EP0308306A1 - PTC thermistor for surface mounting - Google Patents

PTC thermistor for surface mounting Download PDF

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Publication number
EP0308306A1
EP0308306A1 EP88402281A EP88402281A EP0308306A1 EP 0308306 A1 EP0308306 A1 EP 0308306A1 EP 88402281 A EP88402281 A EP 88402281A EP 88402281 A EP88402281 A EP 88402281A EP 0308306 A1 EP0308306 A1 EP 0308306A1
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EP
European Patent Office
Prior art keywords
thermistor according
conductive coating
electrical
ceramic element
ceramic
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EP88402281A
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German (de)
French (fr)
Inventor
Françoise Mallez
Alain Lagrange
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Compagnie Europeenne de Composants Electroniques LCC CICE
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Compagnie Europeenne de Composants Electroniques LCC CICE
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Publication of EP0308306A1 publication Critical patent/EP0308306A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C1/00—Details
    • H01C1/14—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors
    • H01C1/1406—Terminals or electrodes formed on resistive elements having positive temperature coefficient
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/006—Apparatus or processes specially adapted for manufacturing resistors adapted for manufacturing resistor chips

Definitions

  • the invention relates to thermistors with a positive temperature coefficient or PTC and which can be mounted on the surface.
  • the basic products used are essentially perovskite ceramics (alkaline earth titanates) which have been made conductive by valence induction (doping with 3+ or 5+ ions).
  • the CTP effect results from the combination of three causes: a polycrystalline microstructure, a semiconductor material and the ferroelectric / paraelectric phase change. It is due to the formation of electrical potential barriers at the grain boundaries.
  • the overall result is a sharp and abrupt increase in resistivity when passing the Curie point.
  • a thermistor with a positive coefficient hence sometimes the name of posistance.
  • the positive temperature coefficient domain is located just above the Curie point. Its width is of the order of a few tens of degrees and it is all the more narrower the higher the temperature coefficient.
  • the Siemens Company has marketed PTC thermistors consisting of a metallized parallelepiped at its ends. Each electrical termination has two layers: a layer of an alloy of silver, indium and gallium to have good ohmic contact with the ceramic and, this layer being difficult to weld, a layer of silver to provide a surface having good weldability (silver alone providing poor ohmic contact).
  • the disadvantage of these products is that they do not hold up to wettability tests and dewetting tests.
  • the present invention provides PTC thermistors as a component for surface mounting, each electrical termination of which comprises a metallization intended to ensure ohmic contact on the ceramic and a connection or a cover fixed on the metallization and allowing the soldering of the component on a circuit.
  • the invention therefore relates to a thermistor with a positive temperature coefficient for surface mounting, consisting of a ceramic element and two electrical terminations, characterized in that each electrical termination is formed of a conductive coating deposited directly on ceramic and providing good ohmic contact, and a weldable electrical connection attached to the ceramic element and ensuring good electrical contact with the conductive coating.
  • the components for surface mounting can be, in their most basic structure, in two forms: in the form of a parallelepiped supporting metallizations at the ends (chip) or in the form of a rod or a tube supporting weldable metallizations at the ends (melf).
  • FIG. 1 represents a chip comprising a parallelepiped 1 and two metallizations 2 and 3 at its ends.
  • FIG. 2 represents a melf comprising a stick 4 and two metallizations 5 and 6 at its ends.
  • the invention proposes to deposit an ohmic layer, at the places reserved for the terminations to obtain a chip or a melf, then to fix electrical connections or covers on these terminations.
  • FIG. 3 represents a PTC thermistor according to the invention, consisting of a parallelepiped 10 the ends of which are covered with conductive coatings 11 and 12. On these conductive coatings covers 13 and 14 have been fixed. The covers 13 and 14 are weldable and they must ensure good electrical contact with this coating. In Figure 3, they have been given a U-shaped section but other shapes are suitable. One can for example use covers which cover all the metallized sides.
  • the conductive coatings can consist of metallizations deposited by dipping from an ink ensuring good ohmic contact. It is thus possible to deposit a layer of aluminum or of an alloy of silver, indium and gallium, for example. This dip metallization method provides good returns. Metallizations can also be deposited by spraying processes.
  • FIG. 4 represents, in profile view, a detail of PTC thermistor according to the invention.
  • a cover is engaged by pressure which is a clip 22, for example made of nickel-plated and tinned iron.
  • Contact can be made directly on the metallization or else by means of a soldering cream 23 deposited at the bottom of the clip before its engagement.
  • the soldering cream must have a higher melting temperature than that of the solder which will be used for transfer to the printed circuit.
  • FIG. 5 represents, in profile view, a detail of another PTC thermistor according to the invention.
  • a cover 32 of the type shown in FIG. 3 has been engaged.
  • This cover may be made of iron nickel-plated and tinned.
  • the contact can be made by means of a soldering cream 33 deposited at the bottom of the cover before its engagement.
  • the soldering cream must have a higher melting temperature than that of the solder which will be used for transfer to the printed circuit.
  • hoods simple hoods or clips
  • cylindrical rods of Figure 2 can be attached to the same types of hoods (simple hoods or clips) to the cylindrical rods of Figure 2, taking into account of course their geometry.
  • FIG. 6 is a sectional view of a PTC thermistor according to the invention and formed from a ceramic tube 40.
  • the internal and external metallizations are carried out with an aluminum ink.
  • a brush is used for internal metallization.
  • the value of the thermistor can be adjusted by machining a metallization (sandblast, laser beam, etc.).
  • a first conductive coating 41 is thus obtained which covers almost the entire interior of the tube, emerges from one end of the tube and covers a small outer annular portion as shown in FIG. 6.
  • a second conductive coating 42 which also covers most of the outer cylindrical surface of the tube and one of its ends.
  • Hoods 43 and 44 can then be placed at each end using soldering cream.
  • the hoods that can be used can also be circular clips or rings. They are advantageously made of nickel-plated and tinned iron.
  • the tube makes it possible to obtain thermistors with a low ohmic value.
  • FIG. 7 is a side view of a PTC thermistor according to the invention.
  • the largest faces of the parallelepiped 50 are covered with metallizations 51 and 52 which allow alternating margins to remain.
  • the metallizations are for example made of aluminum and obtained by screen printing.
  • the screen printing can relate to a relatively large ceramic plate which will then be cut to obtain individual elements such as that defined by the parallelepiped 50.
  • the layers 53 and 54 are for example silver layers deposited by dipping. Their role is to ensure good electrical contact with the covers 55 and 56 which are fixed at the ends and which can be clips made of nickel-plated and tinned iron. You can also use solder cream to fix the covers.
  • a PTC thermistor it is also part of the invention to mount a PTC thermistor in a box.
  • the thermistor being formed from a parallelepiped or a disc supporting two metallizations obtained for example by aluminum screen printing. It is then possible, using a connection strip such as that described in patent application FR 2 581 827, to manufacture components for surface mounting in series.
  • the housing then consists of a block of molded resin. Electrical connections, welded (for example by laser welding) on the metal coatings of the elements, emerge from the resin block and are pressed against it as taught by the cited patent application. When soldering the component on its circuit of use, the resin will protect the ceramic from the heat of the solder bath.
  • the components according to the invention have the advantage of withstanding wettability tests and satisfying dewetting tests.

