JP6774785B2 - Lead frame and lead frame manufacturing method - Google Patents

Description

The present invention relates to a lead frame and a method for manufacturing a lead frame.

Some of the lead frames constituting the semiconductor package are roughened on a part of the surface in order to improve the resin adhesion. The roughening treatment is generally performed chemically using an etching solution. At that time, a masking tape is attached to protect the portion that is not roughened (for example, the portion where the conductive layer made of a nickel plating layer or the like is formed) (see, for example, Patent Document 1).

JP-A-2010-267730

In recent years, there has been a strong demand for miniaturization (downsizing) of semiconductor packages. In order to meet the demand, it is necessary to effectively utilize the area (area) on the lead frame.

However, a lead frame in which copper or a copper alloy is used as a forming material and a nickel plating layer is partially formed on the surface thereof is disadvantageous in terms of effective utilization of the region, as described below.
For example, as shown in FIG. 3, a lead frame in which a nickel plating layer 22 is partially formed on the surface of a base material 21 made of copper or a copper alloy as a forming material will be considered as an example. In such a lead frame, the ionization tendency in the electrolyte differs depending on the relationship between the natural potentials of copper and nickel (nickel is a base metal), so that the ionization of copper in the vicinity of the boundary with the nickel plating layer 22 is suppressed. , There is a risk that the vicinity of the boundary will not be roughened. Moreover, in that case, it is very difficult to control the range in which roughening is not performed as desired. Therefore, when roughening the lead frame, a masking tape 30 is attached so as to cover the formed portion of the nickel plating layer 22 so that copper and nickel do not come into contact with each other in the electrolyte. Can be considered. However, even when the masking tape 30 is attached, in order to completely cover the nickel plating layer 22, for example, a width of at least 0.5 mm should be set to the attachment margin width of the masking tape 30 (see “W” in the drawing). ), And a non-roughened portion that is not roughened exists in the vicinity of the boundary with the nickel plating layer 22 by that amount.
The existence of such a non-roughened portion is disadvantageous in terms of effectively utilizing the area on the lead frame. Moreover, since the presence of the non-roughened portion does not contribute to the improvement of the resin adhesion, it is not preferable for improving the reliability of the semiconductor package through the improvement of the resin adhesion.

The present invention makes it possible to effectively utilize the region on the lead frame of a lead frame having a partially plated layer and a roughened surface on the surface, and to expect improvement in reliability by improving resin adhesion. The purpose.

One aspect of the present invention is
A base material made of copper or a copper alloy,
A partial plating layer formed on a part of the surface of the base material and having a nickel phosphorus plating layer at least on the surface layer portion,
A roughened surface arranged in a region adjacent to the partial plating layer on the surface of the base material,
It is a lead frame provided with.

According to the present invention, in a lead frame having a partially plated layer and a roughened surface on the surface, the region on the lead frame can be effectively utilized, and reliability can be expected to be improved by improving the resin adhesion.

It is a side sectional view which shows typically the example of the structure of the main part of the lead frame which concerns on one Embodiment of this invention. It is explanatory drawing which shows one specific example of the roughened surface in an Example and a reference example of this invention. It is a side sectional view which shows typically the example of the structure of the main part of the lead frame in the prior art.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

<1. Outline configuration of lead frame>
First, a schematic configuration of the lead frame according to the present embodiment will be described.
FIG. 1 is a side sectional view schematically showing an example of a main part configuration of a lead frame according to the present embodiment.

The lead frame 10 described as an example in the present embodiment is one of the members constituting the semiconductor package, and is configured to include the base material 11, and the partial plating layer 12 is formed on the surface of the base material 11. The roughened surface 13 is arranged on the surface of the base material 11 which is formed and further which the partial plating layer 12 is not formed.

(Base material)
The base material 11 is in the form of a thin plate (for example, a plate thickness of about 0.08 to 3.0 mm) made of copper or a copper alloy as a forming material, and is arranged in or around the element mounting portion on which the semiconductor element is mounted. It is formed into a predetermined shape (hereinafter referred to as "lead frame shape") having a lead or the like. The lead frame shape itself may be appropriately determined according to the semiconductor element mounted on the element mounting portion and the semiconductor package provided with the semiconductor element, and is not particularly limited. Absent.

