JP2737373B2 - Lead frame and integrated circuit manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] In particular, regarding a lead frame on which a substrate on which various devices are mounted on both sides is mounted, a support bar is bent, a stage is lowered by one stage, and a connecting bar provided between the stages The purpose is to prevent the deformation of the lead frame when bending and lowering it by one step. It is provided on the dam bar provided in the outer frame and the support bar protruding inward from the two sides where the dam bar intersects And a connection bar provided between the adjacent stages, and the support bar is bent so that the stage is located one step below the dam bar, and the connection bar is A lead frame which is bent so as to be positioned one step downward, wherein at least an auxiliary member thicker than the support bar is provided between the outer frame and the dam bar in an outward direction opposite to the support bar. Bar is configured as being bridged.

[Industrial applications]

The present invention relates to a lead frame, and more particularly to a lead frame used for mounting a substrate on which various devices are mounted on both sides, and which prevents deformation of a dam bar and prevents bending of a connection bar.

In recent years, the development of monolithic integrated circuits (monolithic ICs) has been remarkable,
ICs are being implemented. As monolithic ICs become more sophisticated, hybrid integrated circuits (hybrid ICs), in which active devices such as monolithic ICs are hybridly integrated with passive devices such as thick-film / thin-film circuits and chip components, are becoming increasingly large substrates. Integration of large-scale functions is being performed.

In a series of manufacturing processes from monolithic ICs to wafers to finishing as semiconductor devices, hybrid technologies are used in the same way that process technology is important.
Process technology is also important for ICs.

However, hybrid ICs incorporate a monolithic IC chip and various other devices on a substrate such as ceramic that is larger than a silicon chip in a monolithic IC, and the two sides of the substrate are used for mounting in various forms. Have been.

Therefore, such a package of a substrate has a difficulty different from a monolithic IC. And, of course, the process of packaging this substrate affects the reliability,
It is said that the price of products such as hybrid ICs is determined, and the importance of streamlining and improving the efficiency of the assembly process is emphasized.

[Conventional technology]

In general, an IC including only passive devices, such as a resistance array in which resistance elements are arranged in rows, is also called a hybrid IC. However, hybrid ICs usually incorporate a mixture of monolithic ICs. The monolithic IC may be incorporated in a chip-like resin-sealed form, but is often incorporated in a bare semiconductor element called a bare chip.

Wire bonding is the most widely used method of incorporating this semiconductor device, but due to the stabilization of semiconductor devices and the improvement of incorporation technology, connection methods such as flip chip and TAB have also been adopted. .

And the function of the hybrid IC is not so advanced,
When the number of leads led out from the substrate is small, for example, terminals are soldered directly to the peripheral edge of the substrate by soldering or the like, and sealing is completed by a simple package by potting or the like.

However, a large-scale hybrid with advanced functions
In the case of an IC, the number of leads derived from the substrate increases to several tens to several hundreds.Therefore, as is often the case with monolithic ICs, the substrate is mounted on a lead frame which is a frame-shaped terminal, and the periphery of the substrate is A so-called plastic package in which wire bonding is performed from the pads of the section to the internal leads of the lead frame, and resin sealing is performed by transfer molding is performed.

FIG. 2 is a partially cutaway perspective view of an example of a resin-sealed hybrid IC, and FIG. 3 is an exploded perspective view of a main part of FIG. 2 before sealing.

In the figure, 1 is a lead frame, 12 is a stage, 13 is an external lead, 14 is an internal lead, 1a is a dam bar, 1b is a support bar, 1c is a connection bar, 2 is a substrate, 2a is a device, 2b is a pad, and 3 is a pad. Package.

Alumina ceramic plate is often used for the substrate 2, but aluminum nitride or beryllia plate is also used for special applications. The substrate 2 may be a single layer, but may be a multi-layer substrate that is connected between layers via through holes or via holes for high-density mounting.

On the substrate 2, a device 2a such as a wiring or a film resistor and a pad on the periphery are formed by a film forming technology such as a thick film or a thin film.
2b, and various devices 2a such as a monolithic IC chip and a chip capacitor are incorporated.

On the other hand, the lead frame 1 is a frame-shaped terminal formed by processing a thin strip or plate of, for example, an iron-based alloy or a copper-based alloy, and is generally formed by stamping and forming, but requires a precise structure. In some cases, it may be made by chemical etching.

A stage 12 is provided at the center so that the substrate 2 is mounted.

In the case of a semiconductor device composed of a monolithic IC, this stage 12 has almost no elements formed on both the front and back surfaces of the chip, and has a small chip shape and a square having a side of at most a dozen mm. It is often provided in a dish shape.

However, in the case of a substrate 2 such as a hybrid IC for high-density mounting, the device 2a is incorporated not only on the front side of the substrate 2 but also on the back side, and it is a large shape such as 20 mm or 30 mm on one side. .

