JPH0547975A - Lead frame and surface package-type semiconductor device - Google Patents

Abstract

PURPOSE:To make maximum the areas of islands within a limited size by a method wherein the pate thicknesses of internal leads and tie bars are made thinner than the plate thickness of the islands and at the same time, the interval between the tip parts of the leads and the islands is made narrow to a value roughly equal to the plate thickness of the leads. CONSTITUTION:A tabular material, which has thin parts for lead part 12 formation use and thick parts for island part 11 formation use and consists of one sheet of a copper material, is subjected to punching work, whereby a lead frame is manufactured. At this time, islands 11 and leads 12 are cut at the thin part of the tabular material and the interval (x) between the islands 11 and the leads 12 is made equal with the plate thickness of the leads 12 or is made narrow to 80% or thereabouts of the plate thickness. Thereby, as a draft which is required for the punching work can be made small, the interval (x) between extension parts 13 of the leads 12 and the islands 11 can be made narrow, the areas of the islands 11 can be increased by the narrowed amount and the lead frame can correspond also to the constitution of two chips.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a surface mounting lead frame and a semiconductor device capable of maximizing an island size.

(B) Conventional technology As one means to realize lighter, thinner, smaller, and smaller devices than before, there are surface-mounted semiconductor packages called CP and PCP, in which leads are face-bonded to the conductive pattern of the printed circuit board ( For example, JP-A-01-184059). FIGS. 8 and 9 show such a device, (1) is a semiconductor chip, (2) is an island on which the semiconductor chip (1) is mounted, and (3) is a tie bar for holding the island (2). , (4) and (5) are leads, (6) is a wire, and (7) is a molding resin.

 In recent years, even with such surface mount type, higher density and higher output have been demanded, and for this reason, the number of semiconductor chips (1) to be mounted is reduced from one to two or larger chips. It is desired to be installed. Therefore, to meet these demands, there was a demand to increase the size of the leadframe island (2). There was also an intention to expose the back surface of the island (2) in terms of heat dissipation.

(C) Problems to be Solved by the Invention However, since the lead frame is manufactured by punching or etching from one plate-shaped material, and the processing requires a margin equal to the plate thickness, the lead (4) The distance between (5) and the island (2) cannot be narrowed, and therefore, there is a drawback in that the area of the island (2) cannot be increased in a package whose outer dimensions are defined.

 As one method to solve this, it is considered that the thickness of the lead frame is reduced to reduce the amount of the clearance. However, with this method, the plate thickness of the island (2) also becomes thin, and the above-mentioned configuration in which the back surface of the island (2) is exposed has the drawback that the crushing process that forms a step around the island (2) cannot be performed. It was If there is no level difference in the crushing process, the adhesion between the island (2) and the resin will be weak and it will not be practical.

(D) Means for Solving the ProblemsThe present invention has been made in view of the above-mentioned drawbacks of the related art, and uses a lead frame in which the lead (12) is thinner than the island (11). Provided is a lead frame and its semiconductor device in which the area of the island (11) is increased by reducing the distance between the tip (13) of the (12) and the island (11) to about the thickness of the lead (12). It is a thing.

(E) Function According to the present invention, the lead (12) can be thinned to reduce the extraction margin and can be used for increasing the area of the island (11). Further, since the land portion (11) has a plate thickness sufficient for crushing, the step (20) can maintain the adhesion between the island (11) and the resin (19).

(F) Embodiment One embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a plan view showing a lead frame of the present invention. (11) is an island for mounting a semiconductor chip, and (12) is a tip extending near the island (11). A lead having an extension portion (13) at the tip, and a tie bar (14) for holding the island (11) in the connecting strip (15). This lead frame is designed for a two-chip configuration, and the first pattern ( 16 ) has one island (11) for sharing the substrate potential of the chip and two islands for different potentials. The second pattern ( 17 ) with (11) can be designed. There are three types of two-chip combinations: transistor-transistor, transistor-diode, and diode-diode. (18) is a holding lead that can be used as a lead for taking out the substrate potential according to the user design, and the first pattern ( 16 ) and the second pattern ( 17 ) have the same shape in the mold. This is because it is possible to share. Although the first and second patterns ( 16 ) and ( 17 ) are mixed in the drawing, a strip-shaped lead frame having a fixed length and one of the patterns formed is used in manufacturing.

 The lead frame is manufactured by punching a sheet of copper-based material having a thin portion for forming the lead (12) portion and a thick portion for forming the island (11) portion. The plate thickness is 0.2 mm in the thin part for the lead (12) and 0.4 mm in the thick part for the island.

 The lead (12) and the island (11) are cut at a thin portion of the plate-like material, so that the distance between them (x in the figure) can be made equal to the plate thickness or can be reduced to about 80% of the plate thickness. The distance between the lead (12) and the tie bar (14) is also the same. The extended portion (13) at the tip of the lead (12) is extended as a bonding post for a gold wire or the like, and for the purpose of preventing the resin (19) from coming off.

 The island (11) has the thin plate thickness at the portion close to the tie bar (14) and the portion to be cut as described above, and the thick plate thickness at the portion not adjacent to the other leads (12). Then, on three sides around the island (11) having a large plate thickness, as shown in the cross-sectional view taken along the line AA in FIG. A crushing process is performed to a depth of about 0.2 mm to form This crushing process becomes difficult unless the plate thickness is 0.4 mm or more.

 The tie bar (14) is punched out from the lead (12) and then bent upward by stamping, as shown in Fig. 3, and bent again at a position where it is approximately half the thickness of the resin (19) and extends horizontally. Let In the figure, (21) is a semiconductor chip, and (22) is a bonding wire.

 In the lead frame of the present application, since the plate thickness of the portion forming the lead (12) is thin, the punching margin required for punching can be reduced. Therefore, the distance between the extended portion (13) of the lead (12) and the island (11) can be narrowed, and the area of the island (11) can be increased by the narrowed distance. Therefore, it is possible to secure the area of the island (11) sufficient to support the 2-chip configuration.

 Further, since the distance between the expansion portion (13) of the lead (12) and the tie bar (14) can be similarly narrowed, the expansion portion (13) can be expanded toward the tie bar (14). .. Since it is sufficient for the expansion portion (13) to have a certain area as a bonding post, the expansion toward the tie bar (14) can contribute to the further increase in the area of the island (11).

FIGS. 4 and 5 and FIGS. 6 and 7 show a semiconductor device constituted by the lead frame. Figures 4 and 5 use the lead frame of the first pattern ( 16 ), and two semiconductor chips (21) are die-bonded to a common island (11), and the surface of the chip (21) is shown. The electrode and the lead (12) are wire-bonded with a bonding wire (22), the main part is molded with a resin (19), and the tie bar (14) and the like are cut and individually divided. A portion of the lead (12) sealed in the resin (19) is called an internal lead (12a), and a portion outside the resin (19) is called an external lead (12b). The resin (19) seals the main part of the back surface of the island (11) so as to expose only the thick part, and the derived external leads (12b) are bent into a lead shape that can be surface-mounted by forming. Be done.

 Since the island (11) is common in this configuration, the mounted chip (21) is limited to a combination in which the substrate potential of the chip (21) can be made common. It is up to the user to take out the substrate potential from the tie bar (14) as a lead or the holding lead (18) as a lead. In the latter case, the tie bar (18) is not needed, so cut it at an appropriate length.

 Each lead (12) is soldered onto the printed circuit board (not shown) so that the back surface of the island (11) is in close contact with the printed circuit board or the wiring pattern formed on the surface of the printed circuit board. The forming of the leads (12) was done in order to prevent a short circuit between the leads (12) and the island (11) due to the formation of a bridge due to solder during the soldering as described above. A space is provided between the portion and the resin (19).

 According to such a semiconductor device of the present invention, the area of the island (11) can be maximized within a limited size, so that a one-package / two-chip configuration can be adopted. Further, by exposing the back surface of the island (11), it is possible to increase the output to some extent, and the crushing process of the land (11) can secure the adhesion between the resin (19) and the eyeland (11). Further, the lead (12) can be easily formed by reducing the plate thickness of the lead (12).

FIGS. 6 and 7 show another embodiment, which utilizes the second pattern ( 17 ) in FIG. The island (11) is cut at the center, and the semiconductor chips (21) are fixed to each of them, and the corresponding leads (12) and the semiconductor chips (21) are wire-bonded by the bonding wires (22). This structure cuts the thick part of the island (11), which naturally increases the removal margin, but since the two islands (11) are electrically independent, the two semiconductor chips (21) It can be used for circuit configurations that cannot share the substrate potential. Further, an example in which the tie bar (14) is cut in the middle to extract the substrate potential from the holding lead (18) is shown.

 According to such a configuration, the substrate potentials of the two semiconductor chips (21) can be made independent of each other, so that it is possible to provide a semiconductor device having a wide range of circuit applications.

(G) Effect of the Invention As described above, according to the present invention, the gap between the tip portion (13) of the lead (12) and the island (11) is reduced by thinning the lead (12). 1 x) can be narrowed, so the area of the island (11) should be increased, especially by increasing the length in the same direction as the extending direction of the leads (12) to form a 2-chip structure. It has the advantage that Further, since the step (20) can be formed in the island (11) by crushing, there is an advantage that the back surface of the island (11) can be exposed. Furthermore, there is an advantage that the forming process of the lead (12) can be easily performed by reducing the plate thickness of the lead (12).

Moreover, the one-package, two-chip configuration also has the advantage of being able to respond to further miniaturization of electronic equipment.

[Brief description of drawings]

FIG. 1 is a plan view showing a lead frame of the present invention, FIGS. 2 and 3 are sectional views and a side view taken along the line AA of FIG. 1, and FIGS. 4 and 5 are first patterns ( 16 ). And FIG. 7 are plan views and side views showing the semiconductor device assembled according to the second pattern ( 17 ), and FIG. 8 and FIG. [Fig. 3] is a plan view and a side view showing a conventional example.

Claims (7)

[Claims] 1. An island for fixing a semiconductor chip,
In a lead frame including an inner lead extending near the tip of the island and having an expanded portion at the tip, and a tie bar for holding the island in a connecting strip, the plate thicknesses of the inner lead and the tie bar are A lead frame, which is thinner than the plate thickness of the island, and narrows a distance between the tip portion of the inner lead and the island to a value substantially equal to the plate thickness of the inner lead. 2. The lead frame according to claim 1, wherein the peripheral end face of the island is crushed. 3. The lead frame according to claim 1, wherein the island is a set of two islands. 4. An island for fixing a semiconductor chip,
An inner lead extending so that its tip is close to the island, a resin whose main part is molded so as to expose the back surface side of the island, and a resin continuously extending from the inner lead to the outside of the resin and In a surface mount type semiconductor device having an external lead formed for surface mounting, the thickness of the inner lead is made thinner than that of the island, and the distance between the inner lead and the island is set to the inner side. A surface-mount type semiconductor device characterized by narrowing the lead thickness to a value that is approximately equal. 5. The surface mount type semiconductor device according to claim 4, wherein two semiconductor chips are mounted. 6. The surface mount semiconductor device according to claim 5, wherein the two semiconductor chips are fixed on one common island. 7. The surface mount type semiconductor device according to claim 5, wherein the two semiconductor chips are respectively fixed on two islands.