Abstract

Positive temperature coefficient thermistor for surface mounting, consisting of a ceramic element (10) and two electrical terminations. Each electrical termination is formed by a conductive coating (11, 12) deposited directly onto the ceramic and establishing good ohmic contact, and by a solderable electrical connection (13, 14) attached to the ceramic element and ensuring good electrical contact with the conductive coating. <IMAGE>

Description

L'invention concerne les thermistances à coefficient de température positif ou CTP et pouvant être montées en surface.The invention relates to thermistors with a positive temperature coefficient or PTC and which can be mounted on the surface.

Les produits de base utilisés sont essentiellement des céramiques pérovskites (titanates alcalino-terreux) que l'on a rendues conductrices par induction de valence (dopage par des ions 3⁺ ou 5⁺). L'effet CTP résulte de la combinaison de trois causes : une microstructure polycristalline, un matériau semiconducteur et le changement de phase ferroélectrique/paraélectrique. Il est dû à la formation de barrières de potentiel électrique aux joints de grains. Le résultat global est une augmentation forte et brutale de la résistivité au passage du point de Curie. On a affaire dans cette zone à une thermistance à coefficient positif d'où parfois le nom de posistance. Le domaine à coefficient de température positif se trouve juste au-dessus du point de Curie. Sa largeur est de l'ordre de quelques dizaines de degrés et elle est d'autant plus étroite que le coefficient de température est plus élevé. Etant donné la grande variété des produits pérovskites (BaTiO₃ - SrTiO₃ - PbTiO₃), il est facile d'établir des posistances à point de Curie (ou point de basculement) situé à n'importe quelle température de service (25°, 50°, 120° C, etc.). Les coefficients varient, selon les cas, de + 5% à + 40% par °C.The basic products used are essentially perovskite ceramics (alkaline earth titanates) which have been made conductive by valence induction (doping with 3⁺ or 5⁺ ions). The CTP effect results from the combination of three causes: a polycrystalline microstructure, a semiconductor material and the ferroelectric / paraelectric phase change. It is due to the formation of electrical potential barriers at the grain boundaries. The overall result is a sharp and abrupt increase in resistivity when passing the Curie point. We are dealing in this zone with a thermistor with a positive coefficient, hence sometimes the name of posistance. The positive temperature coefficient domain is located just above the Curie point. Its width is of the order of a few tens of degrees and it is all the more narrower the higher the temperature coefficient. Given the wide variety of perovskite products (BaTiO₃ - SrTiO₃ - PbTiO₃), it is easy to establish positions at a Curie point (or tipping point) located at any serving temperature (25 °, 50 °, 120 ° C, etc.). The coefficients vary, depending on the case, from + 5% to + 40% per ° C.

