JP2006351846A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the wettability of a lead and a solder material when a semiconductor device is mounted without exposing a raw material for the lead on the end face of the lead for the semiconductor device, and to enhance mounting reliability. <P>SOLUTION: A manufacturing method for the semiconductor device has the leads 2 projected from a package 1 of the semiconductor device having surfaces coated with a solder-material film 3 such as plating and cut in parts of the leads. In the manufacturing method for the semiconductor device, V-shaped trenches 5 are formed at places along the cuts in the leads 2 by laser irradiation or the like before coating with the solder material 3. Approximately, greater parts of end faces of the cut and formed leads 2 are coated with the solder material 3, and a raw material for the lead 2 is not exposed, thus improving wettability with the solder material 6 in the case of the mounting. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor device having a lead frame with improved reliability when mounted on a printed circuit board and a method for manufacturing the same.

  In general, a semiconductor device using a lead frame is manufactured by the process shown in FIG. First, a semiconductor element is mounted on an island of a lead frame, and the electrode and lead of the semiconductor element are bonded and connected with a thin metal wire or the like, and then sealed with a thermosetting epoxy resin to form a package 1 (see the above figure). 4 (a)). Here, the entire structure of the lead frame including the island, the semiconductor element, and the fine metal wires are omitted for the convenience of the drawing.

  The lead 2 protruding from the package 1 is covered with solder plating 3 or the like as shown in FIG. 4B, and is cut at a required location by a press die or a cutting punch 4 as shown in FIG. 4C. Hereinafter, a surface obtained by cutting is referred to as a “cut surface”.

  In the SOP type or QFP type semiconductor device, the lead 2 is bent by a press as shown in FIG.

  Further, in the mini flat package type semiconductor device, the above-described bending of the lead 2 is not performed, and the leading end portion of the lead 2 and the bottom surface of the package 1 are arranged flat as shown in FIG.

The semiconductor device completed through the above steps is placed at a predetermined position on the printed circuit board, and then the tip of the lead 2 and the printed circuit board are soldered and mounted.
Japanese Patent Application 2001-023684 JP-A-1-208146

  In the manufacture of the semiconductor device described above, the solder plating 3 is used to prevent the lead 2 from being oxidized and corroded to ensure electrical conductivity, and also when the printed circuit board is mounted, the soldering wettability with the electrodes on the mounting board It is coated for the purpose of obtaining. Therefore, it is desirable that the entire lead 2 is covered with the solder plating 3.

  However, in the conventional method, the material of the lead 2 is exposed on the cut surface of the cut lead 2.

  Further, when the lead 2 is cut, the solder 3 covering the surface of the cut portion may be mechanically rubbed against the cut surface by the edge of the press die or the cutting punch 4. This phenomenon is hereinafter referred to as “solder dripping”. Even in the conventional method, as shown in FIG. 5, it is possible to cover a part of the cut surface 9 by solder dripping, but the entire cut surface 9 cannot be reliably covered.

  For this reason, in the semiconductor device manufactured by the conventional method, the cut surface 9 of the lead 2 may be oxidized or corroded as shown in FIG. Therefore, as shown in FIG. 6B, when mounting the soldering material 6 such as solder on the printed circuit board 7, the soldering material 6 such as solder gets wet with respect to the portion where the material of the cut surface 9 of the lead 2 is exposed. This makes it difficult to reduce the connection area between the printed circuit board 7 and the leads 2 and reduces the reliability of mounting the semiconductor device. In particular, solder fillets are difficult to be formed on the cut surface 9 and the connection strength is reduced.

  The object of the present invention is to improve the wettability between the cut surface 9 of the lead 2 and the brazing filler metal 3 such as solder when mounted on a printed circuit board, and to improve the reliability of mounting the semiconductor device and its manufacture. It is to provide a method.

  The main present invention for solving the above-described problems includes a step of sealing an island to which a semiconductor element is fixed and a lead electrically connected to the semiconductor element, and a surface of the lead located outside the sealing portion. And forming a semiconductor device by cutting a part of the lead, and forming a V-shaped groove on the lead, and then plating the surface of the lead. The V-groove is cut from the surface on which the V-groove is formed.

