JPH03152962A - Facility for manufacturing semiconductor device lead frame - Google Patents

Abstract

PURPOSE:To improve a lead frame in accuracy, quality, and productivity by a method wherein residual stress in a strip material, which is caused by a rolling process and a slitting process and differs at each slit position, is made uniform through the high frequency annealing of the strip material. CONSTITUTION:A metal strip slitted by a slitter 1 is fed to a first annealing device 2. In the device 2, a high frequency is applied to the metal strip in an oxidation preventing atmosphere to heat the whole face of the metal strip by induction heating. By this annealing process, the residual stress induced in the metal strip by a rolling process and a slitting process is removed. Then, the metal strip is formed into a lead frame 11 in continuous form by a first press 3. In succession, by a second annealing device 4, only inner leads 12 and a die pad 15 of the lead frame 11 in continuous form are heated by partial induction heating in the same manner as of the device 2. By this annealing treatment, residual stress induced by the press 3 is removed. Thereafter, the lead frame 11 in continuous form is plated through a plating device 5 and then cut into individual lead frames by a second press 6. By this setup, a lead frame can be made uniform in residual stress and improved in accuracy, quality, and productivity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to equipment for manufacturing lead frames for semiconductor devices, and the present invention relates to equipment for manufacturing lead frames for semiconductor devices. It relates to equipment that allows for good removal.

[Conventional technology]

Manufacture of lead frames for semiconductor devices is generally performed sequentially according to the following processing steps.

■The process of slitting a wide strip of thin metal sheet into strips of the required width for lead frames.

Strain correction process that removes distortions such as curls in zero-strip materials.

A first pressing process in which unnecessary portions of the zero strip material are sequentially removed and a tie bar that connects and holds the tip of the inner lead is left to form the element mounting stage, inner lead, and outer lead.

■ Bright annealing process that heats the entire surface of the lead frame to remove residual stress.

■Plating process that applies plating to the surface of the required parts of the lead frame.

■Second pressing process in which the tip of the inner lead is held and fixed with tape, then the tie bar is punched out and removed to form the lead frame into the desired shape.

After mounting the device on the semiconductor device mounting stage of the lead frame formed by manufacturing equipment that includes these processes, an electrically conductive circuit is formed between the electrode terminal of this device and the external lead with a thin precious metal wire, and further It is sealed with resin and assembled into a semiconductor device.

When assembling such semiconductor devices, the internal residual stress of the lead frame is released due to the heating when the lead frame undergoes an intermediate heating process, which deforms the tip of the inner lead and causes wire bonding defects, which reduces the yield of semiconductor devices. and was a cause of quality deterioration.

Furthermore, if the metal strip used as material is wide,
The state of internal residual stress that accumulates due to the working history of manufacturing processes such as cold rolling is different between the central portion and both end portions in the width direction. For this reason, when a wide metal strip is slit into multiple strips of the required width, each strip retains different internal residual stresses depending on whether the strip is slit from the center or from both ends. This strip is the first
When forming a lead frame consisting of an element mounting stage, inner leads, outer leads, etc. using a progressive mold in the pressing process, residual stress accumulated by punching out unnecessary parts is released, and the lead The required shape, dimensions, etc. of the frame change. Furthermore, the state of change was different on each strip side, the punching conditions in the progressive die were changed, and the shape and dimensions of the inner lead tip became unstable, causing a decline in the yield and quality of the lead frame.

Conventionally, in order to prevent such problems, there have been methods of fixing the vicinity of the tip of the inner lead with tape or insulating resin;
Alternatively, after forming the lead frame, bright annealing is generally performed to remove internal residual stress remaining in the lead frame.

[Problem to be solved by the invention]

However, in the former method, the residual internal stress is released by the heating during the intermediate heating process in semiconductor device assembly, and the tape and resin that fixed the lead tips soften, expand and contract, and the wire bonding of the lead tips is completed. It has the disadvantage of causing slight deformation in the area.

On the other hand, the latter method is effective in removing internal residual stress remaining in the lead frame.