On désire de plus en plus que les composants passifs traditionnels puissent être insérés automatiquement sur les circuits. Les avantages inhérents à l'insertion automatique sont la réduction des coûts de production et une meilleure sécurité d'implantation. La miniaturisation des équipements est une autre cause du développement de cette technologie.There is an increasing desire that traditional passive components can be automatically inserted into circuits. The inherent advantages of automatic insertion are reduced production costs and better implantation security. The miniaturization of equipment is another cause of the development of this technology.

Cette tendance n'est plus limitée aux seules applications professionnelles. C'est ici qu'il convient de prendre en considération la technologie CMS (composant pour le montage en surface) qui peut répondre à toutes ces exigences. Leurs faibles dimensions, la faculté de s'implanter entre les pistes d'un circuit imprimé, de passer sans dommage dans un bain de soudure sont en effet pour les CMS des atouts indiscutables.This trend is no longer limited to professional applications only. This is where you should consider CMS technology (component for surface mounting) which can meet all these requirements. Their small dimensions, the ability to settle between the tracks of a printed circuit, to pass without damage in a solder bath are indeed for CMS undeniable advantages.

De plus, grâce à l'action conjuguée de mécaniciens et de fabricants de composants, l'implantation automatique de ces composants est une technique maintenant maîtrisée convenablement.In addition, thanks to the combined action of mechanics and component manufacturers, the automatic implantation of these components is a technique now properly mastered.

Jusqu'à présent, le prix de revient d'un composant montable en surface, comparé à celui de son équivalent traditionnel, constituait un handicap. Mais l'accroissement des quantités à produire permettrait de réduire cette différence à condition de maîtriser les problèmes technologiques.Until now, the cost price of a surface mountable component, compared to that of its traditional equivalent, has been a handicap. But increasing the quantities to be produced would make it possible to reduce this difference provided that technological problems are mastered.

Dans le cas des thermistances CTP, le passage à une structure de composant montable en surface est beaucoup plus difficile qu'il n'y paraît. En effet, si on veut déposer des métallisations sur un pavé de thermistance CTP, certaines précautions doivent être prises afin d'obtenir un contact ohmique. Des connexions peuvent ensuite être fixées par soudure sur les métallisations mais cela s'avère très délicat à cause de la grande sensibilité de ces céramiques aux chocs thermiques.In the case of PTC thermistors, switching to a surface mountable component structure is much more difficult than it seems. Indeed, if one wants to deposit metallizations on a PTC thermistor block, certain precautions must be taken in order to obtain an ohmic contact. Connections can then be fixed by welding on the metallizations but this proves to be very delicate because of the great sensitivity of these ceramics to thermal shocks.

La Société Siemens a commercialisé des thermistances CTP constituées d'un parallélépipède métallisé à ses extrémités. Chaque terminaison électrique comporte deux couches : une couche d'un alliage d'argent, d'indium et de gallium pour avoir un bon contact ohmique avec la céramique et, cette couche étant difficilement soudable, une couche d'argent pour fournir une surface présentant une bonne soudabilité (l'argent seul procurant un mauvais contact ohmique). L'inconvénient de ces produits est qu'ils ne tiennent pas aux essais de mouillabilité et aux tests de démouillage.The Siemens Company has marketed PTC thermistors consisting of a metallized parallelepiped at its ends. Each electrical termination has two layers: a layer of an alloy of silver, indium and gallium to have good ohmic contact with the ceramic and, this layer being difficult to weld, a layer of silver to provide a surface having good weldability (silver alone providing poor ohmic contact). The disadvantage of these products is that they do not hold up to wettability tests and dewetting tests.

