JPH0821652B2 - Equipment for manufacturing lead frames for semiconductor devices - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a facility for manufacturing a semiconductor device lead frame, wherein residual stress generated by a working history such as manufacturing of a material strip and forming process of a shape is annealed. The present invention relates to equipment that enables good removal.

[Conventional technology]

Manufacturing of a lead frame for a semiconductor device is generally performed sequentially according to the following processing steps.

The process of slitting a wide strip of metal sheet into a strip of the required width for the lead frame.

A straightening process for removing distortion such as curling of a strip.

A first pressing process for forming an element mounting stage, an inner lead, and an outer lead, while removing unnecessary portions of the strip material in order and leaving a tie bar for connecting and holding the tips of the inner leads.

Bright annealing process in which the entire surface of the lead frame is heated to remove residual stress.

A plating process in which the surface of the required part of the lead frame is plated.

A second pressing step in which the tip portion of the inner lead is held and fixed with tape and then the tie bar is punched and removed to form the lead frame into a desired shape.

Then, after mounting the element on the semiconductor element mounting stage of the lead frame formed by the manufacturing equipment including these steps, the electrode terminal of this element and the external lead are formed into an electrical conduction circuit with a fine wire of noble metal, and It is sealed with resin and assembled into a semiconductor device.

In the assembly of such a semiconductor device, the internal residual stress of the lead frame is released by the heating when the lead frame undergoes the intermediate heating process, the inner lead tip portion is deformed, and the wire bonding failure occurs, and the yield of the semiconductor device is increased. And it was a factor of quality deterioration.

Further, when the metal strip used as the material has a wide width, the state of the residual stress inside which is retained due to the working history of the manufacturing process such as cold rolling differs between the central portion and both end portions in the width direction. For this reason, when a wide metal strip is slit into a plurality of strips having a required width, the internal residual stress in each strip is different depending on which of the central portion and both end portions is slit. When forming a lead frame composed of an element mounting stage and inner leads, outer leads, etc., using this progressive die of the first pressing process, the residual stress that remains due to punching of unnecessary parts Are released, and the required shape and size of the lead frame are changed. Further, the change state varies depending on each strip material, the punching conditions in the progressive die change, the shape and size of the inner lead tip end portion becomes unstable, and the lead frame yield and quality deteriorate.

Conventionally, in order to prevent such a problem, a method of fixing the vicinity of the tip end portion of the inner lead with a tape or an insulating resin, or a bright annealing process after forming the lead frame is performed to remove internal residual stress remaining in the lead frame. Removal is common practice.

[Problems to be Solved by the Invention]

However, in the former method, the internal residual stress that remains due to heating during the intermediate heating step in semiconductor device assembly is released, and the tape and resin that fix the lead tips are softened and expanded to cause wire bonding of the lead tips. There is a drawback that minute deformation occurs in the area.

On the other hand, the latter method is effective for removing the internal residual stress remaining in the lead frame. But first
Since it is applied after the pressing process of, the residual stress is released by punching the strip material that has the residual stress in different states.
There is a problem that the shape and dimensions become unstable, and it is difficult to maintain quality accuracy. On the other hand, in order to maintain the quality accuracy, it is necessary to adjust the progressive die to change the punching conditions for each strip. Therefore, there are drawbacks such that these adjustments occur irregularly for each strip, which deteriorates the productivity of the lead frame and damages the expensive progressive die.

In addition, recently, with the diversification of functions of a semiconductor device using a lead frame and the tendency of increasing the number of pins, the tips of the inner leads have become finer. For this reason, the lead width and its interval are further narrowed, and minute deformation of the inner leads is unacceptable as a product, and high-precision processing equipment is required.

An object of the present invention is to maintain stable punching and forming of a lead frame, improve productivity, and process a lead frame for a semiconductor device with high accuracy and high quality.

[Means for solving the problem]

The present invention provides a lead provided with a slitter for slitting a thin metal plate on a metal strip that matches the width of a lead frame, and a press device arranged downstream of the line of the slitter for punching and pressing the metal conditions into a pattern of the lead frame. In the frame manufacturing facility, a first annealing device is arranged between the slitter and the pressing device, and a second annealing device is laid out downstream of the pressing device.

