JP2005150126A - Lead frame and method of manufacturing resin-sealed semiconductor device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead frame which does not generate resin burr at all which is required particularly in a leadless package, etc. and to provide a method of manufacturing a resin-sealed semiconductor device. <P>SOLUTION: The lead frame includes an island 11 for mounting a semiconductor chip and a plurality of outer leads 12 coupled by a tie bar 13 and provided at the periphery of the island 11. An extension piece 14, coupled to the tie bar 13, is extended and formed to the island 11 side between two pieces of outer leads 12. This extension piece 14 is provided separately from the outer leads 12 and is formed to be brought into contact with a sealing mold set when the distal end 14a of the extension piece 14 is resin-sealed in the lead frame, or slightly held by the mold, and to be brought into contact with the side face of the outer lead 12 being adjacent to the side face of the distal end of the extension piece 14. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lead frame used when a semiconductor device is manufactured by mounting a semiconductor chip and sealing with resin, and a method for manufacturing a resin-encapsulated semiconductor device using the lead frame. More specifically, even in a package that is miniaturized, such as a QFN package, where there is almost no protruding part of the lead, or the bottom surface of the sealing resin and the bottom surface of the lead are almost the same surface, the resin burr between the leads The present invention relates to a lead frame capable of preventing and improving the reliability of soldering and a method of manufacturing a resin-encapsulated semiconductor device using the lead frame.

  As a typical example of a lead frame used in a resin-encapsulated semiconductor device, an SOP package structure shown in FIG. 5 is known. When resin sealing is performed using this lead frame, a lead frame thickness equivalent resin burr (hereinafter referred to as a plate) is formed in a space 8 surrounded by two adjacent outer leads 12 and tie bars 13 of the lead frame 1 shown in FIG. 9 (also referred to as a thickness burr) (see FIGS. 6C and 6D) occurs (see, for example, Patent Document 1). In FIG. 5, 11 is an island, and 5 is a sealing resin portion.

  Therefore, as a method for suppressing the occurrence of plate thickness burrs, a means for forming a dam (dam block) in the space with a resin sealing mold has been put into practical use. In this method, a protrusion is formed from a mold in a plate thickness burr generation area of the mold for resin-sealing the lead frame, and the protrusion prevents the resin from entering. Accordingly, the thickness burr does not occur in the space 8 of the lead frame leaving a clearance with the mold protrusion. However, there is a problem that the mold has to be formed in a special shape, resulting in a very high cost.

  On the other hand, as shown in FIG. 6A, the protrusion 13a for removing the dam resin connected to the tie bar 13 of the lead frame 1 does not reach the side surface of the sealing resin portion 5, and the outer lead 12 The resin is prevented from flowing out (see, for example, Patent Document 2), and is connected to the tie bar 13 and sealed as shown in FIG. 6B. The structure etc. which prevent the outflow of resin by providing another tie bar 13b which connected the edge part by the side of the resin part 5 with the adjacent outer lead 12 (for example, refer patent document 3) are considered. The method solved by this lead frame has the advantage that the resin-sealed mold can be used as it is and the mold structure is not complicated, so that expensive countermeasure costs are not required.

However, the structure shown in FIG. 6A is formed so that the tip of the protrusion 13a does not reach the side surface of the sealing resin portion 5, and the structure shown in FIG. 6B is another tie bar. Since the tip of the sealing resin portion 5 side of 13b is connected to the outer lead 12, it is necessary to cut and separate later, and a gap is indispensable between the tip and the side surface of the sealing resin portion 5. Yes, resin spillage cannot be avoided. Therefore, when resin is sealed, a resin outflow occurs in the gap, and a resin burr 9 is formed. Even if the protrusion 13a and the other tie bar 13b are removed by a punch or the like, FIG. 6C to FIG. As shown in a side view and a plan view of the package, a resin burr 9 is formed on the side surface of the sealing resin portion 5 in the space 8 and the side surface of the outer lead 12.
JP-A-01-321665 Japanese Patent Laid-Open No. 02-097048 Japanese Patent Laid-Open No. 03-0944458

  As described above, the lead frame measures include conventional insertion type packages (a structure in which the lead is extended and inserted into a through hole such as a printed circuit board and soldered), and a package having a gull wing type lead (the lead is outside the resin portion). This technology was developed for the surface mount type in which leads are formed so that they can be soldered simply by placing them on a printed circuit board. It is not considered for packages. For this reason, it is a structure that allows a small amount of resin outflow, and there is a problem that it is impossible to avoid the remaining resin outflow (resin burr) as described above.

