JP2808955B2 - Composite lead frame - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite lead frame,
Especially for manufacturing composite leadframes for semiconductor packages
About the law .

[0002]

2. Description of the Related Art Conventionally, a lead frame for a semiconductor package is manufactured only by press working or photo etching.

When a lead frame for a semiconductor package is manufactured by press working, there is a limit to the production of a die for punching by a press. For this reason, there is the following limit regarding the thickness of the metal plate to be processed, and there is a problem that fine processing cannot be performed.

[0004] That is, the limit of the width (W) of the punched lead is (plate thickness (t) x 0.7) mm. The punching interval (G) is irrelevant to the sheet thickness, and is limited to a punching limit of 0.1 mm.

Therefore, the limit of the lead pitch (P) of the lead frame is (W + G) = (0.7t + 0.1) mm
Is represented by

For example, when the thickness of a metal plate to be processed is 0.1
The limit (P) of the lead pitch by pressing at 5 mm is (0.7 × 0.15 + 0.1) = 0.205 m
m.

However, recently, as shown in Table 1, it is strongly demanded to increase the number of pins and narrow the pitch of the inner side leads.

[0008]

The value of t shown in Table 1 comes from the required limit of the thickness of the outer lead, and if it is smaller than this value, the weight of the semiconductor package cannot be supported. Further, 0.15 mm or more is required in order to prevent bending at the time of transport and to prevent breakage due to thermal fatigue of metal after surface mounting. On the other hand, the lead tip does not need to be strong and a thin metal foil is sufficient and it is sufficient that the lead is electrically connected.

[0010]

On the other hand, in press working, even if the sheet thickness is reduced to 0.1 mm, W = 0.7 ×
From t (mm), W is limited to 0.07 mm, and when G is set to 0.1 mm, P is limited to 0.17 mm from P = (W + G) (mm). At present, the plate thickness is set to 0.
It cannot be thinner than 1 mm.

The value of P in Table 1 is 0.17 mm.
, And cannot satisfy the requirement.

[0012] In addition, when it is formed only by etching, there is a problem that it is expensive. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a method for manufacturing a composite lead frame capable of obtaining a narrow pitch, multi-pin lead frame at low cost.

[0013]

According to the present invention, an inner lead formed by etching and an outer lead formed by pressing are formed by separate members and connected to each other. Integrated
A method for manufacturing a composite lead frame, comprising:
Etch the lead member and outer side lead member respectively
The inner side leads to
And leads on the outer side.
And outer leads are provided in common
Align and connect with pilot hole for alignment
Manufacture of composite lead frames characterized by integration
A method is provided.

Here, it is preferable that the inner lead and the outer lead are formed of different metals.

The inner lead and the outer lead are preferably connected by electric resistance welding, laser welding, an anisotropic conductive sheet or the like.

Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a plan view showing an example of a three-piece series of a composite lead frame manufactured by the method of the present invention.

The composite lead frame 1 has a pilot hole 3 in an outer frame 2 and a chip 7 in the center. 4 is the outer lead, 5 is the inner lead, 6
Is a tie bar.

In the present invention, the outer lead 4 and the inner lead 5 are electrically connected to form a composite lead frame.

The outer lead 4 is a portion outside the connecting portion 9 or 9a and is formed by press working.
The feature of the present invention is that the inner lead 5 is a portion inside the connection portion 9 or 9a, includes the die pad 8, and is formed by etching (hereinafter simply referred to as the outer lead 4). , The inner lead 5). As a result, the cost of a composite lead frame having a fine pattern in which the number of etching portions requiring high processing costs is reduced can be reduced.

Outer side lead 4 and inner side lead 5
Does not have a boundary, and the connection position of where to connect is not limited. Technically, it is preferable that the outer lead 4 is formed to the extent that can be pressed by the die, and the region that cannot be pressed by the die is formed as the inner lead 5 by etching.

However, in the present invention, a major advantage is that the mold for forming the outer lead 4 is made common, thereby facilitating the cost of the mold and reducing the cost. It is advisable to standardize as a boundary line of.

