JPH0513633A - Manufacture of lead frame for semiconductor device - Google Patents

Abstract

PURPOSE:To prevent stress corrosion cracking and completely remove oxide films to improve the adhesion of plating by heat-treating metal members of a lead frame and thus removing internal residual stress before multilayer plating. CONSTITUTION:A press shaping process 10, heat treatment process 11, multilayer plating process 12, curing process 13 to heat treat lead frames multilayer-plated and press working process 14 to stick a tape to the lead frames heat-treated and remove the tiebars in this order are provided. Thus, a heat treatment is given before multilayer plating to remove residual stress produced in the shaping process, which prevents stress corrosion cracking produced in pretreatment processes prior to plating, such as immersion and electrolytic degrease cleaning. Moreover, the heat treatment process with a furnace in an antioxidant atmosphere removes hydrogen occluded into metal members in metal plating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a lead frame for a semiconductor device, and more particularly to hydrogen stored in a lead frame member and an internal part of the lead frame member when multi-layer coating of different metals is performed. The present invention relates to a method of manufacturing a lead frame for a semiconductor device, which removes residual stress to prevent hydrogen embrittlement and also to prevent minute deformation of internal leads and maintain a predetermined dimensional accuracy to provide a highly reliable lead frame.

[0002]

2. Description of the Related Art In recent years, lead frames for semiconductor devices have been
As semiconductor devices become more highly integrated, have higher performance, and semiconductor packages become smaller, the number of pins within the same size is increasing. Therefore, QFP (Quad Flat Packg)
The type e) requires an outer lead pitch of 0.3 mm and a number of pins of 200 to 300, and the lead widths and intervals of outer leads and inner leads of the lead frame tend to be narrow. A conventional method for manufacturing a lead frame for a semiconductor device, which corresponds to the above tendency, is an element for mounting a semiconductor element by removing an unnecessary portion by etching or pressing a metal material such as a Cu-Fe-based or Ni-Fe-based alloy. A mounting portion, an inner lead having a connecting piece at a tip end for connecting the bonding pad of the element via a wire, and a dam bar for connecting external connecting terminals to each other corresponding to the inner lead. A punching process using a progressive die for forming a desired shape of a lead frame including an outer lead, a multi-layer plating process for coating the entire surface of the lead frame or only a required part with a multilayer, and connecting the inner lead tip portion The method of forming the lead frame is generally performed by sequentially performing the processing step of punching and removing the connecting piece.

[0003]

However, when a multi-pin lead frame is manufactured by the above method, in a multi-layer plating process for laminating thin plating layers of different metals, acid immersion / electrolytic degreasing in a pretreatment process is performed. When removing the oxide film and hardened layer on the surface of the lead frame member by washing, if there is residual stress in the tensile direction in the metal member, stress corrosion cracking will occur in the metal part, resulting in metal plating quality and long-term reliability. There was a problem such as deterioration of sex. Further, there is a problem that hydrogen generated by the electrolysis is occluded in the metal member to cause hydrogen brittle fracture, which deteriorates long-term reliability.
When multi-layer plating of different metals is performed, a difference in strain or hardness occurs between the base metal and the plated metal due to a lattice shift (misfit), and residual stress stays. During the heat treatment, when the atoms move in the crystal lattice and return to a state without distortion, the tips of the minute internal leads are twisted, and slight deformations such as leaning and bending occur, which results in semiconductor device yield and quality. Had the problem of decreasing The present invention has been made in view of the above circumstances, and improves the quality of plating, removes hydrogen stored in a plated member to improve long-term reliability of a semiconductor device, and leads of a multi-pin system. An object of the present invention is to provide a method for manufacturing a lead frame for a semiconductor device, which can prevent minute deformation of leads of the frame and obtain a stable lead frame of high quality.