Therefore, the stage 12 has a shape in which the center is hollowed out so that the back surface of the substrate 2 does not come into contact with the stage 12, and is provided so as to support four corners of the substrate 2. And this 4
Each stage 12 is supported by two support bars 1b projecting from two sides of a frame-shaped dam bar 1a.

Also, the substrate 2 and various devices 2a mounted on the substrate 2
The stage 12 has a configuration in which the stage 12 is recessed one step downward by the thickness of the substrate 2 so as not to protrude much from the lead frame 1.

In order to position the stage 12 more stably,
Next to the two protruding stages 12 are connection bars 1c
Are tied together.

On the other hand, on the dam bar 1a, a number of internal leads 14 are arranged in a comb-like shape toward the center.
The outside leading to is an external lead 13.

The substrate 2 on which various devices 2 a are mounted is mounted on the lead frame 1 with four corners fixed to four stages 12. After that, wire bonding is performed between the pad 2b of the substrate 2 and the internal lead 14 for connection. Next, the external leads 13 are set in a mold (not shown) and molded using, for example, an epoxy-based sealing resin so that the external leads 13 protrude. Next, the outer lead 13 is left, the dam bar 1a is cut off and separated, and the lead frame 1 is cut off. Finally, if the external lead 13 is shaped into, for example, a gull wing (gull wing) type, a package 3 called QFP or the like is completed.

By the way, wiring is done on both sides, and the device
In the case of a substrate 2 such as a hybrid IC incorporated on both front and back surfaces 2a, the connection bar 1c is connected so that the connection bar 1c connecting the stages 12 does not contact the back surface of the substrate 2.
As shown in FIG. 3, the stage 12 is bent one more step from the stage 12 which is bent and recessed, and is recessed, and is subjected to a two-stage bending process.

However, the dam bar 1a, the support bar 1b, and the stage 12, and the stage 12 and the connecting bar 1c are respectively connected in a closed frame shape. Therefore, when the stage 12 and the connecting bar 1c are sequentially bent in two steps, an abnormal tensile stress is applied to the dam bar 1a and the connecting bar 1c.

[Problems to be solved by the invention]

 FIG. 4 is an enlarged perspective view of a modified main part of FIG.

In the same figure, if the stage 12 is depressed by one step by bending and the connecting bar 1c is further depressed by another step, the stage 12 is pulled toward the center, so that abnormal stress is applied to the dam bar 1a and the connecting bar 1c. It is inevitable to join.

Therefore, the dam bar 1a is pulled inward and deforms,
It sometimes happens that the connecting bar 1c is loosened and bent upward or downward.

Thus, when the connecting bar 1c bends, the stage
Not only can the position of the substrate 12 not be stably positioned, but if it is bent upward, there is a problem that it short-circuits due to contact with a wiring or a device provided on the back surface of the substrate mounted on the stage 12.

Therefore, an object of the present invention is to provide a lead frame which prevents deformation of a connecting bar by eliminating deformation of a dam bar.

[Means for solving the problem]

The above-mentioned problem is that a dam bar provided in an outer frame, four stages provided on a support bar projecting inward from two sides intersecting the dam bar, and a stage between adjacent stages of the stage are provided. Having a connecting bar provided, and the support bar being bent so that the stage is located one step below the dam bar, and bent so that the connecting bar is located one step below the stage. A lead frame, wherein a reinforcing bar thicker than at least the support bar is erected between the outer frame and the dam bar in an outward direction facing the support bar. A dam bar provided in the frame and the outer frame, four stages provided on a support bar protruding inward from two sides intersecting the dam bar, and a plurality of dam bars extending in the inward direction Internal And a plurality of external leads extending outwardly of the dam bar, a connecting bar extending between adjacent stages, and the support bar between the outer frame and the dam bar. Bending the support bar so that the stage of the lead frame having a reinforcing bar thicker than the support bar installed outward is positioned one step below the dam bar; and Bending the connecting bar so as to be positioned downward, mounting the substrate on the stage, connecting the internal lead and the substrate by wire bonding, and protruding the external lead. And cutting an unnecessary portion after forming the mold.

(Operation)

The lead frame on which the board on which various devices are incorporated on both front and back sides is mounted has a configuration in which the connecting bar connecting the stages is bent in two steps.
According to the present invention, the stage is pulled to the center and an abnormal stress is applied to the dam bar and the connecting bar, thereby deforming the dam bar and bending the connecting bar.

That is, the reinforcing bar is provided between the outer frame and the dam bar in an outward direction opposite to the support bar provided inward of the dam bar for supporting the stage. And make this reinforcement bar at least thicker than the support bar,
The tensile strength is increased.

In this way, when the dam bar is reinforced by the reinforcing bar connected to the outer frame, the dam bar is bent when the support bar is bent to dent the stage one step or when the connecting bar connecting the stage is bent to dent one step. Even if is pulled inward, the support bar and the connecting bar are appropriately extended.

Thus, the dam bar is prevented from being pulled and deformed.

