JP2714002B2 - Method for manufacturing resin-encapsulated semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to a technique for preventing burrs generated in a resin sealing step including a semiconductor element mounted on a lead frame.

(Prior art) In the process of assembling a semiconductor device in which a circuit or a device is built on a semiconductor substrate, a semiconductor device is usually assembled using a lead frame.
Further, it is protected from an external atmosphere by a sealing resin formed in a sealing step. By the way, DIP, SIP and a mixed type of lead frame are known, and as a manufacturing method, of the etching process and the pressing process, the latter is currently exclusively used. In a large multi-pin structure element, it is a fact that the pitch between the outer leads must be reduced.

The outline of a DIP and mixed type lead frame mainly used for mounting such a highly integrated semiconductor element will be described. A plurality of units composed of a metal frame around the periphery are continuously formed. To distinguish between long and short objects. On the other hand, in the metal frame, a lead starting from this point was formed toward the center of the unit body, and a bed was connected between a pair of leads near the center to build a semiconductor element. A semiconductor substrate can be mounted.

The lead end near the semiconductor substrate is in a free state, and a through hole is formed in the metal frame body for each unit, which is useful for transportation and is compatible with automation.

As described above, the connecting frame or dam that forms the bank of the resin sealing step and increases the mechanical strength of both parts is formed on the lead frame provided with the bed portion and the lead terminal. It is formed to be relatively close and extend in a direction crossing the lead.

Then, following the thermocompression bonding step using a thin metal wire for electrical connection between the electrode formed on the semiconductor element and the lead, and the resin sealing step, the vicinity of the dam is cut off to separate the mounting portion from the rest.

As a result, the outer leads led out from the thickness direction, that is, the side portions of the substantially rectangular parallelepiped sealing resin layer are formed into a predetermined shape to form an integrated circuit. Note that the name of the lead formed on the lead frame is changed to the outer lead at the boundary of the sealing resin layer.

By the way, in the resin sealing step using the transfer molding method, a lead frame was arranged between a pair of molds arranged in a dedicated machine, and further, a semiconductor element was mounted via a cull and a runner formed in the mold. The molten resin is introduced into the cavity in which the semiconductor element is arranged, and an aging process is performed at a predetermined temperature to complete the process. As a result, a semiconductor element in which the outer leads are led out from the side of the sealing resin layer formed in a substantially rectangular parallelepiped as described above is manufactured.

Since this semiconductor device is put into a semiconductor element inspection process or inserted into a kit of electronic equipment etc. to form an electric circuit, it must be formed to specifications to prevent poor contact and clogging of sockets. It is.

By the way, so-called burrs frequently occur in the outer leads of products formed by the transfer molding method and provided with a sealing resin layer, and many proposals have been announced as countermeasures, and diligent efforts have been made to remove them. Have been.

As described above, a pair of molds used in the resin sealing process
Although it is manufactured by precision processing, the existence of a gap cannot be denied microscopically, and it is inevitable that the sealing resin flows out during the resin sealing step.

A method for preventing generation of burrs due to the sealing resin will be described with reference to FIG.

As described above, a runner portion branching from the cull formed along the surfaces of the pair of lead frames formed in the shape of a rectangular parallelepiped and extending toward the end of the metal member was provided, and further connected to the gate at the end. A plurality of cavities are provided.

As shown in FIG. 3, a dam 22 intersecting in the axial direction is provided on the lead terminals 21 provided on a metal frame (not shown), but a sealing resin layer 23 and a dam 22 are provided in a resin sealing step. The sealing resin layer 23 is also filled in the voids 24 that can be formed.

(Problems to be Solved by the Invention) Even when the sealing resin layer filled in the voids 24 is removed, a part remains and so-called lattice burrs are generated. For this reason, in a lead frame for a semiconductor device with a large lead pitch, a. A method of placing the frame on purpose, b. A method of forming a convex portion on the mold corresponding to this portion, c. There is known a method of installing by a process. However, in the methods a and b, it is unavoidable that a gap of about 50 μm is formed between the lead 21 and the lead c. Thus, burrs are formed.