[0004]

According to a first aspect of the present invention, there is provided a method of manufacturing a lead frame for a semiconductor device, comprising: a connecting piece for connecting an element mounting portion and a tip portion from a metal material for a lead frame. After performing a process for forming a metal member having a required shape of a lead frame including an inner lead and an outer lead, and forming a multilayer metal coating layer on a required portion of the surface of the metal member, the connecting piece Is a method for manufacturing a lead frame for a semiconductor device, in which the tips of inner leads are separated and formed, wherein a metal member of a lead frame is previously subjected to a heat treatment for removing an internal residual stress that was retained when the metal member was formed. Is used to coat the surface of the metal member of the lead frame with multiple layers of dissimilar metals, and then hydrogen stored in the metal member and residual stress A heat treatment for removing is performed, and then a resin tape for maintaining a mutual position between the inner leads is adhered to a required area of the inner leads, and a pressing process for removing a connecting piece that connects the inner lead tips is performed, It is configured so as to form a required lead frame shape.

[0005]

In the method of manufacturing the lead frame for a semiconductor device according to the first aspect of the present invention, the heat treatment for removing the residual stress caused by the shape processing is applied prior to the multi-layer plating. It has the effect of preventing stress corrosion cracking that occurs in processes such as immersion and electrolytic degreasing cleaning. Further, since it is provided with the heat treatment process of the oxidation preventive atmosphere furnace, it has an action of removing hydrogen occluded in the metal member during metal plating. Further, prior to the removal of the connecting piece, since the resin tape is adhered, the mutual positions of the leads are maintained, and there is an action of preventing deformation due to handling such as deformation or transportation when removing the connecting piece. Then, by adhering the resin tape, the pressing width of the material is widened, the pressing force can be reduced, and there is an effect that the pitch dimension does not change.

[0006]

Embodiments of the present invention will now be described with reference to the accompanying drawings to provide an understanding of the present invention. 1 is a schematic block diagram of a process of one embodiment of the present invention, FIG. 2 is a plan view of a lead frame manufactured in the embodiment, and FIG. 3 is a plan view of a lead frame in an intermediate process of the embodiment. Indicates.

As shown in FIG. 1, a method of manufacturing a lead frame for a semiconductor device according to an embodiment of the present invention comprises a shape processing step 10 by press working, a heat treatment step 11 following the shape working step 11, and a multi-layer plating step 12. A curing treatment step 13 for heat treating the multi-layer plated lead frame,
Attach the tape to the heat treated lead frame,
And a pressing step 14 for removing the connecting piece.
These will be described in detail below.

Shape processing step 10 by the press working
Is equipped with an unwinding device for gradually unwinding a tape-shaped metal material wound in a coil shape on the upstream side of the pressing device, and an intermittent conveying device for feeding the metal material in accordance with a press treatment process. Sending material. In the pressing device, the tape-shaped metal material that is intermittently fed is provided with an element mounting portion 15 at the center, an inner lead 17 provided with a connecting piece 16 at the tip end, and a dam bar 18 as shown in FIG.
A metal member having a required shape of the lead frame such as the outer lead 19 connected by is press-molded and is wound by a winding device arranged on the downstream side.

Next, in the heat treatment step 11, the coil wound by the winding device is unwound by the unwinding device again, and stress relief annealing is performed in a heat treatment furnace in a non-oxidizing atmosphere. As a result, the residual stress generated in the metal member by the press working is removed.

Then, in the multi-layer plating step 12,
First of all, after the pre-treatment process, pickling degreasing, washing with water, electrolytic degreasing, washing with water, pickling degreasing, and washing with water, followed by electrolytic degreasing and washing for smoothing and activation of the surface, and removing the adhering impurities to the surface I do. After that, multilayer plating is performed. In this multilayer plating, a Ni stripe layer is plated on the surface of the metal member, and then the intermediate layer is washed with water or hot water.
This is performed by plating the n-Co alloy layer or the Ni-Co alloy layer, washing again with water or hot water, and then plating the Pd layer on the uppermost portion.

Then, the heat treatment is performed again in the curing process 13. This is carried out in the multi-layer plating step 12 in order to remove the stored hydrogen and the internal residual stress retained between the layers, and it is treated by preheating, heating and cooling in a non-oxidizing atmosphere, The member is wound by the winding device while being sufficiently cooled.

