JP2017117985A - Lead frame manufacturing method - Google Patents

Abstract

A lead frame manufacturing method having high productivity and high adhesion to a sealing resin is provided. A method of manufacturing a lead frame using a metal plate made of Cu or a Cu alloy processed by pressing or etching, comprising: forming a partial Ag plating layer on the outermost surface of the metal plate; A step of roughening the Ag plating layer, or a step of forming a partial Ag plating layer on the outermost surface of the metal plate, a step of roughening the Ag plating layer, and the metal A step of forming a roughened surface on at least a part of the Cu surface or Cu alloy surface of the plate is provided. [Selection] Figure 1

Description

  The present invention relates to a method of manufacturing a lead frame for manufacturing a semiconductor package by performing resin sealing after placing a semiconductor element at a predetermined position, and in particular, forming a roughened surface in a region in contact with the sealing resin. The present invention relates to a lead frame manufacturing method.

  In recent years, the majority of semiconductor packages using semiconductor elements such as IC and LSI have a molded plastic package as an outer shell. This is because the plastic package is small and lightweight and can be mass-produced at low cost.

  As a method of manufacturing such a semiconductor package, a semiconductor element such as an IC or LSI is placed at a predetermined position of a lead frame formed of a metal plate such as Cu, and the semiconductor element and a lead frame terminal are wire bonded. There is known a method in which the resin is electrically connected to each other and sealed with a thermosetting resin or the like.

  As a lead frame used for manufacturing such a semiconductor package, the lead frame is sealed so that the interface between the lead frame and the sealing resin does not peel off during reflow soldering performed after the semiconductor package is manufactured. One having a roughened surface formed in a region in contact with the stop resin is known.

  As a typical technique, a technique of forming a roughened surface by performing an etching process on a lead frame Cu material described in Japanese Patent Application Laid-Open No. 2014-110302 shown as Patent Document 1 is representative.

On the other hand, with respect to the partial Ag plating part that acts on the bonding with the semiconductor chip, it is known that Ag has weaker adhesion with the sealing resin than Cu, and the adhesion between the lead frame and the sealing resin is improved. Is a part that needs improvement.
That is, in order to improve the adhesiveness with the sealing resin, it is also important to improve the adhesiveness with the Cu surface, but although the area is smaller than the Cu surface, the adhesiveness with the sealing resin is smaller than Cu. It is equally important to improve the adhesion to the sealing resin having a weak Ag surface.

  For example, Japanese Patent Laid-Open No. 2010-287741 shown as Patent Document 2 uses a non-cyan solution to improve the adhesion between the silver plating layer and the mold resin in the lead frame. A lead frame is disclosed in which a base silver plating for depositing silver crystal nuclei and a silver plating layer having a roughened surface by two-step silver plating of the main silver plating are formed on the surface of the wire bonding portion. .

  Further, for example, in Japanese Patent Application Laid-Open No. 2007-254855 shown as Patent Document 3, two-stage silver plating using a cyan solution is used for the purpose of achieving both wire bondability and resin adhesion of a silver plating film on a metal member. A silver-plated metal member for electronic parts in which coarse particles are deposited in irregularities is disclosed.

JP 2014-110302 A JP 2010-287741 A JP 2007-254855 A

  The lead frame described in Patent Document 2 is a method using a non-cyan solution, but the non-cyan solution has a problem of low productivity because the liquid property is unstable and the applied current value is low. To do.

  Therefore, in consideration of the productivity of the lead frame, it is desired to form a partial Ag plating portion by using a cyan solution that can stably apply a large current instantaneously and can realize high productivity.

  However, the method of forming a roughened surface by an electrolytic plating method in a cyan solution is very difficult because the stability of the solution is high and smooth plating can be easily formed.

  The metal member described in Patent Document 3 has an average crystal grain size of 0.5 to 1.5 μm and a maximum surface roughness Rmax of 10 to 40 μm by electrosilver plating using a cyan solution. In order to achieve this, the second electroplating process is a manufacturing method in which electroplating is performed at a current density lower than that of the first electroplating process, and crystal growth is performed using silver particles as nuclei. However, since the surface area ratio SA that affects the adhesion with the resin is not taken into account, the adhesion with the sealing resin is insufficient.

  From the above, after forming the partial Ag plating portion by the electrolytic plating method in the cyan solution, it is considered that the roughening treatment is performed in consideration of the surface area ratio SA as an effective production process.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a method for manufacturing a lead frame that has high productivity and high adhesion to a sealing resin. That is.