  Further, the present invention described above is characterized in that a lead is mounted on an electrode on a printed circuit board so that the V-shaped groove forming surface faces up.

  Furthermore, in the present invention, the V-shaped groove is formed by laser irradiation.

  Other main present invention for solving the above-mentioned problem is a semiconductor element mounted on an island, and electrically connected to the semiconductor element, and a portion located outside the sealing portion is plated, In a semiconductor device comprising a lead having a cut end surface, the end surface of the lead has an inclined region in which the plating material is covered by a chemical bond with the material of the lead, and a cut cut by mechanical pressure. And the cut surface is mechanically coated with a plating material.

  In the lead frame of the present invention, the V-shaped groove is formed at a position along the lead cutting surface, so that most of the cutting surface of the lead formed by cutting is covered with the brazing material, and the lead material is almost all. Not exposed. Further, a portion corresponding to the side surface of the V-shaped groove in the cut surface is inclined. Therefore, the wettability between the lead and the brazing material can be improved when mounting the semiconductor device, and the reliability can be improved.

  In addition, when laser irradiation is used as a method for forming a V-shaped groove, it is possible to form a V-shaped groove at a position close to the package and shorten the lead, particularly when manufacturing a mini flat package type semiconductor device. This is advantageous for achieving the above. Furthermore, since the cross-sectional area of the cut portion is small due to the V-shaped groove, most of the cut surface can be covered with solder dripping, and the punching pressure at the time of cutting can be reduced. Wear and the like are reduced.

  First, a method for manufacturing a semiconductor device according to the present invention will be described with reference to FIG. The lead frame has a plurality of islands, and around the island, there are provided a lead 2 arranged at one end thereof, a suspension lead for fixing the island, a diver for fixing the lead 2, and the like. Is configured. Currently, a lead frame having a thickness of about 0.2 mm made of Cu or the like is generally used.

  First, a semiconductor element is mounted on an island, which is a component of a lead frame, and the electrode of the semiconductor element and the lead 2 are bonded and connected with a thin metal wire or the like, and then sealed with a thermosetting epoxy resin, whereby the package 1 is configured. (See FIG. 1A). Here, the entire structure of the lead frame including the island, the suspension lead, and the diver, the semiconductor element, and the thin metal wire are omitted for the convenience of the drawing.

Next, a V-shaped groove 5 is formed at a predetermined cut location on the lead 2 protruding from the package 1. The V-shaped groove 5 can be formed by press cutting with a cutter or laser irradiation. It is desirable that the depth of the V-shaped groove 5 is at least about 1/3 of the thickness of the lead frame. The V-shaped groove 5 is formed on the surface opposite to the surface in contact with the printed circuit board 7 when mounted on the printed circuit board 7 later. The reason for the above V-groove formation condition is clarified by the effect of the embodiment described below. (See FIG. 1 (b) above)
Subsequently, the surface of the lead 2 in which the V-shaped groove 5 is formed is covered with the solder plating 3 as shown in FIG. The thickness of the solder plating 3 is suitably about 0.1 mm. However, the solder 3 is concentrated on the side surface of the V-shaped groove 5 by the action of the surface tension of the solder 3 and the thickness of the solder 3 locally increases. The plating film 3 formed in this step is covered over the entire exposed lead 2, and the material of the lead 2 and the plating film 3 are chemically bonded.

  Next, as shown in FIG. 1D, the lead 2 is cut at the position where the V-shaped groove 3 is formed by the cutting punch 4 or the press die 4. At this time, punching is performed using a cutting punch or a press die 4 from the direction of the surface on which the V-shaped groove 5 is formed.

