GB2419137A

GB2419137A - Solder alloy

Info

Publication number: GB2419137A
Application number: GB0422997A
Authority: GB
Inventors: Gary Cunning; Anthony Ingham
Original assignee: Alpha Fry Ltd
Current assignee: Fernox Ltd
Priority date: 2004-10-15
Filing date: 2004-10-15
Publication date: 2006-04-19
Also published as: GB2433944A; CN101120109A; WO2006040582A1; GB2433944B; GB0709021D0; GB0422997D0; CN100591459C

Abstract

A solder alloy for use in the manufacture of electrical fuses, the alloy comprising: <TAB CO=3 CS="A S"> <ROW><TSB>Copper<CEL AL=C>-<CEL AL=L>from 0.5 to 4 wt.% <ROW><TSB>Silver<CEL AL=C>-<CEL AL=L>from 0.1 to 1 wt.% <ROW><TSB>Antimony<CEL AL=C>-<CEL AL=L>from 0 to 3 wt.% <ROW><TSB>Bismuth<CEL AL=C>-<CEL AL=L>from 0 to 1.5 wt.% <ROW><TSB>Zinc<CEL AL=C>-<CEL AL=L>from 0 to 2 wt.% <ROW><TSB>Nickel<CEL AL=C>-<CEL AL=L>from 0 to 0.3 wt.% <ROW><TSB>Phosphorus<CEL AL=C>-<CEL AL=L>from 0 to 0.01 wt.% <ROW><TSB>Indium<CEL AL=C>-<CEL AL=L>from 0 to 0.2 wt.% <ROW><TSB>Germanium<CEL AL=C>-<CEL AL=L>from 0 to 0.1 wt.% </TAB> <PC>and the balance tin, together with unavoidable impurities, provided that if the silver content is 0.5 wt.% or less, then copper is present in an amount of not less than 0.9 wt.% or more and/or antimony is present in an amount of not less than 0.2 wt.% or more and/or bismuth is present in an amount of not less than 0.1 wt.%.

Description

Solder Alloy The present invention relates to an alloy and, in particular,

a lead-free solder alloy. The alloy is particularly, though not exclusively, suitable for use in the manufacture of electrical fuses.

Electrical fuses are supplied in many forms including the type where a current is passed along a fine wire. If the threshold current is exceeded, then the wire melts and the fuse fails. The fuse wire typically runs though a glass or ceramic tube. End caps (for example nickel coated brass caps) are fitted over the ends of the tube to form terminations.

In the bottom of each cap there may be provided a melted slug of cored solder wire, which performs the dual function of sealing the tube and providing a solder joint to the fuse wire. An example of a conventional solder composition is a tin-lead alloy comprising 35 - 50 wt% tin.

Such an alloy starts to melt at a temperature of about 183 C, but melting is not complete until a higher temperature (about 230 C) has been reached. At an intermediate temperature falling between these two limits, the solder is "pasty" and, as a consequence, relatively immobile. This property is important for processes such as fuse manufacture where the joint may have to be made with the cap inverted so that a fluid solder can run under gravity. Alternatively, if the cap and tube are pressed together so that there is a sudden movement, then a fluid solder may splash up the wire or tube.

For environmental reasons, there is an increasing demand for lead-free replacements for lead-containing conventional alloys. Many lead-free alloys are tin rich, with small additions of elements such as copper, silver, bismuth, indium, antimony and zinc, for example. Lead-free alloys have been developed for use in the electronics industry, although these alloys generally do not exhibit a significant "pasty" range, which, as mentioned above, is an important characteristic for alloys used in the manufacture of electrical fuses.

The present invention aims to address at least some of the problems associated with the prior art. Accordingly, the present invention provides an alloy for use in the manufacture of electrical fuses, the alloy comprising: Copper - from 0.5 to 4 wt.% Silver - from O.l to l wt.% Antimony - from O to 3 wt.% Bismuth - from O to 1.5 wt.% Zinc from O to 2 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to O.Ol wt.% Indium from O to 0.2 wt.% Germanium - from O to O.l wt.% and the balance tin, together with unavoidable impurities, provided that if the silver content is 0.5 wt.% or less, then copper is present in an amount of not less than 0.9 wt.% or more and/or antimony is present in an amount of not less that 0.2 wt.% and/or bismuth is present in an amount of not less than O.l wt.%.

