JPH0580540B2 - - Google Patents

Description

[Detailed description of the invention]

``Object of the Invention'' The present invention relates to an aluminum alloy for lead frames, and an object of the present invention is to provide an aluminum alloy for lead frames that has good strength, hardness, and bending workability after thermal annealing and is inexpensive. Industrial Application Fields Aluminum alloys for lead frames in devices such as ICs and LEDs that use semiconductors as elements. Conventional technology Devices that use semiconductors, such as ICs, LSIs, and LEDs, are made of semiconductor pellets, leads, and bonding wires that are sealed with ceramics or resin, and come in various formats. is used. However, after the lead frames used in this type of equipment are press-punched from a thin plate and formed into a predetermined shape, they are coated with molten solder material to facilitate assembly. Receive history. By the way, the conventional lead frame materials for these devices are:
Kovar (Fe-29%Ni-17%) is used as an iron-based material.
Co), Fe-42%Ni alloy, Fe-Ni alloy clad with Al, and 194% copper-based material.
Alloy (Cu-Fe-Zn-P system), 195 alloy (Cu-Fe
-Co-Sn-P system) etc. have been used. That is, the iron-based materials have excellent heat resistance, strength, etc.
Widely used in MOS type ICs, LSIs, etc., copper-based materials have good thermal conductivity and bendability, and are cheaper than iron-based materials, so they have recently become popular in power transistors, diodes, thyristors, etc. Widely used as lead frame material for individual semiconductors. In recent years, as the degree of integration continues to increase, copper alloys with low electrical resistance, high thermal conductivity, and high strength have been developed and are gradually being used in place of iron-based materials. In addition, it seems that the use of aluminum alloy as a material that is even cheaper than copper alloy is being considered in some cases. Problems to be Solved by the Invention However, the above-mentioned iron-based materials are quite expensive and have the disadvantages of poor thermal conductivity and corrosion resistance. In this regard, copper-based materials are cheaper than iron-based materials and have excellent thermal conductivity and bendability, but they are inferior to iron-based materials in terms of heat resistance and strength, and are also relatively expensive. I have no choice but to do so. Aluminum alloys are the most advantageous in terms of cost, but have the problem of low mechanical properties such as hardness after heat treatment and repeated bending resistance. "Structure of the invention" Means for solving the problem Cu: 3.0 to 6.5 wt%, Mg: 0.02 to 1.7 wt%, Si:
Contains 0.02-0.5wt%, Mn: 0.20-1.2wt%, Cr: 0.10-0.30wt%,
An aluminum alloy for lead frames, characterized in that one or more of Zr: 0.05 to 0.25 wt% and V: 0.05 to 0.20 wt% are added, and the remainder consists of Al and inevitable impurities. Effect By containing Mg, Si, and Cu above the lower limit, Mg ₂ Si, Al−
It precipitates Cu-Mg phase and gives great strength through precipitation hardening. Also, by keeping these values below the upper limit, deterioration in bendability is avoided. Adding one or more of Mn, Cr, Zr, and V in an amount above the lower limit improves heat resistance and refines the crystal grain size, and adding below the upper limit reduces bendability. prevent. Example To further explain the present invention as described above, the present invention attempts to obtain the strength necessary for a lead frame material without increasing the price by incorporating Mg, Si, and Cu as described above. . In other words, these components deteriorate due to aging after solution treatment.
Mg ₂ Si, Al-Cu-Mg phases, etc. precipitate, and the precipitation hardening provides great strength. If the wt% (hereinafter simply referred to as %) of Mg is less than 0.02%, which is less than the upper limit of 0.05% as an impurity, sufficient strength cannot be obtained, while if it exceeds 1.7%, bendability deteriorates. With Si, the above strength cannot be obtained when the impurity content is below 0.02%, which is lower than the upper limit of 0.05%;
If it exceeds 0.02% to 0.5%, the strength will increase but the bendability will deteriorate. Under the above conditions, if Cu is less than 3.0%, sufficient strength cannot be obtained, while if it is added in excess of 6.5%, there is no further increase in strength, and the bendability deteriorates. ~6.5%. The preferred range is 3.0 to 6.2%. Mn, Cr, Zr, and V are added to improve heat resistance, and reduce crystal grain size to prevent surface roughness during press punching and the like. However, when these transition metal elements are dissolved in Al, the electrical conductivity and thermal conductivity decrease. Also, these elements include MnAl ₆ , AlMnSi, CrAl ₇ , ZrAl ₃ ,
Compounds such as VAl ₁₀ have the highest heat resistance when dispersed in a matrix as fine particles. If Mn is less than 0.20%, the heat resistance as in the upper part cannot be effectively obtained, while if it is more than 1.0%, coarse
MnAl ₆ particles are generated and the bendability deteriorates. If Cr is less than 0.10%, the above effect on heat resistance will be insufficient, while if it exceeds 0.30%, the
CrAl ₇ particles are generated and the bendability deteriorates. In order to obtain the above heat resistance, Zr has a poor effect if it is less than 0.05%, and if it is more than 0.25%, coarse _ZrAl3 particles are generated and the bendability is deteriorated, so Zr should be added in an amount of 0.05 to 0.25%. did. If V is less than 0.05%, sufficient heat resistance cannot be obtained, and if it is more than 0.20%, coarse VAl ₁₀ particles are generated and the bendability is deteriorated. The material according to the present invention may contain, in addition to the above-mentioned components, one or both of Ti and B, which are generally added for prevention of casting cracks and refinement of crystal grains. In particular, in the alloy of the present invention, these components have the effect of uniformly distributing the heat resistance-improving elements mentioned above, and these effects are as follows when Ti is 0.01
%, B is less than 0.001%, it is not sufficient, and Ti
exceeds 0.15% and B exceeds 0.01%, TiAl ₃ ,
Ti: 0.01~0.15% _{and B} : 0.001~0.
A suitable addition range is 0.01%. Further, as long as the impurities are in the range of Fe≦0.3% and Zn≦0.3%, the characteristics of the present invention will not be deteriorated. The production of lead frame materials using the alloy of the present invention is as follows:
It is melted in the same way as ordinary aluminum alloys, and the crystal refiners Ti and B described above are continuously added to the melting furnace or the molten metal transfer trough to the casting machine, and then non-containing substances such as oxides in the molten metal It is filtered to remove metal inclusions, and finally it is made into an ingot by semi-continuous casting such as DC casting or continuous casting and rolling such as Hunter casting. Next, the ingot is homogenized, hot rolled or cold rolled to form a plate of a predetermined thickness, and finally heat treated. Note that heat treatment may also be performed at an intermediate stage of rolling. A specific manufacturing example of the product according to the present invention will be described below. The Al-Cu-
Mg-based alloy is melted and cast into an ingot at 500℃.
After heating for 8 hours, it was hot rolled to a thickness of 5 mm. The alloy plate obtained in this way is then subjected to solution treatment of this rolled plate, and after water quenching, 0.5
It was cold rolled to a thickness of mm and then artificially aged at 200°C for 1 hour.