Afin de pallier ces inconvénients, la présente invention propose des thermistances CTP sous forme de composant pour le montage en surface dont chaque terminaison électrique comprend une métallisation destinée à assurer le contact ohmique sur la céramique et une connexion ou un capot fixé sur la métallisation et permettant la soudure du composant sur un circuit.In order to overcome these drawbacks, the present invention provides PTC thermistors as a component for surface mounting, each electrical termination of which comprises a metallization intended to ensure ohmic contact on the ceramic and a connection or a cover fixed on the metallization and allowing the soldering of the component on a circuit.

L'invention a donc pour objet une thermistance à coefficient de température positif pour le montage en surface, constituée d'un élément de céramique et de deux terminaisons électriques, caractérisée en ce que chaque terminaison électrique est formée d'un revêtement conducteur déposé directement sur la céramique et procurant un bon contact ohmique, et d'une connexion électrique soudable rapportée sur l'élément de céramique et assurant un bon contact électrique avec le revêtement conducteur.The invention therefore relates to a thermistor with a positive temperature coefficient for surface mounting, consisting of a ceramic element and two electrical terminations, characterized in that each electrical termination is formed of a conductive coating deposited directly on ceramic and providing good ohmic contact, and a weldable electrical connection attached to the ceramic element and ensuring good electrical contact with the conductive coating.

L'invention sera mieux comprise et d'autres avantages apparaîtront grâce à la description qui va suivre, donnée à titre non limitatif, en relation avec les figures annexées parmi lesquelles :

  • - les figures 1 et 2 sont des représentations de composants respectivement sous forme de chip et de melf,
  • - la figure 3 représente une thermistance CTP selon l'invention et élaborée à partir d'un chip,
  • - les figures 4 et 5 représentent des détails de réalisation de thermistances selon l'invention,
  • - la figure 6 représente une thermistance CTP selon l'invention et élaborée à partir d'un melf,
  • - la figure 7 est une variante d'une thermistance selon l'invention.
The invention will be better understood and other advantages will become apparent from the description which follows, given without limitation, in relation to the appended figures among which:
  • FIGS. 1 and 2 are representations of components respectively in the form of a chip and a melf,
  • FIG. 3 represents a PTC thermistor according to the invention and produced from a chip,
  • FIGS. 4 and 5 show details of the production of thermistors according to the invention,
  • FIG. 6 represents a PTC thermistor according to the invention and produced from a melf,
  • - Figure 7 is a variant of a thermistor according to the invention.

Les composants pour le montage en surface peuvent se présenter, dans leur structure la plus élémentaire, sous deux formes : sous la forme d'un parallélépipède supportant des métallisations aux extrémités (chip) ou sous la forme d'un bâtonnet ou d'un tube supportant des métallisations soudables aux extrémités (melf). La figure 1 représente un chip comprenant un parallélépipède 1 et deux métallisations 2 et 3 à ses extrémités. La figure 2 représente un melf comprenant un bâtonnet 4 et deux métallisations 5 et 6 à ses extrémités.The components for surface mounting can be, in their most basic structure, in two forms: in the form of a parallelepiped supporting metallizations at the ends (chip) or in the form of a rod or a tube supporting weldable metallizations at the ends (melf). FIG. 1 represents a chip comprising a parallelepiped 1 and two metallizations 2 and 3 at its ends. FIG. 2 represents a melf comprising a stick 4 and two metallizations 5 and 6 at its ends.

Si on veut réaliser des thermistances CTP pour le montage en surface, il faut que leurs terminaisons électriques présentent des contacts ohmiques avec la céramique, qu'elles soient soudables et qu'elles présentent des retours suffisants. L'invention propose de déposer une couche ohmique, aux endroits réservés aux terminaisons pour obtenir un chip ou un melf, puis de fixer des connexions électriques ou des capots sur ces terminaisons.If we want to make PTC thermistors for the surface mounting, their electrical terminations must have ohmic contacts with the ceramic, be weldable and have sufficient returns. The invention proposes to deposit an ohmic layer, at the places reserved for the terminations to obtain a chip or a melf, then to fix electrical connections or covers on these terminations.

La figure 3 représente une thermistance CTP selon l'invention, constituée d'un parallélépipède 10 dont les extrémités sont recouvertes de revêtements conducteurs 11 et 12. Sur ces revêtements conducteurs on a fixé des capots 13 et 14. Les capots 13 et 14 sont soudables et ils doivent assurer un bon contact électrique avec ce revêtement. Sur la figure 3, on leur a donné une section en forme de U mais d'autres formes conviennent. On peut par exemple utiliser des capots qui recouvrent tous les côtés métallisés.FIG. 3 represents a PTC thermistor according to the invention, consisting of a parallelepiped 10 the ends of which are covered with conductive coatings 11 and 12. On these conductive coatings covers 13 and 14 have been fixed. The covers 13 and 14 are weldable and they must ensure good electrical contact with this coating. In Figure 3, they have been given a U-shaped section but other shapes are suitable. One can for example use covers which cover all the metallized sides.

