JP2004281490A - Multilayer lead frame and its pre-molded package made of resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the change of a terminal due to the flow pressure of resin in a lead frame having multiple pins and its pre-molded package made of resin. <P>SOLUTION: In a multilayer lead frame composed of two or more lead frames processed so that a distance between adjacent terminals of an inner lead is longer than the thickness of a metal being a raw material, at least one of the lead frames has a vane-like projection in an outer lead of the terminal, this vane-like projection keeps a distance between the adjacent terminals of stacked lead frames constant, and inner lead frame portions of the stacked lead frames are on the same plane. This multilayer lead frame is subjected to insert molding, thereby obtaining a pre-molded package made of resin having multiple pins. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multilayer lead frame and a resin pre-mold package using the lead frame, and more particularly, to a technique for stacking lead frames of a specific shape to achieve high integration and miniaturization.
[0002]
[Prior art]
2. Description of the Related Art Applications of resin pre-mold packages (sometimes called hollow packages) obtained by insert-molding lead frames used for mounting semiconductor chips such as ICs and LSIs are expanding. 2. Description of the Related Art In recent years, demands for a pre-mold package having a large number of inner lead portion terminals have been increasing with the increase in integration of semiconductor chips. Therefore, it is desired to provide a lead frame in which the terminal width of the inner lead portion and the interval between adjacent terminals are narrow, that is, a lead frame having multiple pins.
[0003]
A lead frame used for mounting a semiconductor chip is made of a metal strip made of an iron-based or copper-based metal or the like, and a pressing method of punching the metal strip using a feeding die or a desired wiring pattern. Is exposed and developed to form an etching pattern, the exposed metal portion is removed by etching, and the surface is treated by an etching method or the like.
[0004]
FIG. 10 shows an example of a conventional lead frame. The lead frame includes a terminal 101, a horizontal rail 102, a vertical rail 103, and a tie bar 104 which are finally cut off. The terminal 101 includes an inner lead portion A, a resin coating portion B, and an outer lead portion C.
[0005]
Usually, these lead frames are manufactured by a press working method or an etching working method. The press working method is a method that can manufacture a lead frame at low cost and with good productivity. However, there is a restriction in processing to reduce the terminal width 101a of the inner lead part A. Since it is also difficult to make the space 101b between them smaller than the thickness of the metal material, there is a limit to increasing the number of terminals (sometimes expressed as the number of pins) of the lead frame.
[0006]
On the other hand, according to the etching method, it is possible to manufacture a lead frame in which the terminal width 101a of the inner lead portion A and the interval 101b between adjacent terminals are narrower than the pressing method. However, when the terminal width 101a of the inner lead portion A becomes narrow, the strength of the terminal decreases, and even when the tie bar 104 is present, the terminal of the inner lead portion A may be deformed by the flow pressure of the resin during resin molding. There is a problem that there is a case where the terminals come into contact with each other, and the production of a lead frame having substantially many pins is limited.
[0007]
As one method of manufacturing a lead frame having multiple pins, a method of stacking lead frames has been proposed (for example, see Patent Document 1). However, according to the conventional proposal, when a pre-mold package is manufactured by insert molding, the height of the inner lead portion may be two or more steps, and the wire bonding operation between the inner lead portion and the semiconductor chip becomes complicated. During resin molding, the position of the inner lead portion of the terminal moves due to the flow pressure of the resin, the tip is deformed, and there are problems such as contact with other terminals, and the number of pins in the inner lead portion is substantially increased. There were restrictions to do so.
[0008]
[Patent Document 1]
JP-A-6-177315
[Problems to be solved by the invention]
The present invention solves the above-described problems, and in a multilayer lead frame obtained by laminating two or more lead frames, the distance between adjacent terminals of the inner lead portion forms the lead frame. To provide a multilayer lead frame that is narrower than the thickness of the metal material to be formed, has less terminal deformation due to the flow pressure of the resin, and can be applied to increase the number of pins, and a resin pre-mold package using the multilayer lead frame. And
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a multilayer lead frame formed by laminating a plurality of lead frames each having a width between adjacent terminals of an inner lead portion processed to have a width larger than the thickness of a metal material as a material. The inner lead portion of the laminated lead frame is on the same plane, and the outer lead portion of at least one lead frame has a wide portion for maintaining a constant interval between adjacent terminals of the laminated lead frame. have. The resin pre-mold package of the present invention can be obtained by insert-molding the multilayer lead frame of the present invention.