  On the other hand, leadless packages using lead frames such as SON and QFN have been rapidly spreading recently. In these leadless packages, it is difficult to take the difference in height (standoff) between the lead and the bottom of the resin part, as in a general package, and if a small amount of resin burr occurs, the lead used as an electrode It is difficult to secure a reliable connection when mounted on a substrate. Further, the resin burrs adhering to the package may fall off, which may cause connection failure when the package is mounted on the substrate. For this reason, a slight amount of spilled resin must be avoided, but the above-mentioned lead frame measures cannot prevent the occurrence of satisfactory resin burrs.

  The present invention has been made to solve such problems, and in particular, a lead frame that does not generate any resin burrs, which is required particularly for leadless packages, and a method for manufacturing a resin-encapsulated semiconductor device using the lead frame. The purpose is to provide.

  The lead frame according to the present invention is a lead frame having an island for mounting a semiconductor chip and a plurality of outer leads connected by a tie bar and provided around the island, and the tie bar between the two outer leads. An extension piece that is connected to the island and extends toward the island is provided separately from the outer lead, and the extension piece is a sealing member whose tip is set when the lead frame is sealed with resin. It is characterized in that it is in contact with the mold or slightly sandwiched between the molds, and the side surface of the tip is in contact with the side surface of the adjacent outer lead.

  Here, the outer lead means a lead portion extending outward from the sealing resin portion, and the tie bar means a member connecting a plurality of outer leads, and a side rail in which a feed through hole is formed. It may be shared with.

  It is an extension part that the separation part of at least the tip part of the extension piece and the outer lead is formed by a process that does not substantially generate scrap by a shearing process different from the lead forming process of the lead frame. It is preferable because a gap that causes resin outflow is not formed between the piece and the outer lead. Here, “processing that does not generate scrap (chips) substantially by shearing” is so-called slitting, which is a process of making incision lines, and almost no scrap material is produced on the plate. It means a process for making a cut without forming a gap.

  The shearing process is performed from the surface side of the lead frame on which the semiconductor chip is mounted, and a shoulder sag is formed only on the surface side by the shearing process. It is preferable because it can be flattened by a mold at the time and the resin can be completely prevented from flowing out to the bottom surface of the outer lead that becomes a connection surface when the substrate is mounted.

  Since the gap is formed between the extension piece and the outer lead at a portion other than the tip of the extension piece, the side surface of the outer lead before removing the extension piece is also plated. This is preferable.

  A method for manufacturing a resin-encapsulated semiconductor device according to the present invention includes: (a) an island, an outer lead located on the outer periphery of the island and connected by a tie bar, and extending from the tie bar to the island side between the outer leads. In order to prevent the resin from flowing out, the leading end of the lead frame abuts on a sealing mold set when the lead frame is resin-sealed or extends to a position where the lead frame is slightly clamped by the mold. A lead frame is manufactured by processing a plate-like body so as to have an extended piece to be taken out, and (b) shearing between the extended piece and the outer lead from the surface side on which the semiconductor chip is mounted. (C) a semiconductor chip is mounted on the island, (d) the lead frame is sandwiched by a sealing mold, and resin is transferred to the outer by the extension piece. A resin sealing to prevent leaking between the leads, characterized by cutting the outer leads thereby removing the extension piece (e).

  According to the present invention, the lead frame is provided with the extension piece so that the tip end abuts on the mold at the time of resin sealing or the tip part is slightly sandwiched between the mold, and the extension piece Since the side wall of this is formed in contact with the adjacent outer lead, when the semiconductor chip is mounted on this lead frame and sandwiched between the resin sealing molds and sealed with resin, Resin outflow is completely prevented, and resin does not flow out between the outer leads. On the other hand, since the extension piece and the outer lead are separated, the amount is very small even when the tip is sandwiched by the mold, and is pushed down when removing the tie bar. Only the extension piece is removed at the same time, and the adjacent outer leads are completely independent.

  As a result, it is possible to obtain a lead frame that can prevent the resin from flowing out by simply increasing the number of shearing steps when producing the lead frame without using a complicated and expensive sealing mold. Then, by mounting the semiconductor chip using this lead frame and sealing with resin, the lead interval becomes very narrow, and a package such as QFN in which the resin bottom surface and the lead bottom surface are formed on substantially the same surface can be obtained. Even in the case of manufacturing a semiconductor device having a resin, no resin burr is formed between the outer leads, the slightly exposed lead surface is completely protected from the resin burr, and the reliability of soldering is greatly improved. A semiconductor device is obtained.