In a first preferred aspect, the alloy comprises: Copper - from 1.5 to 3 wt.% Silver - from 0.2 to 0.6 Antimony - from 0.5 to 2 wt.% Bismuth - from 0.5 to 1.5 wt.% Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.

More preferably in this aspect the alloy comprises: Copper - 1.8 to 2.2 wt.% Silver - 0.3 to 0.5 wt.% Antimony - 0.7 to 1.5 wt.% Bismuth - 0.5 to 1.3 wt.% Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium - from O to 0. 03 wt.% and the balance tin, together with unavoidable impurities.

and the balance tin, together with unavoidable impurities.

Still more preferably in this aspect the alloy comprises: Copper approximately 2 wt.% Silver - approximately 0.4 wt.% Antimony approximately 1 wt.% Bismuth - approximately 1 wt.% and the balance tin, together with unavoidable impurities.

In a second preferred aspect, the alloy comprises: Copper - from 1.5 to 3 wt.% Silver - from 0.2 to 0.6 wt.% Antimony - from 0.5 to 2 wt.% Bismuth from O to 0.5 wt.% Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.

lO More preferably in this aspect the alloy comprises: Copper - 1.8 to 2. 2 wt.% Silver - 0.3 to 0.5 wt.% Antimony - 0.7 to 1.5 wt.% Bismuth - O to 0.5 wt.% Is Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium - from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.

Still more preferably in this aspect the alloy comprises: Copper approximately 2 wt.% Silver - approximately 0.4 wt.% Antimony approximately 1 wt.% and the balance tin, together with unavoidable impurities.

In a third preferred aspect, the alloy comprises: Copper - from 1.5 to 3 wt.% Silver - from 0.3 to 1 wt.% Antimony - from 0.3 to 1 wt.% Bismuth from 0.1 to 0.5 wt.% Zinc from O to 0.5 wt.% - s - Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium - from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.

More preferably in this aspect the alloy comprises: Copper - 1.8 to 2.2 wt.% Silver - 0.6 to 0.8 wt.% Antimony - 0.4 to 0.6 wt.% lo Bismuth - 0.2 to 0.4 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium - from O to 0.03 wt.% Is and the balance tin, together with unavoidable impurities.

Still more preferably in this aspect the alloy comprises: Copper approximately 2 wt.% Silver - approximately 0.7 wt.% Antimony approximately 0.5 wt.% Bismuth - approximately 0.3 wt.% and the balance tin, together with unavoidable impurities.

In a fourth preferred aspect, the alloy comprises: Copper - from 0.5 to 2. 5 wt.% Silver - from 0.3 to 0.7 wt.% Antimony - from O to 0.5 wt.% Bismuth - from 0.1 to 0.4 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium - from O to 0. 03 wt.% and the balance tin, together with unavoidable impurities.

More preferably in this aspect the alloy comprises: Copper - 0.7 to 1.3 wt.% Silver - 0.4 to 0.6 wt.% Antimony - O to 0.5 wt.% Bismuth - 0.1 to 0. 3 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% lO Germanium - from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.

Still more preferably in this aspect the alloy comprises: Copper approximately 1 wt.% Silver - approximately 0.5 wt.% Bismuth approximately 0.2 wt.% and the balance tin, together with unavoidable impurities.

The alloys according to the present invention are lead- free or essentially lead-free. These alloys offer environmental advantages over conventional alloys used in the manufacture of electrical fuses.

The alloys according to the present invention are suitable for use in the manufacture of electrical fuses. In particular, the alloys are advantageously used for (i) sealing/joining an end cap to a tube for an electrical fuse, and/or (ii) providing a solder joint between an end cap and a fuse wire. In particular, the alloys according to the present invention have the property of being "pasty" within a sufficiently broad temperature range intermediate between the temperature at which the alloy is fully molten and the temperature at which the alloy is fully solidified.

While not wishing to be bound by theory, it is believed that the alloying elements Cu. Ni, Sb, Zn and Bi may act to form intermetallics. The presence of intermetallics is believed to have a positive effect on the flow properties of the alloys, particularly in relation to the "pasty" range.

While not wishing to be bound by theory, it is believed that alloying elements Ag, Bi and Zn act to widen the ]O temperature difference between liquidus and solidus, and increase the residual liquid phase just above the solidus.

This is believed to have a positive effect on the mechanical properties of the alloys, particularly in relation to the "pasty" range.

The alloys according to the present invention will typically be provided in the form of a wire, preferably a cored wire, which incorporates a flux. The wire is preferably made by the conventional techniques of extrusion and drawing. Accordingly, the alloys according to the present invention posses mechanical properties that are compatible with extrusion and wire drawing processes.

