JP6142380B2 - Lead frame and manufacturing method thereof - Google Patents

Description

  The present invention relates to a lead frame and a manufacturing method thereof, and more particularly to a lead frame subjected to a roughening process by etching.

  In recent years, in order to improve the reliability of a semiconductor package, there is an increasing demand for improving the adhesion between a lead frame and a sealing resin.

  As a lead frame satisfying such a requirement, a structure in which a large number of V grooves are formed on the surface of the lead frame by stamping (pressing) has been proposed (for example, see Patent Document 1).

  However, the lead frame having this configuration has a problem that the flatness is deteriorated due to the formation of the V-groove and the adhesion is insufficient.

  In addition, there are some in which a large number of dimples (recesses) are formed on the surface of the lead frame by punching (for example, see Patent Document 2).

  However, along with the reduction in size and weight of semiconductor packages, the size of lead frames has also been reduced, and there is a problem that it is difficult to secure a processing area when forming dimples by punching.

  In addition, there is a technique in which the surface of the lead frame is roughened by etching to improve the adhesion between the lead frame and the resin.

  In the roughening treatment by etching, the adhesion with the sealing resin can be improved by the anchor effect on the surface of the lead frame and the increase in the specific surface area. Therefore, the lead frame can be reduced in size.

  The lead frame surface is roughened by etching. The punched lead frame is roughened by etching, and the coil material that is the lead frame base material is roughened by etching. Later, there is a method of punching.

  In the former, since the roughening process by etching is performed for each punched sheet, continuous processing cannot be performed, and there is a problem of poor productivity and an increase in cost due to an increase in processes.

  In the latter case, the coil material that is the base material for the lead frame is subjected to a roughing process by etching in advance, so that it is possible to perform a roughing process by etching continuously in the form of a coil. Is excellent.

  However, the roughened surface is surface-treated at the micron level, and if it passes through the punching process after the processing, it becomes the base material for the lead frame for each shot with the upper die and the lower die of the progressive die during the punching process. Since punching or the like is performed while strongly pressing the roughened material, as shown in FIGS. 9 to 11, the roughened surface is easily crushed, and the surface roughness value that is an important quality characteristic is reduced. There's a problem.

  In addition, the roughened strip-shaped lead frame is in contact with each other during product alignment, appearance inspection work, and product packing work, and the roughened surface is scratched as shown in FIG. There is a problem that it is likely to occur, and it is necessary to insert an interlayer paper or a mount for the purpose of preventing scratches between the frames when packing the lead frame, which causes a problem of an increase in process and cost.

  Therefore, a method of forming a roughened surface at a position lower than the reference surface has been proposed in order to ensure roughening quality in a lead frame that has been roughened by etching (see, for example, Patent Document 3). .

  However, in such a processing method that forms a roughened surface at a position lower than the reference surface, it is necessary to mask in advance a portion other than the range to be roughened, which increases the process and cost. Since the shape that can be roughened is limited, there is a problem that the lead frame of various shapes cannot be handled.

JP-A-3-268350 JP-A-5-218275 JP 2010-267730 A

Therefore, it is necessary to obtain a lead frame and a manufacturing method thereof for ensuring the roughening quality with the lead frame subjected to the roughening process by etching.
The present invention has been made in view of such circumstances, and the object of the present invention is a lead frame that has been subjected to a roughening process by etching, in which the deterioration of the roughening quality due to the punching process is suppressed. It is to provide a frame and a manufacturing method thereof.

  In order to achieve the above object, as a result of studying the solution of the problems in the prior art as described above, a lead frame that has been punched with respect to a lead frame that has been roughened by etching, and a manufacturing method thereof It came to invent.

That is, the lead frame according to the present invention has a roughened surface and a pair of V-grooves formed on the roughened surface, and a boundary between the roughened surfaces where no V-groove is formed. Both edge portions of the V-groove formed are raised at substantially the same height at a position higher than the height of the convex and concave portions in the region not formed in the V-groove on the roughened surface .

  The lead frame according to the present invention is characterized in that the roughening treatment is performed by etching the surface of the lead frame.

  In the lead frame according to the present invention, Ra (arithmetic mean roughness) of the roughened surface is 0.25 μm or more, and Rz (maximum height) is 2.0 μm or more. It is characterized by that.

  The lead frame according to the present invention is characterized in that the amount of metal swell at the edge of the V groove is 0.015 mm or more.

