JPH0572455B2 - - 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 history, 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. something is being used. However, the lead frame used in this type of equipment is formed by press punching a thin plate into a predetermined shape, and then attaching the semiconductor, bonding the wire, thermosetting the resin, and applying molten solder material to facilitate assembly. It is coated and subjected to various thermal histories. By the way, the lead frame material for these devices has traditionally been Kovar (Fe-29%Ni-17), which is an iron-based material.
%Co), Fe-42%Ni alloy, Fe-Ni alloy clad with Al, and as a copper-based material.
194 alloy, (Cu-Fe-Zn-P system), 195 alloy (Cu-
Fe-Co-Sn-P system) etc. have been used. That is, the iron-based material has excellent heat resistance, strength, etc.
Widely used in MOS ICs, LSIs, etc., copper-based materials have good thermal conductivity and bendability, and are cheaper than iron-based materials. Widely used as lead frame material for semiconductors.
In recent years, with increasing integration, 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. Note that the use of aluminum alloy is being considered as a material that is even cheaper than some copper alloys, but it has not been put to practical use. Problems to be Solved by the Invention However, the iron-based materials described above are disadvantageous in that they are considerably expensive and have poor thermal conductivity and corrosion resistance. In this point, copper-based materials are cheaper than iron-based materials and have excellent thermal conductivity, corrosion resistance, and bendability.
It is inferior to iron-based materials in terms of heat resistance, strength, etc., and is also relatively expensive. Aluminum alloys are most advantageous in terms of cost, but have the problem of poor mechanical properties such as bendability. "Structure of the invention" Means for solving the problem Contains Mg: 3.0 to 6.0 wt%, Zn: 0.5 to 2.0 wt%, Cu: 0.1 to 0.5 wt%, and Mn: 0.20 to 1.0 wt%, Cr :0.05~0.30wt%, Zr: 0.05~0.25wt%, V: 0.05~0.20wt%, Ti: 0.01~0.15wt%, the total amount of one or more of these is 1.2wt%.
An aluminum alloy for lead frames, characterized in that it contains the following, with the remainder consisting of Al and impurities. Effect Strength can be improved by containing Mg: 3.0% or more, Zn: 0.5% or more, Cu: 0.1% or more.
Moreover, solderability is also improved. By setting Mg: 6.0% or less, Zn: 2.0% or less, Cu: 0.5% or less, bendability is maintained well, and in addition, Mn: 0.20% or more, Cr: 0.05% or more,
By containing one or more of Zr: 0.05% or more, V: 0.05% or more, and Ti: 0.01% or more, crystal grains are made finer and bending workability is improved. Mn: 1.0% or less, Cr: 0.30% or less, Zr: 0.25%
Hereinafter, V: 0.20% or less, Ti: 0.15% or less, and the total amount when these are added in combination is 1.2% or less to avoid deterioration of bending workability due to the formation of coarse compounds. By using aluminum as a base and containing each of the elements in the relationship as described above, a lead frame material can be provided at a lower cost than conventional materials and has preferable characteristics. Note that when the Mg content is 6.0% or less, the tendency to become sensitive to stress corrosion cracking is alleviated, and when the Zn content is 0.5% or more, the solderability is improved.
When Cu is 0.5% or less, corrosion resistance deteriorates completely. EXAMPLE To further explain the present invention described above, in the present invention, as mentioned above, by incorporating appropriate amounts of Mg, Zn, and Cu into aluminum, the strength necessary for a lead frame material can be achieved without increasing the price. This kind of appropriate amount of Mg,
Zn and Cu form a solid solution in Al and provide greater strength through solid solution strengthening and work hardening. In other words, in wt% (hereinafter simply referred to as %), Mg is 3.0
If the content is less than 3.0%, such effects cannot be obtained sufficiently, while if it exceeds 6.0%, the bendability deteriorates and the content becomes sensitive to stress corrosion cracking. By containing Zn in an amount of 0.5% or more, not only strength but also solderability can be improved. but
If it exceeds 2.0%, deterioration of bendability is observed, so this is set as the upper limit. Cu can improve strength by adding 0.1% or more, but if it exceeds 0.5%, bendability deteriorates, so 0.1% or more
~0.5%. In the present invention, the component composition as described above includes Mn: 0.20 to 1.0%, Cr: 0.05 to 0.30%,
Zr: 0.05~0.25%, V: 0.05~0.20%, Ti: 0.01~
By containing 0.15% of one or more of these, crystal grains are made finer and bending workability is improved. In other words, if these substances are below the lower limit, there is little effect, and if they are above the upper limit, intermetallic compounds such as
_MnAl6 , AlMnSi, _CrAl7 , _ZrAl3 , _VAl10 ,
Coarse compounds such as TiAl ₃ are formed and reduce bending workability. In particular, in the case of Mn, Cr, Zr, and V, in addition to the above effects, heat resistance can be imparted.
In such cases, the heat resistance can be imparted more effectively by finely dispersing and producing the above-mentioned compounds of these elements in the matrix. In addition, when adding these elements in combination, the total amount is preferably 1.2% or less,
If it exceeds 1.2%, there is a tendency for bendability to deteriorate. Furthermore, if these elements are dissolved in Al as much as possible, the electrical conductivity and thermal conductivity can be lowered, which is effective when used for LEDs. Further, in the present invention, B is effective in preventing casting cracks and refining crystal grains in a range of 0.001 to 0.1%, and can be added. Also, as an impurity, Fe≦
If Si is in the range of 0.3% and Si≦0.2%, the characteristics of the present invention will not be deteriorated. The production of lead frame material using the alloy of the present invention is as follows:
It is melted in the same way as a normal aluminum alloy, and the above-mentioned Ti or B for grain refinement is continuously added to the molten metal transfer gutter to the melting furnace or casting machine,
The molten metal is then filtered to remove non-metallic inclusions such as oxides, 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. The ingot is then homogenized, hot rolled, or cold rolled to form a plate of a predetermined thickness, and finally heat treated. Note that heat treatment such as intermediate annealing 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. Examples 1 to 9 of the present invention having the components shown in Table 1 below
The Al-Mg-Zn alloys of Comparative Examples A-J were melted and semi-continuously cast to form ingots with a thickness of 70 mm.

