MXPA97005772A - Copper based alloy with electric conductivity and elevated adulted temperature for electronic applications - Google Patents

Abstract

The present invention relates to the use for the manufacture of supports for electronic circuit components intended to be welded with light alloy, glued and / or hot-pressed onto the support of a copper-based alloy containing a mass percentage of 0.1. to 1% nickel and from 0.005% to 0.1% phosphorus, the rest being copper or mainly copper

Description

COPPER-BASED ALLOY WITH ELECTRICAL CONDUCT AND ELEVATED ADULTED TEMPERATURE FOR APPLICATIONS IN ELECTRONICS DESCRIPTION OF THE INVENTION The present invention relates to alloys based on copper intended for application in the field of electronics, for the manufacture of component supports. Copper, an excellent well-known electrical conductor, is used in numerous applications specifically in electronics; it serves as a support for components of electronic circuits (lead frame) for the most diverse components and particularly electronic platelets. For the manufacture of the circuits, the components are usually welded with light alloy, p gatáos and / or inserted and then hot coated with a molding of plastic material on the copper support which must therefore resist the temperature and preserve its characteristics mechanical Due to this resistance to temperature (maintenance in restoration) alloys based on copper have been used; this allows to increase the maintenance in restoration while preserving good conduct. The maintenance in temperature, or what is known as restoration, corresponds to a mechanism that leads to the adulteration of the copper alloy by activating the annihilation of the dislocations by reheating at high temperature. The resistance to restoration is characterized by the maximum duration (for example, greater than 10 minutes) of a high temperature maintenance (for example 450 ° C) after which the hardness of the metal remains higher than a value imposed. The measured conductivity of the alloy gives the percentage corresponds to the conductivity of pure copper equal to 100K. This percentage of conduct is known as IACS con uctivity. For example, the Cu Sn 0.15 alloy is an alloy of copper and tin. The copper supports used in the electronics must not only offer a good mechanical resistance and a good temperature resistance but also have an excellent welding capacity and / or ability to weld with light alloy; for this purpose the copper alloy is coated with a nickel layer. This layer of nickel is applied to the alloy before cutting products such as supports. This translates into a significant amount of nickel-plated copper alloy wastes whose recovery is costly. It is necessary to use electrolysis to separate the copper from the nickel and recover it.

The object of the present invention is to improve the copper-based reactions intended for electronics to obtain alloys having a high temperature resistance and conductivity and which facilitate the recovery of manufacturing waste. For this purpose, the invention relates to the use for the manufacture of supports for electronic circuit components intended for welding with light alloy, glue and / or hot insertion on the support of copper-based alloy containing a mass percentage of 0.1. to VA of nickel and of 0.005 to 0.1% of phosphorus, the rest being copper or mainly copper. According to the present invention, an alloy of this type can also contain up to 0. VA of iron and / or up to 0.5% of zinc. This copper-based alloy has a good conductivity generally higher than 80% IACS in the plates of proposed compositions, as well as a good resistance in temperature, that is to say a resistance to the restoration, especially related to the addition elements: nickel phosphorus. The copper-based alloy according to the invention is also very interesting in the economic aspect since it facilitates the recycling of manufacturing scraps of supports or elements for the electronics, since in the case of alloy according to the present invention it is found coated with a layer of nickel. The mechanical characteristics of this alloy are especially interesting. The alloys according to the present invention offer numerous advantages. For example, its electrical conductivity is very good. It is easy to obtain an electrical conductivity higher than 70% IACS. It is even possible, as shown by the following; examples, ensure a conductivity greater than 80% IACS by varying the addition of phosphorus depending on the addition of nickel and iron, and limiting the contents of residual elements (zic, ....): special manufacturing ranges must be respected to optimize the annealing cycles and the formation of fine precipitates of NialfaPbeta. The residual nickel and phosphorus contents in solution, after the most thorough precipitation possible, ensure a very good resistance to the restoration: the adulterated ones remain very weak, as they show in the following, during the maintenance in a furnace beyond even 450 * C and would be negligible during welding, light alloy welding or plastic encapsulation at temperatures between 370 and 425 ° C. The precipitates formed (from N5P2 according to the most up-to-date or accurate Ni2P thermodynamic calculations according to the analyzes carried out by loss of energy in transmission microscopy) allow a significant hardening of the alloys of «oniness with the present invention. They increase the resistance to relaxation in parallel. The alloys according to the present invention are economical. They only use common addition elements. They also allow economic recycling of nickel-plated copper waste. Small amounts of impurities (zinc, silicon) can be tolerated: they degrade, according to known laws, the conductivity of the product. The marginal addition of other alloying elements such as iron (up to 1000 ppm but preferably less than 100 ppm) can allow the acceleration of the anneals, gain in terms of mechanical characteristics with little effect on the conductivity. The alloys according to the present invention are therefore particularly suitable for electronic applications (grids, power components, ...) and would replace with advantage the alloys co or for example Cu Sn 0.15. The alloy according to the present invention can be manufactured by means of casting processes usually employed for copper-based alloys. The particular process, chosen for casting the alloy, has no particularly critical influence on the product obtained. However, a prior homogenization of the alloy by putting it back into high temperature solution (800QC or more) of all the alloying elements is however desirable, particularly in the case of the addition of > iron for example. For the «production» of plates, it is possible, for example, to strain the alloy into strips, to mill it, and then, after a light cold shake, to subject it to a homogenization annealing (from 800 to 850 ° C for 1 approximately hour), followed by a tempering.

