JPH0513657A - Semiconductor device and lead frame use therefor - Google Patents

Abstract

PURPOSE:To prevent a short circuit between adjoining inner leads and improve electrical reliability, by applying an insulator to the surface of inner leads other than outer leads in the plurality of leads. CONSTITUTION:In a quad flat package(QFP) structure, one of inner leads 2B and one of external terminals of a semiconductor pellet 4 are electrically connected with each other. A plurality of inner leads 2B and the semiconductor pellet 4 are sealed with a resin sealer 6. Then, an insulator 7 is applied to the surface of the inner leads 2B other than outer leads 2C in the plurality of leads. When an external stress is applied to a lead, particularly to an inner lead 2B, the inner lead 2B may be deformed. However, there is the insulator 7 remaining between the inner leads 2B, even when the adjoining inner leads are almost contacted with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a technique effectively applied to a semiconductor device in which a semiconductor pellet is sealed with a sealing body.

[0002]

BACKGROUND ART QFP (Q uad F lat P ackage ) resin-sealed semiconductor device which employs the structure is suitable for relatively high pin count of the surface mounting, in high demand. The resin-encapsulated semiconductor device adopting the QFP structure is an external terminal (bonding pad) of the semiconductor pellet mounted on the surface of the tab.
And the inner lead of the lead are electrically connected, and the semiconductor pellet, the inner lead and the tab are sealed with a resin sealing body. The inner leads are integrally formed with the outer leads and electrically connected to each other, and a plurality of the outer leads are arranged on the outer surface of the resin encapsulant.

Each of the tab, the inner lead, and the outer lead is integrally connected to the same lead frame before the lead cutting / molding step in the assembly process of the resin-sealed semiconductor device, and after the lead cutting / molding step, from the lead frame. To be separated. The lead frame is, for example, F
It is formed of an e-Ni alloy plate and is formed into a predetermined pattern by etching using photolithography technology or punching using a press machine.

Bonding wires are used to connect the external terminals and the inner leads of the semiconductor pellet.
For the purpose of improving bondability, for example, an Ag plating layer is usually formed on the surface of the region where the bonding wire of the inner lead is bonded.

The resin encapsulant is molded by a so-called transfer molding method in which a fluid resin is injected into a molding die and the fluid resin is cured. For example, an epoxy resin is used.

Regarding the resin-sealed semiconductor device,
For example, Nikkei Electronics, separate volume Micro Devices, June 11, 1984, pages 148 to 159.
Page.

[0007]

SUMMARY OF THE INVENTION In the resin-sealed semiconductor device adopting the above QFP structure, the present inventor has found the following problems.

(1) The resin-encapsulated semiconductor device adopting the QFP structure has a fine pitch due to the increased number of pins (increase in the number of outer leads). Out of the lead
Since a plurality of inner leads are concentrated from the periphery of the resin encapsulation toward the center of the inner leads, the inner leads are formed with the smallest lead width dimension and arranged at the smallest arrangement pitch. That is, of the lead
The mechanical strength of the tip of the inner lead is the lowest. Therefore, external stress is applied to the tips of the inner leads and the tips of the inner leads are deformed at any of the carrying step, the bonding step, the resin sealing step, etc. of the assembly process of the resin-encapsulated semiconductor device, and the tips of the inner leads are adjacent to each other. An electrical short circuit occurs between the leads. The electrical short circuit between the inner leads does not have electrical reliability as a resin-sealed semiconductor device, and the yield in the assembly process decreases.

(2) In the resin-sealed semiconductor device adopting the QFP structure, either an Ag-plated layer formed on the surface of the bonding area of the inner lead, a step of forming the Ag-plated layer, or a resin-sealed body. Conductive foreign matter is generated from the. The conductive foreign matter is electrically short-circuited when it adheres between the adjacent leads, particularly between the tips of the adjacent inner leads arranged at the minimum arrangement pitch.

(3) In the resin-encapsulated semiconductor device adopting the QFP structure, the diameter of the bonding wire itself for connecting the inner lead and the external terminal of the semiconductor pellet is reduced with the finer pitch of the lead. Tends to become. That is, the mechanical strength of the bonding wire against external stress is reduced. Therefore, particularly in the resin sealing step (when resin is injected in the transfer molding step), the bonding wire is deformed by the flow of the fluid resin at the time of resin injection, and the bonding wire and the tab are electrically short-circuited. .