Les revêtements conducteurs peuvent être constitués de métallisations déposées au trempé à partir d'une encre assurant un bon contact ohmique. On peut ainsi déposer une couche d'aluminium ou d'un alliage d'argent, d'indium et de gallium, par exemple. Cette méthode de métallisation par trempé assure de bons retours. On peut encore déposer des métallisations par des procédés de pulvérisation.The conductive coatings can consist of metallizations deposited by dipping from an ink ensuring good ohmic contact. It is thus possible to deposit a layer of aluminum or of an alloy of silver, indium and gallium, for example. This dip metallization method provides good returns. Metallizations can also be deposited by spraying processes.

Plusieurs solutions sont possibles quant à la fixation des capots. Ils peuvent être selon les cas engagés en force ou fixés par un moyen quelconque sur les parties métallisées.Several solutions are possible for fixing the covers. Depending on the case, they may be forcibly engaged or fixed by any means on the metallized parts.

La figure 4 représente, en vue de profil, un détail de thermistance CTP selon l'invention. On y reconnaît une partie du parallélépipède de céramique 20 et l'un des revêtements conducteurs d'extrémité et portant la référence 21. Sur ce revêtement conducteur on a engagé par pression un capot qui est un clip 22 par exemple en fer nickelé et étamé. Le contact peut être pris directement sur la métallisation ou bien par l'intermédiaire d'une crème à souder 23 déposée au fond du clip avant son engagement. La crème à souder doit avoir une température de fusion supérieure à celle de la soudure qui sera utilisée pour le report sur le circuit imprimé.FIG. 4 represents, in profile view, a detail of PTC thermistor according to the invention. We recognize a part of the ceramic parallelepiped 20 and one of the conductive end coatings and bearing the reference 21. On this conductive coating, a cover is engaged by pressure which is a clip 22, for example made of nickel-plated and tinned iron. Contact can be made directly on the metallization or else by means of a soldering cream 23 deposited at the bottom of the clip before its engagement. The soldering cream must have a higher melting temperature than that of the solder which will be used for transfer to the printed circuit.

La figure 5 représente, en vue de profil, un détail d'une autre thermistance CTP selon l'invention. On y reconnaît une partie du parallélépipède de céramique 30 et l'un des revêtements conducteurs d'extrémité et portant la référence 31. Sur ce revêtement conducteur on a engagé un capot 32 du type représenté à la figure 3. Ce capot peut être en fer nickelé et étamé. Comme précédemment, le contact peut être effectué par l'intermédiaire d'une crème à souder 33 déposée au fond du capot avant son engagement. De même, la crème à souder doit avoir une température de fusion supérieure à celle de la soudure qui sera utilisée pour le report sur le circuit imprimé.FIG. 5 represents, in profile view, a detail of another PTC thermistor according to the invention. One recognizes there a part of the ceramic parallelepiped 30 and one of the end conductive coatings and bearing the reference 31. On this conductive coating a cover 32 of the type shown in FIG. 3 has been engaged. This cover may be made of iron nickel-plated and tinned. As before, the contact can be made by means of a soldering cream 33 deposited at the bottom of the cover before its engagement. Likewise, the soldering cream must have a higher melting temperature than that of the solder which will be used for transfer to the printed circuit.

Les mêmes types de capots (capots simples ou clips) pouvent être fixés sur les bâtonnets cylindriques de la figure 2 en tenant compte bien sûr de leur géométrie.The same types of hoods (simple hoods or clips) can be attached to the cylindrical rods of Figure 2, taking into account of course their geometry.

La figure 6 est une vue en coupe d'une thermistance CTP selon l'invention et formée à partir d'un tube de céramique 40. Les métallisations internes et externes sont réalisées avec une encre à l'aluminium. On se sert d'un goupillon pour la métallisation interne. La valeur de la thermistance peut être ajustée par usinage d'une métallisation (jet de sable, faisceau laser, etc). On obtient ainsi un premier revêtement conducteur 41 qui recouvre presque tout l'intérieur du tube, ressort par l'une des extrémités du tube et recouvre une petite portion annulaire extérieure comme le montre la figure 6. On obtient aussi un second revêtement conducteur 42 qui recouvre la majeure partie de la surface cylindrique extérieure du tube et l'une de ses extrémités. On peut poser ensuite des capots 43 et 44 à chaque extrémité en utilisant de la crème à souder. Les capots utilisables peuvent aussi être des clips circulaires ou des bagues. Ils sont avantageusement réalisés en fer nickelé et étamé. Le tube permet d'obtenir des thermistances à faible valeur ohmique.Figure 6 is a sectional view of a PTC thermistor according to the invention and formed from a ceramic tube 40. The internal and external metallizations are carried out with an aluminum ink. A brush is used for internal metallization. The value of the thermistor can be adjusted by machining a metallization (sandblast, laser beam, etc.). A first conductive coating 41 is thus obtained which covers almost the entire interior of the tube, emerges from one end of the tube and covers a small outer annular portion as shown in FIG. 6. A second conductive coating 42 which also covers most of the outer cylindrical surface of the tube and one of its ends. Hoods 43 and 44 can then be placed at each end using soldering cream. The hoods that can be used can also be circular clips or rings. They are advantageously made of nickel-plated and tinned iron. The tube makes it possible to obtain thermistors with a low ohmic value.

D'autres configurations sont possibles pour obtenir de faibles valeurs ohmiques. On peut pour cela déposer les revêtements conducteurs sur les plus grandes faces d'un parallélépipède de céramique comme le montre la figure 7 qui est une vue de côté d'une thermistance CTP selon l'invention. Les plus grandes faces du parallélépipède 50 sont recouvertes de métallisations 51 et 52 qui laissent subsister des marges alternées. Les métallisations sont par exemple en aluminium et obtenues par sérigraphie. La sérigraphie peut concerner une plaque relativement grande de céramique qui sera ensuite découpée pour obtenir des éléments individuels tels que celui défini par le parallélépipède 50. Avant de fixer les capots, il est avantageux de déposer une couche d'un matériau conducteur pour assurer la continuité électrique entre chaque métallisation et l'extrémité correspondante du parallélépipède. On a ainsi une couche conductrice 53 qui prolonge la métallisation 51 et une couche 54 qui prolonge la métallisation 52. Les couches 53 et 54 sont par exemple des couches d'argent déposées au trempé. Leur rôle est d'assurer un bon contact électrique avec les capots 55 et 56 qui viennent se fixer aux extrémités et qui peuvent être des clips en fer nickelé et étamé. On peut aussi utiliser de la crème à souder pour fixer les capots.Other configurations are possible to obtain low ohmic values. For this, it is possible to deposit the conductive coatings on the largest faces of a ceramic parallelepiped as shown in FIG. 7 which is a side view of a PTC thermistor according to the invention. The largest faces of the parallelepiped 50 are covered with metallizations 51 and 52 which allow alternating margins to remain. The metallizations are for example made of aluminum and obtained by screen printing. The screen printing can relate to a relatively large ceramic plate which will then be cut to obtain individual elements such as that defined by the parallelepiped 50. Before fixing the covers, it is advantageous to deposit a layer of a conductive material to ensure continuity electric between each metallization and the corresponding end of the parallelepiped. There is thus a conductive layer 53 which prolongs the metallization 51 and a layer 54 which prolongs the metallization 52. The layers 53 and 54 are for example silver layers deposited by dipping. Their role is to ensure good electrical contact with the covers 55 and 56 which are fixed at the ends and which can be clips made of nickel-plated and tinned iron. You can also use solder cream to fix the covers.

Il entre également dans le cadre de l'invention de monter une thermistance CTP dans un boîter. La thermistance étant constituée à partir d'un parallélépipède ou d'un disque supportant deux métallisations obtenues par exemple par sérigraphie d'aluminium. On peut alors en utilisant une bande de connexion telle que celle décrite dans la demande de brevet FR 2 581 827, fabriquer en série des composants pour le montage en surface. Le boîtier est alors constitué d'un bloc de résine surmoulée. Des connexions électriques, soudées (par exemple par soudure laser) sur les revêtements métalliques des éléments, émergent du bloc de résine et sont plaquées contre lui comme l'enseigne la demande de brevet citée. Lors de la soudure du composant sur son circuit d'utilisation, la résine protégera la céramique de la chaleur du bain de soudure.It is also part of the invention to mount a PTC thermistor in a box. The thermistor being formed from a parallelepiped or a disc supporting two metallizations obtained for example by aluminum screen printing. It is then possible, using a connection strip such as that described in patent application FR 2 581 827, to manufacture components for surface mounting in series. The housing then consists of a block of molded resin. Electrical connections, welded (for example by laser welding) on the metal coatings of the elements, emerge from the resin block and are pressed against it as taught by the cited patent application. When soldering the component on its circuit of use, the resin will protect the ceramic from the heat of the solder bath.

Les composants selon l'invention présentent l'avantage de tenir aux essais de mouillabilité et de satisfaire les tests de démouillage.The components according to the invention have the advantage of withstanding wettability tests and satisfying dewetting tests.