[0011]
ADVANTAGE OF THE INVENTION According to the multilayer leadframe of this invention, by laminating two or more leadframes of a specific shape, even if the space | interval between the adjacent terminals of an inner lead part is narrowed, it can be kept constant and multi-pin is possible. It becomes. Also, since the intervals between terminals of the individual lead frames constituting the multilayer lead frame are wide, the terminal width can be widened.In particular, by increasing the terminal width of the resin coating portion, the strength of the terminals is increased, Deformation due to the flow pressure of the resin during resin molding can be reduced. Further, since the terminals of the inner lead portions of the stacked lead frames are on the same plane, the wire bonding operation between the inner leads and the semiconductor chip is facilitated. Further, the formation of the multilayer lead frame of the present invention is a simple method of setting individual lead frames constituting the multilayer lead frame in a predetermined shape in a mold prior to molding of a resin pre-mold package. Can be done with
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The multilayer lead frame of the present invention is composed of two or more lead frames. The thickness of the metal material forming the lead frame is 0.1 to 2 mm, preferably 0.15 to 0.5 mm. FIG. 1 shows a part of a multilayer lead frame formed by laminating two lead frames, and FIGS. 2 and 3 show each lead frame to be laminated. The terminals 201 and 401 of each lead frame include an inner lead portion A, a resin coating portion B, and an outer lead portion C.
[0013]
The lead frame shown in FIG. 2 is composed of a terminal 201, a horizontal rail 203, and a vertical rail 204. The terminal 201 has a blade-like shape for maintaining a constant distance between adjacent terminals of the lead frame on an outer lead portion C. It has a protruding part (wide part) 205. The lead frame shown in FIG. 3 includes a terminal 401, a horizontal rail 403, and a vertical rail 404. The terminal 401 has a wing-like protrusion (wide part) 405 only in a part thereof, and the terminal 401 has other protrusions. I do not have.
[0014]
The terminal width 201a of the terminal 201 in the inner lead portion A is smaller than the terminal width 401b of the other terminal 401, and the terminal width 401a of the terminal 401 in the inner lead portion A is also the terminal width 201b of the other terminal 201. Less than. This terminal-to-terminal width 201b is larger (wider) than the thickness (thickness) of the material metal material due to the material processing.
[0015]
The horizontal rails 203 and 403 of each lead frame overlap on the horizontal rail portion of the multilayer lead frame, and the vertical rails 204 and 404 of each lead frame overlap on the vertical rail portion. The space 301b between the terminal 201 having the wing-shaped protrusion 205 in the inner lead portion A shown in FIG. 2 and the terminal 401 having no protrusion except for a part shown in FIG. The thickness is designed to be smaller than the thickness (thickness) of the metal material constituting the lead frame. However, if the number of pins can be increased, there may be a portion having an interval larger than the thickness of the metal material partially in relation to the semiconductor chip. The distance 205c between the tip of the wing-shaped protrusion 205 and an adjacent terminal is in the range of 0.01 to 2 mm, preferably 0.01 to 1 mm. Within this range, the distance between the tip of each wing-shaped protrusion 205 and the adjacent terminal may not be the same.
[0016]
The lead frame shown in FIG. 2 is bent at the bending surface 206 by bending as shown in FIGS. 2B and 4, and the respective terminals 201 and 401 of the stacked lead frames are bent. It is almost coplanar from the surface 206 to the tip of the inner lead portion A. The term “substantially on the same plane” means that the difference in height between the upper surface of one of the adjacent terminals and the upper surface of the other terminal is within two times, preferably within one time, the thickness of the metal material of the lead frame. means.