(4) The resin-encapsulated semiconductor device adopting the QFP structure is miniaturized and thinned for the purpose of high packaging density when a memory circuit system is mounted on a semiconductor pellet, for example. This reduction in size and thickness is achieved by reducing the size of the resin sealing body itself. However, the size reduction of the resin encapsulation body is caused by the heat generation during actual operation of the resin encapsulation type semiconductor device adopting the QFP structure and the temperature cycle due to the usage environment. The adhesive interface with either of the tabs is peeled off, and the concentration of repeated stress under the tab or between the inner leads increases rapidly due to the difference in thermal expansion coefficient between the resin sealing body and the inner lead. In addition, when the adhesive interface between the resin encapsulant and either the inner lead or the tab is peeled off, moisture is condensed on the interface, which is condensed by the heat of solder reflow when mounting the resin-encapsulated semiconductor device. A phenomenon occurs in which the generated water rapidly vaporizes and expands. These phenomena cause cracks in the resin encapsulant, which makes the resin-encapsulated semiconductor device defective, or deteriorates the moisture resistance.

The objects of the present invention are as follows.

(1) In a semiconductor device in which an external terminal and an inner lead of a semiconductor pellet are connected to each other and these are sealed with a sealing body, a short circuit between adjacent inner leads is prevented, and electrical reliability is improved. To do.

(2) In a semiconductor device in which an external terminal and an inner lead of a semiconductor pellet mounted on the surface of a tab are connected with a wire and these are sealed with a sealing body, short circuit of the tab and the wire is prevented. And improve electrical reliability.

(3) In addition to the purpose (1) or the purpose (2), the generation of cracks in the sealing body is prevented. Also, the moisture resistance is improved.

(4) A lead frame which achieves any one of the above objects (1) to (3).

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0018]

Among the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

(1) Any of the inner leads of the plurality of leads and any of the plurality of external terminals of the semiconductor pellet are electrically connected to each other, and the inner leads of the plurality of leads and the semiconductor pellet are In a semiconductor device sealed with a sealing body, the surfaces of the inner leads of the plurality of leads excluding the outer leads are covered with an insulator.

(2) The inner lead of the lead and the external terminal of the semiconductor pellet mounted on the surface of the tab are electrically connected by a wire, and the inner lead of the lead, the tab and the semiconductor pellet are sealed. In the semiconductor device sealed with, the surface of at least the semiconductor pellet of the tab and the side surface surrounding the surface are covered with an insulator.

(3) The sealing body according to any one of the means (1) and the means (2) is a resin sealing body, and the insulator covering the surface of the inner lead or the surface of the tab is the above-mentioned. The adhesive force between the resin sealing body and the inner leads or the tabs is higher than that between the resin sealing body and the inner leads or the tabs.

(4) A lead frame in which the surface of the inner lead or the surface of the tab described in any one of the means (1) to (3) is covered with an insulator is formed.

[0023]

According to the above-mentioned means (1), even when external stress is applied to the leads, especially the inner leads, and the inner leads are deformed and adjacent inner leads come into contact with each other, the insulator is interposed between the inner leads. Therefore, the electrical reliability of the semiconductor device can be improved without electrical short circuit.

Further, even if a conductive foreign substance (for example, a residual substance of conductive plating) adheres to the tip of the inner lead, an electrical short circuit can be prevented, so that the electrical reliability of the semiconductor device can be improved. .

According to the above-mentioned means (2), even when external stress is applied to the wire and the wire is deformed so that the wire and the tab come into contact with each other, the insulator is interposed between the wire and the tab. Therefore, the electrical reliability of the semiconductor device can be improved without electrical short circuit.

According to the above-mentioned means (3), the adhesive force between the resin encapsulant and the inner lead or the tab can be increased with the insulator formed of the resin interposed. As a result, it is possible to prevent the resin encapsulant from cracking due to the peeling between the resin encapsulant and the inner lead or the tab, so that the reliability of the semiconductor device can be improved. Further, the moisture intrusion route generated between the resin encapsulant and the inner lead or the tab can be blocked, and the corrosion of the external terminals of the semiconductor pellet can be reduced, so that the moisture resistance of the semiconductor device can be improved.

According to the above-mentioned means (4), it is possible to provide a lead frame which can prevent an electrical short circuit between the adjacent inner leads, or can prevent an electrical short circuit between the tab and the wire.

The structure of the present invention will be described below together with an embodiment in which the present invention is applied to a resin-sealed semiconductor device adopting a QFP structure.

In all the drawings for explaining the embodiments, those having the same function are designated by the same reference numerals, and the repeated description thereof will be omitted.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a resin-sealed semiconductor device adopting a QFP structure, which is an embodiment of the present invention, is shown in FIG. 1 (cross-sectional view) and FIG. 2 (plan view of an essential part during an assembly process).

As shown in FIGS. 1 and 2, the resin-encapsulated semiconductor device 1 employing the QFP structure has a semiconductor pellet 4,
Inner lead 2 of tab (die pad) 2A and lead
B is sealed with the resin sealing body 6. The semiconductor pellet 4 is mounted on the surface of the tab 2A, and the external terminal (bonding pad) 4P of the semiconductor pellet 4 is electrically connected to the inner lead 2B.

The semiconductor pellet 4 is formed of, for example, a planar rectangular single crystal silicon, and a predetermined circuit system is mounted on the element formation surface. Although not limited to this arrangement,
In the peripheral region of the element forming surface of the semiconductor pellet 4, a plurality of external terminals 4P to be the input / output regions of the circuit system are arranged along each side of the rectangle. The external terminal 4P is usually
The wiring in the circuit system, for example, is formed of the same conductive layer as the uppermost aluminum alloy wiring.

The tab 2A is formed in a planar rectangular shape which is larger than the planar shape of the semiconductor pellet 4, and as shown in FIG. 2, the tab suspension lead 2 is formed at each corner of the planar shape.
Supported by E. On the surface of the tab 2A and the semiconductor pellet 4
An adhesive layer 3 is interposed between the adhesive layer 3 and the back surface of the semiconductor pellet 4, and the semiconductor pellet 4 is fixed on the front surface of the tab 2A via the adhesive layer 3. As the adhesive layer 3, for example, an Ag paste material, an epoxy adhesive, or a polyimide adhesive is used.

The inner leads 2B extend in a direction intersecting with the rectangular sides of the tab 2A, and a plurality of inner leads 2B are arranged along the rectangular sides of the tab 2A. Inner lead 2
One end of the semiconductor pellet 4 side of B is a bonding wire 5
Is connected to the external terminal 4P of the semiconductor pellet 4. For example, an Au wire is used as the bonding wire 5, and the Au wire has a diameter of, for example, about 30 [μm].

The other end of the inner lead 2B is integrally formed with and electrically connected to the outer lead 2C. A plurality of outer leads 2C are arrayed on the outer surface along each side of the resin encapsulation body 6 formed in a planar rectangular shape, and configured in a so-called four-direction lead array structure. The outer lead 2C is molded in a gull wing shape.

Each of the above-mentioned tab 2A, inner lead 2B, outer lead 2C, and tab suspension lead 2E is shown in FIG.
As shown in FIG. 2, the lead frames are connected to the same lead frame before the cutting and molding process. Before the lead cutting and molding process, the outer lead 2C and the tab suspension lead 2E are connected to each other by a tie bar 2D, and are also connected to a frame (not shown in FIG. 2).

The lead frame is made of a Fe--Ni alloy (for example, the Ni content is 42% or 50%).
[%]), Cu, or a Cu alloy.
It is formed with a plate thickness of about 0 to 150 [μm]. This lead frame is formed by either etching using photolithography technology or punching using a press machine.

Although not shown in FIGS. 1 and 2, at least the surface of the lead frame, which is the bonding region of the inner lead 2B, is covered with an Ag plating layer for the purpose of improving bondability. . In addition, in the lead frame, particularly on the surface of a region of the outer lead 2B to be mounted on a mounted body such as a printed wiring board, although not shown, in order to improve wettability with the solder paste, Covered with a solder layer. The solder layer may be a so-called solder-preliminary plating layer formed before the resin sealing body 6 is formed, a solder plating layer formed after the resin sealing body 6 is formed, or a solder dip layer.

The resin encapsulant 6 is made of epoxy resin, and is molded by a transfer molding method in which a fluid resin is injected into a molding die and then the fluid resin is cured.

As shown in FIGS. 1 and 2, the resin-encapsulated semiconductor device 1 adopting the QFP structure constructed as described above has respective surfaces of the lead tab 2A, the inner lead 2B, and the tab suspension lead 2E. Specifically, all surfaces of the upper surface, the side surface, and the lower surface are covered with the insulator 7.

The insulator 7 has a thickness of about 200-in the process of assembling the resin-sealed semiconductor device 1 which employs the QFP structure.
Since there are high temperature processes of 300 [° C.], they are formed of a material that can withstand these high temperature processes. As the high temperature process, there are a curing process of the adhesive layer 3 for fixing the semiconductor pellet 4 on the surface of the tab 2A, a bonding process with a wire bonding device, a solder reflow process, a resin sealing process and the like.

