comprising: covering the case with a cover.   The process of holding the element body above the bottom wall of the case with the case and cover sandwiching the lower middle part of the lower lead and the upper middle part of the upper lead so that the center part of the lower surface of the element body does not contact the case A process for producing a packaged thermistor according to claim 15. Forming at least one step on the inner peripheral wall at a position higher than the bottom wall of the case;
The method for producing a package-enclosed thermistor according to claim 11, further comprising: attaching a thermistor element to the case by bringing the edge of the element body into contact with the step of the case. At least one claw having an inclined surface and a locking surface disposed at the lower end of the inclined surface is formed outside the inner peripheral wall of the case, and an opening at a position corresponding to the claw on the inner peripheral wall of the case is used as a cover Forming, and
After sliding the cover along the inclined surface of the nail, the cover is attached to the case by snapping the opening formed in the cover to the locking surface of the nail by using the elasticity of the cover itself. The method for producing a packaged thermistor according to claim 11, further comprising a step.

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