JPH0472658A - Lead frame - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] In particular, regarding a lead frame on which a substrate with various devices mounted on both sides is mounted, the stage is lowered one step by bending the support bar, and the connecting bar is installed between the stages. In order to prevent the deformation of the lead frame that occurs when the lead frame is bent and lowered one step, a dam bar is installed inside the outer frame and a support bar protrudes inward from the two intersecting sides of the dam bar. The support bar is bent so that the stage is positioned one step below the dam bar, and the connecting bar is bent so that the stage is located one step below the dam bar. The lead frame is bent so as to be positioned one step downward, and a reinforcing bar that is at least thicker than the support bar is installed between the outer frame and the dam bar in an outward direction facing away from the support bar. Configure it so that

[Industrial application field]

The present invention relates to a lead frame, and more particularly to a lead frame that is used for mounting a substrate on which various devices are mounted on both sides, and that eliminates deformation of dam bars to prevent deflection of connecting bars.

In recent years, monolithic integrated circuits (monolithic ICs) have made remarkable progress, and ICs are being used in all industrial and consumer fields. With the increasing functionality of monolithic ICs, hybrid integrated circuits (hybrid ICs), which are hybrid integrated circuits of active devices such as monolithic ICs and passive devices such as thick-film/thin-film circuits and chip components, are becoming more and more sophisticated.
) has also begun to integrate large-scale functions onto large substrates.

Just as process technology is important in a series of manufacturing steps for monolithic ICs from the wafer stage to completion as a semiconductor device, process technology is also important for hybrid ICs.

However, hybrid ICs incorporate a mixture of monolithic IC chips and various other devices on a ceramic substrate that is larger than the silicon chip in monolithic ICs, and there are also various forms in which both sides of the substrate are used for mounting. has been done.

Therefore, packaging such a substrate has different difficulties than monolithic ICs. Of course, the process of packaging this board affects its authenticity,
It is said that it determines the price of products such as hybrid ICs.
There is an emphasis on streamlining and increasing efficiency of the assembly process.

[Conventional technology]

Generally, an IC consisting only of passive devices, such as a resistor array in which resistive elements are arranged in a row, is also called a hybrid IC. However, a hybrid IC usually incorporates a mixture of monolithic ICs. Although this monolithic IC is sometimes installed in the form of a resin-sealed chip, it is also often installed in the form of a bare semiconductor element, also called a pair chip.

Wire bonding is the most widely used method for incorporating semiconductor elements, but as semiconductor elements become more stable and integration technology improves, connection methods such as flip-chip and TAB are also being adopted. .

And the functions of the hybrid IC are not that advanced,
When the number of leads led out from a board is small, for example, terminals are soldered directly to the periphery of the board, and sealing is done by botting, etc., to create a simple package.

However, large-scale hybrid I with advanced functions
In the case of C, the number of leads led out from the board increases from tens to hundreds, so the board is mounted on a lead frame, which is a frame-shaped terminal, as is often done in monolithic ICs, and the periphery of the board is A so-called plastic puff cage is performed in which wire bonding is performed from the internal pad of the lead frame to the internal lead of the lead frame, and the resin is sealed using transfer molding.

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 the main part of FIG. 2 before sealing.

In the figure, I is a lead frame, 12 is a stage, 13 is an external lead, 14 is an internal lead, Ia is a dam bar, 1b is a support bar, lc is a connecting bar, 2 is a substrate, 2a is a device,
2b is a pad, and 3 is a package.

For the substrate 2, an alumina ceramic plate is often used, but aluminum nitride or beryllia plates may also be used for special purposes. Although the substrate 2 may be a single layer,
For high-density mounting, there are cases in which the board is a multilayer board in which layers are connected through through holes or via holes.

On this substrate 2, devices 2a such as wiring and film resistors and pads 2b are provided on the periphery using film forming techniques such as thick film and 1lJIl, and various devices 2a such as monolithic IC chips and chip capacitors are provided. It has been incorporated.

