HK1104947A - Safety fuse for a chip - Google Patents

Description

Fuse protector for chip

Technical Field

The invention relates to a fuse cutout in the form of a chip, which is applied to a fuse cutout made of Al₂O₃Of ceramic compositionA carrier substrate with a fusible metal conductor which is applied and structured by means of thin-film technology and has a cover layer, and a cost-effective method for producing a chip fuse.

Background

The chip fuse is formed on the ceramic base material by means of methods known to the person skilled in the art, such as photolithography. Other support materials, such as FR-4 epoxy or polyimide, are also known. Chip fuses are typically designed for voltages up to 63V.

In order to avoid damage to other electronic components due to faults in the power supply, which cause overvoltages or too large currents, it is known to provide a fuse in the power supply. The fuse cutout is essentially composed of a carrier material and a metal conductor, for example composed of copper, aluminum or silver. The maximum possible current intensity that can flow through this conductor without melting it is determined by the geometry and cross-section of the conductor. If this value is exceeded, the electrical conductor melts due to the heat generated in its interior due to its electrical resistance and thus interrupts the supply of power before the downstream electronic component is overloaded or damaged.

In a method for producing a chip fuse using thick-film technology, in which a fuse element and a contact layer are applied as a paste to a substrate base having a low thermal conductivity using screen printing, sufficient precision in the geometry of the fuse element layer can only be achieved inadequately as a result of the screen printing method, depending on the process. For thick layer fuses of higher value, the fuse element or the fusible metal conductor must therefore be processed by means of an additional laser cutting method.

Generally, will be glazed over the entire surface with high Al₂O₃A proportional ceramic substrate, or a ceramic substrate with low alumina content with low thermal conductivity, is selected as the substrate base. The two types of substrates are more than those used for the production of passive components, for example, made of 96% Al₂O₃By thick film quality groupsConventional ceramic substrates are significantly more expensive.

In a method for producing a fuse element using thin-film technology, a fusible metal conductor is applied by electrochemical methods or by sputtering. In this case, a particularly high precision of the disconnection or fusing behavior is achieved by photolithographic structuring of the sputtered layers, in which case a substrate with a low aluminum oxide content with a low thermal conductivity is used as a base.

JP2003/173728A discloses a method for manufacturing a chip fuse using thin-film technology, wherein a fuse 14 and a cover layer 15 are arranged on a substrate 11. Fuse cutout 14 is structured using photolithography. Substrate 11 has a low thermal conductivity such that it does not conduct heat in electrical conductor 14 caused by the current flowing through electrical conductor 14 and thus facilitates melting of electrical conductor 14. The electrical conductor 14 is in direct contact with the substrate 11.

JP2002/140975a describes a fuse comprising a metal conductor 14 composed of silver, which is also arranged directly on a substrate 11 having a low thermal conductivity, wherein the metal conductor 14 is deposited galvanically or is formed as a thick layer.

JP2003/151425A discloses a fuse comprising a glass ceramic substrate 11 with low thermal conductivity and a metal conductor 14 using thick film technology.

JP2002/279883a also describes a fuse for chips, in which the fusible regions 17 of the conductor 15 are produced by complex laser machining. This requires additional time-consuming and costly processing steps.

JP2003/234057a discloses a safety resistor comprising a resistor 30 on a substrate 10, wherein an additional thermal storage layer 42 is provided between the resistor 30 and the substrate 10 to store heat generated in the resistor 30. The fusible areas are also produced by laser machining.

JP08/102244a describes a fuse 10 using thick-film technology, which fuse comprises a glass layer 2 with low thermal conductivity, wherein the glass layer 2 is arranged on a ceramic substrate 1 and a fuse 3 is applied to the glass layer 2.

JP10/050198A discloses another fuse with a complex layer structure using thin-film technology, in which a further elastic silicone layer 6 is formed on the conductor 3 and the glass layer 5.

DE19704097a1 describes an electrical fuse element with a fuse conductor using thick-film technology and a carrier, wherein the carrier consists of a material with poor thermal conductivity, in particular a glass ceramic.

DE69512519T2 discloses a surface-mounted fuse in which a laminar fuse conductor is arranged on a substrate and the substrate is preferably FR-4 epoxy or polyamide.

Thus, on the one hand, it is known to use special ceramics or even Al with thick-film technology₂O₃Methods for producing chip fuses using ceramic and insulating intermediate layers and, on the other hand, also chip fuses using thin-film technology using special ceramics or other special carrier materials are known.

Disclosure of Invention

Objects, solutions, and advantages

It is therefore an object of the present invention to provide a generic fuse protector which can be produced cost-effectively and with sufficient precision, wherein its fusing behavior can be determined precisely. Additionally, a method of manufacturing a fuse cutout will be provided.

These objects are achieved by the features of claim 1 or 11.

The core concept of the invention is to combine the advantages of the cost-effective production method of passive components with the advantages of thin-film technology and precision-photolithography structuring, in Al₂O₃The use of a thermal insulating interlayer on the ceramic is achieved in combination with thin film technology and precision photolithographic structuring.