  In order to achieve the above object, a lead frame manufacturing method of the present invention is a method for manufacturing a lead frame using a metal plate made of Cu or Cu alloy processed by pressing or etching, wherein the metal plate The method comprises a step of forming a partial Ag plating layer on the outermost surface and a step of roughening the Ag plating layer.

  The lead frame manufacturing method of the present invention is a lead frame manufacturing method using a metal plate made of Cu or a Cu alloy that has been processed by pressing or etching, and is partially on the outermost surface of the metal plate. A step of forming an Ag plating layer, a step of roughening the Ag plating layer, and a step of forming a roughened surface on at least a part of the Cu surface or Cu alloy surface of the metal plate are provided. And

  In the lead frame manufacturing method of the present invention, the roughening treatment of the Ag plating layer is preferably performed so that the surface area ratio is in the range of SA = 1.30 to 1.65.

  In the lead frame of the present invention, an Ag plating layer having a partially roughened surface is formed on the outermost surface on a metal plate made of Cu or a Cu alloy that has been processed by pressing or etching. A roughened surface is formed on at least a part of the Cu surface or Cu alloy surface of the metal plate.

  In the lead frame of the present invention, the roughened surface of the Ag plating layer preferably has a surface area ratio of SA = 1.30 to 1.65.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a lead frame with high productivity and high adhesiveness with sealing resin can be provided.

It is a schematic sectional drawing which shows the manufacturing method of the lead frame and semiconductor package which concern on the Example of this invention in order of a process. It is a flowchart which shows the manufacturing method shown in FIG.

  Embodiments of a lead frame manufacturing method and a semiconductor package manufacturing method using the lead frame according to the present invention will be described below with reference to the drawings. In addition, description of each process and drawing are simplified. In addition, the materials, chemicals, plating thickness, and the like to be used are merely examples of aspects of the present invention, and the present invention is not limited to the exemplified aspects.

A lead frame manufacturing method and a semiconductor package manufacturing method using the lead frame according to the embodiment will be described below with reference to FIGS. FIG. 1 is a schematic cross-sectional view showing a method of manufacturing a lead frame and a semiconductor package according to this embodiment in order of steps. FIG. 2 is a flowchart showing the manufacturing method shown in FIG. Of the reference numerals in the figure, 1 is a metal plate, 2 is a Cu strike plating layer, 3 is a substituted Ag plating layer, 4 is a partial Ag plating layer, 5 is a roughened surface, 6 is a semiconductor element, and 7 is a bonding wire. , 8 indicates a sealing resin.
In addition, although the example which gave the substitution Ag plating layer 3 as a lower layer of the partial Ag plating layer 4 used as the outermost surface was shown in the present Example, the part where the outermost surface becomes Ag plating in at least one part on the metal plate 1 The Ag plating layer 4 should just be formed.

  First, pretreatment such as degreasing and acid cleaning is performed on the entire area of both surfaces of the metal plate 1 made of Cu or Cu alloy that has been processed by pressing or etching as shown in FIG. 1A (step S11 in FIG. 2). (Step S12 in FIG. 2).

  Thereafter, as shown in FIG. 1B, a Cu strike plating layer 2 (plating thickness of about 0.01 to 1.00 μm) consisting of one layer is formed by electrolytic Cu plating on the metal plate 1 made of Cu or Cu alloy. They are formed in all areas on both sides (step S13 in FIG. 2).

  The Cu strike plating bath used when forming the Cu strike plating layer 2 is preferably composed of cuprous cyanide (CuCN) and potassium cyanide (KCN) as main components.

  Next, as shown in FIG.1 (c), the substitutional Ag plating layer 3 (plating thickness of about 0.05-0.5 micrometer) which consists of one layer is formed on the Cu strike plating layer 2 by substitution plating. (Step S14 in FIG. 2). Since the replacement Ag plating layer 3 is intended to improve the adhesion with the partial Ag plating layer 4 to be applied later, the example shown in the drawing is applied to the entire surface of the metal plate 1, but at least the partial Ag plating layer 4 is formed. It only has to be in place. In some cases, the substituted Ag plating layer 3 may be omitted.

The substituted Ag plating bath used when forming the substituted Ag plating layer 3 is preferably composed of an Ag salt such as potassium potassium cyanide (KAg (CN) ₂ ), and immediately after the substitution preventing step. It is necessary to perform processing.