On the other hand, the lead frame 1 is a frame-shaped terminal made of a thin strip or plate of iron-based alloy or copper-based alloy, for example.
They are generally made by stamping and molding, but can also be made by chemical etching if a precise configuration is required.

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

In the case of a semiconductor device consisting of a monolithic IC, this stage 12 has a square shape because elements are almost never formed on both the front and back sides of the chip, and the shape of the chip is small and rectangular with a side of at most 10-odd millimeters. It is often provided in a plate shape.

However, in the case of a board 2 such as a hybrid IC intended for high-density packaging, the device 2a is incorporated not only on the front side of the board 2 but also on the back side, and the − side is 20
It has a large shape such as mm or 30 mm.

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

In addition, the substrate 2 and various devices 2a mounted on the substrate 2
The stage 12 is recessed one step downward by the thickness of the substrate 2 so that it does not protrude too much from the lead frame 1.

Furthermore, in order to stably position the stage 12,
Neighbors of the two protruding stages 12 are connected to each other by connecting bars 1c.

On the other hand, in the dam bar 1a, a large number of internal leads 14 are arranged in a comb-teeth pattern toward the center, and external leads 13 are connected to the internal leads 14 on the outside.

A substrate 2 on which various devices 2a are mounted is mounted on a lead frame 1 with its four corners fixed to four stages 12. After that, wire bonding is performed between the pads 2b of the substrate 2 and the internal leads 14 to connect them.Then, the external leads are set in a mold (not shown) and sealed with, for example, an epoxy sealing resin. 3 is molded so that it protrudes. Next, leaving the external leads 13, the dam bar 1a is cut off and separated, and the lead frame l is cut off. Finally, if the external lead 13 is shaped into a gull wing shape, for example, the QF
A package 3 called P etc. is completed.

By the way, wiring is done on both the front and back sides, and device 2
In the case of a board 2 such as a hybrid IC in which a is also incorporated on both the front and back sides, the link bar 10 is bent one step and recessed so that the link bar 10 connecting the stages 12 does not come into contact with the back surface of the board 2. As shown in FIG. 3 from the stage 12, it is bent one more step and concave, resulting in a two-step bending process.

However, the dam bar 18, the support bar 1b, and the stage 12
, the stage 12, and the connecting bar IC are each connected in a closed frame shape. Therefore, when the ζ stage 12 and the connecting bar 10 are sequentially bent into two stages, abnormal tensile stress is applied to the dam bar 18 and the connecting bar 10.

[Problem to be solved by the invention]

FIG. 4 is an enlarged perspective view of a modified main part of FIG. 2.

In the figure, when the stage 12 is bent one step and the connecting bar 10 is bent another step, the stage 12 is pulled toward the center, which causes abnormal stress to be applied to the dam bar 1a and the connecting bar 10. Participation is inevitable.

Therefore, the dam bar 13 is pulled inward and deformed,
Occasionally, the connecting bar 10 becomes slack and bends upward or downward.

If the connecting bar 10 bends in this way, not only will it become impossible to stably position the stage 12, but if it bends upward, it may come into contact with wiring or devices provided on the back side of the board mounted on the stage 12. There was a problem with a short circuit.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lead frame that eliminates deformation of dam bars and prevents deflection of connecting bars.

[Means for solving CtJ, M] The problem described above is solved by the dam bar installed in the outer frame and the four stages installed on the support bar protruding inward from the two intersecting sides of the dam bar. , has a connecting bar installed between adjacent stages, the support bar is bent so that the stage is located one step below the dam bar, and the connecting bar is located one step below the stage. The lead frame is bent in such a manner that a reinforcing bar that is at least thicker than the support bar is installed between the outer frame and the dam bar in an outward direction facing away from the support bar. This is solved by a lead frame.