The core concept of the invention is therefore to provide an intermediate layer between the cost-effective ceramic substrate as a carrier with high thermal conductivity and the actual fusible metal conductor, which is formed by a cost-effective method, preferably a low-melting inorganic glass paste applied in an island printing method (Inseldruck), or by an organic layer applied in an island printing. Due to the low thermal conductivity of this intermediate layer, the heat generated in the metal conductor by the current flowing through it is not conducted away downwards through the carrier substrate, which has a generally higher thermal conductivity, so that the conductor melts in the desired manner at a defined current density in the conductor. This interlayer serves as a thermal insulator. A low-melting inorganic glass paste is preferably used as intermediate layer, which is applied to the carrier substrate, in particular in a screen-printing process. This offers a significant advantage over other substrates with low thermal conductivity, since the latter can be provided or produced almost exclusively as a special production form, while, on the contrary, with the application of glass islands as an insulating interlayer, it is now possible to use standard ceramics which are advantageous in terms of price, where even those with only moderate surface properties (thick-film quality) can be used. In an alternative embodiment, the intermediate layer is an organic intermediate layer which is applied in particular in island printing and is subsequently fired or cured by the action of heat into the carrier substrate in a manner known to the person skilled in the art. In this case, any shaping of the intermediate layer, and Al can also be obtained by a simple island printing process₂O₃Ceramics may be used as support material.

The advantage of the invention is that standard ceramics which are cost-effective, insulating interlayers which can be produced cost-effectively by means of screen printing methods can be combined with the advantages of thin-film technology and photolithographic structuring. In this way, a fuse cutout for protecting an electronic component against fault currents with a cutout can be produced in a miniaturized embodiment with high precision and cost.

Advantageous embodiments of the invention are characterized in the dependent claims.

Alumina substrates, which are advantageously used as carrier substrates for fuse fuses, are available at low cost and in any shape and size from almost all manufacturers of ceramic substrates of this type and are used, for example, in mass production by resistor manufacturers. This type of alumina ceramic substrate may already have pre-scribes in the shape of chips that are provided by the manufacturer to be subsequently fabricated from the substrate. In both embodiments described above, the intermediate layer is applied, for example, in the pre-scored region predetermined by the manufacturer, in order to separate the carrier substrate in a known manner during the subsequent chip separation process without damaging the intermediate layer as a result of the breaking process.

To improve the adhesion of the metal conductor to the intermediate layer, an inorganic or organic adhesion promoter layer can be applied directly to the intermediate layer by spraying or by sputtering.

In an advantageous embodiment, the metal conductor is formed by a low-resistance metal layer, in order to be able to set the melting point of the fuse cutout precisely.

In a first embodiment, this metal layer is applied to the intermediate layer or adhesion promoter layer by sputtering. If the sputtered metal layer is applied to a carrier substrate which is glazed over the entire surface, this leads to reduced adhesion, so that delamination of the metal layer in the pre-contact region can occur during the separation by fracture. Since the smooth surface is produced by these glass islands in the area of the fuse, the photolithographic structuring of the fuse can be carried out particularly precisely, since, in contrast, the carrier substrate composed of a ceramic with poor thermal conductivity has a higher surface roughness, which is disadvantageous for the precise photolithographic structuring, so that a good adhesion of the metal layer in the contact area to the rougher aluminum oxide ceramic is ensured by applying the metal layer to the heat insulation islands in the form of an intermediate layer with low thermal conductivity.

To structure the metal conductor in the form of the desired fuse, it is proposed that this be done by positive or negative photolithography. In a positive photolithographic process, for example, a metal layer, such as copper, is deposited over the entire surface of the underlying layer, and the desired structures are then photolithographically etched into the layer. In a negative-working lithographic process, a photoresist is first deposited, for example sprayed, onto the underlying layer, i.e. the intermediate layer or the adhesion promoter layer, and subsequently structured photolithographically in the desired manner. Subsequently, a metal layer, such as a sputtered copper film, is deposited thereon, and the remaining photoresist regions containing the metal film thereon are stripped.

To protect the fuse, one or more cover layers, which may also be formed in particular from inorganic barrier layers, are applied coveringly to the metal conductor or preferably to the entire fuse. The organic cover layer is in particular a polyamide, polyimide or epoxy, and can also be embodied in multiple layers.

For the contact-making of the fuse, the end contact of the metal conductor is produced by galvanic deposition of a metal barrier layer, typically consisting of nickel, and a final layer, which can be soldered or glued, typically consisting of tin or a tin alloy.

Detailed Description

In the following, the invention is explained in more detail on the basis of the drawings.

FIG. 1: a method of manufacturing a fuse cutout using six steps is shown.

In the method of manufacturing the fuse cutout 100 shown in fig. 1, the insulating interlayer 11 is first deposited (step b)) in island form on the carrier substrate 10 (step (a)), preferably an alumina ceramic. An adhesive layer 12 for improving the adhesion of the metal conductor 13 to the base is applied to this intermediate layer 11 and the surrounding carrier substrate 10 (step c)). Subsequently, a metal conductor 13 is applied to the adhesion layer 12, for example a copper layer is sputtered on, and structured in a desired manner by photolithography (step d)).

