JP2012124220A - Method of manufacturing composite material for lead frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a composite material for lead frame which allows for provision of a composite material having less variation in thickness and processing at a lower cost.SOLUTION: When manufacturing a composite material 1 composed by sequentially laminating three layers of copper or a copper alloy 2, titanium or a titanium alloy 3, and copper or a copper alloy 2, rolling reduction ratio of bonded clad rolling is set at 60% or higher, a rolling reduction ratio of finish rolling to final board thickness is set at 5% or lower, and cold bonded clad rolling and finish rolling are performed in the atmosphere.

Description

  The present invention relates to a method for manufacturing a composite material for lead frames used in semiconductor devices.

  In recent years, high-density mounting substrates have been demanded as semiconductor devices are highly integrated, multi-pinned, downsized, and electronic devices are downsized and lightened.

  As for the method for connecting the semiconductor chip and the lead frame, research and development have been conducted on bumped metal leads capable of reducing the assembly process, package size, cost, and the like as compared with conventional wire bonding. In this method, a bump that protrudes from the tip of a lead is formed, and the package can be thinned by bonding to the semiconductor chip via this bump.

  As one of the bump forming methods, an attempt has been made to use a three-layer clad plate in which an etching stop layer is formed inside a clad plate processed by chemical etching as a metal material for producing a lead frame.

  As an etching stop layer, there is a method for manufacturing a lead frame using a three-layer clad plate using aluminum, an iron-based alloy, titanium, or the like. The composite material is produced by cold rolling, but other than that, for example, in the method disclosed in Patent Document 1, the composite material is produced by a method of cold rolling at a low pressure under a vacuum atmosphere.

  Furthermore, as another method for manufacturing a lead frame, there is a method of depositing a metal thin film by a vapor deposition method.

International Publication No. 00/019533 JP 2010-103305 A JP 2001-251090 A JP-A-11-126828

  However, when these are manufactured by cold rolling, usually an annealing process is required to soften the material after clad rolling, but a hard and brittle intermetallic compound is formed at the bonding interface between the copper layer and the titanium layer by annealing heat treatment. Layers are formed, and problems such as peeling may occur.

  Further, when a three-layer clad plate including an etching stop layer (titanium or a titanium alloy) is manufactured by vacuum rolling (method of Patent Document 1), in order to prevent oxidation of titanium, the oxygen concentration in the atmosphere during rolling must be reduced. Don't be. In particular, since titanium is a metal that easily oxidizes, rolling must be performed in an environment with a higher degree of vacuum. Therefore, there is a problem that process costs such as equipment and running costs for clad rolling processing, and time required for evacuation increase significantly.

  Also, in the lamination by the method of vapor-depositing a metal film, if the vapor deposition rate is increased, the film quality is not dense and pores are generated in the thin film, and if the vapor deposition rate is decreased, the manufacturing time increases and the workability deteriorates. In addition, this method also has a problem that equipment costs and running costs such as consumables become high.

  An object of the present invention is to solve the above-mentioned problems, and to provide a method for manufacturing a lead frame composite material that can be processed at a lower cost and can provide a composite material with less variation in plate thickness.

  In order to achieve the above object, the present invention reduces the rolling reduction ratio of bonded clad rolling when a composite material comprising three layers of copper or copper alloy, titanium or titanium alloy, and copper or copper alloy is sequentially laminated. A method for producing a composite material for a lead frame in which the reduction ratio of finish rolling to the final thickness is 5% or less, and the laminating clad rolling and the finish rolling are performed in the cold in the atmosphere. It is.

  The cross-sectional hardness of titanium or titanium alloy before the bonding clad rolling may be 120 Hv or less, and the cross-sectional hardness of copper or copper alloy before the bonding clad rolling may be 100 Hv or more.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the composite material for lead frames which can be processed at low cost and can provide the composite material with few board | plate thickness fluctuation | variations can be provided.

It is a cross-sectional view which shows the structure of the composite material for lead frames. It is a figure explaining the evaluation method of the board thickness fluctuation | variation of a titanium layer.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a lead frame composite material manufactured by the lead frame composite material manufacturing method of the present invention.

  As shown in FIG. 1, the leadframe composite 1 according to the present invention has a three-layer structure in which copper or copper alloy 2, titanium or titanium alloy 3, and copper or copper alloy 2 are sequentially laminated.

  As the copper or copper alloy 2 used as the material, lead frame copper alloy (C194 or the like) can be used in addition to oxygen-free copper (C1020). The titanium or titanium alloy 3 is preferably pure titanium (1 type, 2 type) in consideration of workability.

  In the method for manufacturing a lead frame composite material of the present invention, first, three coils of a pure copper strip, a pure titanium strip, and a pure copper strip wound in a coil shape are respectively set in a feeding device.

  The material (copper and titanium) sent out from the coil passes through the cleaning tank for cleaning the bonding surface, oil and foreign matter on the bonding surface are removed, and further passes through the brushing tank to join the bonding surface. The oxide film on the surface is scraped to expose the active surface and harden the bonding surface.