  Further, instead of the substituted Ag plating layer 3, a thin Ag plating layer by electrolytic plating may be formed. As the plating bath used in this case, an Ag strike plating bath is preferable, and the replacement prevention step immediately after is unnecessary. In this case, the bath composition is preferably composed mainly of silver cyanide (AgCN) and potassium cyanide (KCN).

  Next, as shown in FIG.1 (d), the partial Ag plating layer 4 which consists of one layer is formed in the predetermined area | region on the substituted Ag plating layer 3 by electrolytic plating (step S15 of FIG. 2).

In addition, as a plating bath used when forming the partial Ag plating layer 4, what comprises silver potassium cyanide (KAg (CN) ₂ ) and potassium cyanide (KCN) as a main component is preferable.

  Further, the plating thickness is expected to be reduced by about 1.0 to 3.0 [mu] m under the condition of a processing time of 30 to 90 s due to the subsequent peeling treatment, so that the thickness is 5.0 to 10.0 [mu] m. It is desirable to form.

  As a process after forming the partial Ag plating layer 4, as shown in FIG. 1E, the replacement Ag plating layer in the region where the partial Ag plating layer 4 is not formed with respect to the entire region of the metal plate 1. 3 is removed, and the partial Ag plating layer 4 is subjected to a roughening process to form a roughened surface 5 (step S16 in FIG. 2).

  As this stripping solution, either electrolysis or immersion treatment can be used, but it is desirable to use an immersion treatment type mainly composed of hydrogen peroxide and organic acids such as acetic acid. In this example, Sbag AG-601 manufactured by Sasaki Chemicals was used. In addition, what is necessary is just to select suitably the content of stripping solution from the relationship between the surface area ratio SA assumed later and processing time.

  The peeling is performed by bringing the metal plate 1 into contact with the electrolytic stripping solution at room temperature until all of the replacement Ag plating layer 3 in the region where the partial Ag plating layer 4 is not formed is removed. If such a process is performed, only the partial Ag plating layer 4 and the replacement Ag plating layer 3 formed therebelow on the metal plate 1 due to the film thickness difference between the replacement Ag plating layer 3 and the partial Ag plating layer 4. Can leave.

  Moreover, about the roughening of the partial Ag plating layer 4, the uneven | corrugated shape, ie, the roughened surface 5, can be formed according to the peeling form of the Ag plating part by the partial Ag plating layer 4 and peeling liquid contacting. The roughened surface 5 formed at this time preferably has a surface area ratio of SA = 1.30 to 1.65, and the treatment time is preferably about 60 seconds.

  The surface area ratio SA is defined as the surface area of a roughened surface having an XY plane area equal to the surface area of the ideal surface having no irregularities on the surface (becomes larger than 1 because of the roughness). SA. In general, the surface area increases = the contact area increases and the contact force improves, so it is desirable that the surface area ratio SA is large. However, if the surface area ratio is too large, problems may occur in the assembly process of the lead frame. It is preferable to be in the range.

  Here, Table 1 shows the surface area ratio and the plating thickness of the partial Ag plating layer 4 for each peeling treatment time in this example. In addition, the value of the surface area ratio of 1.19 at the treatment time of 0 second is a measurement value before the peeling treatment in the present example.

From Table 1, it can be seen that, according to the treatment time, the surface area ratio increases, while the plating thickness decreases. Further, it was confirmed that discoloration of the Ag plating occurred in the 120 s treatment in the plating appearance.
On the other hand, for the 60 s treatment recommended as the stripping treatment time, it has been confirmed that the partial Ag plating layer having a surface area ratio of SA = 1.19 has increased to a surface area ratio of SA = 1.43. Although there was a decrease in the color, no abnormalities such as discoloration in the appearance were observed.
In addition, the surface area ratio of the partial Ag plating layer for lead frames that is commercially available is almost SA = 1.00 to 1.20. When the surface area ratio SA is about 1.00 to 1.20, reliable adhesion to the sealing resin cannot be obtained.

  Thereafter, the surface treatment on the metal plate 1 is completed by performing post-treatment such as neutralization, washing and drying of the metal plate 1 (step S17 in FIG. 2).

  Thereafter, by performing a post-processing step such as downset, the metal plate 1 can form a strip-shaped lead frame (step S18 in FIG. 2).

  Thereafter, as shown in FIG. 1 (f), the semiconductor element 6 is placed in one of the regions where the partial Ag plating layer 4 of the lead frame is formed, and the partial Ag plating layer formed in the other region. 4 and the semiconductor element are electrically connected by wire bonding using a bonding wire 7. And as shown in FIG.1 (g), resin sealing is performed using the sealing resin 8 (step S19 of FIG. 2), and a semiconductor package is formed. At this time, the formed roughened surface 5 is inside the sealing resin.