In addition, the insulator 7 has a larger adhesive force between the tab 2A, the inner lead 2B and the tab suspension lead 2E than the adhesive force between the resin sealant 6 and the tab 2A, the inner lead 2B and the tab suspension lead 2E. Both the adhesive force and the adhesive force with the resin sealing body 6 are formed of a material having a high adhesive force. Insulator 7
Is formed of a material having high mechanical strength such that damage such as cracking does not occur even if some external stress is applied.

Specifically, the insulator 7 is formed of a resin material such as a polyimide resin, an epoxy resin, a fluorine resin, a silicon resin, a liquid crystal polymer, or a derivative thereof. [μm]. The insulator 7 formed of any resin material is coated by, for example, spray coating by spraying or dip coating. The covering of the insulator 7 is incorporated before the semiconductor pellet 4 is mounted on the surface of the tab 2A, that is, in the lead frame processing process. The insulator 7 applied by this type of method can selectively cover all surfaces of the tab 2A, the inner lead 2B, and the tab suspension lead 2E except the surface of the outer lead 2C. Outer lead 2C
When the insulator 7 is formed on all the surfaces of the above, the step of removing the insulator 7 needs to be performed in another independent step for the opening 7B formed on the surface of the bonding area of the inner lead 2B. Since the assembly process must be changed significantly, the surface of the outer lead 2C basically does not cover the insulator 7.

On the surface of the bonding region of the inner lead 2B, the insulator 7 is selectively removed by the etching process which also uses the photolithography technique, and the opening 7B is formed. The bonding wire 5 is bonded to the surface of the bonding area of the inner lead 2B (the surface of the Ag plated layer) through the opening 7B formed in the insulator 7. Further, since the bonding is usually performed by using thermocompression and ultrasonic vibration together, the bonding wire 5 is directly bonded on the surface of the insulator 7, and the insulator 7 is partially forcibly destroyed to perform the bonding. The wire 5 may be bonded to the surface of the bonding area of the inner lead 2B. In this case, the photolithography technique and the etching process are unnecessary, and the number of steps of the lead frame processing process or the assembly process can be reduced.

The insulator 7 is not limited to a single resin material, but may be a composite resin material, or a non-resin material such as alumina or ceramic.

Thus, any one of the inner leads 2B of the plurality of leads and any one of the plurality of external terminals 4P of the semiconductor pellet 4 are electrically connected to each other,
In the resin-sealed semiconductor device 1 adopting the QFP structure in which the inner lead 2B of the plurality of leads and the semiconductor pellet 4 are sealed by the resin sealing body 6, the inner leads other than the outer lead 2C of the plurality of leads are excluded. The surface of the lead 2B is covered with the insulator 7. With this configuration, external stress is applied to the leads, particularly the inner leads 2B, the inner leads 2B are deformed, and the adjacent inner leads 2B are
Even if they contact each other, the insulator 7 is interposed between the inner leads 2B, so that the electrical reliability of the resin-sealed semiconductor device 1 adopting the QFP structure can be improved without electrical short circuit. The external stress causes artificial handling and transportation in the assembly process. Further, not only a short circuit between the adjacent inner leads 2B but also a short circuit between the adjacent inner leads 2B and the tab suspension leads 2E can be prevented. Further, even when a conductive foreign substance (for example, a residual substance of the Ag plating layer) adheres to the tip of the inner lead 2B, the entire surface of the inner lead 2B is covered with the insulator 7, so that it is electrically connected. Short circuit can be prevented.

Also, the inner lead 2B of the lead and the external terminal 4P of the semiconductor pellet 4 mounted on the surface of the tab 2A are electrically connected by a bonding wire 5, and the inner lead 2B of the lead and the tab 2A are electrically connected. Also, in the resin-sealed semiconductor device 1 adopting the QFP structure in which the semiconductor pellet 4 is sealed with the resin sealing body 6, the tab 2
At least the surface of A on which the semiconductor pellet 4 is mounted and the side surface surrounding the surface are covered with the insulator 7.
With this configuration, even when external stress is applied to the bonding wire 5 and the bonding wire 5 is deformed and the bonding wire 5 and the tab 2A come into contact with each other, the insulator 7 is provided between the bonding wire 5 and the tab 2A. Is interposed, the electrical reliability of the resin-encapsulated semiconductor device 1 employing the QFP structure can be improved without electrical short circuit.
External stress applied to the bonding wire 5 is particularly likely to occur when a fluid resin is injected into the molding die by the transfer molding method.