  Immediately thereafter, the three metal strips are cold-bonded and rolled in a clad rolling mill, and the joining of the metal layers is completed.

  After completion of the bonding, if necessary, heat treatment can be performed to such an extent that a metal compound layer is not formed at the copper / titanium bonding interface, and mutual diffusion between the metal layers can be promoted to increase the bonding strength.

  In the method for producing a composite material for a lead frame of the present invention, it is desirable that the rolling reduction (sheet thickness reduction rate before and after rolling) of clad rolling (bonding rolling) is 60% or more. When the rolling reduction is less than 60%, the bonding between the metal layers deteriorates and peeling occurs. In addition, if the input plate thickness of titanium or a titanium alloy strip is made thin in order to make the final plate thickness of the lead frame composite material constant, the lead frame composite material is likely to be broken by the pretreatment brushing. Furthermore, since titanium or a titanium alloy is an etching stop layer, it is not necessary to make it thicker than necessary, and an increase in the input plate thickness leads to an increase in material cost.

  Further, when rolling down (finish rolling) to a predetermined thickness after clad laminating rolling, the rolling reduction is preferably 5% or less. If it exceeds 5%, the degree of ripple (necking of the metal layer due to fluctuations in the sheet thickness ratio) generated during clad laminating rolling becomes more prominent, and the surface flatness and roughness after etching deteriorate during assembly. It ’s not right.

  The ripple described above may occur due to a difference in mechanical properties (hardness and the like) between metal layers.

  Therefore, in the method for manufacturing a lead frame composite material of the present invention, it is desirable that the cross-sectional hardness of copper or copper alloy before clad rolling is 100 Hv or more, and the cross-sectional hardness of titanium or titanium alloy before clad rolling is 120 Hv or less. . When the difference in hardness between copper and titanium increases, the difference in deformation resistance between the two increases and ripples are likely to occur.

  In short, according to the manufacturing method of the composite material for a lead frame of the present invention, the reduction rate at the time of laminating rolling is set to 60% or more, and the reduction rate at the time of finish rolling is set to 5% or less. It is possible to suppress plate thickness fluctuations such as ripples generated in the stop layer. Further, according to the present invention, since the composite material is produced by cold rolling, the lead frame composite material can be produced at a lower cost.

  Examples of the present invention will be described below.

[Example 1]
Total using a coiled pure copper plate having a thickness of 0.23 mm (cross section hardness 140 Hv), a coiled pure titanium plate having a thickness of 0.046 mm (cross section hardness 110 Hv), and a pure copper plate having a thickness of 0.37 mm (cross section hardness 130 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.129 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Example 2]
Total using a coiled pure copper plate having a plate thickness of 0.46 mm (cross section hardness of 135 Hv), a coiled pure titanium plate having a thickness of 0.09 mm (cross section hardness of 105 Hv), and a pure copper plate having a plate thickness of 0.73 mm (cross section hardness of 125 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.128 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Example 3]
Total using a coiled pure copper plate having a thickness of 0.31 mm (cross section hardness 110 Hv), a coiled pure titanium plate having a thickness of 0.06 mm (cross section hardness 90 Hv), and a pure copper plate having a thickness of 0.5 mm (cross section hardness 120 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.13 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Example 4]
Total using a coiled pure copper plate having a thickness of 0.2 mm (cross section hardness 120 Hv), a coiled pure titanium plate having a thickness of 0.04 mm (cross section hardness 94 Hv), and a pure copper plate having a thickness of 0.32 mm (cross section hardness 120 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.13 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Example 5]
Total using a coiled pure copper plate having a thickness of 0.27 mm (cross section hardness 112 Hv), a coiled pure titanium plate having a thickness of 0.05 mm (cross section hardness 108 Hv), and a pure copper plate having a thickness of 0.42 mm (cross section hardness 113 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.126 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Example 6]
Total using a coiled pure copper plate having a thickness of 0.21 mm (cross section hardness of 106 Hv), a coiled pure titanium plate having a thickness of 0.04 mm (cross section hardness of 98 Hv), and a pure copper plate having a thickness of 0.34 mm (cross section hardness of 118 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.125 mm (that is, it was not necessary to perform finish rolling).

[Comparative Example 1]
Total using a coiled pure copper plate having a thickness of 0.13 mm (cross section hardness 120 Hv), a coiled pure titanium plate having a thickness of 0.03 mm (cross section hardness 110 Hv), and a pure copper plate having a thickness of 0.2 mm (cross section hardness 105 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.18 mm.

  The obtained composite material was finish-rolled aiming at a plate thickness of 0.125 mm to obtain a composite material having a plate thickness of 0.125 mm.