The alloys according to the present invention may also be provided in the form of sphere or a preform cut or stamped from a strip or solder. These may be alloy only or coated with a suitable flux as required by the soldering process. The alloys may also be supplied as a powder blended with a flux to produce a solder paste.

If the bismuth level is too high, the alloy can become difficult to draw. The bismuth level therefore preferably does not exceed 0.5 wt.%.

If the copper level is too high, the alloy can become more difficult to draw. The copper level therefore preferably does not exceed 2 wt.%.

Indium may be present in an amount of up to 0.2 wt.%, but preferably does not exceed 0.1% wt.%. The presence of indium can benefit the wetting properties of the alloys.

The alloys will typically comprise 94 to 99 % tin, more typically 95 to 98 % tin.

It will be appreciated that the alloys according to the present invention may contain unavoidable impurities, although, in total, these are unlikely to exceed l wt.% of the composition. Preferably, the alloys contain unavoidable impurities in an amount of not more than 0.5 wt.% of the composition, more preferably not more than 0.3 wt.% of the composition.

The alloys according to the present invention may consist essentially of the recited elements. It will therefore be appreciated that in addition to those elements which are mandatory (i.e. Sn, Cu and Ag) other nonspecified elements may be present in the composition provided that the essential characteristics of the composition are not materially affected by their presence.

The present invention also provides an electrical fuse comprising a fuse wire, a tube for the fuse wire, and at least one end cap for the tube, wherein the end cap is at least partially joined and/or sealed to the tube by virtue of a solder alloy as herein described. The present invention also provides an electrical fuse comprising a fuse wire, a tube for the fuse wire, and at least one end cap for the tube, wherein the fuse wire is joined to the end cap by a solder alloy as herein described.

The present invention also provides a process for making an electrical fuse comprising: (a) providing a fuse wire, a tube for the fuse wire, and at least one end cap for the tube, 1S (b) providing a solder alloy as herein described, (c) placing the solder alloy in the end cap (d) joining the fuse wire to the end cap by contacting the fuse wire with the solder alloy in the end cap, and heating the solder alloy whereby a solder joint is formed between the end cap and the fuse wire. The process may further involve at least partially sealing the end cap by placing the end cap over one end of the tube, heating the solder alloy in the end cap, and applying pressure to the tube and end cap whereby the solder alloy contacts and fills an end portion of the tube and at least partially seals any space between an outer wall of the tube and an inner wall of the cap.

It will be appreciated that the alloys according to the present invention preferably possess adequate wetting characteristics to enable them to be used for the desired purpose.

- lo -

Examples

The following alloys were found to exhibit the characteristic of being "pasty" within a sufficiently broad temperature range intermediate between the temperature at which the alloy is fully molten and the temperature at which the alloy is fully solidified. These alloys could be also be formed into a cored wire by conventional techniques and, furthermore, possessed good "wetting" characteristics.

Eg 1: 97.0Sn - 2.0Cu - 1.0Sb - 1.OBi - 0.4Ag Eg 2: 97.0Sn - 2.0Cu - 1.OSb - 0.4Ag Eg 3: 96.5Sn - 2.0Cu - 0.7Ag - 0.5Sb - 0.3Bi Eg 4: 98.8Sn - 1.0Cu - 0.5Ag - 0.2Bi The properties of these alloys make them suitable for use in sealing/joining an end cap to a tube for an electrical fuse, and providing a solder joint between an end cap and a fuse wire.

The following alloys are provided by way of comparison.

CEg 1: 97.0Sn - 3.0Cu CEg 2: 98.0Sn - 2.0Cu CEg 3: 99.0Sn - 0.7Cu - 0.3Ag Each of these alloys is characterized by being too fluid, i.e. exhibiting an insufficient "pasty" range. The properties of CEg 3 can be improved by the addition of antimony or bismuth. - I 1

CEg 4: Sn - Zn Tin-Zinc alloys were found to have poor wetting characteristics.

CEg 5: 94.4Sn - 2Cu - l.OSb - 2.OBi 0.6 - Ag This alloy proved difficult to draw into a wire.