(Partial plating layer)
The partial plating layer 12 is formed on a part of the surface of the base material 11 in order to improve the bondability of dies, wires and the like. The term "part" as used herein means that the surface is not entirely formed but is partially formed. Therefore, on the surface of the base material 11, the partial plating layer 12 may be formed at a plurality of locations as long as it is partially formed. The number, area, and the like on which the partial plating layer 12 is formed may be appropriately determined according to the semiconductor element mounted on the element mounting portion and the semiconductor package provided with the semiconductor element, and in particular. It is not limited.

Further, the partial plating layer 12 has a nickel phosphorus plating layer 12a on the surface layer portion. The nickel phosphorus plating layer 12a is a layer formed by a nickel (Ni) -phosphorus (P) plating treatment and composed of a coating film containing Ni as a main precipitate and P containing about 2 to 15%. The nickel phosphorus plating layer 12a may be formed at least on the surface layer portion of the partial plating layer 12. That is, it is conceivable that the partial plating layer 12 is entirely formed by the nickel phosphorus plating layer 12a, but the present invention is not necessarily limited to this, and at least the surface layer portion of the partial plating layer 12 (that is, the partial plating layer 12). As long as it covers the exposed surface), the nickel phosphorus plating layer 12a may be partially formed.

For this reason, the partial plating layer 12 is not entirely formed by the nickel phosphorus plating layer 12a, but the nickel plating layer 12b as the base plating layer and the nickel formed so as to cover the nickel plating layer 12b. It is conceivable to have a phosphorus-plated layer 12a and the like. The nickel plating layer 12b is a layer made of a Ni coating formed by a Ni plating treatment. With such a configuration, the precipitation speed of the Ni plating process is generally faster than the precipitation speed of the Ni-P plating process, so that the efficiency of forming the partial plating layer 12 can be improved.

When the partial plating layer 12 has a multilayer structure of the nickel phosphorus plating layer 12a and the nickel plating layer 12b, it is assumed that the nickel phosphorus plating layer 12a is formed with a thickness of 0.4 μm or more. This is to ensure that the effect (details will be described later) of covering the surface layer portion with the nickel phosphorus plating layer 12a can be obtained. However, from the viewpoint of improving efficiency as described above, it is preferable that the nickel phosphorus plating layer 12a is as thin as possible. Therefore, it is conceivable that the thickness of the nickel phosphorus plating layer 12a is, for example, about 0.5 μm. When the thickness of the nickel phosphorus plating layer 12a is about 0.5 μm, for example, if the total thickness of the partial plating layer 12 is about 1.5 μm, the thickness of the nickel plating layer 12b is 1. It will be about 0.0 μm.

(Roughened surface)
The roughened surface 13 is a surface that has been roughened to improve the adhesion of the resin material that seals the semiconductor package, and is to the extent that an anchor effect can occur (for example, Ra (arithmetic mean roughness)). A surface having a surface roughness of about 0.20 μm or more and Rz (maximum height) of about 2.0 μm or more).

Further, since the roughened surface 13 is a surface obtained by roughening the surface of the base material 11, a portion where the partial plating layer 12 is not formed on the surface of the base material 11 (that is, the partial plating layer). It is arranged in the non-formed portion of 12), but is particularly arranged in the region adjacent to the partial plating layer 12. The "adjacent region" here means a region located so as to be in contact with the edge of the partial plating layer 12 (that is, the boundary with the exposed surface of the base material 11), but the edge of the partial plating layer 12 It suffices to have a portion in contact with the region, and the plan-view shape, size (range), and the like of the region are not particularly limited.

<2. Lead frame manufacturing procedure>
Next, a procedure for manufacturing the lead frame 10 having the above-described configuration, that is, an example of the lead frame manufacturing method according to the present embodiment will be briefly described. Here, the case where the partial plating layer 12 has a multilayer structure of the nickel plating layer 12b and the nickel phosphorus plating layer 12a will be taken as an example.

In manufacturing the lead frame 10 having the above-described configuration, at least a plating step of forming the partial plating layer 12 (step 10, hereinafter the step is abbreviated as “S”) and a roughening step (S20) of performing a roughening treatment And go through. Hereinafter, each of these steps will be described.