Next, in the press working step 14, the unwinding device first intermittently feeds the press device through the intermittent transfer device, and the inner press is carried out by the press device as shown in FIG. The resin tape 20 is adhered onto the leads 17 and the connecting piece 16 (see FIG. 3) is removed. As a result, the inner leads 17 can be kept at a predetermined distance even if the connecting piece 16 is removed. After that, the metal member connected to the winding device is wound again, and the manufacturing of the semiconductor device lead frame is completed. In addition, in FIG. 2 and FIG.
1 indicates a support lead.

As described above, according to this embodiment, the heat treatment step 11 is performed between the shape processing step 10 and the multi-layer plating step 12.
Since the residual stress generated by the shape processing is removed by the provision of the above, it is possible to prevent stress corrosion cracking that occurs in the pretreatment step and the plating step of the next step in the multilayer plating step 12 of the next step. In addition, the multi-layer plating process 12
Adhesion of tape and tape, formation of inner lead tip and connecting piece 1
By providing a heat treatment process at a low temperature annealing temperature adapted to the plating layer between the press working process 14 including the removing process 6 and the press working process 14, the multi-layer plating process 12 occludes the metal part of the lead frame during plating. It is possible to remove the hydrogen and alleviate the effect of residual stress that is retained in the member that is multilayer-coated with thin plating layers of different metals.
Further, in the steps of tape adhesion, formation of the tips of the inner leads 17 and removal of the connecting piece 16, the resin tape 20 is adhered prior to the removal of the connecting piece 16, so the mutual positions of the inner leads 17 are maintained. However, since the pressing force can be reduced when the connecting piece 16 is removed, damage due to handling such as deformation or transportation can be prevented. Although the thermosetting resin is used as the resin tape 20 in this embodiment, other synthetic resin materials may be used.

[0014]

As is apparent from the above description, the method of manufacturing a lead frame for a semiconductor device according to the first aspect of the present invention is a lead frame in which internal residual stress is removed by performing heat treatment in advance when performing multilayer plating. Since the metal member of No. 3 is used, stress corrosion cracking is prevented, the oxide film is completely removed, strong bonding occurs between metals, and plating adhesion is improved. After the plating process, the heat treatment process removes or relieves residual stress in the metal member,
The internal lead is not twisted, bent, or deformed to a certain extent to improve the accuracy of the wiring, and hydrogen absorbed in the metal member is removed to prevent hydrogen embrittlement damage. Since the resin tape is adhered so as to maintain the mutual position between the inner leads, there is no damage due to punching and removal of the connecting pieces or extension of the pilot pitch, and there is less damage in the subsequent process, improving yield, etc. It is possible to obtain a high quality semiconductor device in which the long-term reliability of the lead frame is maintained.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of steps of an embodiment of the present invention.

FIG. 2 is a plan view of a lead frame manufactured according to an embodiment of the present invention.

FIG. 3 is a plan view of a lead frame in an intermediate process according to an exemplary embodiment of the present invention.

[Explanation of symbols]

 10 Shape Processing Step 11 Heat Treatment Step 12 Multilayer Plating Step 13 Cure Processing Step 14 Press Processing Step 15 Element Mounting Part 16 Connection Piece 17 Inner Lead 18 Dam Bar 19 Outer Lead 20 Resin Tape 21 Support Lead

Claims (1)

Claim: What is claimed is: 1. A metal having a required shape of a lead frame including an inner lead and an outer lead, which are made of a metal material for a lead frame and include a connecting piece for connecting an element mounting portion and a tip portion. After performing a process for forming a member and forming a multi-layer metal coating layer on a required portion of the surface of the metal member,
A method of manufacturing a lead frame for a semiconductor device, in which the connecting pieces are removed and the tips of the inner leads are separately formed, wherein the lead frame is previously subjected to a heat treatment for removing an internal residual stress that has remained during the formation of the metal member. Using the metal member of, the multi-layered coating of different metals on the surface of the metal member of the lead frame, and then heat treatment to remove the hydrogen absorbed in the metal member and residual stress retained therein, Forming the required lead frame shape by applying a resin tape that maintains the mutual position between the inner leads to the required area of the inner leads and removing the connecting piece that connects the tips of the inner leads. A method for manufacturing a lead frame for a semiconductor device, comprising: