JP2503029B2 - Method for manufacturing thin semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a thin package structure used for an IC card or the like.

(Prior Art) Semiconductor integrated circuits used in wristwatches, cameras, IC cards, etc. require an extremely thin package structure with a thickness of about 0.5 to 2 mm.

As a conventional semiconductor device having an extremely thin package structure, for example, there is one disclosed in Japanese Patent Laid-Open No. 55-56647. This is a so-called COB, in which a semiconductor element such as a semiconductor integrated circuit is directly mounted on a PCB (printed circuit board) made of glass epoxy, etc., and the metal wiring on the PCB is wire-connected and then sealed with epoxy resin or the like.
(Chip on board). FIGS. 3 and 4 are structural diagrams of the conventional semiconductor device having a thin package structure. FIG. 3A is a plan view of a conventional semiconductor device, and 1 is a PCB made of a glass epoxy substrate or the like.
Reference numeral 2 is a plastic resin sealing portion such as an epoxy resin.
3 is a lead terminal formed on the back surface of the PCB. FIG. 3B is a sectional view of this semiconductor device. A metal pattern that forms electrodes is printed on the front and back surfaces of the PCB1. The metal pattern on the back side of PCB1 is lead terminal 3
To form. This serves as an electrical connection terminal of the semiconductor device mounted on the IC card or the like to an external device. In the resin sealing portion 2, the semiconductor element 4 is directly fixed on the PCB 1 with an adhesive, and the metal pattern on the semiconductor element 4 and the PCB 1 are connected by the wire 5. The metal pattern on the PCB1 is connected to the metal pattern forming the lead terminal 3 on the back surface of the PCB1 by a through hole. Resin sealing part 2
Is formed by mounting the semiconductor element 4 on the PCB 1 and connecting the wire 5 and then by transfer molding or the like.
FIG. 4 is a structural diagram of another conventional semiconductor device. Fourth
FIG. 7A is a plan view thereof, and FIG. 8B is a sectional view thereof. The structure of the semiconductor device shown in FIG. 4 is the same as that of the semiconductor device shown in FIG. 3 except that the plate member 6 and the spot facing 7 are provided. The plate member 6 is for matching the heights of the resin sealing portion 2 and its surface to make the surface flat. The plate member 6 is a glass epoxy substrate or the like, and can be easily realized by using a PCB of a two-layer structure glass epoxy substrate together with the PCB 1. The counterbore 7 is a concave portion on the PCB 1 and is useful for reducing the position of the semiconductor element 4 to reduce the thickness of the entire package. The manufacturing method for obtaining the structure of FIG. 4 is the same as the manufacturing method of the structure shown in FIG. 3 except that a PCB having a two-layer structure in which the plate member 6 and the PCB 1 are integrated is used.

In the structure of the semiconductor device shown in FIG. 4, the surface can be made flat with respect to the plate member 6 and the resin-sealed portion 2. Therefore, the semiconductor device is suitable for being incorporated in a thin device having a flat surface such as an IC card.

(Problems to be Solved by the Invention) However, in such a conventional COB (chip on board) semiconductor device, cost reduction required for an IC card or the like and further reduction in thickness are required. , There was a limit described below.

That is, in the conventional COB structure, since the PCB is used, the manufacturing cost is relatively high, and when the PCB having the two-layer structure shown in FIG. 4 is used to flatten the surface, the manufacturing cost is further increased. There was a problem of doing. In addition, P.
A glass epoxy substrate is generally used as the CB, but when this is used, if it is made too thin, problems such as cracking occur, and there is a limit to thinning. Thicker PCB,
The thickness of the semiconductor element and the thickness of the resin sealing portion have to be reduced, which causes a problem in the reliability of the semiconductor element.

(Means for Solving Problems) In order to solve the above-described problems of manufacturing cost and thinning, the present invention replaces COB with a lead terminal of a metal lead frame and a molding material of an outer frame. Is fixed, and after mounting the semiconductor element and the wire, it is fixed by the molding material of the inner frame.

(Operation) In the present invention, a lead frame having lead terminals made of metal is used without using a PCB, and the lead frame is fixed by a two-stage molding material to manufacture. Therefore, the lead terminal plays the role of the conventional PCB, the metal patterns formed on the front and back surfaces of the PCB, and the lead terminal. or,
The mold material for the outer frame is the same as the conventional plate material 6 in FIG.
It plays the role of C.B1.