  The lead frame according to the present invention is characterized in that a plurality of the V-grooves are formed on one surface.

The lead frame manufacturing method according to the present invention includes a step of subjecting a necessary portion of the lead frame to a roughening process, and then performing a pair of V-grooves at a predetermined position of the roughened part , thereby performing the roughening process. Both edges of the V groove forming a boundary with a region not subjected to V-groove processing in the portion subjected to the roughening treatment are irregularities in the region not subjected to V-groove processing in the portion subjected to the roughening treatment A step of raising the metal portions of both edge portions of the V-groove to substantially the same height so as to be higher than the height of the convex portion.

  The lead frame manufacturing method according to the present invention is characterized in that the roughening treatment roughens the surface of the metal lead frame by etching.

  In the lead frame manufacturing method according to the present invention, Ra (arithmetic mean roughness) of the roughened surface is 0.25 μm or more, and Rz (maximum height) is 2.0 μm or more. It is characterized by being.

  The lead frame manufacturing method according to the present invention is characterized in that a metal bulge amount at an edge of the V groove is 0.015 mm or more.

  In the manufacturing method in which the surface of the lead frame is roughened by etching, V-groove processing is performed on the roughened surface side of the lead frame, and the metal bulge at the edge of the V-groove formed by the V-groove processing It is possible to supply a lead frame that does not deteriorate the surface roughening quality due to punching.

  Further, it is possible to perform a punching process continuously by performing a roughening process by etching on the coil material which is a base material for the lead frame.

  In addition, it is possible to suppress the occurrence of scratches due to contact between the strip-shaped lead frames in the inspection and packing operation of the strip-shaped lead frames after punching.

It is principal part sectional drawing of the lead frame which concerns on this invention. It is the surface photograph of the lead frame in which V-groove processing was given. It is the surface photograph (5000 times) before the punching process of the roughening process surface of a lead frame. It is the surface photograph (20000 times) before the punching process of the roughening process surface of a lead frame. It is a cross-sectional photograph (10000 times) before punching of the roughened surface of the lead frame. It is a surface photograph (5000 times) before the punching process of the roughening process surface of the lead frame in Example 1. FIG. It is the surface photograph (20000 times) after the punching process of the roughening process surface of the lead frame in Example 1. FIG. 3 is a cross-sectional photograph (10,000 times) after punching of the roughened surface of the lead frame in Example 1. FIG. 3 is a surface photograph (5000 times) after punching of a roughened surface of a lead frame in Comparative Example 1; It is the surface photograph (20000 times) after the punching process of the roughening process surface of the lead frame in the comparative example 1. It is a cross-sectional photograph (10000 times) after the punching process of the roughened surface of the lead frame in Comparative Example 1. It is a photograph which shows the contact damage in the roughening process surface of a lead frame. It is a graph which shows the dispersion | variation in the surface roughness Ra after the punching of Example 1 and Comparative Example 1. It is a graph which shows the dispersion | variation in the surface roughness Rz after the punching of Example 1 and Comparative Example 1. It is a graph which shows the relationship between the amount of swelling of the V-groove and the surface roughness Ra after punching in the present invention. It is explanatory drawing of a abrasion test. (A) is a surface photograph of the scratch test of Example 1, and (b) is a surface photograph of the scratch test of Comparative Example 1.

Hereinafter, the lead frame and the manufacturing method thereof according to the present invention will be described. Note that the present invention is not limited to the following detailed description unless otherwise specified.
An embodiment of a lead frame to which the present invention is applied and a manufacturing method thereof will be described in detail in the following order.
1. 1. Lead frame base material 2. Roughening process step V-groove processing step 4. 4. Punching process Inspection and packing process

  Specifically, the lead frame manufacturing method according to the present invention includes a roughening process, a V-grooving process, a punching process, and an inspection and packaging process.

1. Lead Frame Base Material The lead frame base material is, for example, a thin plate made of a metal material having a predetermined thermal conductivity and a predetermined electrical conductivity according to the characteristics of the semiconductor element used (for example, the plate thickness is 0 0.08 mm to 3.00 mm). As the metal material, copper, copper alloy, aluminum, aluminum alloy, or the like can be used. Furthermore, a predetermined amount of additive elements such as iron, zinc, phosphorus, tin, and nickel can be added to the metal material for the purpose of causing the lead frame to exhibit characteristics such as predetermined strength and heat resistance. In addition, the form of the lead frame base material can be a flat strip or a material (deformed strip) obtained by metallurgically joining a thin plate made of a predetermined metal material to both surfaces of a thin plate made of a predetermined metal material. .