[Table] Each ingot as described above was heated at 530° C. for 4 hours and then hot rolled to a thickness of 6 mm. It was further cold rolled to a thickness of 0.5 mm and finally annealed at 500°C for 10 minutes. These plates were heated at 275° C. for 30 seconds, which corresponds to soldering, and then their strength, hardness, repeated bendability, and electrical conductivity were measured, and the results are shown in Table 2 below.

【table】

[Table] The evaluation criteria for repeated bendability in Table 2 above is that those that do not crack even after repeated bending operations three or more times are rated as "good", and those that crack are rated as "poor". . Regarding the overall evaluation, overall strength, hardness, and repeated bendability were judged and evaluated. Also, when used as an LED lead frame,
Conductivity less than 35% IACS after heating at 275℃ for 30 seconds,
Preferably it is required to be 30% IACS or less,
Good reflectance is required over the entire wavelength range of visible light. 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 materials of the present invention as described above It has good reflection properties without the need for any treatment, 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 manufacturing example, Sn-Pb-based eutectic solder was used,
The results of ultrasonic soldering and dip type soldering using flux are shown in Table 3 below.

[Table] "Effects of the Invention" According to the present invention as explained above, it is possible to create a material that has a suitable balance of heat resistance, especially strength, hardness, and bendability required for this type of lead frame. This invention is industrially very effective because it has good solderability and can provide a desirable lead frame at a low cost.

Claims (1)

[Claims] 1 Contains Mg: 3.0 to 6.0 wt%, Zn: 0.5 to 2.0 wt%, Cu: 0.1 to 0.5 wt%, and Mn: 0.20 to 1.0 wt%, Cr: 0.05 to 0.30 wt%. , Zr: 0.05-0.25wt%, V: 0.05-0.20wt%, Ti: 0.01-0.15wt%, the total amount of one or more of these is 1.2wt%
An aluminum alloy for lead frames, characterized in that it contains the following, with the remainder consisting of Al and impurities.