In the resin-sealed semiconductor device 1 adopting the QFP structure, the insulator 7 covering the surface of the inner lead 2B or the surface of the tab 2A is the resin-sealed body 6 and the inner lead 2B or. Compared with the adhesive force with the tab 2A, the resin sealing body 6, the inner lead 2B
Alternatively, the tabs 2A are formed of a resin material having a high adhesive force. With this configuration, the adhesive force between the resin sealing body 6 and the inner lead 2B or the tab 2A can be increased with the insulator 7 formed of the resin material interposed. As a result, it is possible to prevent cracks from occurring in the resin encapsulation body 6 due to stress concentration due to peeling between the resin encapsulation body 6 and the inner lead 2B or the tab 2A and dew expansion of water. The reliability of the resin-sealed semiconductor device 1 adopted can be improved. The repetition of stress concentration occurs, for example, during actual operation after mounting or due to a temperature cycle due to the use environment, and dew expansion of water occurs due to, for example, a solder reflow step when mounting on a mounted body. In addition, a water intrusion path generated between the resin sealing body 6 and the inner leads 2B or the tabs 2A can be blocked, and corrosion of the external terminals 4P of the semiconductor pellet 4 can be reduced. The moisture resistance of the semiconductor device 1 can be improved.

In the lead frame used in the resin-sealed semiconductor device 1 adopting the QFP structure,
The surface of the inner lead 2B or the surface of the tab 2A is covered with the insulator 7. With this configuration, it is possible to provide a lead frame capable of preventing the above-mentioned electrical short between the adjacent inner leads 2B or preventing the electrical short between the tab 2A and the bonding wire 5.

Further, by providing the insulator 7 between the inner leads 2B or between the bonding wire 5 and the tabs 2A and the inner leads 2B, the flexibility of lead frame designing, working, or wiring designing, working is greatly increased. It is possible to improve, shorten the design development period, standardize specifications, and standardize.

The inventions made by the present inventors are as follows.
Although the present invention has been specifically described based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

For example, the present invention is not limited to the resin-sealed semiconductor device adopting the QFP structure, but the SOJ structure, PL
It can be applied to all resin-encapsulated semiconductor devices regardless of surface mounting type or pin insertion type such as CC structure and DIP structure.

Further, the present invention can be applied to a ceramic-sealed semiconductor device (glass-sealed semiconductor device) in which a lead frame is incorporated in a ceramic-sealed body.

[0054]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) In a semiconductor device in which an external terminal and an inner lead of a semiconductor pellet are connected to each other and these are sealed with a sealing body, a short circuit between adjacent inner leads is prevented, and electrical reliability is improved. it can.

(2) In a semiconductor device in which an external terminal and an inner lead of a semiconductor pellet mounted on the surface of a tab are connected with a wire and these are sealed with a sealing body, short circuit of the tab and the wire is prevented. And electrical reliability can be improved.

(3) In the semiconductor device described above, it is possible to prevent the occurrence of cracks in the sealing body. In addition, the moisture resistance of the semiconductor device can be improved.

(4) It is possible to provide a lead frame used in the semiconductor device.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a QFP structure resin-sealed semiconductor device that is an embodiment of the present invention.

FIG. 2 is a plan view of a main part of the resin-sealed semiconductor device during an assembly process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Resin-sealed semiconductor device, 2A ... Tab, 2B ... Inner lead, 2C ... Outer lead, 4 ... Semiconductor pellet, 4P ... External terminal, 5 ... Bonding wire, 6 ... Resin encapsulation body, 7 ... Insulator, 7B ... Open.

Claims (4)

[Claims] 1. An inner lead of a plurality of leads and any one of a plurality of external terminals of a semiconductor pellet are electrically connected to each other, and the inner lead of the plurality of leads and the semiconductor pellet are sealed. In the semiconductor device sealed with a stopper, the surface of the inner leads of the plurality of leads excluding the outer leads is covered with an insulator. 2. The inner lead of the lead and the external terminal of the semiconductor pellet mounted on the surface of the tab are electrically connected by a wire, and the inner lead of the lead, the tab and the semiconductor pellet are sealed by a sealing body. In the semiconductor device to be sealed, at least the surface of the tab on which the semiconductor pellet is mounted and the side surface surrounding the surface are covered with an insulator. 3. The encapsulant according to claim 1 or 2 is a resin encapsulant, and the insulator covering the surface of the inner lead or the surface of the tab is the resin encapsulant. The resin sealing body, the inner lead or the tab is formed of a resin having a higher adhesive force than the adhesive force between the body and the inner lead or the tab. 4. A lead frame, wherein the surface of the inner lead or the surface of the tab according to each of claims 1 to 3 is covered with an insulator.