- It is also possible - and preferable - to cast this alloy in trays of cam dimensions, and then to laminate it first hot (from 650 to 1000 ° C, depending on the alloy elements) to a thickness of a few millimeters, and then cold . The alloy can then be cold rolled to the desired thickness with intermediate annealing DS. A greater possible reduction of at least 50% between the two successive anneals is preferred: the duration of each annealing thus decreases markedly to obtain an improved final conductance. The optimum annealing temperatures are between 400 and 600 ° C, with maintenance of the temperature of recovery for at least two hours and, if possible, four hours. More important durations generally ensure a more important conductivity, except in the unfavorable case of competitive precipitations of addition elements with phosphorus, for example. The present invention will now be explained on the basis of two exemplary embodiments of copper-based alloys. The results of the hardness and conductivity measurements appear in the attached figures 1 and 2. Figure 1 is a temperature resistance diagram at 425 ° C; on the abscissa, time is presented and on the ordinates the hardness HV. The diagram gives the curves of Cu Sn, Cu Ni 0.4, Cu Ni 0.2 and alloy FPG, that is to say a copper alloy containing between 950 and 1000 ppm of Fe and between 330 and 370 ppm «of P. The test consisted of rise to the temperature of 425 ° C and remain at this temperature for a period that extended beyond the scale of the diagram Figure 2 represents the conductivity curves for different SACS percentages, the abscissas represent the mass in ppm Ni and the ordinates the mass in ppm of P in the copper-based alloy EXAMPLE 1 The alloys according to this example are prepared in the following manner: Copper-phosphorus alloy cuts (Cu-bl), Cu-b2) coated with nickel are melted in a channel induction furnace: at the end of the fusion, from an analysis performed with a spectrometer, a phosphorus titration makes it possible to guarantee the desired composition. The melt is then kept for a few minutes at a temperature (approximately 1200 ° C) under an open reduction of charcoal. The casting is carried out in a water-cooled mold of 200 x 400 mm, for example. The CDm 'D i i n of the alloys prepared for this example is given in the following table. Ni P Fe Zn Cu Ni 0.2 2060 305 - 3200 Cu Ni 0.4 4410 300 - 800 (All these data are given in ppm by mass). Trays cast in this way fall back to a temperature above 840 ° C, and then hot rolled from 200 to 13 mm. They can then, at a temperature above 600 ° C, be tempered or not, which is indifferent. The roughing is then milled, then cold rolled to a thickness of 1.5 mm. An annealing under hood with maintenance at a temperature of 480'C for 4 hours was carried out. The hardness in the annealed state is between 54 and 57 HV. The conductivities of the alloys Cu Ni 0.4 and Cu Ni 0.2 measured in this state are respectively 78.1% IACS and 79.4% IACS.

High contents of residual zinc significantly affect conductivity. From the known effect of zinc in solution on conductivity, it can be said that it alloys Cu ions. Ni 0.2 and Cu Ni 0.4, which do not contain any other element of addition than nickel and phosphorus in the indicated contents, would have respectively 83% IACS and 79% IACS conducts. In this metallurgical state, after a further rolling reduction of 20%, the conductivity hardly changes, and the hardness reaches 1C7 to 110 HV. It is equivalent to the hardness obtained in the same conditions with a Cu Sn 0.15 alloy. At this level of cold beating, strip samples are annealed at different temperatures, from 360 to 480 * C, for 10 minutes. The low «of the hardness with the temperature in the case of the Cu Sn 0.4 alloy is on with the low of the hardness measured for an alloy Cu Si 0.15. The adulting temperature of the Cu Ni 0.4 alloy is higher than 460 ° C while the adulting temperature of the Cu Si alloy 0.15 is of the order of 440 ° C. EXAMPLE 2 New alloys, following this example, have been prepared in the manner indicated below. High purity copper is melted in a channel induction furnace: the alloying elements are supplied in the form of pure nickel, copper 85-15 phosphide and silicon metal until the expected composition is achieved . the melt is then kept at a temperature (about 1200 ° C or a charcoal cover) The composition is progressively modified to obtain a wide range of different alloys, pieces of the bath are sewn and cast for each new composition (diameter : 25 mm height: 40 m) The composition of each alloy prepared for this example is within the ranges listed in the table below: Ni P Fe Minimum 2870 I10 '10 0 maximum 4300 910 80 100 (All contents are given in ppm by mass.) Each of these pieces is homogenized by means of a maintenance at a temperature of 850 ° C for 1 hour followed by an annealing in water. 70% (height reduction) by applying it to the hydraulic press, they are then subjected to an annealing "in such a way that," so that, for each alloy, the maximum conductivity is reached. s correlations between these measured values of conductivity and the compositions of the alloys. These correlations also present the previous characterizations, recalled in the table "of Example 1. Lines of the same conductivity can then be plotted on the plane of the nickel and phosphorus compositions, outside" of any other element of addition, for copper alloys. nickel phosph «Dro pure. This results are shown in Figure 2.

Claims (4)

1. CLAIMS 1. The use for the manufacture of electronic circuit component supports intended for welding with light alloy, glue and / or hot insert on the support of a copper-based alloy containing the. In mass "from 0.1 to 1% of nickel and from 0.005 to 0.1% of phosphorus, the. remaining being either or p incipalmente • robre.
2. 2. The use in accordance with the rei indicates ion 1, characterized in that the alloy contains fine precipitates of NialphaPbeta.
3. 3. The use according to any of claims 1 and 2, wherein the alloy contains up to 0.1% iron.
4. 4. The use according to any of claims 1 to 3, characterized in that the alloy contains up to 0.5% zinc.