However, since this is applied after the first pressing process, the residual stress is released by punching the strips that retain residual stress in different states, making the shape and dimensions unstable, making it difficult to maintain quality accuracy. There's a problem. On the other hand, in order to maintain quality accuracy, it is necessary to make adjustments to the progressive die to change the punching conditions on the strip side. therefore,
These adjustments occur irregularly on the strip side, resulting in poor lead frame productivity and damage to expensive progressive molds.

Furthermore, in recent years, with the diversification of functions of semiconductor devices using lead frames and the trend towards multi-bin design, the tips of inner leads have become finer. For this reason, the lead width and the spacing between the leads have become narrower, and minute deformation of the inner leads cannot be tolerated as a product, necessitating highly accurate processing equipment.

An object of the present invention is to improve productivity by maintaining stable punching of lead frames, and to enable processing of high-precision, high-quality lead frames for semiconductor devices.

[Means to solve the problem]

The present invention includes a slitter that slits a thin metal plate into a metal strip matching the width of a lead frame, and a press device that is disposed downstream of the slitter and punches and presses the metal strip into a lead frame pattern. The lead frame manufacturing equipment includes a first slitter and a press device and a first slitter downstream of the press device. It is characterized by the layout of the second annealing device.

The first annealing device is equipped with a high frequency induction heating means that applies high frequency waves of 15 to 500 KHz to the entire surface of the metal strip in an oxidation-preventing atmosphere to remove residual stress caused by slitting.

Further, the second annealing device is equipped with a high-frequency induction partial heating means for partially applying a high frequency of 15 to 500 KHz to the inner leads of the pattern of the lead frame and/or the element mounting stage portion in an oxidation-preventing atmosphere. Removes residual stress caused by punching process.

[Effect]

Since the manufacturing equipment of the present invention is configured as described above, the first annealing device removes residual stress that differs for each strip due to the processing history of the metal strip after rolling and slitting the thin metal sheet. Moreover, the width of each metal strip is much smaller than the thin metal sheet used as the material.
The degree of stress relief of each metal strip is made uniform. For this reason, the punching process using the progressive die after being transported to the first press device can be performed well because the residual stress distribution of the metal strip is smoothed, and stable punching can be maintained to form the lead frame. A pattern is formed.

In addition, after punching and forming by the first press device, the second annealing device removes residual stress only in the inner leads and/or the element mounting stage, so that it can be used in plating processing, subsequent press processing, semiconductor device assembly, etc. It is possible to obtain a lead frame that maintains the required precision shape and quality even when heated by heating.

〔Example〕

Regarding one embodiment of the present invention having the above configuration and operation,
The explanation will be based on the attached 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 at an intermediate stage of manufacturing a lead frame used in a general semiconductor device.

In FIG. 2, a lead frame 11 formed in an intermediate process includes a plurality of inner leads 12 arranged radially apart from an element mounting stage 15 in the center and connected at their tips with tie bars 14, and Outer leads 13 are formed extending opposite to the outer leads 12, respectively. A support par 17 that holds the element mounting stage 15 and a dam bar 16 that connects the outer leads are formed, and reference pin holes 19 are formed at both ends of the lead frame 110 at a predetermined pitch.

In FIG. 1, a metal sheet B of material is slit into a metal strip A by a slitter 1, and then a first annealing device 2. First press device 3. It is supplied to the pass line to the second annealing device 4, and then further transported intermittently to the plating device 5 and the second press device 6. Hereinafter, the steps from metal sheet B to press forming of the lead frame will be explained in order.

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

The slitted 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 includes a high frequency induction heating section, and applies high frequency waves of 15 to 500 KHz in an oxidation-preventing atmosphere to induction heat the entire surface of the metal strip A. Through this annealing process, the metal strip A produced by the rolling of the metal sheet B and the slitting by the slitter 1
residual stress is removed. Note that bright annealing, which is used in general metal heat treatment, may be used instead of high-frequency induction heating.

The metal strip A that has been subjected to the residual stress removal process is intermittently conveyed to the first press device 3 equipped with a progressive die. and,
Unnecessary portions are successively removed using a mold, and finally a continuous body of lead frame 11 having a predetermined shape shown in FIG. 2 is formed by press working.