[0017]
In the above description, an example in which the lead frame having the wing-shaped protruding portions 205 shown in FIG. 2 and the lead frame shown in FIG. 3 are stacked is described. However, the multilayer lead frame of the present invention has a structure similar to the structure shown in FIG. In the case of a multi-layered lead frame, lead frames having blade-shaped protrusions may be combined with each other, or three or more lead frames may be stacked. The wing-shaped protrusions may be provided on both sides of the terminal as shown in FIG. 2, or may be provided on one side of the terminal as shown in FIG. Also, any of the lead frames constituting the multilayered lead frame may be bent as long as the portion from the bent surface 206 of the terminal to the tip of the inner lead portion A can be laminated on substantially the same plane. Further, the multilayer lead frame shown in FIG. 1 is an example in which the lead frame of FIG. 2 and the lead frame of FIG. 3 are closely adhered and laminated. It is also possible.
[0018]
Next, a lead frame having the wing-shaped projecting portion 205 shown in FIG. 2 will be described with reference to FIG. The terminals of the lead frame are divided into an inner lead portion A, a resin coating portion B, and an outer lead portion C. The wing-shaped protrusion 205 is located on the outer lead portion C, and the distance 201c between the upper side of the wing-shaped protrusion 205 and the lower side of the resin coating B is 0.01 to 10 mm, preferably 0.05 to 3 mm. It is. If it is less than 0.01 mm, the resin of the pre-mold package may be damaged when cutting and removing the wing-shaped protrusion 205. If it is larger than 10 mm, it is not preferable because it is difficult to remove burrs generated at this location when molded into a pull mold package.
[0019]
The vertical width 205a of the wing-shaped protrusion 205 is not particularly limited and can be set arbitrarily. The vertical width 205a is set so that the distance between adjacent terminals does not fluctuate as much as possible due to the flow pressure of the resin at the time of molding. Usually, the vertical width 205a is 0.5 to 50 times the thickness of the metal material forming the lead frame. Times, preferably in the range of 1 to 30 times. The width 205b is determined by the width between pins of the target multilayer lead frame. Usually, it is often in the range of 0.5 to 30 times the thickness of the metal material forming the lead frame. The wing-shaped protrusion 205 is desirably on the same plane as the terminal 201. Even if they are not on the same plane, as shown in FIG. 6, if the height difference 205d between the upper surface and the lower surface of the wing-shaped protrusion 205 is within three times the thickness of the metal material of the lead frame material, it is inclined. You may. Further, the shape of the wing-shaped protrusion 205 may be the same shape on the left and right, or may be different on the left and right.
[0020]
The multilayer lead frame of the present invention can be used for a resin-made pre-molded package by known insert molding. In the insert molding of the resin pre-mold package, the individual lead frames constituting the multilayer lead frame were set on guide pins of a mold heated to a predetermined temperature so as to have the shape of the multilayer lead frame of the present invention. Thereafter, the mold is closed, and the molding is performed by a molding method such as injection molding, casting molding, transfer molding or the like. Each lead frame may be strip-shaped or hoop-shaped. The multi-layer lead frame of the present invention can be formed simply by installing it in a mold during insert molding, and is excellent in workability.
[0021]
FIG. 7 shows an example of a resin pre-mold package 701 (resin-coated portion) obtained by insert-molding the multilayer lead frame of the present invention after molding. An inner lead 702 is provided on the outer periphery of the semiconductor chip mounting portion 703. The wing-shaped protrusion 205 is outside the resin coating. After the wing-shaped protrusion 205 is cut and removed by press working or the like, a semiconductor chip is mounted. FIGS. 8A and 8B show an example of a resin pre-molded package in which the multilayer lead frame of the present invention is insert-molded, after the blade-shaped protruding portions have been cut and removed.
[0022]
FIG. 9 shows an example in which a metal radiator plate 1003 is provided in a resin pre-mold package obtained by insert-molding the multilayer lead frame of the present invention. As shown in FIG. 9, the heat radiating plate 1003 is attached to the lower surface of the hollow portion 1004 of the resin pre-mold package 1001, and its size is smaller than the outer shape of the resin pre-mold package 1001. Normally, a resin pre-mold package 1001 having a size smaller than the vertical and horizontal lengths by 1 mm or more and larger than １ ／ of the vertical and horizontal lengths is used. The thickness is smaller than the thickness of the bottom surface of the hollow portion 1004, and usually a plate-like metal having a thickness of 0.1 to 3 mm, preferably 0.3 to 1.5 mm is used. As the metal material used for the heat sink, iron, copper, nickel, aluminum and alloys thereof are used. The heat sink may be attached to the resin pre-mold package by insert molding simultaneously with the multilayer lead frame of the present invention, or may be attached to the molded resin pre-mold package with an adhesive or the like.
[0023]
Examples of the resin used for insert molding include aliphatic nylons such as nylon 6, nylon 66, aromatic nylons such as nylon 9T, nylon 6T, and nylon MXD, polybutylene terephthalate, polyphenylene oxide, polyphenylene sulfide, polyether sulfone, and polyamide. There are thermoplastic resins such as imide and liquid crystal polymer, and thermosetting resins such as epoxy resin, polyimide resin and phenol resin. The molding of a thermoplastic resin is mainly performed by an injection molding method, and the molding of a thermosetting resin is performed by a transfer molding method or a casting method.
[0024]
【The invention's effect】
As described above, according to the multilayer lead frame of the present invention, the interval between the inner lead portions of the adjacent terminals can be reduced, so that the number of pins can be increased. Further, since it is not necessary to reduce the width of the terminal, the terminal is less likely to be deformed by the flow pressure of the molding resin. Further, the formation of the multilayer lead frame requires only that the individual lead frames forming the multilayer lead frame be set in a mold during the molding of the resin pre-mold package, which is excellent in workability.
[Brief description of the drawings]
FIG. 1 is a partial plan view of a multilayer lead frame according to an embodiment of the present invention.
FIG. 2 (a) is a partial plan view of a lead frame having one wing-like protrusion to be laminated, and FIG. 2 (b) is a cross-sectional view taken along the line II-II of FIG.
FIG. 3 is a partial plan view of the other lead frame to be laminated.
FIG. 4 is a sectional view taken along line II of FIG. 1;
FIG. 5 is an enlarged view of a terminal having a blade-shaped protrusion.
FIG. 6A is an enlarged view of a terminal having a wing-like protrusion, and FIG. 6B is a diagram showing an inclination of the wing-like protrusion.
FIG. 7 is a partial plan view showing an example of a resin pre-mold package immediately after insert molding of the multilayer lead frame of the present invention.
FIGS. 8A and 8B are plan views showing a state after cutting and removing a blade-shaped protrusion of a resin pre-mold package.
9A is a plan view showing an example of a resin pre-mold package having a heat sink, and FIG. 9B is a cross-sectional view taken along line III-III of FIG. 9A.
FIG. 10 is a partial plan view showing an example of a conventional lead frame.
[Explanation of symbols]
A Inner lead portion B Resin coating portion C Outer lead portion 201 Terminal 201a (having wing-shaped protrusion) Terminal width 201b of inner lead portion Interval between adjacent terminals of inner lead portion 205 Wing-shaped protrusion (wide portion)
206 Bending surface 301b Spacing between adjacent terminals of inner lead portion of laminated lead frame 401 Terminal 401a Width of terminal of inner lead portion 401b Spacing between adjacent terminals of inner lead portion 701 Resin pre-mold package 702 immediately after molding Inner Lead 703 Semiconductor chip mounting surface 1001 Resin pre-mold package 1002 having heat sink 1002 Outer lead 1003 Heat sink

Claims (4)

A multilayer lead frame formed by laminating a plurality of lead frames in which the interval between adjacent terminals of the inner lead portion is processed to have a width wider than the thickness of the metal material of the material,
The inner lead part of the laminated lead frame is on the same plane,
A multilayer lead frame having a wide portion for maintaining a constant interval between adjacent terminals of a stacked lead frame in an outer lead portion of at least one lead frame. 2. The multilayer lead frame according to claim 1, wherein an interval between adjacent terminals of the inner lead portion of the laminated lead frame is smaller than a thickness of a metal material forming the lead frame. A resin pre-mold package obtained by insert-molding the multilayer lead frame according to claim 1 or 2. A resin pre-molded package, wherein the multilayer lead frame according to claim 1 or 2 is insert-molded, and a heat sink is integrally provided on the lead frame.

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