JP2837068B2 - Lead frame manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame for a semiconductor device, and more particularly to a quad flat package (hereinafter referred to as a QFP) having a large number of pins and a fine pitch.
The present invention relates to a method for manufacturing a lead frame used for a semiconductor device.

[0002]

2. Description of the Related Art As a conventional general method for manufacturing a lead frame for a semiconductor device, there is known an etching process utilizing a corrosion treatment by a photographic technique and a press process of punching using a press die. Both are efficient processing methods, but these are generally used depending on the stable state of product quality and the production amount.

In recent years, higher density mounting and higher integration of semiconductor elements have been increasingly demanded, and with this, the number of pins of the QFP has been demanded. There are two methods for realizing a multi-pin QFP, that is, increasing the number of output pins. The first method is to increase the number of pins by fixing the external lead pitch.
In the case of a square QFP with 0 pins, its dimensions are 40 mm x
It prevents the high integration of the circuit board to be mounted as a large thing of about 40 mm, and even if it tries to increase the number of pins, it causes handling and transportation problems due to the increase in the internal stress and weight of the mold resin. The method is not practical.

The second method is to fix the external dimensions of the QFP,
This is a method of narrowing (narrowing) the external lead pitch. If this method is adopted, the above-mentioned problem of the first method is almost solved. In this case, close the inner lead and the semiconductor chip so that the wire connecting the inner lead and the semiconductor chip does not sag,
It is necessary to provide a flat portion of about 100 μm for performing stable wire bonding at the inner lead portion, or to enable all the inner leads connected to the semiconductor chip to be connected to the outside as outer leads. As described above, a major problem for increasing the number of pins in a QFP is how to reduce the gap between leads of a lead frame and manufacture the lead frame with stable quality.

[0005] However, the above-mentioned etching and pressing can produce only a gap of about 80% of the thickness of the metal plate used together, and it is impossible to satisfactorily process a gap smaller than that. That is, the plate thickness of the material most frequently used at present is about 0.15 mm to 0.125 mm, and the gap of 80% thereof is 0.12 mm to 0.1 mm. The punch for removing the wire may be broken without being able to withstand the pressing pressure, or even if it is not broken, large processing distortion may occur. On the other hand, in the case of etching, even if etching is performed from both sides with high efficiency, the center part in the cross-sectional direction will not be completely melted, or it will be forced to separate by etching and the lead parts on both sides that should not be processed Etching is performed more than necessary, resulting in a defective shape.

On the other hand, Japanese Patent Application Laid-Open No. 3-13063 discloses a system in which a laser beam is used for processing part or all of a lead frame. According to the processing method using the laser beam, unlike the conventional etching processing and pressing processing, it is possible to process the gap between the leads without giving a mechanical strain to the inner lead portion. Further, since the laser beam can be focused on an extremely small spot, extremely fine processing can be performed. Therefore, the gap between the leads is probably 1 regardless of the thickness of the material used.
A gap of about μm can be processed, and the pitch between the inner leads can be significantly reduced.

[0007]

As described above, Japanese Patent Laid-Open No.
According to the method described in JP-A-123063, fine processing can be performed with stable quality by using a laser beam, but generally, CO ₂ that is industrially practically used is used.
Since laser or YAG laser processing is processing that uses melting by heat input, the molten metal scatters during processing and adheres to the lead frame surface as spatter, or the molten metal aggregates and re-solidifies as dross. It remains on the end face etc. of the cut part.

When these spatters and dross adhere to the surface of the lead frame or the end face of the lead frame, they tend to be the main cause of performance defects such as short-circuits, and also lead to deterioration of adhesion at the time of joining with other parts in a later process. And dross adhesion should be avoided as much as possible. However, in the processing using the laser beam, spatter or dross is an inevitable phenomenon to some extent.

An object of the present invention is to provide a method for manufacturing a lead frame capable of manufacturing a lead frame having a clean surface free from spatter and dross.