[For production]

The lead frame on which the board with various devices installed on both sides is mounted has a structure in which the connecting bar connecting the stages is bent in two stages, so that the stage is pulled to the center and the dam bar or When abnormal stress is applied to the connecting bar, the dam bar is deformed and the connecting bar is bent. However, according to the present invention, the dam bar is prevented from being deformed.

That is, a reinforcing bar is installed between the outer frame and the dam bar in an outward direction opposite to a support bar provided inward of the dam bar to support the stage. The reinforcing bar is made smaller (and thicker than the supporting bar) to increase tensile strength.

In this way, if the dam bar is reinforced with a reinforcing bar connected to the outer frame, the dam bar will be Even if it is pulled inward, the support bar and the connecting bar will stretch appropriately.

This prevents the dam bar from being pulled and deformed.

If the dam bar does not deform, it is possible to prevent the stages pulled toward the center from approaching each other and causing the connecting bar to loosen and bend.

〔Example] FIG. 1 is an enlarged perspective view of essential parts 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, Ib is a support bar, 1c is a connecting bar, I (I is a reinforcing bar, 2 is a It is a board.

In the figure, a 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.

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

The internal leads 14 are connected to the board 2 by wire bonding, and the number of leads led out from the board 2 is, for example, several tens per side, and the width is, for example, 0.4 mm.
The pitch is as fine as 0.8mm.

On the other hand, a pair of supporting bars 1b having a width of, for example, 0.3 mm are provided inwardly protruding from two orthogonal sides of each of the four corners of the dam bar 1a, and each of the supporting bars 1b has, for example, one side. A 2 mm rectangular stage 12 is provided.

In addition, these four stages 12 have a width of 0, for example.
．． They are connected in a square shape by a 4mm connecting bar 10.

Further, 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 the outward direction opposite to the support bar 1b protruding inward from the dam bar 1a.

Since such a planar lead frame l requires a precise structure, it is made by chemical etching, for example.

On the other hand, the substrate 2 is placed on and supported by the stages 12 provided at each of the four corners, but the thickness of the substrate 2, for example, is about 9.5 mm, and the support bar 1b is bent and recessed downward. ing.

Further, the connecting bar 10 connecting the stages 12 is bent downward by, for example, 0.5 mm so as not to touch the back surface of the substrate 2.

This downward bending process is performed by a press, but the dam bar 1a is attached to the outer frame 11 by the reinforcing bar 1d.
Since the dam bar 1a is supported by the dam bar 1a, there is no possibility that the dam bar 1a is deformed or that the connecting bar IC is bent as a result.

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

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

〔Effect of the invention〕

If the lead frame on which the board with various devices installed on both sides is mounted is subjected to a two-step bending process that recesses the stage and then recesses the connecting bar, the dam bar may deform or the connecting bar may bend. On the other hand, the introduction of the reinforcing bar according to the present invention completely eliminates the deformation.

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

[Brief explanation of the drawing]

FIG. 1 is an enlarged perspective view of a main part of an embodiment of the present invention, FIG. 2 is a partially cutaway perspective view of an example of a hybrid IC sealed with resin, and FIG. 3 is a sealing of the main part of FIG. FIG. 4 is an exploded perspective view before stopping, and FIG. 4 is an enlarged perspective view of the main part of FIG. 2 which has been deformed. In the figure, 1 is a lead frame, 11 is an outer frame, and 1a is a dam bar 1c is a connecting bar. 12 is a stage, 1b is a support bar, ld is a reinforcing bar.

Claims (1)

[Claims] A dam bar (1a) provided in an outer frame (11);
Four stages (12
) and a connecting bar (1c) installed between adjacent stages (12), and the support bar is arranged such that the stage (12) is located one step below the dam bar (1a). (1b) is bent, and the connecting bar (1c) is bent so as to be positioned one step below the stage (12), the outer frame (11) and the dam bar (1a), and a reinforcing bar (1d) that is at least thicker than the support bar (1b) is installed in an outward direction facing away from the support bar (1b). flame.