The roughening treatment can be performed on both sides or one side of the material.
However, when the roughening process is performed only on one side, a mask member such as a masking tape is applied to the non-roughened surface of the lead frame base material before the roughening process, thereby protecting the roughening process. be able to.

  The masking tape is formed of a material that can mechanically and / or chemically withstand an etching process in a roughening process described later, for example, a polymer material such as polypropylene or polyethylene terephthalate. The mask member may be a mechanical mask that mechanically fixes a mask made of rubber or the like to the surface of the lead frame base material.

2. Roughening treatment process A roughening treatment surface is formed on the surface of the leadframe base material to form a roughened leadframe base material. The roughening treatment is performed using an etching solution (hereinafter referred to as “etchant”) that can roughen the surface of the lead frame base material by etching. For example, a sulfuric acid-based etchant can be used for copper strips. As a result, a roughened surface is formed on the surface of the copper strip made of the lead frame base material.

  The surface roughness of the roughened surface after the roughening treatment is preferably Ra (arithmetic average roughness) of 0.25 μm or more, and Rz (maximum height) of 2.0 μm or more. Is preferable. When Ra is less than 0.20 μm, a sufficient anchor effect cannot be obtained for the sealing resin, and adhesion and reliability cannot be obtained.

  Similarly, when Rz (maximum height) is less than 2.0 μm, a sufficient anchor effect cannot be obtained for the sealing resin, and adhesion and reliability cannot be obtained.

  When winding the strip-shaped lead frame after the roughening treatment, it is wound with dustless paper or interlayer paper made of resin film, so that the interlayer paper is inserted between the coil layers, and between the coil layers with respect to the roughening surface. Scratches can be prevented.

3. V-groove machining step V-groove machining can be performed on the roughened surface side using a roughened lead frame base material. Even in the case of an irregular shaped article, the V-groove processing can be performed on the roughening surface side without limiting the thick plate portion and the thin plate portion.

  The roughened lead frame base material is preferably subjected to V-groove processing before punching. When V-groove processing and punching are performed continuously, it is preferable to install a V-groove processing step before punching. As the V-groove processing arrangement in the mold is closer to the exit process than the entrance process, the number of times the roughened lead frame base material is strongly pressed by the upper and lower molds of the mold increases. Since the roughened surface is crushed and the surface roughness value is lowered at the stage before processing, it is preferable to install a V-groove processing step in the mold entrance step.

  As shown in FIG. 1, when the V-groove 3 is processed in the lead frame 1, a metal bulge portion 4 is formed at the edges (left and right sides in FIG. 1) of the V-groove 3 on the surface of the base material. As shown in FIG. 1, it is preferable to set the V-groove processing depth so that the swell amount J is higher than the convex portion of the roughened surface 2 having irregularities formed by the roughening process. As the depth 3 increases, the metal swell amount J at the edge of the V-groove 3 increases, and the roughened surface 2 can be protected in the next punching process.

As shown in FIG. 2, in Example 1, two V grooves 3 are provided, but there are one or three or more.
Further, the arrangement direction of the V-groove 3 is not limited to the vertical direction and the horizontal direction, and can be arranged according to the product shape of the lead frame.

  As shown in FIG. 2, the processing position of the V-groove 3 on the product is preferably provided on the roughening treatment surface 2 between the sealing resin boundary part and the element mounting part. When the V-groove is arranged in the non-product part that does not remain in the lead frame shape, as shown in FIG. 12, the strip-shaped lead frame at the time of alignment of the strip-shaped lead frame product after the punching process, the appearance inspection work, or the shipping packing work There is a problem that the products touch each other and scratches occur.

  The angle of the V groove 3 is preferably 45 degrees or more. If it is less than 45 degree | times, stress concentrates locally and fear that it will fall into a component becomes high.