(Embodiment) FIG. 1 is an explanatory view of a method for manufacturing a semiconductor device showing an embodiment of the present invention. FIG. 1A is a plan view of the lead frame. Where 10 is the lead frame,
11 is a frame. Reference numeral 12 is a lead terminal, and 13 is a semiconductor element mounting portion. The lead terminals 12 are composed of four rows in each of the upper and lower sides of one semiconductor device, for a total of eight lead terminals. One of the lead terminals is the semiconductor element mounting part 13
It is configured integrally with. A semiconductor element is mounted here, and the lead terminals are electrically connected to the substrate of the semiconductor element. The leadframe is metal, the thickness is usually
The thing of about 0.1 mm to 0.15 mm is used. When it is not necessary to take out the lead terminal 12 of the semiconductor element, the semiconductor element mounting portion 13 is separated from the lead terminal 12.

FIG. 1 (b) shows that a die for forming a molding material for the outer frame is set on the lead frame 10. The lead frame 10 is placed on a flat metal base and covered with a mold from above. The mold holds the lead frame 10 with a load of about 3 tons per cavity.
Reference numeral 15 is the outside of the mold, and mainly the frame frame 11 of the lead frame is pressed. Reference numeral 16 denotes the inside of the die, which holds the semiconductor element mounting portion 13 of the lead frame and the tip end portions 18 of the lead terminals 12. Reference numeral 17 is a mold cavity, which is where the molding material of the outer frame is injected and forms a cavity on the outside and inside of the mold. The thickness (height) of the void is 0.
It is about 5 mm.

It is extremely important to press the respective tip portions 18 of the lead terminals 12 of the lead frame 10 inside the mold 16 as shown in the drawing when injecting the molding material of the outer frame. That is, when the mold material is injected, the tip portions 18 of the lead terminals 12 are firmly pressed by the mold, so that the mold resin is prevented from wrapping around around the back surface of the lead terminals 12.
Since the lead terminal 12 plays a role of an electrode terminal for making an electrical connection with an external device after being mounted on the IC card, even if the mold resin as the insulator adheres to the lead terminal 12 even if it is thin, it serves as an electrode terminal. This is because the function of will be lost. Further, once attached, its removal is very troublesome, which causes quality deterioration and cost increase.

FIG. 1C shows a case where the molding material for the outer frame is formed, the semiconductor elements are mounted, and the wires are connected. The molding material forming step of the outer frame is performed by transfer molding an epoxy plastic resin. This process condition is the same as that of a general plastic mold IC manufacturing process. Through this step, the molding material 20 for the outer frame is formed. The molding material 20 of the outer frame is made from the lead frame surface such as lead terminals according to the dimension of the void of the mold.
The surface is formed flat with a thickness (height) of 5 mm.
The gap between the lead terminals 12 of the lead frame is filled with a molding resin. Therefore, as seen from the back surface of the lead frame, as is apparent from FIG. 1C, the molding material 20 of the outer frame is formed so as to surround the outside of the lead terminal 12 and the semiconductor element mounting portion 13, and the lead terminal is also formed. The metal surface of 20 is exposed, and the gap between the lead terminals is filled with mold resin so that the gaps between the lead terminals are flush with the lead terminals. When viewed from the surface of the lead frame, the metal surface of the tip portion 18 of the lead terminal 12 and the central portion of the semiconductor element mounting portion 13 is exposed inside the molding material 20 of the outer frame. After forming the molding material 20 for the outer frame, the semiconductor element 4 is mounted on the semiconductor element mounting portion.
Die bond to 13. Die bonding is performed by adhering the semiconductor element to a metal surface with a resin such as silver paste. Next, the pad on the semiconductor element 4 and the tip portion 18 of the lead terminal are connected by the wire 5. This wire connection is also the same condition as the manufacturing process of general mold material IC,
Connect the gold wire with a wire bonder.

The lead frame whose wire connection has been completed is loaded into the molding apparatus again to form the molding material 21 of the inner frame. FIG. 1 (d) shows the molding material 21 for the inner frame. This is because the lead frame is sandwiched between the flat lower mold and the flat upper mold, and the outer frame molding material 20
This is performed by injecting a plastic resin such as an epoxy resin from a resin injection port 22 provided in the constricted portion.
An air vent 23 is provided in the other constricted portion of the molding material 20 of the outer frame. Since the upper mold and the lower mold are flat and a pressure of about 3 tons is applied to each cavity, the injected mold resin has the same upper surface as the upper surface of the molding material 20 of the outer frame. The bottom surface is the same surface as the back surface of the lead terminals of the lead frame. The molding conditions for forming the molding material 21 of the inner frame are the same as the conditions of a general mold IC manufacturing process, and the existing mold IC manufacturing equipment can be used as it is.