(Plating process: S10)
In the plating step (S10), first, a predetermined pretreatment (degreasing, pickling, etc.) is performed on the base material 11 constituting the lead frame 10 or the copper strip before forming the lead frame shape, which is the base thereof. Further, a masking process (attachment of masking tape, etc.) is performed to expose only the planned formation portion of the partial plating layer 12.

After that, in the plating step (S10), a Ni plating process for forming the nickel plating layer 12b is performed. Specifically, the Ni plating treatment is performed under treatment conditions (treatment time, treatment temperature, etc.) such that the thickness of the nickel plating layer 12b is, for example, about 1.0 μm. As a result, a nickel plating layer 12b having a thickness of, for example, about 1.0 μm is formed as a base plating layer at the planned formation location of the partial plating layer 12. The detailed contents of the Ni plating treatment (type of plating bath to be used, specific method, etc.) may be those using known techniques, and the description thereof will be omitted here.

After the nickel plating layer 12b is formed, in the plating step (S10), a cleaning treatment or the like is performed as necessary, and then a Ni-P plating treatment for forming the nickel phosphorus plating layer 12a is performed. Specifically, the Ni-P plating treatment is performed under treatment conditions (treatment time, treatment temperature, etc.) such that the thickness of the nickel phosphorus plating layer 12a is, for example, about 0.5 μm. As a result, a nickel phosphorus plating layer 12a having a thickness of, for example, about 0.5 μm is formed at the planned formation location of the partial plating layer 12 so as to cover the surface of the nickel plating layer 12b. That is, a multi-layered partial plating layer 12 having a nickel phosphorus plating layer 12a is formed on the surface layer portion. The detailed contents of the Ni-P plating process (type of plating bath to be used, specific method, etc.) may be those using known techniques, and the description thereof will be omitted here.

After the formation of the partial plating layer 12, the masking treatment is released (peeling of the masking tape, etc.) to expose the masked portion (that is, the non-formed portion of the partial plating layer 12).

(Roughening step: S20)
In the roughening step (S20) performed after the plating step (S10), after undergoing a predetermined pretreatment (degreasing, pickling, etc.), the roughening surface 13 is formed on the non-formed portion of the partial plating layer 12. Perform the plating process. The roughening treatment is chemically performed using a predetermined roughening treatment liquid which is an etching solution (etchant). The predetermined roughening treatment solution is not particularly limited as long as it can roughen the surface of the base material 11, but for example, it may be a mixed solution of an acidic aqueous solution such as sulfuric acid and an oxidizing solution such as hydrogen peroxide. An example is one containing an additive.

By the way, in the roughening step (S20), the roughening treatment does not require a masking treatment for the formed portion of the partial plating layer 12. This is because the roughening treatment liquid used in the roughening step (S20) does not react with the nickel phosphorus plating layer 12a covering the surface layer portion of the partial plating layer 12, and does not require protection against the partial plating layer 12.

Moreover, since Ni-P constituting the nickel phosphorus plating layer 12a contains a non-metal element, even if it is present in the electrolyte and the copper constituting the base material 11, there is a difference in ionization tendency in the electrolyte. It won't end up. Therefore, if the surface layer portion of the partial plating layer 12 is covered with the nickel phosphorus plating layer 12a, copper ionization in the vicinity of the boundary with the partial plating layer 12 is performed without masking the formed portion of the partial plating layer 12. Is not suppressed, and the roughening treatment is also performed on the surface to be treated including the region adjacent to the partial plating layer 12 on the surface of the base material 11.

That is, in the roughening step (S20), the roughened surface 13 is also formed in the region adjacent to the partial plating layer 12.

After the roughened surface 13 is formed, surface oxides and rust preventive treatment after the roughening treatment are performed as post-treatment.

The lead frame 10 according to the present embodiment is manufactured by going through the procedure described above.

<3. Effect in this embodiment>
According to this embodiment, one or more of the following effects are exhibited.