  In particular, in a semiconductor device in which the bottom surface of the sealing resin and the bottom surface of the outer lead are formed on substantially the same surface, the above shearing process is performed on the surface side of the lead frame (the side on which the semiconductor chip is mounted and resin-sealed). Since the bottom surface of the outer lead becomes a flat surface without shoulder sag, resin leakage to the bottom surface of the outer lead can be completely prevented, and a sharp shape that does not cause resin burrs can be achieved. At the same time, the reliability of soldering to a mounting board or the like can be greatly improved.

  Next, a lead frame of the present invention and a method of manufacturing a semiconductor device using the same will be described with reference to the drawings. A lead frame according to the present invention is connected to an island 11 for mounting a semiconductor chip (not shown) by a tie bar 13 and a plurality of surroundings around the island 11 as shown in FIG. The outer lead 12 is provided, and an extension piece 14 connected to the tie bar 13 is formed between the two outer leads 12 so as to extend to the island 11 side. The extension piece 14 is provided separately from the outer lead 12, and the distal end portion 14 a abuts on a sealing mold set when the lead frame is resin-sealed, or is attached to the mold. It is characterized in that it is formed so that it is slightly sandwiched and the side surface of the tip part abuts the side surface of the adjacent outer lead 12.

The lead frame 1 is included in an island 11 or an inner lead (inside the lead sealing resin portion 5) of a desired shape by punching or etching a plate-like body having a thickness of about 0.1 to 0.25 mm, for example. Part) 12a, tie bar 13 for connecting outer leads 12, and the like are formed. Although these portions are the same as those of a normal lead frame, in the present invention, as shown in FIG. 1, an extension piece 14 (shaded portion) connected to the tie bar 13 is formed between the outer leads 12. It is characterized by being.

  As shown in FIG. 1, the extension piece 14 has a tip 14a that abuts against the side wall of the sealing resin portion 5, that is, the side wall of the mold used for resin sealing, or slightly depending on the mold. The length is such that it is sandwiched, and at least the side wall of the distal end portion 14 a is formed so as to contact the side wall of the adjacent outer lead 12, and is separated from the outer lead 12. In the example shown in FIG. 1, the side wall of the extension piece 14 is formed in a shape that contacts the side wall of the outer lead 12 over the entire length (from the front end portion 14 a to the tie bar 13) as well as the front end portion 14 a. However, as shown in FIG. 3 to be described later, a space may be formed at a place other than the tip end portion 14 a so as to be separated from the outer lead 12.

  In order to separate the outer lead 12 from the outer lead 12 while the side wall of the extension piece 14 is in contact with the outer lead 12, for example, FIG. 2 is an image diagram in which a plate-like body is subjected to shearing (also referred to as slitting or cutting). As shown in FIG. 2, for example, an angle is formed on the punch to be processed from the back side of the plate-like body in FIG. 2, and cutting is started from the tip of the punch and stopped in the middle of the inclination angle, thereby leaving an uncut portion A. In addition, it is possible to form a cutting process having a desired shape without producing scrap. In other words, the fact that no scrap is generated means that there is no gap in the cut portion, and the side wall portion is abutted against the plate-like body by pushing back the portion B bent during processing as shown in the figure. It becomes planar while being in contact with each other, and can be connected at the A part to separate parts other than the A part. In addition, as FIG. 2 shows, this shearing process can be formed not only in the edge part of a plate-shaped body but in the inside of a plate-shaped body.

  When shearing is applied to the boundary between the outer lead 12 and the extension piece 14 in the lead frame 1 of FIG. 1, the surface side of the lead frame 1, that is, the side on which the semiconductor chip is mounted and the sealing resin portion 5 is mainly formed. It is preferable to perform the processing using the punch described above. By doing so, a shear sag (shoulder sag) 12b is formed on the surface side of the outer lead 12 during the shearing process, as shown in FIG. 4 which is a side view showing a portion of the outer lead 12 after resin sealing. Although it occurs, no sag occurs on the back side, and the burr 12c is formed. Since this burr 12c is crushed and flattened by a mold at the time of resin sealing, the bottom surface becomes a flat surface at the time of resin sealing, and it is possible to completely prevent resin leakage to the bottom surface. This is because a resin burr does not occur on the back surface of the outer lead 12.

