JPH03195052A - Lead frame and manufacture thereof - Google Patents

Abstract

PURPOSE:To comply with the large size and the high-density mounting of a semiconductor element by a method wherein one part of a lead is extended to the lower part of a die pad and the electrical connection part of the lead protrudes to the outside from the die pad. CONSTITUTION:Parts 4a of inner leads 4 are extended in such a way that they are situated partially at the lower part of a die pad 2; the inner leads 4a and the die pad 2 do not come into geometrical contact with each other. The inner leads 4a are bent perpendicularly to two short-side directions of the die pad 2 at the lower-part position of the die pad 2; their tips 4b protrude to the outside of the die pad 2 from short sides of the die pad 2. Consequently, the degree of extraction freedom of a lead frame is enhanced, and a package is made small. Thereby, it is possible to comply with the large size by a large capacity of a semiconductor element and to comply with the small size of a semiconductor device by the high-density mounting of the element.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a lead frame on which a semiconductor element is mounted and a method for manufacturing the same, and particularly relates to a lead frame equipped with a die pad on which a semiconductor element is mounted and a method for manufacturing the same. be.

[Prior art] Currently, general-purpose LSI packages are SMD (Surfac
On the other hand, there are two trends toward miniaturization using e-Mount devices and pin-pitch shrinkage, while on the other hand, DRAM (Dy
namic Random Access Memory
y), the element size is 1.5 due to an increase in memory capacity.
They are becoming larger at a rate of double/generation.

FIG. 8 is a diagram showing the structure of a conventional plastic package in which a DRAM element having a capacity of 1 Mbit is mounted. As shown in Fig. 8, this package consists of mounting an ST element 3 on a die plate 2 of a lead frame 1, and
The inner leads 4 of the lead frame 1 are arranged in a plane approximately equal to this die pad 2, and the bonding wires 5
electrically connect the bonding pad 6 on the St element 3 and the inner lead 4 of the lead frame 1 using
The structure is then molded A with a sealing resin.

[Problem to be solved by the invention] However, when the memory capacity exceeds IM, the element area becomes even larger, and it becomes extremely difficult to accommodate such a large-area element in a standardized package size. That is, for example, as shown in FIG.
When housed in a 5 mil SOJ package, the ratio of the element area to the package is 54% to 85%. When such a large-area device is to be housed in the lead frame 1 having the die pad 2 described above, the inner leads 4 and the die pad 2 are arranged in the same plane in the lead frame 1. However, the area for arranging the inner leads 4 inside the package cannot be secured. Therefore, when a large-area element is mounted as in the conventional package structure, the inner leads 4 cannot be routed.

Therefore, in order to cope with the increase in the size of DRAM elements, a die padless mold package (S
OJ) etc. have been developed.

For example, as shown in FIG. 10, a package with an area wire device structure has been developed for IM DRAM, and this package can accommodate larger devices and has now reached the practical stage. Also, the 11th
As shown in Figure (a), an insulating film 13 made of polyimide or polyetheramideimide is pasted on the upper surface of the inner leads 4 of the lead frame 1, and the element 3 is placed on the insulating film 13.
On Lead) type package structure, and
As shown in Figure (b), an LOG (Lead On Chip) type package structure in which an insulating resin film 13 is bonded to the lower surface of the inner lead 4 and the element 3 is arranged on the lower surface has also been developed ( For example, see Japanese Patent Publications No. 63-232360, No. 63-293961, No. 77152-1982, etc.).

By the way, in order to guarantee high-speed access using high-speed devices such as C-MOS, it is necessary to supply high voltage (specifically 5°Ov) to both the external power supply and the memory array. A RAM element with a large memory capacity in its class consumes 500m of power.
It exceeds W.

However, with the lead frame 1 without a die pad as described above, the heat generated from the element cannot be effectively dissipated, so the thermal resistance of the package increases, which makes the element 3 more likely to fail. There is a problem. As described above, it is extremely difficult for the lead frame 1 without the die pad 2 to reliably cope with the increase in the size of the DRAM element.

For this reason, the lead frame 1 with the die pad 2 can more easily cope with the increase in the size of the DRAM element, but the lead frame 1 with the die pad 2 must solve the above-mentioned problems.

The present invention has been made in view of the above circumstances, and its purpose is to enable inner leads to be routed even if a lead frame is provided with a die pad, thereby reliably responding to the increase in size of semiconductor devices. It is an object of the present invention to provide a lead frame that can further reduce the size of the package and reliably respond to high-density packaging.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a lead frame including at least a die pad on which a semiconductor element is mounted and a lead electrically connected to an electrode pad of the semiconductor element. , a part of the lead extends below the die pad, and a connection end of the lead to be electrically connected protrudes outward from the die pad.