[0010]

According to the present invention, there is provided, according to the present invention, a plurality of inner leads connected to respective terminals of a semiconductor chip, and outer leads continuous outside the inner leads. in forming the lead frame, the method for fabricating a lead frame formed by irradiation of a laser beam at least part of the lead frame, after processing by the irradiation of the laser beam, of the lead frame, year laser beam irradiation
A method for manufacturing a lead frame is provided , wherein a large number of fine particles are made to collide with the lead frame at a high speed from the surface side opposite to the irradiated surface side .

In the above method for manufacturing a lead frame,
Preferably, a particle size of the fine granular material is equal to or less than a minimum width between leads in the lead frame.

[0012]

[0013]

[0014] Preferably, the fine particles are caused to collide with the lead frame from both sides of the lead frame .

[0015]

[0016]

According to the present invention constructed as described above, a portion of the lead frame formed by the laser beam irradiation is irradiated with the laser beam of the lead frame.
From the side opposite to the surface side, by impinging a large number of fine granulate fast, dross or the like attached to the lead frame by the kinetic energy is removed. Therefore,
Thereafter, the surface of the lead frame becomes a clean surface without dross or the like .

Further, since the particle size of the fine particles is smaller than the minimum width between the leads in the lead frame, the fine particles can pass through any gap between the leads. Can be reliably removed even if it adheres to the end face of the lead. Further, even when the fine granular material collides from one side of the lead frame, the fine granular material passes through the gap between the leads and goes around to the opposite side of the lead frame to clean the surface to some extent.

Further, the fine granular material is applied to both sides of the lead frame.
By impinging from the side to the lead frame, both sides of the sputtering and dross is removed at the same time efficiently and reliably clean the surface of the lead frame is obtained.

[0019]

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for manufacturing a lead frame according to the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of a lead frame manufactured according to the present embodiment, and FIG. 2 is a process diagram illustrating a method of manufacturing the lead frame according to the present embodiment. In FIG. 1, a semiconductor chip (not shown) is provided at a central portion of the lead frame 301.
Is provided, and a number of inner leads 303 and outer leads 304 connected to the inner leads 303 are provided so as to surround the die pad 302. The adjacent inner lead 303 and outer lead 304 are connected to each other by a dam bar 305 so as to be connected to each other. The notch 30 around the die pad 302 except for the arm 302a.
The inner lead 303 is separated from the die pad 302 by the notch 306, and the adjacent inner lead 303 is divided by the notch 306. Further, the lead frame 30
A positioning hole 307 is provided in the outer peripheral portion of the semiconductor device 1 for positioning when connecting the terminal of the semiconductor chip and the inner lead 303. The dam bar 305 has a role of blocking the resin when molding the semiconductor chip and the inner lead 3.
03 and the role of reinforcing the outer lead 304,
Removed after molding.

The inner lead 303 extends so as to converge toward the die pad 302, and the tip of the inner lead 303 is electrically connected by wire bonding or the like performed after a semiconductor chip (not shown) is mounted on the die pad 302. Is wide enough to do. Therefore, the gap 303a between adjacent leads has an extremely fine structure in which the inside of the inner lead 303 is narrower than the plate thickness, and the processing of this part is most dimensional accuracy and cleanliness in lead frame processing. Is the tough part.

Hereinafter, the steps of this embodiment will be described. First,
In step S1 of FIG. 2, a metal plate is processed by laser beam irradiation to form a lead frame as shown in FIG. At this time, processing by a laser beam is performed, for example, using YAG.
What is necessary is just to carry out by the conventional method using a laser. However, the part to be processed by the laser beam is at least the inner lead 3
Small portions inside the portion 03 and other large portions such as the outer lead 304 may be formed by conventional etching or press working.

According to the above-mentioned processing method using a laser beam, unlike the conventional etching processing and pressing processing, it is possible to process the gap between the leads without giving a mechanical strain to the inner lead portion. . further,
Since the laser beam can be focused on an extremely small spot, extremely fine processing can be performed. Therefore, the gap between the leads can be processed to a gap of about 1 μm irrespective of the thickness of the material to be used, the pitch between the inner leads can be significantly reduced, and the fine processing can be performed with stable quality. It can be carried out.