  As in the example shown in FIGS. 6C to 6D, in the case of a QFN package in which the bottom surface of the sealing resin portion 5 and the bottom surface of the outer lead 12 are formed substantially flush with each other, Since it is mounted on a printed circuit board or the like by soldering on the bottom surface, if a resin burr adheres to the bottom surface of the outer lead 12, the reliability of soldering decreases, but this is because shearing is performed from the surface side. This is particularly preferable from the viewpoint of improving the reliability of soldering.

In the lead frame shown in FIG. 1, the extension piece 14 remains as a portion where the connection portion A with the tie bar 13 is not cut by such a shearing process, and the boundary with the outer lead 12 is separated by the shearing process. However, it is pushed back after the shearing process to form a flat surface, and is in contact with the side wall of the outer lead 12. The extension piece 14 abuts against the side wall of the mold when the tip 14a is resin-sealed when punching to form the island 11, the outer lead 12, the tie bar 13, etc. in advance, or the gold The tip 14a is formed in such a length that the tip 14a is slightly sandwiched between the molds. After the resin sealing, as shown in FIG. It is formed to bite in.

  After the resin sealing, the extension piece 14 is removed together with the tie bar 13 by separating the tie bar 13 from the outer lead 12 or by separating the outer lead 12 on the island 11 side from the tie bar 13. That is, it is separated from the outer lead 12, and the tip portion 14a is in contact with the sealing resin portion 5 or slightly bites into the sealing resin portion 5, The amount of biting in is very small, and it can be easily separated just by pushing down and removed together with the tie bar 13. Although not shown in FIG. 1, the outer side of the outer lead 12 is connected to the outer lead 12 and a side rail formed with an index hole for feeding a lead frame for mounting a semiconductor chip or the like. Is provided. However, if the tie bar 13 of FIG. 1 is made a little wider and an index hole or the like is formed, the side rail and the tie bar 13 can be used together, and the outer lead 12 does not need to be further extended outward. That is, the tie bar 13 only needs to connect a plurality of outer leads 12.

  FIG. 3 is a plan view illustrating only a portion of the extension piece 14 in a modification of the lead frame of the present invention. That is, in the example shown in FIG. 1 described above, the side wall of the extension piece 14 is in contact with the side wall of the outer lead 12 up to the tie bar 13 as well as the tip portion 14a. The example shown in FIG. 2 is different in that only the front end portion is in contact with the outer lead 12 and a gap portion 15 is formed between the outer lead 12 on the tie bar 13 side. The gap 15 can be formed at the same time by punching the island 11, outer lead 12, tie bar 13 and the like from the plate-like body by simply forming a protrusion on the mold. As shown in FIG. 3 (a), it may be triangular, or it may be rectangular as shown in FIG. 3 (b), and can be formed in various shapes. Even if such a gap portion 15 is formed, resin leakage can be completely prevented by the side wall of the tip portion 14a being in contact with the outer lead 12, and conversely, the gap portion 15 is formed. Therefore, the side surface of the outer lead 12 can be plated in advance.

  According to the present invention, the extension piece 14 extended from the tie bar 13 is formed between the outer leads of the lead frame, and the extension piece 14 is a mold when the tip portion 14a is resin-sealed. The lead is formed in such a length that it abuts against the side wall or is slightly sandwiched between the molds, and further, at least the tip portion 14a of the side wall is formed so as to abut on the side wall of the adjacent outer lead 12. When the resin is sealed by sandwiching the frame with a mold, even if the resin tries to flow out between the outer leads, it is completely dammed by the extension piece 14 and the resin does not flow out to the side wall of the outer lead 12. In addition, since the extension piece 14 is separated from the outer lead 12, the extension piece 14 can be moved together with the tie bar 13 simply by cutting the outer lead 12 after resin sealing and pushing down the tie bar 13 and the extension piece 14. Can be removed. When the outer lead 12 is subjected to exterior plating or solder plating, only the extension piece 14 is cut and removed, and then the outer lead 12 is cut, so that the tie bar 13 is removed from the outer lead 12. It may be removed.

  Further, as shown in FIG. 3, when the gap 15 is formed between the extension piece 14 and the outer lead 12, the removal work of the extension piece 14 after resin sealing becomes easy. At the same time, plating on the side surface of the outer lead 12 can be performed before resin sealing, and plating can be performed after resin sealing and before the extension piece 14 is removed. Even in the case of this structure, it is possible to remove only the extension piece 14 after the resin sealing, and to cut the plating, the tie bar 13 and the outer lead 12, and to set the order of the plating step and the cutting step as appropriate. Can do.