The first annealing apparatus is provided with a high frequency induction heating means for applying a high frequency of 15 to 500 KHz to the entire surface of the metal strip in an oxidation preventing atmosphere, and removes residual stress due to slitting.

In addition, the second annealing device is
A high frequency induction partial heating means for partially applying a high frequency of 15 to 500 KHz is provided on the inner lead of the pattern of the lead frame and / or the element mounting stage section, and residual stress generated by punching by a press machine is removed.

[Action]

Since the manufacturing equipment of the present invention is configured as described above, the residual stress that is different for each strip due to the processing history for the metal strip after rolling the thin metal plate and after slitting is removed by the first annealing device. In addition, since the width of each metal strip is much smaller than that of the thin metal plate of the raw material, the degree of stress relief of each metal strip is made uniform. Therefore, the punching process by the progressive die after being conveyed to the press machine can be performed satisfactorily because the residual stress distribution of the metal strip is smoothed, and the stable punching can be maintained to obtain the lead frame pattern. It is formed.

Further, after the punching and forming by the press machine, the residual stress of only the inner lead and / or the element mounting stage part is removed by the second annealing machine. It is possible to obtain a lead frame that maintains the required precision shape and quality even with heating.

〔Example〕

An embodiment of the present invention having the above configuration and operation will be described with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram showing the processing steps of the manufacturing equipment of the present invention, and FIG. 2 is a plan view of a lead frame used in a general semiconductor device at an intermediate stage of manufacturing.

In FIG. 2, a lead frame 11 formed in an intermediate step is provided with a plurality of inner leads 12 which are radially arranged apart from the element mounting stage 15 in the central portion and whose tip portions are connected by tie bars 14, and the inner leads 12. Outer leads 13 are formed so as to extend so as to face 12 respectively.
Then, the support bar 17 that holds the element mounting stage 15
Also, a dam bar 16 for connecting the outer leads is formed, and reference pin holes 19 are formed at both ends of the lead frame 11 at a predetermined pitch.

In FIG. 1, a metal thin plate B of a material is slitted to a metal strip A by a slitter 1, and then supplied to a pass line to a first annealing device 2, a first pressing device 3 and a second annealing device 4, After that, it is intermittently conveyed to the plating device 5 and the second pressing device 6. Hereinafter, the steps from the metal thin plate B to the press forming of the lead frame will be sequentially described.

The wide metal sheet B of Fe-Ni alloy formed through the rolling process is continuously supplied from the uncoiler 1a to the slitter 1 in a loop as shown in FIG. The metal strip A having a size corresponding to the width is slit and wound around the coiler 1b.

The slit metal strip A is transferred from the coiler 1b to the uncoiler 2a shown in FIG. 3 and then supplied to the first annealing device 2. The first annealing device 2 is provided with a high frequency induction heating unit, and applies a high frequency of 15 to 500 KHz in an oxidation preventing atmosphere to induction-heat the entire surface of the metal strip A. By this annealing process, the residual stress of the metal strip A generated by the rolling process of the thin metal plate B and the slitting by the slitter 1 is removed. Note that bright annealing used in general metal heat treatment may be used instead of high frequency induction heating.

The metal strip A from which the residual stress has been removed is intermittently conveyed to the first press device 3 equipped with a progressive die. Then, unnecessary portions are sequentially removed by a die, and finally a continuous body of the lead frame 11 having a predetermined shape shown in FIG. 2 is formed by press working.

The second annealing device 4 is provided with a high frequency induction heating unit similarly to the first annealing device 2, and applies a high frequency of 15 to 500 KHz in an oxidation preventing atmosphere to induction-heat the continuous body of the lead frame 11.
This induction heating region corresponds to the inner lead 12 and the element mounting stage 15 inside the vicinity of the resin sealing line 18 of the lead frame 11, and masking processing is performed on the region other than these regions. Then, high frequency is applied from the back surface side of the continuous body of the lead frame 11 to perform partial heating. By this annealing treatment, residual stress due to punching, pushing pressure, coining and the like when forming the continuous body of the lead frame 11 of FIG. 2 by the first pressing device 3 is removed. After this, the lead frame annealed by intermittent feeding
The 11 continuums are wound around the coiler 4a and collected.