If the deformation of the dam bar does not occur, it is possible to prevent the stages pulled in the center direction from approaching each other, causing the connecting bar to be slackened and bent.

〔Example〕

 FIG. 1 is an enlarged perspective view of a main part of an embodiment of the present invention.

In the figure, 1 is a lead frame, 11 is an outer frame, 12 is a stage, 13 is an external lead, 14 is an internal lead, 1a is a dam bar,
1b is a support bar, 1c is a connection bar, 1d is a reinforcing bar, and 2 is a substrate.

In FIG. 1, a lead frame 1 is a frame-shaped terminal formed by processing a thin strip or plate such as an iron-based alloy or a copper-based alloy.

In the case of a package lead frame 1 called QFP in which leads are led out from the four sides shown here, the external leads 13 project in a comb-like shape from four sides of the rectangular outer frame 11 inward. Has been established. The end of the external lead 13 is an internal lead 14, and a dam bar 1a is provided in the middle in a rectangular shape so as to cross the comb teeth.

The internal leads 14 are connected to the substrate 2 by wire bonding, and are provided with the number of leads derived from the substrate 2, for example, dozens of leads on one side, and have, for example, a width of 0.4 mm and a pitch of 0.8 mm. It is fine.

On the other hand, a support bar 1b having a width of, for example, 0.3 mm is provided so as to protrude inward from two orthogonal sides of the four corners of the dam bar 1a, and each of the support bars 1b has a side of, for example, 2 mm. A rectangular stage 12 is provided.

The four stages 12 have a width of, for example, 0.
It is tied squarely by a 4mm connecting bar 1c.

Furthermore, a support bar protruding inward from the dam bar 1a
A reinforcing bar 1d having a width of, for example, 0.9 mm is provided between the dam bar 1a and the outer frame 11 in an outward direction opposite to 1b.

Since the lead frame 1 having such a planar shape requires a precise structure, it is made by, for example, chemical etching.

On the other hand, the substrate 2 is placed on and supported by the stages 12 provided at the four corners, and has a configuration in which the thickness of the substrate 2, for example, the support bar 1b is bent to about 0.6 mm and is recessed downward. .

The connection bar 1c connecting the stage 12 is connected to the substrate 2
In order to avoid touching the back surface of the device, it is bent, for example, by 0.5 mm and is recessed downward.

Although the bending process of making the recess is performed by pressing, since the dam bar 1a is supported by the outer frame 11 by the reinforcing bar 1d, the dam bar 1a may be deformed, and as a result, the connecting bar 1c may be bent. There was none.

Various modifications can be made to the shape of the lead frame and the dimensions of each part exemplified here.

Further, the substrate is not limited to a hybrid IC, and can be applied to, for example, a monolithic IC silicon chip, and various modifications are possible.

〔The invention's effect〕

A lead frame on which a substrate with various devices incorporated on both sides is mounted, the stage is recessed, and the connection bar is further recessed.If the bending process is performed in two steps, the dam bar will be deformed or the connection bar will bend. In contrast, the introduction of the reinforcing bar according to the present invention eliminates any deformation.

As a result, since the dimensional accuracy is high and the lead pitch is fine, the yield in the bending of the lead frame formed by etching can be improved, and the present invention greatly contributes to the improvement of the manufacturing efficiency of the lead frame.

[Brief description of the drawings]

FIG. 1 is an enlarged perspective view of an essential part of an embodiment of the present invention, FIG. 2 is a partially cutaway perspective view of an example of a resin-sealed hybrid IC, and FIG. 3 is a sealing of an essential part of FIG. FIG. 4 is an exploded perspective view of the main part of FIG. 2 before deformation. In the figure, 1 is a lead frame, 11 is an outer frame, 12 is a stage, 1a is a dam bar, 1b is a support bar, 1c is a connection bar, and 1d is a reinforcing bar.

Claims (2)

(57) [Claims] 1. A dam bar provided in an outer frame, four stages provided on a support bar projecting inward from two sides intersecting the dam bar, and four stages provided between adjacent stages. The support bar is bent so that the stage is located one step below the dam bar, and the connection bar is bent such that the connection bar is located one step below the stage. A lead frame, wherein a reinforcing bar thicker than at least the support bar is provided between the outer frame and the dam bar in an outward direction facing the support bar. 2. A dam bar provided in an outer frame, four stages provided on a support bar projecting inward from two sides intersecting the dam bar, and a stage extending in the inward direction of the dam bar. A plurality of internal leads and a plurality of external leads extending outwardly of the dam bar; a connection bar erected between adjacent stages; and the support bar between the outer frame and the dam bar. And a step of bending the support bar so that the stage of the lead frame having a reinforcing bar thicker than the support bar installed in the outward direction opposite to the back bar is located one step below the dam bar. Bending the connecting bar so as to be positioned one step below the stage; mounting a substrate on the stage; connecting the internal lead and the substrate by wire bonding; and the external lead And cutting an unnecessary portion after forming the mold so that the protrusions protrude.