[Table] Regarding these boards, the
After heating at 275℃ for 30 seconds, strength, hardness,
The results of measuring the repeated bendability and conductivity of 90° bending are shown in Table 2 below. Those with no cracks even after three or more tests were evaluated as good, and those with cracks were evaluated as poor. Regarding the comprehensive evaluation, overall strength, hardness, and repeated bendability were judged and evaluated.

[Table] When used as a lead frame for LED,
The frame has a conductivity of 40 after heating at 275℃ x 30sec.
%IACS or less, preferably 35%IACS or less, and good reflectance over the entire wavelength range of visible light is required. Conventional copper alloy materials and iron-based materials that are plated with copper have poor reflectance on the short wavelength side of visible light, so they are plated with silver, but the material of the present invention as described above has good reflective properties. i.e. 0.38～
65~ for a normal finish plate in the wavelength range of 0.77μm
75%, and 75-80% can be obtained with bright finish board. Furthermore, for the soldering evaluation of the above-mentioned production examples and comparative examples, Sn was used as solder.
-Using Pb-based eutectic solder, ultrasonic soldering and dip-type soldering using flux were performed, and the evaluation results are as shown in Table 3.

[Table] "Effects of the Invention" According to the present invention as explained above, the heat resistance required for this type of lead frame, especially the strength, hardness, and bendability, are achieved in a favorable balance, and the stable state is excellent. Since the adhesive properties are also good, this invention is industrially very effective.

Claims (1)

[Claims] 1 Cu: 3.0 to 6.5 wt%, Mg: 0.02 to 1.7 wt%,
Contains Si: 0.02-0.5wt%, Mn: 0.20-1.0wt%, Cr: 0.10-0.30wt%,
An aluminum alloy for lead frames, characterized in that one or more of Zr: 0.05 to 0.25 wt% and V: 0.05 to 0.20 wt% are added, and the remainder consists of Al and inevitable impurities.