On the other hand, in a lead frame having a small lead pitch, it is difficult to install such a frame.

In any case, the removal of the grid burrs was not complete even if an expensive deburring machine was required or a lot of time was spent. For this reason, there are drawbacks such as difficulty in insertion in an inspection process or the like and damage to a precision die for a press process required for a cut and bend process for a subsequent dam.

An object of the present invention is to provide a novel method for manufacturing a resin-encapsulated semiconductor device that eliminates the above-mentioned difficulties, and in particular, to suppress generation of lattice burrs.

[Constitution of the Invention] (Means for Solving the Problems) In order to achieve this object, in a method of manufacturing a resin-encapsulated semiconductor device according to the present invention, a bed portion is formed near the ends of a plurality of metal leads. And preparing a lead frame on which a dam for connecting the lead is arranged in a direction intersecting the longitudinal direction of the lead, and cutting a portion of the dam between the leads from the bed portion side along the lead along a part of the dam. Forming, fixing a semiconductor element to the bed portion, electrically connecting the semiconductor element to a lead, and a resin sealing expected position on a bed portion side end face of the dam in which the cut is formed. And a step of forming a sealing resin layer surrounding the semiconductor element and cutting the dam from the lead.

(Operation) In the lead frame used in the method of manufacturing such a resin-encapsulated semiconductor device, the cut c is formed in the dam in a direction along the longitudinal direction of the lead by the half punching process in the step of forming the cut. (See FIGS. 1a and 1b),
After the formation, it becomes almost flat, and the generation of burrs between the dam and the sealing resin is suppressed.

The half-punching step is a step of using a punch whose cutting surface is formed obliquely. Since the punch b to be brought into contact with an area to be cut of the dam 2 has the cutting surface formed obliquely as described above, When the dam 2 is cut, the surface d and the dam 2 that have not yet been cut except for the cut c are continuous.

In the step in which the cut c is formed by the half-punching step, a part of the dam in contact with the set position h of the sealing resin layer 3 in the longitudinal direction of the dam sandwiched by the two outer leads 1 is set. A part is cut from the bed portion side along the lead 1 to form a cut c. The remaining outer leads 1 are in a mechanically continuous state as described above.

Therefore, in addition to the place where the two cuts c of the dam are formed, the dam portion adjacent to the set position h of the sealing resin layer is in a discontinuous state, so that both portions are hung.

The entire lead frame including the portion in which the cut-out state is formed has a flat shape, similarly to the state in which the cut c is not formed. However, if the cut c is not released and becomes flat, it is restored to a flat state. After that, the process moves to a subsequent cutting process.

After such a pressing step, a step of thermocompression bonding the thin metal wire between the electrode of the semiconductor element and the lead, a resin sealing step, and a step of cutting the dam 2 are performed as in the prior art. This dam 2
In the cutting step, since a semiconductor element having the outer lead 1 having almost no burrs can be obtained, difficulties such as clogging of a socket at the time of measuring the semiconductor element and breakage of a mold of a precision machine for a press step are eliminated. You.

(Example) The present invention will be described in detail with reference to Figs. 1a, 1b, 1c and 2.

FIG. 1A is a perspective view showing a sealing resin layer, outer leads and dams of a resin-sealed semiconductor device completed by the method of the present invention. FIG. 1B is a top view of FIG. 1A and FIG. c is
FIG. 2A is a view showing a step of half-punching a dam, and FIG.
FIG. 2 is a partially cutaway perspective view of a resin-encapsulated semiconductor device in which components existing before a resin encapsulation step according to the method of the present invention are indicated by solid lines, and components manufactured thereafter are indicated by dotted lines, and FIG. FIG. 2 is a perspective view of a resin-sealed semiconductor device.

Lead frame (not shown) with outer leads 1 as revealed by FIGS. 1a, b and 2a etc.
Is a DIP type for a multi-pin integrated circuit element and having outer leads with a narrow pitch. The structure is the same as that of the prior art section, and therefore, detailed description is omitted. In this lead frame, a dam 2 necessary for assembling a semiconductor element, that is, a special structure essential for the present invention is formed.