Claims (12)

1. Thermistance à coefficient de température positif pour le montage en surface, constituée d'un élément de céramique (10) et de deux terminaisons électriques, caractérisée en ce que chaque terminaison électrique est formée d'un revêtement conducteur (11, 12) déposé directement sur la céramique et procurant un bon contact ohmique, et d'une connexion électrique soudable (13, 14) rapportée sur l'élément de céramique et assurant un bon contact électrique avec le revêtement conducteur.1. Thermistor with positive temperature coefficient for surface mounting, consisting of a ceramic element (10) and two electrical terminations, characterized in that each electrical termination is formed of a conductive coating (11, 12) deposited directly on the ceramic and providing good ohmic contact, and a weldable electrical connection (13, 14) attached to the ceramic element and ensuring good electrical contact with the conductive coating. 2. Thermistance selon la revendication 1, caractérisée en ce que le revêtement conducteur est une couche d'aluminium.2. Thermistor according to claim 1, characterized in that the conductive coating is a layer of aluminum. 3. Thermistance selon la revendication 2, caractérisée en ce que ladite couche d'aluminium est déposée au trempé.3. Thermistor according to claim 2, characterized in that said aluminum layer is deposited by dipping. 4. Thermistance selon l'une quelconque des revendications 1 à 3, caractérisée en ce que ladite connexion électrique est un capot (32) ou un clip (22).4. Thermistor according to any one of claims 1 to 3, characterized in that said electrical connection is a cover (32) or a clip (22). 5. Thermistance selon la revendication 4, caractérisée en ce que le capot ou le clip sont en fer nickelé et étamé.5. Thermistor according to claim 4, characterized in that the cover or the clip are made of nickel-plated and tinned iron. 6. Thermistance selon l'une des revendications 4 ou 5, caractérisée en ce que le capot ou le clip sont fixés sur leur revêtement conducteur par l'intermédiaire d'une crème à souder (23, 33).6. Thermistor according to one of claims 4 or 5, characterized in that the cover or the clip are fixed to their conductive coating by means of a soldering cream (23, 33). 7. Thermistance selon l'une quelconque des revendications 1 à 6, caractérisée en ce que l'élément de céramique à la forme d'un parallélépipède (10, 50).7. Thermistor according to any one of claims 1 to 6, characterized in that the ceramic element in the form of a parallelepiped (10, 50). 8. Thermistance selon la revendication 7, caractérisée en ce que chaque terminaison électrique est formée d'un revêtement conducteur (51, 52) s'étendant sur l'une des grandes faces dudit élément (50) et une connexion électrique (55, 56) rapportée à l'une des extrémités de l'élément, le contact électrique entre le revêtement conducteur et la connexion se faisant par l'intermédiaire d'une couche conductrice supplémentaire (53, 54).8. Thermistor according to claim 7, characterized in that each electrical termination is formed of a conductive coating (51, 52) extending over one of the large faces of said element (50) and an electrical connection (55, 56 ) attached to one end of the element, the electrical contact between the conductive coating and the connection being made by means of an additional conductive layer (53, 54). 9. Thermistance selon la revendication 8, caractérisé en ce que ladite couche conductrice supplémentaire (53, 54) est en argent.9. Thermistor according to claim 8, characterized in that said additional conductive layer (53, 54) is silver. 10. Thermistance selon l'une des revendications 1 à 6, caractérisée en ce que l'élément de céramique à la forme d'un bâtonnet ou d'un tube (40).10. Thermistor according to one of claims 1 to 6, characterized in that the ceramic element in the form of a stick or a tube (40). 11. Thermistance selon la revendication 10, caractérisée en ce que l'élément de céramique est un tube (40), l'un des revêtements conducteur (41) s'étendant de l'intérieur du tube jusqu'à l'une des extrémités, l'autre revêtement conducteur (42) s'étendant sur l'extérieur du tube et sur son autre extrémité, des capots ou des clips (43, 44) étant fixés sur ces extrémités.11. Thermistor according to claim 10, characterized in that the ceramic element is a tube (40), one of the conductive coatings (41) extending from the inside of the tube to one of the ends , the other conductive coating (42) extending over the outside of the tube and at its other end, covers or clips (43, 44) being fixed on these ends. 12. Thermistance selon l'une quelconque des revendications 1 à 11, caractérisée en ce qu'une résine de surmoulage enrobe l'élément de céramique.12. Thermistor according to any one of claims 1 to 11, characterized in that an overmolding resin coats the ceramic element.
EP88402281A 1987-09-15 1988-09-09 PTC thermistor for surface mounting Withdrawn EP0308306A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8712776 1987-09-15
FR8712776A FR2620561B1 (en) 1987-09-15 1987-09-15 CTP THERMISTOR FOR SURFACE MOUNTING