Further, the continuous body of the lead frame 11 which has been subjected to the treatment for removing the residual stress is transferred to the uncoiler 5a of the plating apparatus 5 shown in FIG. 5 and continuously supplied to the plating apparatus 5. In this plating apparatus 5, required partial plating is performed on the tip portion of the inner lead 12 of the lead frame 11 and the element mounting stage 15. And the processed lead frame
The 11 continuums are wound and collected on the coiler 5b.

Then, the lead frame 11 which is subjected to predetermined partial plating
6, the continuous body is transferred to the uncoiler 6a in the preceding stage of the second press device 6 and intermittently conveyed to the second press device 6 equipped with the progressive die. In the second press device 6, the tie bar 14 connecting the tip end portions of the inner leads 12 of the lead frame 11 in FIG. 2 is removed so that the lead frame 11 becomes a strip shape including a required number of pieces. A process of cutting intermittently is performed.

The strip-shaped lead frame 11 is supplied to the process of assembling the semiconductor device, and the processes such as die bonding, wire bonding, and resin sealing are performed as the final process.

〔The invention's effect〕

In the present invention, different residual stresses at each slit position of the strip material such as rolling and slitting are subjected to high-frequency annealing to be uniformized, so that the progressive die is adjusted for each strip material as in the conventional case. There is no need, the initial adjustment can be maintained, the lead frame can be stably formed, the material yield and the operating rate are improved, and the damage of the fine blade of the expensive progressive die can be suppressed.

Further, since the partial annealing is performed by masking and heating the non-heated portion, the functions other than the heated portion do not change, and the shape and dimension can be maintained in the initial state. Therefore, there is no deformation in the heating process of the semiconductor device assembling process, and the positioning accuracy is improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing a process diagram of the manufacturing equipment of the present invention, and FIG.
The figure is a plan view of the lead frame at the intermediate stage processed by the first press machine, FIG. 3 is the layout view of the apparatus from the first annealing apparatus to the second annealing apparatus, and FIG. 4 is the slitting process of the metal strip. FIG. 5 is a layout diagram of the plating device, FIG. 5 is a layout diagram of the plating device, and FIG. 6 is a layout diagram of the second press device. 1: slitter, 1a: uncoiler 1b: coiler 2: first annealing device, 2a: uncoiler 3: first pressing device 4: second annealing device, 4a: coiler 5: plating device, 5a: uncoiler 5b: coiler 6: first 2 Press machine, 6a: Uncoiler 11: Lead frame, 12: Inner lead 13: Outer lead, 14: Tie bar 15: Element mounting stage, 16: Dam bar 17: Support bar, 18: Resin sealing line 19: Reference pin hole A : Metal strip, B: Thin metal plate

Claims (3)

[Claims] 1. A slitter for slitting a thin metal plate on a metal strip material matching the width of a lead frame, and a press device arranged downstream of the slitter for punching and pressing the metal strip material into a pattern of a lead frame. A lead frame manufacturing facility having a first annealing device arranged between the slitter and the pressing device, and a second annealing device laid out downstream of the pressing device. Lead frame manufacturing equipment. 2. The first annealing apparatus is provided with high frequency induction heating means for applying a high frequency of 15 to 500 KHz to the entire surface of the metal strip in an oxidation preventing atmosphere. Manufacturing equipment for lead frames for semiconductor devices. 3. The second annealing apparatus has a high frequency induction partial heating means for applying a high frequency of 15 to 500 KHz to the inner lead of the pattern of the lead frame and / or the element mounting stage section in an oxidation preventing atmosphere. The facility for manufacturing a semiconductor device lead frame according to claim 1.