(A) According to the present embodiment, in the lead frame 10 having the partial plating layer 12 and the roughened surface 13 on the surface of the base material 11, the surface layer portion of the partial plating layer 12 is covered with the nickel phosphorus plating layer 12a. A roughened surface 13 is arranged in a region adjacent to the partial plating layer 12. That is, in forming the roughened surface 13, the roughening treatment can be performed without requiring a masking treatment, and even in that case, the ionization of copper in the vicinity of the boundary with the partial plating layer 12 is suppressed. Never. Therefore, the existence of the non-roughened portion in the vicinity of the boundary with the partial plating layer 12 can be eliminated, and the region (area) on the lead frame 10 can be effectively utilized. Moreover, since the roughened surface 13 can be increased by eliminating the non-roughened portion, it is preferable in improving the reliability of the semiconductor package through the improvement of the resin adhesion.
As described above, according to the present embodiment, in the lead frame 10 provided with the partial plating layer 12 and the roughened surface 13 on the surface of the base material 11, the region on the lead frame 10 can be effectively utilized. It is expected that reliability will be improved by improving resin adhesion.

(B) In the present embodiment, the partial plating layer 12 includes a nickel plating layer 12b as a base plating layer and a nickel phosphorus plating layer 12a formed so as to cover the nickel plating layer 12b. ing. With such a configuration, the precipitation speed of the Ni plating process is generally faster than the precipitation speed of the Ni-P plating process, so that the entire partial plating layer 12 is formed by the nickel phosphorus plating layer 12a. , The efficiency of forming the partial plating layer 12 can be improved.

(C) In the present embodiment, the nickel phosphorus plating layer 12a is formed with a thickness of 0.4 μm or more. With such a configuration, the effect of covering the surface layer portion of the partial plating layer 12 with the nickel phosphorus plating layer 12a (that is, the region on the lead frame 10 is effectively utilized, and the reliability is improved by improving the resin adhesion. The effect that can be expected) will be surely obtained.
In particular, as described in the present embodiment, when the thickness of the nickel phosphorus plating layer 12a is about 0.5 μm, the nickel phosphorus plating layer 12a is used as much as possible while ensuring the above-mentioned effects. By making the thickness thinner, it becomes possible to improve the efficiency when forming the partial plating layer 12.

<4. Modification example>
Although one embodiment of the present invention has been described above, the above-mentioned disclosure contents show one of the exemplary embodiments of the present invention. That is, the technical scope of the present invention is not limited to the above-described embodiment.

For example, in the above-described embodiment, specific numerical values (P content of the nickel phosphorus plating layer 12a, surface roughness of the roughened surface 13, etc.) have been described as examples, but the present invention is limited to these numerical values. It may be changed as appropriate without departing from the gist of the present invention.

Hereinafter, examples of the present invention will be specifically described. However, it goes without saying that the present invention is not limited to the following examples.
FIG. 2 is an explanatory diagram showing a specific example of the roughened surface in the examples and reference examples of the present invention.

(Reference example)
First, a reference example for comparison with Examples 1 and 2 described later will be described.
In the reference example, a nickel plating layer having a thickness of 1.5 μm was formed on a base material using a copper alloy as a forming material to form a partial plating layer. That is, in the reference example, the partial plating layer is not a multi-layer structure but a single-layer structure consisting of only a nickel plating layer. Then, the roughening treatment for forming the roughened surface was performed without masking the partially plated layer. The roughening treatment is performed by using "Mold Prep" manufactured by Atotech Japan Co., Ltd. as the roughening treatment liquid and immersing the base material having the partial plating layer formed in the roughening treatment liquid at 40 ° C. for 60 seconds. It was.

FIG. 2A shows a plan view of the vicinity of the boundary between the partially plated layer and the roughened surface in the lead frame thus obtained. According to the illustrated example, it can be seen that the roughened untreated region is widely present in the vicinity of the boundary between the partially plated layer and the roughened surface (see the discolored portion in part A in the figure). This is because the ionization tendency in the electrolyte differs depending on the relationship between the natural potentials of copper and nickel, so that the ionization of copper in the vicinity of the boundary with the partial plating layer composed of the nickel plating layer is suppressed, and the vicinity of the boundary is suppressed. Is presumed to be due to the fact that

(Example 1)
Next, Example 1 will be described.
In the first embodiment, the configuration of the partial plating layer 12 is different from that of the reference example. That is, in Example 1, the partial plating layer 12 does not have a single-layer structure as in the case of the reference example, but has a multi-layer structure of a nickel phosphorus plating layer 12a and a nickel plating layer 12b. Specifically, in Example 1, a nickel plating layer 12b as a base plating layer is formed with a thickness of 1.3 μm on a base material 11 made of a copper alloy as a forming material, and nickel phosphorus covering the nickel plating layer 12b is formed. The plating layer 12a was formed to have a thickness of 0.2 μm to form a partial plating layer 12. Others (masking treatment, roughening treatment, etc.) are the same as in the reference example.