Claims

CLAIMS: 1. An alloy for use in the manufacture of electrical fuses, the

alloy comprising: Copper - from 0.5 to 4 wt.% Silver - from 0.1 to 1 wt.% Antimony - from O to 3 wt.% Bismuth - from O to 1.5 wt.% Zinc from O to 2 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium from O to 0.2 wt.% Germanium - from O to 0.1 wt.% and the balance tin, together with unavoidable impurities, provided that if the silver content is 0.5 wt.% or less, then copper is present in an amount of not less than 0.9 wt.% or more and/or antimony is present in an amount of not less that 0.2 wt.% and/or bismuth is present in an amount of not less than 0.1 wt.%.
2. An alloy as claimed in claim 1 comprising: Copper - from 1.5 to 3 wt.% Silver - from 0.2 to 0.6 Antimony - from 0.5 to 2 wt.% Bismuth - from 0.5 to 1.5 wt.% Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium - from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.
3. An alloy as claimed in claim 2 comprising: Copper - 1.8 to 2.2 wt.% Silver - 0.3 to 0.5 wt.% Antimony - 0.7 to 1.5 wt.% Bismuth - 0.5 to 1.3 wt.% Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium - from O to 0. 03 wt.% and the balance tin, together with unavoidable impurities.
4. An alloy as claimed in claim 1 comprising: Copper - from 1.5 to 3 wt.% Silver - from 0.2 to 0.6 wt.% Antimony - from 0.5 to 2 wt.% Bismuth - from O to 0.5 wt.% Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.
5. An alloy as claimed in claim 4 comprising: Copper - 1.8 to 2.2 wt.% Silver - 0.3 to 0.5 wt.% Antimony - 0.7 to 1.5 wt.% Bismuth - O to 0.5 wt. % Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium - from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.
6. An alloy as claimed in claim 1 comprising: Copper - from 1.5 to 3 wt.% Silver - from 0.3 to 1 wt.% Antimony - from 0.3 to 1 wt.% Bismuth - from 0.1 to 0.5 wt.% - Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.
7. An alloy as claimed in claim 6 comprising: Copper - 1.8 to 2.2 wt.% Silver - 0.6 to 0.8 wt.% Antimony - 0.4 to 0.6 wt.% Bismuth - 0.2 to 0.4 wt.% Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to 0.01 wt.% Indium - from O to 0.2 wt.% Germanium - from O to 0. 03 wt.% and the balance tin, together with unavoidable impurities.
8. An alloy as claimed in claim 1 comprising: Copper - from 0.5 to 2.5 wt. % Silver - from 0.3 to 0.7 wt.% Antimony - from O to 0.5 wt.% Bismuth from O.l to 0.4 wt.% Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to O.Ol wt.% Indium - from O to 0.2 wt.% Germanium from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.
9. An alloy as claimed in claim 8 comprising: Copper - 0.7 to 1.3 wt.% Silver - 0.4 to 0.6 wt.% Antimony - O to 0.5 wt.% Bismuth - O.l to 0.3 wt. % Zinc from O to 0.5 wt.% Nickel - from O to 0.3 wt.% Phosphorus - from O to O.Ol wt.% Indium - from O to 0.2 wt.% Germanium - from O to 0.03 wt.% and the balance tin, together with unavoidable impurities.
lO. An electrical fuse comprising a fuse wire, a tube for the fuse wire, and at least one end cap for the tube, wherein the end cap is at least partly sealed to the tube by virtue of a solder alloy as defined in any one of claims l to 9.
ll. An electrical fuse comprising a fuse wire, a tube for the fuse wire, and at least one end cap for the tube, wherein the fuse wire is joined to the end cap by a solder alloy as defined in any one of claims l to 9.
12. A process for making an electrical fuse, the process comprising: (a) providing a fuse wire, a tube for the fuse wire, and at least one end cap for the tube, (b) providing a solder alloy as defined in any one of claims 1 to 9, (c) placing the solder alloy in the end cap, (d) joining the fuse wire to the end cap by contacting the fuse wire with the solder alloy in the end cap and heating lO the solder alloy whereby a solder joint is formed between the end cap and the fuse wire.
13. A process as claimed in claim 12, wherein the process involves at least partially sealing the end cap by IS placing the end cap over one end of the tube, heating the solder alloy in the end cap, and applying pressure to the tube and the end cap, whereby the solder alloy contacts and fills an end portion of the tube and at least partially seals any space between an outer wall of the tube and an inner wall of the cap.
14. A cored solder wire comprising an alloy as defined in any one of claims 1 to 9.
15. A sphere or strip comprising an alloy as defined in any one of claims 1 to 9.
16. An alloy substantially as hereinbefore described with reference to any one of the Examples (excluding the Comparative Examples).