The present invention also provides a method for manufacturing a lead frame comprising at least a die pad on which a semiconductor element is mounted and a lead electrically connected to an electrode pad of the semiconductor element, in which tie bars supporting the die pad are press-molded. By upsetting the die pad and then press-molding a dam bar that supports the leads, a portion of the leads can be extended under the die pad and the connecting ends of the leads to be electrically connected can be It is characterized in that it protrudes outward from the die pad.

[Function] In the lead frame of the present invention having such a configuration, a part of the i-L lead extends below the die pad, and the connecting end of the lead to be electrically connected is Since the lead frame is designed to protrude outward from the die pad, the degree of freedom in routing the lead frame is improved, and for example, it is possible to reliably cope with the increase in size of semiconductor devices such as DRAM devices due to their increased capacity. Become.

Further, since a part of the lead extends under the die pad, the package becomes smaller, so that it is possible to reliably respond to the miniaturization of semiconductor elements accompanying high-density packaging.

Furthermore, even if the amount of heat generated by the element due to power consumption increases,
Since the generated heat is effectively dissipated from the die pad, the failure rate of semiconductor devices is reduced.

Further, in the lead frame manufacturing method of the present invention, #
Since a pressing step is simply added to the conventional lead frame manufacturing method, the lead frame can be manufactured easily and at low cost without changing the manufacturing line.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a lead frame according to the present invention, and as an example of a semiconductor device, three
00 ll1il or 350 mil width resin-sealed DIP (Dual In1ine Pack)
age) and S OJ (Small 0utlin
FIG. 2 is a plan view of a lead frame for e. Note that the same components as those of the conventional lead frame described above are given the same reference numerals, and their explanations will be omitted.

Lead frame IIL shown in FIG. 1(a)
Rectangular die pad 2, many inner leads 4.4.・
...and this inner lead 4 and the same number of outer leads 7.7. It consists of 42%N i −
A material made of Fe alloy, 50% Ni-Fe alloy, copper alloy, etc. and having a thickness of about 0 to 1 m/m is made into a predetermined shape by photolithography, followed by wet etching or the like. ing.

Inner lead 4,4. Part of...4 a, 4
al... are partially extended to be located below the die pad 2, and these inner leads 4a, 4a,
... and the die pad 2 are arranged so that they are not in geometric contact with each other. These inner leads 4a, 4a
, . . . are below the die pad 2.
The tips 4b, 4 are bent at right angles to the short side direction of the
b, ... is from the short side of die pad 2 to die pad 2
protrudes outside.

The die pad 2 is supported by a pair of frames 9, 9 by a pair of tie bars 8, and the inner leads 4 and outer leads 7 are supported by two pairs of dam bars 10.10 extending parallel to these leads 4, 7.・Supported by

Each tie bar 8 is formed with a bent portion 8a (sixth
(as clearly shown in the figure), this bent portion 8a allows the die pad 2 to
It is set up in a higher position. This prevents the inner leads 4a and the die pad 2 from geometrically contacting each other as described above. Moreover, as clearly shown in FIG. 1(b), each dam bar 10 has curved portions 10a, 10a, . . . that curve downward.
is formed.

If the material of the lead frame 1 is soft or thin, insulation can be achieved by insulating a part of the back surface of the die pad 2 or by insulating the whole or part of the inner lead 4. It has a three-layer structure including a layer 13 (as clearly shown in FIGS. 6 and 7), an inner lead 4a, an insulating layer 13, and a die pad 2. This avoids contact between the inner leads 4 and the die pad 2, and also makes it possible to maintain a constant impedance inside the package. FIGS. 2(a) to 2(C) show an example of this insulation treatment. In the lead frame 1 shown in FIG. 2(a), the insulation treatment is applied to the four corners of the back surface of the die pad 2
In the lead frame 1 shown in FIG. 2B, the insulation treatment a is applied to the entire back surface of the die pad 2. In the lead frame 1 shown in FIG. In addition, in the lead frame 1 shown in FIG.
is applied.

The insulating layer 13 can be formed by applying a liquid insulating material such as a thermosetting polyimide resin and a thermosetting paste, and then performing heat treatment, or by applying a liquid insulating material such as a thermosetting polyimide resin or a thermosetting paste, There is a method of forming by pasting any one of a film-like insulating material, a thermoplastic adhesive, and a thermosetting polyimide resin adhesive. In that case, by attaching a film-like insulating material such as a thermosetting polyimide resin to a portion of the inner leads 4, the inner leads 4 are connected to each other by force (taping). This prevents the inner leads 4 from coming into contact with each other.

To manufacture such a lead frame 1, first the third
The original shape of a flat lead frame 1'' having approximately the same size as a conventional lead frame as shown in the figure is formed. In this original lead frame 1, the inner leads 4a, 4
The tips 4b, 4b, . . . of a, . . . are located outside the periphery of the die pad 2, and are not located below the die pad 2. Next, the tie bars 8 of this original lead frame 1 are press-molded to form the bent portions 8a, and thereby the die pad 2 is set with hairs above the inner leads 4 and the outer leads 7. After performing the upset of the die pad 2, FIGS. 4(a) and (b)
), two locations on one side of the dam bar 10 that is horizontal to the outer lead 7, a total of four locations (indicated by b in FIG. 3), are press-formed at a predetermined pressure using molds 11 and 12. I do. As shown in FIG. 5, the mold 11 has four protrusions 11a, lla, approximately semicircular in cross section at positions corresponding to the four predetermined locations b of the dam bar 10 so as to be able to press only four predetermined locations. ... is provided.

Through this press forming, the lead frame 1 is attached to the dam bar 10.
A curved portion 10a is formed that curves downward perpendicular to the plane.

When the curved portion 10a is formed in the dam bar 10, the length of the dam bar 10 in the left-right direction in FIG. 3 is reduced by the amount of the curve. Therefore, the left and right inner leads 4 and outer leads 7 move toward each other, so that some of the inner leads 4a partially extend below the die pad 2, as shown in FIG. together with their tips 4b
comes to protrude outward from the short side of the die pad 2.

In that case, the length of the dam bar 10c in the left-right direction is reduced, and thereby the left-right dimensions of the lead frame are reduced.

Finally, the lead frame 1 is shaped as partially shown in FIG. 6 through the cutting process of the dam bar 10 and the forming process of the outer leads 7 in the same manner as in the prior art. In the lead frame 1 formed in this way,
Since the inner leads 4 are located below the die pad 2, the inner leads 4 can be routed.

Further, since a pressing step is simply added to the conventional manufacturing method of the lead frame 1, the lead frame 1 can be manufactured easily and inexpensively without changing the conventional manufacturing line.

Bonding post 4 at the tip 4b of the inner lead 4
For example, in the case of Ni-Fe alloy system,
By performing Ag plating or the like, wire bonding 5 for electrically connecting with the LSI element 3 mounted on the die pad 2 is made possible.

After mounting the LSI element 3 on the die pad 2 of the lead frame 1 formed in this way, the electrode pads of the LSI element 3 and the inner leads 4 corresponding to the pads are electrically connected by bonding wires 5. do.

In this case, the tip portion 4b of the inner lead 4 extends to the vicinity of the electrode pad of the element 3, so that the length of the bonding wire 5 can be shortened. After that, packaging is completed by molding the predetermined part with resin,
A resin-sealed semiconductor device in a packaged state as shown in FIG. 7 is obtained. The resin-sealed semiconductor device thus obtained becomes compact because the left and right dimensions of the lead frame 1 are shortened.

Note that the present invention is not limited to the above-described embodiments, and various design changes are possible.

For example, in the above-mentioned embodiment, as shown in FIG. 1, the tip portion 4b of the inner lead 4 located below the die pad 2 is formed in the same plane as the other inner leads and the outer lead 7, that is, the tip portion 4b Although the upper and lower positions of the die pad 2 and the die pad 2 are different from each other, the tip 4b of the inner lead 4 located below the die pad 2
E. By performing step processing in the shape of a gal wing, the tip portion 4b can be disposed at substantially the same vertical position as the die pad 2, that is, in substantially the same plane as the die pad 2.

In addition, in the above-mentioned embodiment, as an example of the semiconductor element,
Although the present invention has been described using a 300 mail or 35011i1 width resin-sealed DIP or SOJ lead frame for a dynamic random access memory device, the present invention is applicable to, for example, S-RAM (S-RAM).
tatic Random Access Me+no
ry), E P ROM (Erasable-Pro
gramable Read 0nly Memory
)E2ROM(Electrically Eraser)
ble Programmable Read 0nly
Semiconductor devices such as memory), ZIP (Zig-w
ag In1ine Package), S OP (
The present invention can be similarly applied to lead frames compatible with bottle insertion type and surface mount type packages such as small 0utline packages.

[Effects of the Invention] As is clear from the above description, according to the lead frame of the present invention, it is possible to route the lead frame in a form having a conventional die pad. It becomes possible to reliably cope with the increase in size of semiconductor devices such as DRAM devices due to their increased capacity.

Further, according to the present invention, it is possible to improve the moisture resistance of inner leads that are shallowly buried and thin, such as those found in large-capacity memory semiconductor devices, and
It is possible to prevent a decrease in the pull-out strength of the lead.

Furthermore, the package can be made smaller by the amount that some of the leads extend under the die pad, that is, the overlap between the die pad and the inner leads, which contributes to the miniaturization of semiconductor devices due to higher density packaging of elements. You will be able to respond with certainty.

Furthermore, even if the amount of heat generated by the element due to power consumption increases,
Since the generated heat is effectively dissipated from the die pad, the failure rate of semiconductor devices is reduced. In other words, it becomes possible to cope with an increase in heat generation due to higher integration of memory.

Furthermore, since the tip of the lead extends to the vicinity of the electrode pad of the element, the length of the bonding wire can be shortened, and the cross-sectional area of the lead inside the package can be kept constant. The three-layer structure enables constant impedance inside the repackage. This improves the high frequency characteristics of the semiconductor device and enables high-speed access.

Furthermore, according to the lead frame manufacturing method of the present invention, a pressing process is simply added to the conventional lead frame manufacturing method, so lead frames can be easily and inexpensively manufactured without changing the manufacturing line. can be manufactured.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of a lead frame according to the present invention, (a) is a plan view of the embodiment, (b) is a sectional view taken along line IB-IB in (a), and (C) is ( A cross-sectional view along the IC-IC line in a), FIG. 2(a),
(b) and (c) are diagrams showing the parts to be insulated, Figure 3 (a), (b), and (c) are diagrams similar to Figure 1 showing the original form of this embodiment, and Figure 4. (a), (b)
is a diagram explaining the press forming process, FIG. 5(a),
(b) and (c) show the molds used for this press molding. Figure 6 is a partially enlarged view of the lead frame of this example, and Figure 7 shows packaging using the lead frame of this example. 8 is a partially enlarged view showing the structure of a conventional SOJ (SOP) package, and FIG. 9 is a diagram showing the occupation state of the DRAM element in the package of each semiconductor device. , 1st
Figure 0 is a perspective view showing a semiconductor device with a conventional area-wire device structure, Figure 11 shows a conventional package structure, and (a) is a COL (Chip On L).
a perspective view partially showing a package structure of an ead) type;
(b) is a perspective view partially showing an LOG (Lead On Chip) type package structure. 1... Lead frame, 2... Die pad, 3
... Insulating layer, 4... Inner lead, 5... Bonding wire, 7... Outer lead, 8...
・Tie bar 10°°. Dam bar, 11.12... Press molding die, 1
3...Insulating layer, A...Resin mold

Claims (9)

[Claims] (1) A lead frame including at least a die pad on which a semiconductor element is mounted and a lead electrically connected to an electrode pad of the semiconductor element, in which a part of the lead extends below the die pad, and A lead frame characterized in that a connecting end portion of the lead to be electrically connected protrudes outward from the die pad. (2) Claim 1, wherein the connection end of the lead protrudes outward from the short side of the die pad.
Lead frame listed. (3) The lead frame according to claim 1, wherein the connection end portion of the lead is stepped into a gal wing shape with respect to the die pad surface. (4) The lead frame according to any one of claims 1 to 3, wherein an insulating layer is formed on part or all of the back surface of the die pad. (5) The lead frame according to any one of claims 1 to 3, wherein an insulating layer is formed on a portion of the lead extending below the die pad. (6) The insulating layer is formed by applying a liquid insulating material such as a thermosetting polyimide resin and a thermosetting paste, and performing heat treatment. Lead frame. (7) The insulating layer is formed by applying any one of a film-like insulating material such as a thermosetting polyimide resin, a thermoplastic adhesive, and a thermosetting polyimide resin adhesive. The lead frame according to claim 4 or 5, characterized in that: (8) The insulating layer is formed by pasting a film-like insulating material such as a thermosetting polyimide resin, and adjacent leads are connected to each other by taping using the film-like insulating material. The lead frame according to claim 5. (9) A method for manufacturing a lead frame comprising at least a die pad on which a semiconductor element is mounted and a lead electrically connected to an electrode pad of the semiconductor element, wherein the die pad is formed by press-molding tie bars that support the die pad. By upsetting and then press-molding a dam bar that supports the leads, a portion of the leads are extended below the die pad, and the electrically connected connection ends of the leads are moved from the die pad. A method for manufacturing a lead frame, characterized in that the lead frame is made to protrude outward.