However, since the processing using a CO ₂ laser or a YAG laser which is generally put into practical use in the industry is a processing utilizing melting by heat input, as shown in FIG. It scatters and adheres to the surface of the lead frame 301 as spatter 10, or the molten metal is coagulated and re-solidified and remains on the end face or the like of the portion cut as dross 11. In particular, the sputter adheres to the surface on the opposite side of the lead frame, for example, by being reflected by a holder or the like supporting the lead frame. If these spatters 10 and dross 11 adhere, they tend to be a main cause of performance defects such as short circuits, and also lead to deterioration of adhesion at the time of joining with other parts in a later process. Therefore, this must be avoided as much as possible. This is a phenomenon that cannot be avoided to some extent in processing using a laser beam.

Next, in step S2, the fine particles are made to collide at high speed from one surface of the lead frame. The state at this time is shown in FIG. In FIG. 4, the lead frame 301 processed in step S1 is
00. Further, the fine granular material 101 stored in the granular material tank 100 is supplied to the granular material nozzle 120 through the conduit 110, and the fine granular material 101 is accelerated by the high-pressure air 131 from the high-pressure air source 130 to be accelerated. Spouts from the tip. Then, the fine granular material 101 collides with the surface of the lead frame 301 at a high speed, and the spatter 1 adhered during the processing by the laser beam.
Zero and dross 11 are removed by the kinetic energy. This process is an application of a technique called shot blast employed for deburring precision machined parts.
Further, the granular material nozzle 120 is moved (scanned) along the entire portion processed by the laser beam, and the sputter 10 and the dross 11 are all removed to clean the surface.

The fine granular material 101 used at this time is a relatively hard granular material such as a resin or a glass ball having a particle size of about 200 μm or less. In addition, these fine granular materials 101
Is smaller than the minimum gap 303 a between the leads (the gap between the inner leads) in the lead frame 301. Thus, the fine granular material 101 can pass through any gap between the leads. For example, even if a very large dross adheres to the end face of the lead, it can be reliably removed. Further, the fine granular material 101 passes through the gap between the leads, is reflected by the holder 200, and also wraps around to the opposite side of the lead frame, and also removes spatter on the surface thereof to some extent cleans.

Next, in step S3, the lead frame 301 is turned upside down and placed on the holder 200, and the fine particles are made to collide at a high speed from the other surface. This is performed in the same manner as in step S2. By this step S3, the spatter 10 and the dross 11 on the other surface of the lead frame 301, which have not been sufficiently removed in step S2, are reliably removed.

Finally, in step S4, the lead frame 3
01 is removed by washing or the like, and the production is completed.

In the present embodiment as described above, the fine granular material 101 collides at a high speed with the portion formed by the irradiation of the laser beam on the lead frame 301.
The spatter 10 and dross 11 adhered to the surface are removed.
Therefore, the surface of the subsequent lead frame 301 is a clean surface free of spatter and dross.

Further, since the particle size of the fine particles 101 is equal to or less than the width of the gap 303a between the smallest leads (between inner leads) in the lead frame 301, the fine particles may pass through any gap between the leads. For example, even if a very large dross adheres to the end face of the lead, it can be reliably removed. Further, the fine granular material 101 can pass through the gap between the leads and also reach the opposite side of the lead frame to clean the surface to some extent.

In the case of a lead frame whose surface cleanliness is not so strict, there is no need to perform step S3 in FIG. 2, and it is sufficient to make the minute particulate matter collide only from one side. In this case, as described above, the fine particles 101 wrapping around the opposite side of the lead frame remove spatter on the surface, and the surface on the opposite side is also cleaned to some extent.

Next, another embodiment of the method for manufacturing a lead frame according to the present invention will be described with reference to FIG. In the present embodiment, as shown in FIG. 5, the nozzle 150 for the laser beam and the nozzle 120 for the granular material are fixed closely by the arm 156. In FIG. 5, a laser beam 152 generated from a laser oscillator 151 is processed by a processing head 153.
After being changed in direction by a bending mirror 154 provided in the processing head 153,
Condensing lens 15 in lower laser beam nozzle 150
The light is condensed at 5 and irradiates the metal plate material to be the lead frame 301.