The second annealing device 4 is equipped with a high-frequency induction heating section like the first annealing device 2, and is heated at 15 to 500 K) in an oxidation-preventing atmosphere.
The continuous body of the lead frame 11 is heated by induction by applying a high frequency wave of 2. This induction heating area is the lead frame 1
Corresponding to the inner leads 12 and the element mounting stage 15 inside the vicinity of the first resin sealing line 18, a process of masking is performed on areas other than these areas. Then, high frequency waves are applied from the back side of the continuous body of the lead frame 11 to perform partial heating. By this annealing treatment, the first press tool W3
Residual stress caused by punching, pressing, coining, etc. when forming the continuous body of the lead frame 11 shown in FIG. 2 is removed by this process. Thereafter, the continuous body of the lead frame 11 annealed by intermittent feeding is wound around the coiler 4a and collected.

Furthermore, the continuous body of the lead frame 11 that has been subjected to the treatment to remove residual stress is transferred to the uncoiler 5a of the plating apparatus 5 shown in FIG. 5, and is continuously supplied to the plating apparatus 5. In this plating apparatus 5, required partial plating is applied to the tip portions of the inner leads 12 of the lead frame 11 and the element mounting stage 15. The continuous body of the lead frame 11 after the treatment is then wound up and collected by the coiler 5b.

Then, the lead frame 11 is plated in a predetermined area.
As shown in FIG. 6, the continuous body is transferred to an uncoiler 6a at the front stage of the second press device 6, and is intermittently conveyed to the second press device 6 equipped with a progressive die. In this second press device 6, the tie bar 14 connecting the tips of the inner leads 12 of the lead frame 11 in FIG. Cutting is performed intermittently.

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

〔Effect of the invention〕

In the present invention, the residual stress that differs depending on the slit position of the strip during rolling and slitting is uniformized by high-frequency heating annealing, so it is not necessary to adjust the progressive die for each strip as in the conventional method. There is no need for 1 2 initial adjustment, the lead frame can be formed stably, the material yield and operation rate are improved, and furthermore, damage to minute blades of expensive progressive molds can be suppressed.

In addition, since it is partial annealing in which the non-heated parts are masked and heated, there is no change in the functions other than the heated parts, and the shape and dimensions can be maintained in the initial state. Therefore, there is no deformation during the heating step of the semiconductor device assembly process, and positioning accuracy is improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a process diagram of the manufacturing equipment of the present invention;
8! j is a plan view of the intermediate stage lead frame processed by the first press device, FIG. 3 is a layout diagram of the device from the first annealing device to the second annealing device, and FIG. 4 is the slitting process of the metal strip. FIG. 5 is a layout diagram of the plating device, and FIG. 6 is a layout diagram of the second press device. 1 Nisritta 1a: Uncoiler 1b: Coiler 2: First annealing device 3: First press device 42 Second annealing device 5: Plating device 5b: Coiler 6: Second press device 11: Lead frame 13: Outer lead 15: Element Mounting stage 17: Support par 19 2 Reference bottle hole A: Metal strip 2a: Uncoiler 4a: Coiler 5a: Uncoiler: Uncoiler: Inner lead: Tie bar: Dam bar 2 Resin sealing line B: Metal thin plate

Claims (1)

[Claims] 1. A slitter that slits a thin metal plate into metal strips that match the width of a lead frame, and a press that is arranged downstream of the slitter and punches and presses the metal strips into the pattern of the lead frame. A lead frame manufacturing facility for semiconductor devices, characterized in that a first annealing device and a second annealing device are arranged between the slitter and the press device and downstream of the press device, respectively. production equipment. 2. The first annealing device is in an oxidation-preventing atmosphere,
2. The manufacturing equipment for a lead frame for a semiconductor device according to claim 1, further comprising a high frequency induction heating means for applying a high frequency of 15 to 500 KHz to the entire surface of the metal strip. 3. The second annealing device is in an oxidation-preventing atmosphere,
Inner leads of the lead frame pattern and/or
2. The manufacturing equipment for lead frames for semiconductor devices according to claim 1, further comprising high frequency induction partial heating means for applying high frequency waves of 15 to 500 KHz to the element mounting stage section.