  As described above, in the manufacturing method of the present embodiment, after the partial Ag plating layer 4 is formed, the stripping treatment of the Ag layer is performed using a stripping solution mainly composed of hydrogen peroxide and an organic acid such as acetic acid. By carrying out, the roughened surface 5 can be formed on the partial Ag plating layer 4.

  In addition, the lead frame manufactured by the manufacturing method of this example has a larger surface area ratio of the partial Ag plating layer 4 than the lead frame manufactured by the conventional manufacturing method, so that the adhesion with the sealing resin is improved. doing.

  With respect to this point, the relationship between the surface area ratio SA of the Ag plating layer and the resin adhesion strength will be described based on the experimental data shown in Table 2. Although there is no standard for the resin adhesion strength, the resin adhesion strength is 9.5 to 9.7 MPa at a normal surface area ratio (SA = 1.00 to 1.20). Was set to 10.0 MPa, and if it was more than this, it was judged that the resin adhesion strength was good. On the other hand, if the value of the surface area ratio SA exceeds 1.65, there is a problem that it is difficult to remove the burrs because the adhesion of the resin is too good. In some cases, the surface area ratio SA may be 1.65 or more.

  From Table 2, if the surface area ratio SA is 1.30 or more, the resin adhesion strength is 10.0 MPa or more. On the other hand, when the surface area ratio SA is 1.62, the resin adhesion strength is 11.1 MPa, and it is usually preferable that the surface area ratio SA be in the range of about 1.30 to 1.65.

  In the above embodiment, roughening is performed by peeling treatment on the Ag surface, but by providing a Cu roughening step in the subsequent steps, roughening not only on the Ag surface but also on the Cu surface is possible. It is.

  The Cu roughened surface at this time removes the Cu strike plating layer 2 in the region where the substituted Ag plating layer 3 of the metal plate 1 is not present, and forms a roughened surface in that region.

  As Cu roughening liquid, what contains the organic compound (for example, benzotriazole etc. which react with copper) which reacts with the metal-type raw material which forms the metal plate 1, and suppresses etching is preferable. In this embodiment, benzotriazole, hydrogen peroxide and sulfuric acid are the main components of the roughening solution. If it is a roughening liquid containing such an organic compound, the organic compound reacts with the metal-based material forming the metal plate 1 to suppress etching, and the region in contact with the roughening liquid of the metal plate 1 is fine. This is because an uneven shape, that is, a roughened surface can be easily formed.

  The lead frame whose Ag and Cu surfaces are roughened by these methods has a surface area ratio SA of the Ag and Cu surfaces larger than that of the lead frame manufactured by the conventional manufacturing method, so that it adheres to the sealing resin. Is further improved.

  The present invention is extremely useful for improving the productivity and quality of a lead frame and a semiconductor package using the lead frame.

DESCRIPTION OF SYMBOLS 1 Metal plate 2 Cu strike plating layer 3 Substitution Ag plating layer 4 Partial Ag plating layer 5 Roughening surface 6 Semiconductor element 7 Bonding wire 8 Sealing resin

Claims (5)

  A method of manufacturing a lead frame using a metal plate made of Cu or a Cu alloy that has been processed by pressing or etching, the step of forming a partial Ag plating layer on the outermost surface of the metal plate, and the Ag plating A lead frame manufacturing method comprising a step of roughening a layer.   A method of manufacturing a lead frame using a metal plate made of Cu or a Cu alloy that has been processed by pressing or etching, the step of forming a partial Ag plating layer on the outermost surface of the metal plate, and the Ag plating A lead frame manufacturing method comprising: a step of roughening a layer; and a step of forming a roughened surface on at least a part of a Cu surface or a Cu alloy surface of the metal plate.   The lead frame manufacturing method according to claim 1, wherein the roughening treatment of the Ag plating layer is performed so that the surface area ratio is in a range of SA = 1.30 to 1.65.   On the metal plate made of Cu or Cu alloy processed by pressing or etching, an Ag plating layer having a partially roughened surface is formed on the outermost surface, and the Cu surface or Cu alloy surface of the metal plate A lead frame, wherein a roughened surface is formed on at least a part of the lead frame.   5. The lead frame according to claim 4, wherein the roughened surface of the Ag plating layer has a surface area ratio of SA = 1.30 to 1.65.

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