In FIG. 2 in which one piece in FIG. 1 is enlarged, the connecting portion 9 is located at a position where the number of outer-side leads is relatively large. However, the connecting portion 9a may have a number of inner-side leads. 8 is a die pad. FIG. 3 is a sectional view of the lead frame 1 shown in FIG.

Another advantage of the present invention is that the outer lead 4 and the inner lead 5 can be combined with different kinds of metal layers, and the combination of materials is not limited.

Another advantage of the present invention is that different thickness combinations are possible for the outer lead 4 and the inner lead 5, and the thickness combinations are not limited.

For example, the inside is made of a material having high conductivity, the outside is made of a material having high strength, or vice versa. The inside is made of a cheap material, the outside is made of an expensive material, or vice versa. It can be made of a high material, a material having an inner coefficient of thermal expansion matched to that of the silicon chip, a material excellent in heat dissipation, or a material excellent in electrical characteristics.

Further, the inside or the outside is made of a material capable of reducing the weight, and the outside is made of a material having excellent solderability, a material having excellent folding resistance, a material resistant to fatigue fracture, a material having a long mold life, or plating. It is easy to use, and the inside is made of a material with excellent adhesion to the mold resin, a material with excellent wire bonding properties, a material that is easy to process finely, or a material that is easy to plate, or these can be freely combined as appropriate. .

As one specific example of the combination of different metals,
For example, the etching material for the inner lead is made of a copper alloy, and the pressing material for the outer lead is made of 42% Ni.
-A combination such as Fe.

As a material of the inner lead, for example, 9
When 9.9% pure copper is used, not only is the electrical conductivity improved, but copper has an advantage that the pitch is easily narrowed due to its excellent fine etching processability.

In the case of a 42% Ni-Fe alloy,
The relationship between the limit of the etching process using iron and the plate thickness (t) is as follows. 0.03 mm <t <0.15 mm lead width _{(W A) = 0.03mm (W} A denotes the width of the flat portion) lead spacing _{(G A) = {G B} + (t / 3)} mm where , G _B = 0.02mm (minimum mask opening width) lead pitch _{(P A) = {0.03 +} G B + (t /
3)} mm Therefore 0.15Mmt, if the 42% Ni-Fe alloy _{W A = 0.03mm G A = 0.02} + (0.15 ÷ 3) = 0.070mm P A = 0.03 + 0.07 = 0 .10 mm. For a 0.10 mmt 42% Ni-Fe alloy, W _A = 0.03 mm G _A = 0.02 + (0.10 ÷ 3) = 0.053 mm P _A = 0.03 + 0.053 = 0.083 mm .

When this is compared with the pressing method, the pressing method also uses 0.10 mmt, and G = 0.1 mm and W = 0.10 × 0.7 = 0.07 in the case of a 42% Ni—Fe alloy.
mm, P = 0.17 mm, and the minimum value required for wire bonding of W = 0.07 mm can be achieved.
Since it is as large as 0.1 mm, narrow pitch cannot be achieved.

[0031] In the case of etching using _{99.99% Cu G A = {(} G B = 0.02) + (t / 4)} mm
Therefore, fine processing can be performed accordingly.

In the present invention , the inner lead and the outer lead are preferably electrically connected by electric resistance welding, laser welding, anisotropic conductive sheet or the like, but are not limited thereto. is not.

The inner lead and the outer lead are each provided with a pilot hole 3 for common alignment, and a pilot pin (not shown) can be inserted therethrough for accurate alignment. During mass production,
By making the alignment with the pilot pin, the tool contact, the power feeding means, the frame loading means and the like continuous lines, unmanned connection work is also possible.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments.

(Example 1) A composite lead frame was prepared using the position indicated by reference numeral 9 in FIG. 2 as a connecting portion.

