JPH05251603A - Composite leadframe - Google Patents

Abstract

PURPOSE:To reduce the manufacturing cost of a lead frame having narrow pitches and a large number of pins by connecting inner side leads, in which parts of the leads formed through etching are pressed by a tape, and outer side leads formed through press working. CONSTITUTION:Outer side leads 4 and inner side leads 5 are joined electrically, thus constituting a composite lead frame. The outer side leads 4 are positioned at the external sections of connecting sections 9, and shaped through press working. The inner side leads 5 are positioned at the internal sections of the connecting sections 9, include die pads, and are formed through etching. Parts of the front end sections of the inner side leads 5 are held down and fixed by a tape 10, thus forming a composite lead frame. Accordingly, etching work having high processing cost is reduced, thus cutting down the manufacturing cost of the lead frame while allowing combination of different kind of metals in the outer side lead and the inner side lead.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a composite lead frame,
In particular, it relates to a composite lead frame for semiconductor packages.

[0002]

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

When a lead frame for a semiconductor package is manufactured by press working, there is a limit in manufacturing a die for punching by pressing. Therefore, there is a problem that the fine processing cannot be performed because of the following limits regarding the thickness of the metal plate to be processed.

That is, the lead width (W) to be removed is limited to (plate thickness (t) × 0.7) mm. Further, the punching interval (G) is irrelevant to the plate thickness, and the working limit of the punching punch is 0.1 mm.

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

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

However, recently, as shown in Table 1, it has been strongly demanded that the inner leads have a large number of pins and a narrow pitch.

[0008]

The value of t shown in Table 1 comes from the required limit of the plate thickness of the outer side lead, and if it is thinner than this value, the weight of the semiconductor package cannot be supported. In addition, 0.15 mm or more is required in order to prevent bending during transportation and prevention of breakage due to metal thermal fatigue after surface mounting. On the other hand, the tip of the lead need not be strong, and a thin metal foil is sufficient, and it is sufficient if it is electrically conducted.

[0010]

On the other hand, in press working, even if the plate thickness is thinned to 0.1 mm, W = 0.7 ×
From t (mm), W has a limit of 0.07 mm, and when G is 0.1 mm, P has a limit of 0.17 mm from P = (W + G) (mm). At present, the plate thickness is 0.
Cannot be thinner than 1 mm.

The values of P in Table 1 are all 0.17 mm.
It is less than and cannot satisfy the requirement.

In recent wire bonding, for example, a gold wire of 30 μm φ is connected to the tip of a lead wire having a width of 90 μm.
Therefore, when the inner side lead moves in the width direction, there is a big problem that the wire sticks out.

In addition, there is a problem in that the cost is high when it is formed only by etching. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a composite lead frame in which a lead frame having a narrow pitch and a large number of pins can be obtained at low cost.

[0014]

In order to achieve the above object, according to the present invention, an inner lead in which a part of the tip of a lead formed by etching is held by a tape and an outer formed by pressing are formed. There is provided a composite lead frame characterized by being connected to side leads.

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

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

The tape is preferably an insulating film such as a polyimide film with an adhesive or an adhesive polyimide film.

The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a plan view showing an example of a three-piece string of the composite lead frame of the present invention.

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

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

The outer side lead 4 is a portion outside the connecting portion 9 or 9a and is formed by press working.
The inner side lead 5 is an inner part of the connecting portion 9 or 9a, includes the die pad 8, is formed by etching, and the tip of the inner side lead 5 is partially covered with the tape 10. Is a feature of the present invention (hereinafter, simply referred to as outer side lead 4 and inner side lead 5). As a result, it is possible to reduce the cost of the composite lead frame having a fine pattern in which the number of etching-processed parts, which is expensive, is reduced.

Outer side lead 4 and inner side lead 5
Since there is no boundary between and, the connection position of where to connect is not limited. Technically, it is preferable that the outer side lead 4 is formed up to a range that can be pressed by the mold, and the region that cannot be pressed by the mold is formed as the inner side lead 5 by etching.

However, in the present invention, a great advantage is that the mold for forming the outer side leads 4 is made common to facilitate the mold cost and reduce the cost, so that the positions where the molds can be made common are connected. It is a good idea to standardize it as the boundary line of.

In FIG. 1, the connecting portion 9 is located at a position where the outer side leads are relatively large, but it may be a connecting portion 9a having a large number of inner side leads. 8 is a die pad. FIG. 2 is a sectional view of the lead frame 1 shown in FIG.

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

Another advantage of the present invention is that the outer leads 4 and the inner leads 5 can be combined in different thicknesses, and the thickness combinations are not limited.

For example, the inside may be made of a material having high conductivity, the outside may be made of a material having high strength, or vice versa, or the inside may be made of a cheap material, the outside may be made of an expensive material, or vice versa, or the outside may be made of a corrosion resistant material. The material may be a high material, a material having an internal thermal expansion coefficient matched to that of the silicon chip, a material having excellent heat dissipation property, or a material having excellent electrical characteristics.

Further, the inside or outside is made of a material that can be made lighter, the outside is made of a material having excellent solderability, a material having excellent folding endurance, a material that is resistant to fatigue fracture, a material having a long die life, or plated. A material that is easy to use and has excellent adhesion to the mold resin, a material that has excellent wire bonding properties, a material that is easy to perform microfabrication, or a material that is easy to perform plating, and these can be freely combined as appropriate. ..

As one specific example of the combination of different metals,
For example, the etching processing material of the inner side lead is copper alloy, and the pressing processing material of the outer side lead is 42% Ni.
An example of the combination is an alloy such as -Fe.

As the material of the inner side lead, for example, 9
When pure copper of 9.99% is used, not only the electrical conductivity is improved, but also copper has an excellent fine etching workability, which is advantageous in that the pitch can be easily narrowed.

First chloride, in the case of a 42% Ni-Fe alloy
The relationship between the limit of etching with 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 = 0.02 mm (minimum mask opening width) Lead pitch (P _A ) = {0.03 + G _B + (t /
3)} mm Therefore, in the case of 0.15 mmt, 42% Ni-Fe alloy W _A = 0.03 mm G _A = 0.02 + (0.15 ÷ 3) = 0.070 mm P _A = 0.03 + 0.07 = 0 It becomes 10 mm. Further, in 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 ..

Comparing this with the pressing method, 0.10 mmt in the pressing method and G = 0.10 mm, W = 0.10 × 0.7 = 0.07 in the case of 42% Ni-Fe alloy.
mm, P = 0.17 mm, and the minimum value required for wire bonding W = 0.07 mm can be achieved, but G =
Since it is as large as 0.1 mm, it is not possible to achieve a narrow pitch.

[0033] In the case of etching using _{99.99% Cu G A = {(} G B = 0.02) + (t / 4)} mm
Therefore, fine processing can be performed correspondingly.

The inner side lead and the outer side lead of the present invention are preferably electrically connected by electric resistance welding, laser welding, anisotropic conductive sheet or the like, but are not limited to these. ..

The inner side lead and the outer side lead are each provided with a pilot hole 3 for common positioning, through which a pilot pin (not shown) can be inserted for accurate positioning. In this way, the inner side lead 5 is overlaid and electrically connected, for example, on the outer side lead 4 from which the inside of the connecting portion 9 in FIG. 1 has been removed by pressing. During mass production, unmanned connection work can be performed by aligning the position with the pilot pin, abutting the tool, energizing feeding means, frame loading means and the like on a continuous line. In the present invention, when connecting the inner side lead 5 and the outer side lead 4, a part of the tip of the inner side lead 5 is held in advance by a tape 10 as shown in FIGS.

Here, the hold-down tape 10 is preferably an insulating film such as a polyimide film with an adhesive or an adhesive polyimide film. The adhesive polyimide film is as high as 230 ° C. as compared with the sticking temperature of the acrylic film of 120 ° C., but it is particularly preferable because it has high reliability because no adhesive is used.

The tape 10 may be attached by joining the tips of the inner leads 5 as shown in FIG. 3 and fixing them so that they do not move. Since the tips of the inner leads 5 extend from the four sides toward the center as shown in FIG. 1, the tips in the four directions are fixed separately or continuously. After that, the outer side leads 4 pressed as described above are connected. Since the tips of the inner leads 5 are fixed by the tape 10 in this manner, the wire is prevented from protruding during wire bonding, and deformation during transportation or the like can be prevented.

[0038]

EXAMPLES The present invention will be specifically described below based on examples.

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

First, an inner lead of 304 pins was formed by etching. The material is 0.10 mmt
No. 42% Ni-Fe alloy is etched by ferrous chloride, and the lead width (W _A ) of the inner side lead =
0.09 mm, and lead spacing (G _A) = 0.05mm, a lead pitch (P _A) = 0.14mm. The tip of the inner side lead 5 before connection was fixed with a 25 μm t polyimide film with an acrylic adhesive of 19 μm t. Adhesive width of the tape 10 is 1mm, 1m from the tip of the lead
As a wire bonding portion, m was attached to the rear side (outer side), and Ag plating for wire bonding was applied to a thickness of 3 μm as indicated by reference numeral 11 in FIG. The tape 10 has the tips in four directions fixed separately so that the tips of the inner leads 5 do not move. As shown in FIG. 4, the shape before connection is such that the half etching groove 1 is formed at a position corresponding to the connection portion 9.
2 is machined, pilot hole for common alignment 3
Was established.

The outer side leads were formed by pressing. The material was 0.15 mmt of 42% Ni-Fe alloy.

The connection method was resistance welding with a tool having a convex shape that abuts the line of the connection portion 9. The outer lead also has a common alignment hole 3 formed by pressing, and the pilot pin can be inserted into the common hole 3 to accurately align the lead.

Then, the resistance welding tool is abutted,
The connection was continuously made by energizing.

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

(Embodiment 3) A composite lead frame (inventive examples 7 to 7 of the present invention) was prepared under the same conditions and conditions as in Example 1 except that 99.99% pure copper (t = 0.1 mm) was used as the inner 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.

(Embodiment 4) The same lead material as in Embodiment 1 was used except that the inner lead material was 42% Ni-Fe of 0.15 mmt, which is the same as that on the outer side. 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 inner side lead,
Current W _ASince the necessary limit of P is 0.07 mm, P_A
0.14 mm was the practical minimum pitch. This place
Even if it is 0.1mmt, 42% Ni-Fe mold press of 0.1mmt
The pitch could be narrowed by P = G + W = 0.1 + 0.07 = 0.17 mm in the process.

(Example 5) A composite lead frame (inventive examples 13, 14 and 13 of the present invention) was prepared under the same conditions and conditions as in Example 1 except that a polyimide-based adhesive film having adhesiveness was used as the insulating film. 15) was created.
Although the film sticking temperature was as high as 230 ° C., there was no adhesive, so a highly reliable lead frame was obtained, and in each case, the fine patterns could be continuously connected as in the case of Example 1.

(Embodiment 6) In Embodiment 1, an automatic alignment machine equipped with a mechanism capable of correcting the amount of deviation after recognizing the positions of the inner lead and the outer lead by image processing without using a common alignment hole. The position was adjusted to the regular position by means of, and then the welding tool was used to join in the same manner. In this method, since it is not necessary to form the common alignment hole on the outside by etching, the shape of the etching frame can be minimized, and thus the entire frame can be manufactured at low cost.

[0050]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, a narrower pitch and a larger number of pins can be achieved as compared with the conventional one made only by press working. In addition, compared with the conventional product made only by etching, the mold can be shared, and the processing cost can be reduced to 1/2 to 1/4 by pressing the outer side lead. Also, the inner side lead and the outer side lead can be freely selected by combining different kinds of metals, and the degree of freedom in material selection can be greatly increased.

Further, since the tips of the inner leads are fixed, the following effects are obtained. When the bonding tool is brought into contact with the ultrasonic wire bonder, lateral displacement does not occur and wire bondability is improved.

The inner side lead is not deformed during package transportation. Compared to the case where the inner and outer leads are collectively manufactured by a press, residual stress of the press does not occur. It is possible to completely prevent deformation of the inner side lead during connection work with the outer side lead or during die bonding.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of FIG.

FIG. 3 is a perspective view showing tips of inner leads.

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

[Explanation 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 10 Tape 11 Ag Plating 12 Half Etching Groove

Claims (1)

[Claims] 1. A composite lead frame comprising: an inner side lead formed by etching a part of the tip end of the lead; and an outer side lead formed by pressing.