  FIG. 15 is a graph showing the relationship between the metal swell amount J at the edge of the V groove 3 with the depth of the V groove 3 changed and the surface roughness of the roughened surface 2 after punching. As shown in FIG. 15, the V-grooving swell amount J is Ra (arithmetic average roughness), and the V-grooving swell amount J that can maintain the surface roughness of 0.25 μm to 0.35 μm is 0. 015 mm or more is preferable. By setting the V-grooving bulge amount J to 0.015 mm or more, it is possible to prevent the surface roughness of the roughened surface 2 from being lowered due to punching. When the V-grooving bulge amount J is less than 0.015 mm, the bulge portion 4 is struck by a die in the punching process of the next process and becomes low, and the reduction in the surface roughness of the roughened surface 2 cannot be prevented. .

4). Punching process The lead frame to be punched includes, for example, a dam bar for preventing the flow of sealing resin during molding, an island on which a semiconductor element is placed, a suspension lead that supports the island from the dam bar, and a dam bar. And a plurality of inner leads extending radially toward the island. These dam bars, islands, suspension leads, and inner leads are formed integrally with a roughened lead frame base material that has been processed into a V-groove, for example, by punching using a progressive die. It is manufactured by bending and cutting.

5). Inspection and Packing Process The strip-shaped lead frame products after the punching process are aligned and packaged and shipped after a product appearance inspection is performed in the next process. Since the work is performed on the strip-shaped lead frame product, the strip-shaped lead frame products are rubbed with each other by handling, and the occurrence of scratches on the roughened surface becomes a problem. According to the lead frame and the manufacturing method of the present invention, in the contact between the strip-shaped lead frame products after the punching process, the V-groove bulge becomes a contact point and the roughened surface is protected, so that scratches are generated. Suppression and quality improvement.

  Specific examples to which the present invention is applied will be described below, but the present invention is not limited to these examples.

Example 1
In Example 1, a PET masking tape was applied to the non-roughening surface side of the 1.5 mm thick strip-shaped copper alloy lead frame base material with the same width in order to protect it from the roughening treatment in the next step.

Next, a roughened surface was formed by performing a roughening process on the roughened surface side using a sulfuric acid-based etchant.
As for the surface roughness of the roughened surface, Ra (arithmetic average roughness) and Rz (maximum height) were measured using a contact-type surface roughness measuring instrument in accordance with JIS B0601 '2001. Ra (arithmetic mean roughness) was 0.25 μm to 0.33 μm, and Rz (maximum height) was 2.1 μm to 3.4 μm.

  The strip-shaped lead frame after the roughening treatment was wound into a coil together with an interlayer paper made of PET film while peeling the masking tape.

  Next, a V-groove processing device is installed on the inlet side of the punching die, and a V-groove 3 having a width of 0.24 mm, a depth of 0.12 mm, and an angle of 90 degrees is formed on the roughened lead frame base material. Then, two strips were processed at intervals of 6 mm to form a raised portion 4 having a height of 0.02 mm at the edge of the V groove.

  Subsequent to the above, a lead frame having a strip shape was obtained by punching, bending, and cutting into a predetermined shape. Arithmetic mean roughness Ra (arithmetic mean roughness) and maximum height Rz of the roughened surface of the strip-shaped lead frame after the punching process were measured at n number of 18 points.

  Next, the strip-shaped lead frame products after the punching process were aligned, and a product appearance inspection was performed in the next process to obtain a final product.

Comparative Example 1
Comparative Example 1 was the same as Example 1 except that V-groove processing was not performed, and the strip-shaped lead frame products after the punching process were aligned and subjected to a product appearance inspection in the next process to obtain a final product. Got.

  Table 1 below shows the surface roughness after the roughening treatment step and the surface roughness after the punching step, and FIGS. 3 to 5 show the roughened surface after the roughening treatment step and a micrograph of the cross section. 6 to 8 show micrographs of the roughened surface after the punching process in Example 1 and its cross-section, and FIGS. 9 to 11 show micrographs of the roughened surface after the punching process in Comparative Example 1 and its cross-section. showed that. FIG. 13 shows a graph showing the variation in Ra (arithmetic mean roughness) after punching in Example 1 and Comparative Example 1, and FIG. 14 shows Rz after punching in Example 1 and Comparative Example 1. The graph which shows the dispersion | variation in (maximum height) was shown.

  From the results shown in Table 1, FIGS. 3 to 11, FIGS. 13 and 14, in Example 1, the surface roughness after the punching process is Ra (arithmetic mean roughness), as is the surface roughness after the roughening process. Was in the range of 0.25 μm to 0.35 μm and Rz (maximum height) was in the range of 2.0 μm to 3.5 μm.