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2222311A (en) * 1988-08-26 1990-02-28 Dale Electronics Resistor with terminal pads for surface mounting
EP0429633A1 (en) * 1989-06-19 1991-06-05 Dale Electronics Thermistor and method of making the same.
EP0522863A1 (en) * 1991-07-12 1993-01-13 Daito Communication Apparatus Co. Ltd. Positive temperature coefficient device
WO1994001876A1 (en) * 1992-07-09 1994-01-20 Raychem Corporation Electrical devices
GB2265761B (en) * 1992-03-30 1996-07-17 Dale Electronics Bulk metal chip resistor
US5852397A (en) * 1992-07-09 1998-12-22 Raychem Corporation Electrical devices
US5952911A (en) * 1996-10-09 1999-09-14 Murata Manufacturing Co., Ltd. Thermistor chips and methods of making same
US6081181A (en) * 1996-10-09 2000-06-27 Murata Manufacturing Co., Ltd. Thermistor chips and methods of making same
US6292088B1 (en) 1994-05-16 2001-09-18 Tyco Electronics Corporation PTC electrical devices for installation on printed circuit boards
US6640420B1 (en) 1999-09-14 2003-11-04 Tyco Electronics Corporation Process for manufacturing a composite polymeric circuit protection device
US20100090332A1 (en) * 2008-10-09 2010-04-15 Joinset Co., Ltd. Ceramic chip assembly

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3996447A (en) * 1974-11-29 1976-12-07 Texas Instruments Incorporated PTC resistance heater
DE2816593A1 (en) * 1978-04-17 1979-10-18 Siemens Ag Doped barium titanate PTC resistor tube - which occupies less space than an equiv. disc PTC resistor
GB2146488A (en) * 1983-09-09 1985-04-17 Tdk Corp A ptc resistor device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3996447A (en) * 1974-11-29 1976-12-07 Texas Instruments Incorporated PTC resistance heater
DE2816593A1 (en) * 1978-04-17 1979-10-18 Siemens Ag Doped barium titanate PTC resistor tube - which occupies less space than an equiv. disc PTC resistor
GB2146488A (en) * 1983-09-09 1985-04-17 Tdk Corp A ptc resistor device

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2222311B (en) * 1988-08-26 1993-04-28 Dale Electronics Surface mount wirewound resistor and method of making the same
GB2222311A (en) * 1988-08-26 1990-02-28 Dale Electronics Resistor with terminal pads for surface mounting
EP0429633A1 (en) * 1989-06-19 1991-06-05 Dale Electronics Thermistor and method of making the same.
EP0429633A4 (en) * 1989-06-19 1992-12-23 Dale Electronics, Inc. Thermistor and method of making the same
EP0522863A1 (en) * 1991-07-12 1993-01-13 Daito Communication Apparatus Co. Ltd. Positive temperature coefficient device
GB2265761B (en) * 1992-03-30 1996-07-17 Dale Electronics Bulk metal chip resistor
DE4310288B4 (en) * 1992-03-30 2005-11-10 Vishay Dale Electronics, Inc. (n.d.Ges.d. Staates Delaware), Columbus Surface mountable resistor
US6651315B1 (en) 1992-07-09 2003-11-25 Tyco Electronics Corporation Electrical devices
WO1994001876A1 (en) * 1992-07-09 1994-01-20 Raychem Corporation Electrical devices
US5852397A (en) * 1992-07-09 1998-12-22 Raychem Corporation Electrical devices
US7355504B2 (en) 1992-07-09 2008-04-08 Tyco Electronics Corporation Electrical devices
US6292088B1 (en) 1994-05-16 2001-09-18 Tyco Electronics Corporation PTC electrical devices for installation on printed circuit boards
US5952911A (en) * 1996-10-09 1999-09-14 Murata Manufacturing Co., Ltd. Thermistor chips and methods of making same
US6100110A (en) * 1996-10-09 2000-08-08 Murata Manufacturing Co., Ltd. Methods of making thermistor chips
US6081181A (en) * 1996-10-09 2000-06-27 Murata Manufacturing Co., Ltd. Thermistor chips and methods of making same
US6640420B1 (en) 1999-09-14 2003-11-04 Tyco Electronics Corporation Process for manufacturing a composite polymeric circuit protection device
US20100090332A1 (en) * 2008-10-09 2010-04-15 Joinset Co., Ltd. Ceramic chip assembly

Also Published As

Publication number Publication date
FR2620561A1 (en) 1989-03-17
FR2620561B1 (en) 1992-04-24

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