First, 304 pin inner leads were formed by etching. Material is 0.10mmt
42% Ni-Fe alloy was etched with ferrous chloride, and the lead width (W _A ) at the tip of the lead was 0.0
7 mm, lead spacing (G _A) = 0.053mm, and the lead pitch (P _A) = 0.12mm. Where W _A =
The reason why the thickness is set to 0.07 mm is that at least a lead width of at least 0.07 mm is required for wire bonding. Before the connection, as shown in FIG. 4, a half-etched groove 10 was formed at a position corresponding to the connection portion 9, and a pilot hole 3 for common alignment was provided.

The outer leads were formed by press working, a method using a YAG laser, and a method using an anisotropic conductive film (Examples 1, 2 and 3 of the present invention). The material is 0.1
A 42 mm Ni-Fe alloy of 5 mmt was used.

The connection method was resistance welding using a tool having a convex shape of the wire of the connection portion 9. The outer side lead also had the common alignment hole 3 opened by press working, and the pilot pin was inserted through the common hole 3 to accurately align the positions.

Thereafter, the above-mentioned resistance welding tool is brought into contact,
The connection was continuously made by applying the current.

(Embodiment 2) The connecting portion is denoted by reference numeral 9 in FIG.
Composite lead frames (Examples 4, 5, and 6 of the present invention) were prepared using the same materials and under the same conditions as in Example 1 except for the position of a. In each of Inventive Examples 4 to 6, fine patterns could be continuously connected in the same manner as in Example 1.

(Example 3) Composite lead frame (Examples 7 to 7 of the present invention) under the same conditions and under the same conditions as in Example 1 except that 99.99% pure copper (t = 0.1 mm) was used as the inner-side lead material. 9) was created. Lead spacing G _A of the inner side lead of the present invention Examples 7-9 are all _{(G B = 0.02) + (} 0.1 ÷ 4) = 0.045mm , and the could very fine processing.

(Example 4) A composite lead frame under the same conditions and under the same conditions as in Example 1 except that the inner-side lead material was the same as that of the outer side, ie, 0.15 mmt of 42% Ni-Fe (Examples 10 to 12 of the present invention) It was created.

In this case, W_A= 0.03 mm, G_A=
0.02+ (0.15 ÷ 3) = 0.07 mm, P_A=
0.10mm is the processing limit of the inner lead,
Current W _AIs 0.07 mm, so P_A
The minimum pitch for practical use was 0.14 mm. This place
Even in the case of 0.1 mmt 42% Ni-Fe mold press processing
P = G + W = 0.1 + 0.07 = 0.17 mm in the process The pitch could be narrowed more.

[0044]

Since the present invention is constructed as described above, it is possible to increase the number of pins with a narrower pitch and to facilitate mass production as compared with the conventional press working alone .
In addition, compared with the conventional method using only the etching process, the mold can be shared and the processing cost can be reduced to 1/2 to 1/4 by pressing the outer lead. In addition, the inner lead and the outer lead can be freely selected by a combination of dissimilar metals, and the degree of freedom in material selection can be greatly increased.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a three-piece series of a composite lead frame manufactured by the method of the present invention.

FIG. 2 is an enlarged view of one piece of FIG. 1;

FIG. 3 is a sectional view of FIG. 2;

FIG. 4 is a sectional view of an outer lead and an inner lead before connection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Composite lead frame 2 Outer frame 3 Pilot hole 4 Outer side lead 5 Inner side lead 6 Tie bar 7 Chip 8 Die pad 9, 9a Connection part 10 Half etching groove

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-47-41266 (JP, A) JP-A-62-114254 (JP, A) JP-A-63-148667 (JP, A) Information processing handbook, Society Information Processing Society of Japan, Ohmsha, (May 30, 1989), p. 213, 350-351, 391-397, 864-866 (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01L 23/50

Claims (1)

(57) [Claims] 1. A composite in which an inner lead formed by etching and an outer lead formed by pressing are formed as separate members and connected and integrated.
A method for manufacturing a lead frame, comprising:
The member and outer lead member are each etched.
The inner side lead and
Forming the outer lead, the inner lead and
Common alignment for each outer lead
With pilot hole for connection and integrated connection
A method of manufacturing a composite lead frame.