The maximum current flow is predetermined here by the thickness and width of the bridge piece (Steg) in the central region of the metal conductor 13, and if this maximum current flow is exceeded, this bridge piece melts and thus protects the other electronic components from damage. The thermal conduction into the carrier substrate 10 is strongly suppressed by the thermally insulating intermediate layer, so that the melting point of the fuse cutout 100 can be precisely determined.

Subsequently, the fuse protector 100 or the central region of the metal conductor 13 is covered with an organic cover layer 14, such as polyamide or epoxy, to protect the fuse protector 100 from damage.

For contacting, the end contacts 15 of the metal conductors 13 are plated, for example, with nickel and tin.

List of reference numerals

100 fusing safety device

10 carrier substrate

11 intermediate layer

12 adhesive layer

13 metallic conductor

14 coating layer

15 end contact

Claims (20)

1. Fuse (100) in the form of a chip structure having a fusible metal conductor (13) on a carrier substrate (10) made of ceramic, the metal conductor (13) being applied and structured using thin-film technology and having a cover layer (14), characterized in that the carrier substrate (10) is Al with a high thermal conductivity₂O₃Ceramic, wherein an intermediate layer (11) having a low thermal conductivity is arranged between a carrier substrate (10) and a metal conductor (13), and the intermediate layer (11) is a low-melting inorganic glass paste, preferably applied in a screen-printing method, or an organic intermediate layer (11), havingThe organic intermediate layer (11) is preferably applied in island printing, and the fusible metal conductor (13) is applied by sputtering or vapor diffusion coating and structured using lithographic techniques.

2. A fuse protector as claimed in claim 1 characterised in that the carrier substrate (10) is of alumina ceramic of thick or thin film quality.

3. A fuse protector as claimed in claim 1 or 2 characterised in that an adhesive layer (12) is provided on the intermediate layer (11).

4. A fuse protector as claimed in any one of claims 1 to 3 characterised in that the metal conductor (13) is formed from a low resistance metal layer.

5. A fuse element as claimed in any one of claims 1 to 3, characterised in that the metal conductor (13) is formed of low resistance Cu, Au, Ag, Sn or a Cu-, Au-, Ag-, Sn-alloy.

6. A fuse protector according to claim 4 characterised in that the metal layer is preferably sputtered by vacuum means, vapour diffusion coated or deposited by other physical or chemical means.

7. A fused fuse device as claimed in any one of claims 1 to 6 characterised in that the metal conductor (13) is structured using positive or negative lithographic methods.

8. A fuse protector as claimed in any one of claims 1 to 8 characterised in that the cover layer (14) is formed on the metal conductor (13) from an inorganic or organic layer, in particular from polyamide, polyimide, polyamideimide or epoxy, and in particular is formed as a multilayer.

9. A fuse protector as claimed in any one of claims 1 to 8 characterised in that an inorganic barrier is formed between the cover layer (14) and the metal conductor (13).

10. A fuse protector according to any of claims 1-9 characterised in that the end contacts (15) of the fuse protector (100) are formed by dipping or preferably by galvanic deposition, in particular of copper, nickel, tin and tin alloys.

11. Method for producing a fuse (100) in the form of a chip design, in which method

-applying an intermediate layer (11) with low thermal conductivity onto a carrier substrate (10) consisting of an Al2O3 ceramic with high thermal conductivity,

-the intermediate layer (11) is formed by a low-melting inorganic glass paste applied in a screen printing method or by an organic intermediate layer (11) applied in island printing,

-applying a metal conductor (13) onto the intermediate layer (11),

-applying a cover layer (14) onto the metal conductor (13).

12. Method according to claim 11, characterized in that Al is of thick or thin film quality₂O₃An alumina ceramic is used as a carrier substrate (10).

13. Method according to claim 11 or 12, characterized in that an adhesive layer (12) is applied to the intermediate layer (11).

14. A method according to any of claims 11-13, characterized in that the metal conductor (13) is formed by a low-resistance metal layer.

15. A method according to claim 14, characterized in that the metal layer is sputtered, preferably by vacuum, vapor-deposited or deposited by other physical or chemical means.

16. Method according to claim 14, characterized in that the metal layer is formed of low-resistance Cu, Au, Ag, Sn or Cu-, Au-, Ag-, Sn-alloys.

17. A method according to any of claims 11-15, characterized in that the metal conductor (13) is structured using a positive or negative lithographic method.

18. Method according to any one of claims 11 to 17, characterized in that the cover layer (14) is formed from an inorganic or organic layer, in particular from polyamide, polyimide, polyamideimide or epoxy, and may also be formed in multiple layers.

19. A method according to any one of claims 11-17, characterized in that an inorganic barrier layer is formed between the covering layer (14) and the metal conductor (13).

20. Method according to one of claims 11 to 18, characterized in that the end contact (15) of the fuse cutout (100) is formed by dipping or preferably by galvanic deposition, in particular from galvanic deposition of copper, nickel, tin or tin alloys.