FIG. 2B shows a plan view of the vicinity of the boundary between the partially plated layer 12 and the roughened surface 13 in the lead frame 10 thus obtained. According to the illustrated example, unlike the case of the above-mentioned reference example, it can be seen that a wide roughened untreated region does not exist. It is presumed that this is because the partial plating layer 12 has a multi-layer structure and is covered with the nickel phosphorus plating layer 12a. However, in Example 1, a small amount of unroughened untreated region remains near the boundary between the partially plated layer 12 and the roughened surface 13 (see part B in the figure).

(Example 2)
Subsequently, Example 2 will be described.
In the second embodiment, the partial plating layer 12 has a multi-layer structure as in the case of the first embodiment, but the thickness of the nickel phosphorus plating layer 12a and the nickel plating layer 12b constituting the partial plating layer 12 is the thickness of the first embodiment. Not the case. That is, in Example 2, the nickel plating layer 12b as the base plating layer is formed with a thickness of 1.0 μm, and the nickel phosphorus plating layer 12a covering the nickel plating layer 12b is formed with a thickness of 0.5 μm to form a partial plating layer. Twelve were configured. Others (masking treatment, roughening treatment, etc.) are the same as in the case of Example 1.

FIG. 2C shows a plan view of the vicinity of the boundary between the partially plated layer 12 and the roughened surface 13 in the lead frame 10 thus obtained. According to the illustrated example, it can be seen that the roughened surface 13 is also arranged in the region adjacent to the partial plating layer 12.

(Evaluation)
Comparing the results obtained in Examples 1 and 2 and Reference Examples as described above, if the surface layer of the partial plating layer 12b is a multilayer structure covered with the nickel phosphorus plating layer 12a, the partial plating layer 12 and Since a wide unroughened untreated region does not exist near the boundary with the roughened surface 13, it can be seen that it is useful for effectively utilizing the region (area) on the lead frame 10.

Moreover, if the nickel phosphorus plating layer 12a is formed with a thickness of 0.5 μm as in the case of Example 2, the thickness (specifically, the effect of covering the surface layer portion with the nickel phosphorus plating layer 12a) can be obtained. Is more than 0.4 μm thick), so that a small amount of unroughened untreated region does not remain near the boundary, and it is possible to ensure effective utilization of the region (area) on the lead frame 10. it can.

10 ... Lead frame, 11 ... Base material, 12 ... Partial plating layer, 12a ... Nickel phosphorus plating layer, 12b ... Nickel plating layer, 13 ... Roughened surface

Claims (4)

A base material made of copper or a copper alloy,
A partial plating layer formed on a part of the surface of the base material and at least the surface layer portion is covered with a nickel phosphorus plating layer.
A roughened surface arranged in an adjacent region located in contact with the edge of the partial plating layer on the surface of the base material on which the partial plating layer is not formed.
Lead frame with. The partial plating layer is
A nickel plating layer as a base plating layer and
With the nickel phosphorus plating layer formed so as to cover the nickel plating layer,
1. The lead frame according to claim 1. A plating step of forming a partial plating layer in which at least the surface layer portion is covered with a nickel phosphorus plating layer on a part of the surface of a base material made of copper or a copper alloy.
A roughening step of performing a roughening treatment on a surface to be treated including an adjacent region located in contact with an edge of the partial plating layer on the surface of the base material on which the partial plating layer is not formed.
Equipped with a,
A method for manufacturing a lead frame in which the roughening step does not perform masking treatment on the formed portion of the partial plating layer . The method for manufacturing a lead frame according to claim 3 , wherein in the roughening step, the surface to be processed is etched.