Next, when cut along the cutting surface 24 shown in FIG. 1 (d) and the outside of the molding material 20 of the outer frame by pressing or the like,
The semiconductor device of the present invention shown in FIGS. 2A and 2B is completed.

FIG. 2 is a structural view of a semiconductor device according to an embodiment of the present invention, which is a plan view (a) and a sectional view (b). An example of the dimensions of this semiconductor device is 10 mm vertically, 12 mm wide, and 0.6 mm thick. The lead terminal 12 made of metal is fixed by the molding material 20 of the outer frame, and the tip portion 18 of the lead terminal is connected to the semiconductor element 4 by the wire 5. Also, the semiconductor element 4
Is bonded to the semiconductor element mounting portion 13 made of metal and connected to one lead terminal 12. The semiconductor element mounting portion 13 does not need to be connected to the lead terminal when electrical connection is unnecessary. And these are being fixed by the molding material of an inner frame. The upper surface is formed by the molding material of the inner frame and the outer frame, but the surface is flat. The lower surface is filled with a metal surface such as the lead terminal 12 and the semiconductor element mounting portion 13 and the space between the metal surfaces is filled with a molding material for the outer frame and the inner frame. Therefore, the lower surface is also flat because the metal surface and the plastic resin surface are the same. Since the outer frame and the inner frame are molded in two steps on the metal surface, there is no burr adhesion and the like, and it functions as a connection terminal to the outside as an electrically good conductor. Further, the semiconductor element 4 is mounted on the semiconductor element mounting portion 13 made of metal, and the structure is such that this is directly exposed, and the heat dissipation characteristics are good. Further, since the semiconductor element mounting portion is made of metal, it also serves as an electrostatic shield.

Regarding the thickness direction, the thickness of the lead frame plate is 0.
It is 1 mm to 0.15 mm, and the semiconductor element is about 0.2 mm to 0.25 mm. Therefore, the molding material is
The thickness of 0.6 mm to 0.65 mm can be taken from the bottom surface of 0.5 mm, which is sufficient for ensuring reliability. Since the standard thickness of the IC card is 0.76 mm, the total thickness of this thin semiconductor device is 0.6 mm to 0.65 mm, which is a sufficient size.

(Effect of the Invention) In the semiconductor device having a thin structure of the present invention, the semiconductor element mounted on the lead frame is formed by the molding material of the outer frame and the inner frame. It can be made extremely thin. Further, since the semiconductor element mounting portion is a metal surface and is directly exposed, it has excellent heat dissipation characteristics.

Further, since the metal lead frame is used instead of the PCB, the strength as the substrate is not lowered, and the reliability can be secured and further thinning can be achieved.

Further, according to this semiconductor device manufacturing method, since a general plastic mold IC manufacturing line can be used as it is without using a PCB, it is possible to reduce the component cost and the manufacturing man-hour, and to reduce the manufacturing cost. be able to.

[Brief description of drawings]

1 (a), (b), (c) and (d) are explanatory views of a method for manufacturing a semiconductor device according to an embodiment of the present invention, and FIGS. 2 (a) and (b) are semiconductors according to an embodiment of the present invention. Structural drawing of the device, FIG. 3 (a)
4B is a structural diagram of a conventional semiconductor device, FIG. 4A
FIG. 6B is a structural diagram of another conventional semiconductor device. 4 ... Semiconductor element, 5 ... Wire, 12 ... Lead terminal, 13 ... Semiconductor element mounting part, 18 ... Lead terminal tip part, 20 ... Outer frame molding material, 21 ... Inner frame molding material .

Claims (1)

(57) [Claims] 1. A lead frame having a plurality of lead terminals and a semiconductor element mounting portion, the tip end of each of the plurality of lead terminals and the front and back surfaces of the semiconductor element mounting portion are fixed by a mold and resin-molded, A step of forming a molding material for an outer frame that fixes the periphery of each tip portion, and a step of mounting a semiconductor element on the semiconductor element mounting portion and connecting a wire to each tip portion after the step; After the step, a step of forming an inner molding material for fixing the semiconductor element and the wires and the respective tip portions by resin molding in a gap portion formed by the molding material of the outer frame, Method for manufacturing a semiconductor device having a thin structure.