[Comparative Example 2]
Total using a coiled pure copper plate having a thickness of 0.13 mm (cross section hardness 118 Hv), a coiled pure titanium plate having a thickness of 0.03 mm (cross section hardness 112 Hv), and a pure copper plate having a thickness of 0.21 mm (cross section hardness 110 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.17 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Comparative Example 3]
Total using a coiled pure copper plate having a thickness of 0.26 mm (cross section hardness 112 Hv), a coiled pure titanium plate having a thickness of 0.05 mm (cross section hardness 103 Hv), and a pure copper plate having a thickness of 0.42 mm (cross section hardness 118 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.147 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Comparative Example 4]
Total using a coiled pure copper plate having a plate thickness of 0.34 mm (cross section hardness 110 Hv), a coiled pure titanium plate having a plate thickness of 0.07 mm (cross section hardness 111 Hv), and a pure copper plate having a plate thickness of 0.54 mm (cross section hardness 126 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.14 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Comparative Example 5]
Total using a coiled pure copper plate having a thickness of 0.38 mm (cross section hardness 62 Hv), a coiled pure titanium plate having a thickness of 0.075 mm (cross section hardness 110 Hv), and a pure copper plate having a thickness of 0.6 mm (cross section hardness 80 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.126 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Comparative Example 6]
Total using a coiled pure copper plate having a thickness of 0.26 mm (cross section hardness 75 Hv), a coiled pure titanium plate having a thickness of 0.05 mm (cross section hardness 112 Hv), and a pure copper plate having a thickness of 0.41 mm (cross section hardness 105 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.13 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Comparative Example 7]
Total using a coiled pure copper plate having a thickness of 0.19 mm (cross section hardness 121 Hv), a coiled pure titanium plate having a thickness of 0.04 mm (cross section hardness 162 Hv), and a pure copper plate having a thickness of 0.31 mm (cross section hardness 116 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.13 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Comparative Example 8]
Total using a coiled pure copper plate having a thickness of 0.2 mm (cross section hardness 125 Hv), a coiled pure titanium plate having a thickness of 0.04 mm (cross section hardness 188 Hv), and a pure copper plate having a thickness of 0.33 mm (cross section hardness 121 Hv) For the three layers, cleaning and brushing are performed on each joint surface to expose a clean active surface and harden the surface of the joint surface to superimpose the three layers. Cold rolling). The thickness of the composite material obtained after bonding was 0.126 mm.

  The obtained composite material was finish-rolled to obtain a composite material having a thickness of 0.125 mm.

[Conventional example]
Total using a coiled pure copper plate having a thickness of 0.045 mm (cross section hardness 102 Hv), a coiled pure titanium plate having a thickness of 0.01 mm (cross section hardness 96 Hv), and a pure copper plate having a thickness of 0.072 mm (cross section hardness 108 Hv) For the three layers, cleaning and plasma etching are performed on each joint surface at a vacuum degree of 1 × 10 ⁻⁴ Pa in the chamber, and the three active layers are exposed, and the three layers are overlaid and pasted with a rolling roll. Combined rolling (cold rolling) was performed. The thickness of the composite material obtained after bonding was 0.125 mm.

  The composite material produced by the above Example, the comparative example, and the prior art example was cut out by 20 mm x 20 mm, and the cross-sectional investigation was performed for each 20 mm length about the rolling direction and the plate width direction. As shown in FIG. 2, the maximum and minimum values of the plate thickness of the pure titanium layer are measured, the difference between the maximum and minimum values is considered as the plate thickness variation, the finish of the composite material is examined, and the finished titanium layer plate Thickness fluctuations within ± 3 μm were rated as “Good” (accepted), and those with larger fluctuations were marked as “X” (failed). In addition, the processing cost of the finished product was also evaluated.

  Table 1 shows the overall evaluation of the finished product with respect to the clad reduction ratio, finish rolling reduction ratio, and cross-sectional hardness of each material before rolling.

  As shown in Table 1, Examples 1 to 6 of the present invention were able to obtain a material with little variation in plate thickness by cold rolling in the air, which is low-cost processing.

  On the other hand, about Comparative Examples 1-8 and the prior art example, comprehensive evaluation became x for the following reason.

  In Comparative Examples 1 and 2, since the rolling reduction of the clad rolling process was low, the metal layers were not sufficiently bonded and peeled off. In Comparative Examples 3 and 4, since the rolling reduction of finish rolling was high, the plate thickness variation was large. In Comparative Examples 5 and 6, since the cross-sectional hardness of the copper layer was soft (less than 100 Hv), the plate thickness variation was significant. In Comparative Examples 7 and 8, since the cross-sectional hardness of the titanium layer was hard (greater than 120 Hv), the plate thickness variation was significant. In addition, since the conventional example is processing under vacuum, the processing cost is high.

1 Composite 2 Copper or copper alloy 3 Titanium or titanium alloy

Claims (2)

  When manufacturing a composite material composed of three layers of copper or copper alloy, titanium or titanium alloy, and copper or copper alloy in sequence, the reduction ratio of the laminated clad rolling is set to 60% or more, and the final thickness is reached. A method for producing a composite material for a lead frame, wherein the rolling reduction of the finish rolling is 5% or less and the laminating clad rolling and the finishing rolling are performed in the air in the cold.   2. The lead frame composite according to claim 1, wherein a cross-sectional hardness of the titanium or titanium alloy before the bonded clad rolling is 120 Hv or less, and a cross-sectional hardness of the copper or copper alloy before the bonded clad rolling is 100 Hv or higher. Manufacturing method.