  In Example 1, the roughened surface and cross-sectional micrograph after the punching process were not changed from the roughened surface and cross-sectional micrograph after the roughening treatment step.

  On the other hand, in Comparative Example 1, the surface roughness after the roughening treatment step is Ra (arithmetic mean roughness), 0.25 μm to 0.33 μm, and Rz (maximum height), 2.1 μm to 3.4 μm. However, the surface roughness after the punching process is Ra (arithmetic mean roughness), 0.21 μm to 0.26 μm, and Rz (maximum height) is 1.8 μm to 2.3 μm. Roughness decreased.

  Moreover, in the comparative example 1, it turns out that it is hit by punching and the roughened surface is crushed.

  From the above results, in the manufacturing method in which the roughening process by etching is performed on the surface of the lead frame, the V-groove processing is performed on the roughening surface 2 side of the lead frame. It is possible to supply a lead frame that does not deteriorate the surface roughening quality.

  As is apparent from the above description, the present invention provides a roughening method for overcoming the above-mentioned problems and improving reliability in a manufacturing method having a leadframe surface roughening process prior to a punching process that is superior in productivity. V-groove processing is performed on the roughened surface 2 side of the lead frame 1 so as not to deteriorate the quality function of the surface, and the roughened surface 2 is protected by the raised portion 4 generated by the V-groove processing. A lead frame is provided.

Next, the strip-shaped lead frame product of the present invention was brought into contact, and the state of occurrence of scratches was confirmed. In the scratch test shown in FIG. 16, two strip-shaped lead frame products were stacked and rubbed 5 times in the width direction and in the longitudinal direction, respectively, and then the appearance of the roughened surface 2 was inspected. In Comparative Example 1, the appearance of the roughened surface 2 was inspected in the same manner as in Example 1 except that V-groove processing was not performed.
Table 2 below and FIG. 17 show the occurrence of scratches on the roughened surface 2.

  From the results shown in Table 2 and FIG. 17, in Example 1, since the raised portion 4 of the V-groove was present, the generation of scratches on the roughened surface 2 was minimal.

  On the other hand, in Comparative Example 1, two strip-shaped lead frame products were stacked, resulting in surface contact and numerous scratches.

  From the above results, according to the lead frame and the manufacturing method of the present invention, in the contact between the strip-shaped lead frame products after the punching process, the raised portion 4 of the V groove becomes the contact portion, and the roughened surface 2 It can be seen that since is protected, the generation of scratches can be suppressed and the quality can be improved.

1: Lead frame 2: Roughened surface 3: V groove 4: V groove raised portion J: V groove processed raised amount

Claims (9)

And a pair of V grooves formed on the roughened surface roughening treatment surface, both edges of the V-groove forming the boundary of the region that is not V-shaped groove is formed in the roughened surface A lead frame that rises at a height substantially equal to a height higher than the height of the convex and concave portions in the region not formed in the V-groove on the roughened surface .   The lead frame according to claim 1, wherein the roughening treatment is performed by etching a surface of the lead frame.   The Ra (arithmetic mean roughness) of the roughened surface is 0.25 μm or more, and Rz (maximum height) is 2.0 μm or more. Lead frame as described in.   4. The lead frame according to claim 1, wherein an amount of metal swell at the edge of the V-groove is 0.015 mm or more. 5.   The lead frame according to any one of claims 1 to 4, wherein a plurality of the V-grooves are formed on one surface. After undergoing a roughening process on the necessary portion of the lead frame, a pair of V-grooves are formed at predetermined positions on the roughened part , and a V-groove process is performed on the roughened part. are both edges of the V-groove forming the boundary between the not no region is such that said V grooves at the portion subjected to roughening treatment is higher than the height of the convex portion of the unevenness of the region not carried out, the A method of manufacturing a lead frame, comprising a step of raising metal portions at both edges of the V-groove to substantially the same height .   The lead frame manufacturing method according to claim 6, wherein the roughening treatment is performed by etching a surface of a metal lead frame.   The Ra (arithmetic mean roughness) of the surface subjected to the roughening treatment is 0.25 µm or more, and Rz (maximum height) is 2.0 µm or more. A method for manufacturing a lead frame according to claim 1.   The lead frame manufacturing method according to any one of claims 6 to 8, wherein a rising amount of metal at an edge portion of the V groove is 0.015 mm or more.