That is, as shown in FIG. 1a, the dam 2 disposed adjacent to the set position h of the sealing resin layer (see FIG. 1a, b, c) is located on the extension of the lead, that is, the inner lead. The portions other than the outer leads 1 are mechanically discontinuous with the set position h of the sealing resin layer 3.

A part of the dam 2 in contact with the outer lead 1 in the longitudinal direction is cut along the lead 1 from a bed portion side to be described later by the half-punching process shown in FIG.
To form As a result, the other portion h ′ of the dam 2 in contact with the set position h of the sealing resin layer, that is, the place adjacent to the set position h of the sealing resin layer 3 and the two cuts c are:
The other part of the dam 2 is separated from the other part.

The details of the half punching step for forming the cut c are as described in the operation section, and an oblique punch is used for the cut surface. In FIG. 2a, a location h 'adjacent to the set scheduled position h of the sealing resin layer 3, a cut c and a thin metal wire 6 described later
Are shown only in one place, and the others are omitted.

Thus, a dam 2 having a special structure is installed in a direction intersecting the longitudinal direction of the leads 1 formed on a metal frame (not shown) constituting a part of the lead frame. .

The dam 2 in which the cut c is formed by the half punching process is hung as described above, but if it is not flat compared to other portions, it is corrected by the pressing process.

A process of assembling a semiconductor element on a lead frame having a special dam 2 will be described with reference to FIG. 2A. That is, as in the prior art, a semiconductor element 5 is fixed to a bed 4 disposed near the ends of a plurality of metal leads 1, and an electrode (not shown) formed on the semiconductor element 5 and a thin metal wire 6 are attached to the lead 1.
Are electrically connected by thermocompression bonding. These are covered with a sealing resin layer and subjected to a resin sealing step of protecting the semiconductor element from the outside atmosphere. The position is the end face of the bed 2 side of the dam 2 where the cut c is formed. In other words, the sealing resin layer 3 surrounding the semiconductor element is located at a set position h of the sealing resin layer, and the transfer mold is formed by a known transfer mold. It is formed by a method.

Further, the dam 2 having the special structure as described above is cut from the sealing resin layer 3 and then subjected to a bend process, an aging process, and an exterior process which are applied to the resin seal shown in FIGS. 2A and 2B. The fixed semiconductor device is completed.

In the resin-encapsulated semiconductor device having such a structure, since the molten resin does not flow into the dam 2 during the resin encapsulation process, the sealing resin layer 3 is led out of the outer leads 1 without burrs. As a result, insertion into the socket is smooth, and damage to the precision mold during the pressing process can be prevented.

[Effects of the Invention] As described above, in the method of the present invention, since grid burrs hardly remain, the deburring process, which had to be performed conventionally, is simplified, and troubles due to the remaining grid burrs are eliminated. As a result, productivity was improved.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a sealing resin layer, outer leads and dams of a resin-sealed semiconductor device completed by the method of the present invention. FIG. 1B is a top view of FIG. 1A and FIG. 2C is a view showing a step of half-punching the dam, FIG. 2A is a partially cutaway perspective view showing a structure in a manufacturing step of the resin-sealed semiconductor device according to the method of the present invention, and FIG. FIG. 3 is a perspective view of a resin-sealed semiconductor device completed by the method, and FIG. 3 is a top view of a lead frame applied to the conventional method.

Claims (1)

(57) [Claims] A step of preparing a lead frame in which a bed portion is formed near the ends of a plurality of leads made of metal, and a dam for connecting the leads in a direction intersecting the longitudinal direction of the leads is provided; Forming a cut from the bed portion side along the lead in a part of the dam between the leads, fixing a semiconductor element to the bed portion, and electrically connecting the semiconductor element and the lead; A step of forming a sealing resin layer surrounding the semiconductor element at a position where the resin sealing is to be performed is in contact with an end surface on the bed portion side of the dam in which the cut is formed; and a step of cutting the dam from the lead. Method of manufacturing resin-encapsulated semiconductor device characterized by the following