Immediately after the processing by the laser beam, the fine granular material 101 is ejected from the granular material nozzle 120 fixed close to the laser beam nozzle 150 in the same manner as in the above-described embodiment, and the lead frame 301 is formed. Colliding fast. However, in FIG.
The nozzle 50 and the granular material nozzle 120 move from left to right on the paper as shown by arrows 150A and 120A in the figure, and the hatched portion on the right side of the laser beam nozzle 150 has not been processed yet. . Other manufacturing methods are the same as those of the embodiment described with reference to FIGS.

According to this embodiment as described above, the same effects as those of the embodiment described with reference to FIGS.
Processing by laser beam and removal of spatter and dross by collision of fine granular material can be performed in one process,
Manufacturing efficiency is improved.

Next, still another embodiment of the method for manufacturing a lead frame according to the present invention will be described with reference to FIGS. In this embodiment, as shown in FIG.
The granular material nozzle 120a is also arranged at a position opposite to the lead frame 301 of the granular material nozzle 120.
However, the lead frame 301 is the holder 2 shown in FIGS.
Instead of being supported by 00, only the end of the lead frame (not shown) is supported. In addition, the nozzle 120 for granular material
a is the fine granular material 1 stored in the granular material tank 100a.
01a is carried by the conduit 110a and the high pressure air source 13
0a from the high-pressure air 131a.
a is accelerated and spouted from the tip of the granular material nozzle 120a. That is, the fine granular material collides from both sides of the lead frame 301 at the same time, and spatter and dross on both sides are simultaneously removed. Therefore, a clean surface can be obtained efficiently and reliably.

Hereinafter, the steps of this embodiment will be described. First,
In step S11 of FIG. 7, the metal plate is processed by laser beam irradiation to form a lead frame.
This step is the same as step S1 in FIG. Next, in step S12, the fine granular material is collided simultaneously from both sides of the lead frame by the method shown in FIG. In this step, steps S2 and S3 in FIG. 2 are performed simultaneously. Finally, in step S13, the fine granular material 101 remaining on the surface of the lead frame 301 is removed by washing or the like, and the manufacturing is completed.

As described above, according to this embodiment, the same effects as those of the embodiment described with reference to FIGS.
The fine particles 101 and 101a are
Since both sides of the lead frame 301 collide, spatter and dross on both sides of the lead frame 301 are simultaneously removed, and a clean surface can be obtained efficiently and reliably.

It should be noted that the lead frame may be suspended vertically in a vertical plane, and fine particles may collide from both sides thereof, and the suspended lead frame may be moved up and down.

Next, still another embodiment of the method for manufacturing a lead frame according to the present invention will be described with reference to FIG. This embodiment is an embodiment in which fine particles are mixed into an etching solution when a large portion other than a fine portion such as an inner lead is processed by conventional etching. However, it is assumed that a resist process based on an etching pattern of a portion to be processed by etching is performed in advance by a conventional method.

In this embodiment, the fine particles are mixed with an etching solution, and this mixture is caused to collide with a lead frame.
In FIG. 8, a mixture 161 of fine particulate matter and an etching solution stored in a mixture tank 160 is pumped to a mixture nozzle 180 by a pump 171 provided in a pipeline 170, and is supplied by high-pressure air 191 from a high-pressure air source 190. The mixture 161 is accelerated and spouts from the tip of the mixture nozzle 180. Then, the mixture 161 collides with the surface of the lead frame 301 at a high speed, and spatters 10 and dross 11 attached during processing by a laser beam are removed by the kinetic energy of the fine granular material in the mixture 161 and the mixture 161 is removed. Sputter and dross are also removed by corrosion due to the etching solution inside, and the lead frame surface is further cleaned. Further, the mixture nozzle 1
80 moves along the entire lead frame (scan)
Then, the portion processed by the laser beam is cleaned of the surface by removing the sputter 10 and dross 11, etc.
The portion where the resist processing based on the etching pattern has been performed is subjected to conventional etching.

As described above, according to this embodiment, not only the same effects as those of the embodiment described with reference to FIGS. 1 to 4 can be obtained, but also spatter and dross are removed by corrosion by an etching solution, and the lead frame is removed. The surface becomes even cleaner.

In the above four embodiments, the nozzle for ejecting the fine granular material is moved (scanned) on the surface of the lead frame. However, the ejection port which can cover the entire lead frame is used to cover the entire lead frame. You may make a minute granular material collide at once. In this case, it is not necessary to move (scan) the above-described ejection port.

[0043]

According to the present invention, a fine granular material is made to collide with a portion formed by laser beam irradiation on a lead frame at a high speed, so that the surface of the lead frame has a clean surface free from spatter and dross. Can be.

Also, since the particle size of the fine particles is equal to or less than the minimum width between the leads in the lead frame, the fine particles can pass through any gap between the leads,
Spatter and dross can be reliably removed. In addition, the surface of the micro-granular material lead frame can also be cleaned to some extent by wrapping around the surface on the opposite side.

Further, immediately after the irradiation of the laser beam, the fine particles are made to collide with the portion processed by the laser beam, so that the processing by the laser beam and the removal of spatter and dross by the collision of the fine particles are performed in one step. And the production efficiency is improved.

Further, since the fine granular material collides from both sides of the lead frame, spatter and dross on both sides of the lead frame are simultaneously removed, and a clean surface can be obtained efficiently and reliably.

Further, since the fine particulate matter is mixed with the etching solution and collides with the lead frame, spatter and dross are removed even by corrosion by the etching solution, and the lead frame surface is further cleaned.

Further, according to the present invention, each of the lead ends of the lead frame is chamfered, and the semiconductor chip is mounted on the lead frame, wire bonding, molding, press cutting of the outer peripheral portion than the outer lead, and outer are performed. In a post-process such as lead bending, corner portions are not caught and handling is facilitated.

In addition, countless fine dents are generated on the surface of the lead frame due to the collision of the fine particles, and the surface becomes a matte surface, and the solder wettability is improved when solder plating is performed later. Furthermore, since the satin-like surface is in a residual compressive stress state, that is, in a work-hardened state,
The strength of the lead frame itself is improved, and the fatigue strength is also improved. Even if the semiconductor device is further densified and internal heat is generated, thermal fatigue of the lead frame does not matter.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a lead frame manufactured according to an embodiment of the present invention.

FIG. 2 is a process chart showing a method for manufacturing the lead frame of FIG. 1;

FIG. 3 is a diagram showing a situation in which spatter or dross adheres to a lead frame with processing by a laser beam.

FIG. 4 is a view showing a state in which a fine granular material collides from one surface of a lead frame after irradiation with a laser beam in the manufacturing process of FIG. 2;

FIG. 5 is a diagram illustrating a method for manufacturing a lead frame according to another embodiment of the present invention.

FIG. 6 is a view illustrating a method of manufacturing a lead frame according to still another embodiment of the present invention.

FIG. 7 is a process chart showing a method for manufacturing a lead frame in the case of FIG. 6;

FIG. 8 is a view illustrating a method of manufacturing a lead frame according to still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Sputter 11 Dross 100, 100a Granular body tank 101, 101a Fine granular body 120, 120a Granular body nozzle 130, 130a High-pressure air source 150 Laser beam nozzle 151 Laser oscillator 155 Condensing lens 160 Mixture tank 161 (with fine granular body Mixture with etchant 171 Pump 180 Mixer nozzle 190 High pressure air source 301 Lead frame 303 Inner lead 303a Gap (between leads) 304 Outer lead

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 23/50

Claims (3)

(57) [Claims] When forming a lead frame having a number of inner leads connected to respective terminals of a semiconductor chip and outer leads continuous outside the inner leads, at least a part of the lead frame is formed by a laser. the method of manufacturing a lead frame formed by irradiation of a beam, after processing by the irradiation of the laser beam, the Ridofu
Opposite to the side of the frame where the laser beam was irradiated
A method for manufacturing a lead frame , comprising: colliding a large number of fine particles at a high speed with the lead frame from the opposite side . 2. The method for manufacturing a lead frame according to claim 1, wherein a particle size of said fine granular material is equal to or smaller than a minimum width between leads in said lead frame. 3. The method of manufacturing a lead frame according to claim 1, wherein the fine granular material is formed on both sides of the lead frame.
Colliding the lead frame from the surface side
Lead frame manufacturing method.