The method for manufacturing a semiconductor device according to the present invention is as follows. First, as shown in FIG. 1 described above, an island 11, an outer lead 12 positioned on the outer periphery thereof and connected by a tie bar 13, and a tie bar between the outer leads 12. The lead frame is manufactured by processing the plate-like body so as to have the extension piece 14 that extends from 13 to the island 11 side and prevents the resin from flowing out when the resin is sealed. Further, the extension piece 14 and the outer lead 12 are separated by shearing. As a result, the lead frame 1 shown in FIG. 1 is formed.

  Next, a semiconductor chip (not shown) is mounted on the island 11 of the lead frame 1 and wire bonding is performed. The lead frame 1 is sandwiched by a sealing mold (not shown), and the resin is transferred to the outer lead 12 by the extension piece 14. Seal with resin to prevent leakage. That is, the mold is set so that the side wall of the sealing mold comes into contact with the tip portion 14a of the extension piece 14 or the tip portion 14a of the extension piece 14 is slightly sandwiched, and the molten resin is poured into the mold. By injecting into the mold, the mold gap between the outer leads is closed by the extension piece 14, and the side wall of the tip 14 a is in contact with the side wall of the outer lead 12. The interval is completely closed by the extension piece 14, and the molten resin can be completely dammed up. As a result, it is possible to completely prevent the molten resin from flowing between the outer leads.

  Thereafter, the tie bar 13 and the extension piece 14 are removed to separate the outer lead 12 and cut the tip of the outer lead 12 to obtain a semiconductor device. As described above, the extension piece 14 is removed together with the tie bar 13 by simply pressing lightly by cutting between the tie bar 13 and the outer lead 12 because the boundary with the outer lead 12 is separated. Is done. As described above, the plating of the outer lead 12 can be performed after the extension piece 14 has been removed first, or can be extended by forming a gap portion 15 as shown in FIG. Plating can be performed before the removal of the piece 14.

It is a plane explanatory view showing the important section of one embodiment of a lead frame by the present invention. It is image explanatory drawing of the shearing process performed between the extension piece of FIG. 1, and an outer lead. It is a plane explanatory view showing a modification of the shape of the extension piece shown in FIG. It is side surface explanatory drawing explaining the state which gave the shearing process of the outer lead. It is a plane explanatory view showing an example of a conventional lead frame. It is a plane explanatory view showing other examples of the conventional lead frame, and an explanatory view of the plane and side after resin sealing showing the state of the resin flowing out.

Explanation of symbols

1 Lead frame 11 Island 12 Outer lead 13 Tie bar 14 Extension piece 15 Air gap

Claims (5)

  In a lead frame having an island for mounting a semiconductor chip and a plurality of outer leads connected by a tie bar and provided around the island, the island side is connected to the tie bar between two of the outer leads. An extension piece extending to the outer lead is provided separately from the outer lead, and the extension piece abuts a sealing mold set when the lead frame is resin-sealed, or A lead frame characterized in that the lead frame is formed so as to be slightly sandwiched between the molds and to have the side surface of the tip end in contact with the side surface of the adjacent outer lead.   The separation part of at least a front-end | tip part of the said extension part piece, and the said outer lead is formed by the process which does not take out a scrap substantially by the shearing process of a different process from the lead formation process of a lead frame. Lead frame.   3. The lead frame according to claim 2, wherein the shearing process is performed from a surface side of the lead frame on which the semiconductor chip is mounted, and a shoulder sag is formed only on the surface side.   The lead frame according to claim 1, 2, or 3, wherein a gap is formed between the extension piece and the outer lead at a portion other than the tip of the extension piece. (A) an island, an outer lead located on the outer periphery and connected by a tie bar, and the tip of the outer lead extending from the tie bar to the island side to prevent the resin from flowing out during resin sealing The plate has a plate-like shape so as to have an extension piece that abuts a sealing mold set when the lead frame is resin-sealed, or extends to a position where the lead frame is slightly sandwiched by the mold. Create a lead frame by processing the body,
(B) The extension piece and the outer lead are separated by shearing from the surface side on which the semiconductor chip is mounted,
(C) mounting a semiconductor chip on the island;
(D) The lead frame is sandwiched by a sealing mold, and the resin sealing is performed so that the resin does not leak between the outer leads by the extension piece.
(E) A method of manufacturing a resin-encapsulated semiconductor device, wherein the extension piece is removed and the outer lead is cut.

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