  In the punching process, the V-shaped groove 5 which is a feature of the present invention has the effects described below. As shown in FIG. 2, since the punching is performed in the vicinity of the substantially center of the V-shaped groove 5, the tip of the cut lead 2 includes a side surface 8 of the V-shaped groove 5 and a cut surface 9 obtained by cutting. . Here, the side surface 8 of the V-shaped groove and the cut surface 9 are collectively referred to as an “end surface” for convenience of explanation. In the lead 2 according to the present invention, since the area of the cut surface 9 is reduced to 2/3 or less of the cross-sectional area of the lead 2, the surface area of the lead material that can be exposed by cutting becomes small. Further, when the lead 2 is cut, solder dripping occurs on the surface of the cut surface 9, so that the solder plating coverage is increased in the cut surface 9 having a small area. Moreover, since the solder 3 is densely packed at the bottom of the V-shaped groove 5 and the coating thickness is large, more solder sagging can be obtained, and the cut surface 9 is almost entirely covered by the solder sagging.

  The coating of the solder 3 on the cut surface 9 is mechanically coated with a thin burr of solder and has a coating form different from that of chemical coating. Since the cut surface 9 is covered with the solder dripping in this way, the cross section can be covered only by applying heat when soldering with the electrode on the mounting substrate. In addition, since the solder dripping is in contact, it is effective in preventing corrosion and the like.

  Further, since the cross-sectional area of the cut portion is reduced by the V-shaped groove 5, the punching pressure at the time of cutting can be reduced, and the wear of the cutting punch or the press die 4 can be reduced.

  Subsequently, for the SOP type or QFP type semiconductor device, the lead 2 is bent by pressing as shown in FIG. 1E, and for the mini flat package type semiconductor device as shown in FIG. The lead 2 is not bent, and the end of the lead 2 and the bottom surface of the package 1 are arranged flat. Since the mini-flat package semiconductor device does not require bending of the leads 2, in the following cases, the leads 2 can be cut at a shorter place to be miniaturized.

  First, when the V-shaped groove 5 is formed by a blade, there is a means for holding or supporting the blade, and therefore it may be difficult to form the V-shaped groove 5 near the package 1. On the other hand, when the V-shaped groove 5 is formed by laser irradiation, since there is no such restriction, the lead 2 can be extremely shortened. Therefore, the formation of the V-shaped groove 5 by laser irradiation is effective particularly when miniaturization of the mini flat package type semiconductor device is achieved.

  The semiconductor device is completed through the above steps. The completed semiconductor element is mounted by soldering the leading end of the lead frame 2 to a predetermined location on the printed circuit board.

  Next, the effect in the mounting process on the printed circuit board 7 will be described with reference to FIGS. 2, 3, and 5 again. The end face of the lead 2 according to the invention is composed of the side surface 8 of the V-shaped groove and the cut surface 9 obtained by cutting, and it has already been described that the coating form of the brazing material 3 is different.

  First, as shown in FIG. 5, the end face of the lead 2 of the semiconductor device according to the conventional method comprises only a cut surface 9 having a weak effect of preventing oxidation and corrosion. Therefore, since the material of the lead 2 is exposed on the cut surface 9, solder failure due to oxidation or corrosion occurs.

  On the other hand, as shown in FIG. 2, the end face of the lead 2 according to the present invention has not only the side face 8 having a strong effect of preventing oxidation and corrosion, but also most of the cut face 9 is covered with the brazing material 3. ing. Accordingly, oxidation and corrosion of the end face of the lead 2 can be effectively prevented. As described above, when the semiconductor device is mounted on the printed circuit board 7, as shown in FIG. 3B, the brazing material 6 such as solder is sufficiently wetted with the end surface of the lead 2, and the mountability can be improved.

  The effect of preventing the oxidation and corrosion by the coating of the solder 3 on the cut surface 9 is expected to be weaker in chemical bond than the coating on the side surface 8, so that the area of the cut surface 9 is made smaller. ing. Moreover, the area can be reduced by making the V-shaped groove 5 deeper in the step of forming the V-shaped groove 5.

  Further, at the end face of the lead 2, the cut surface 9 is substantially perpendicular to the surface of the lead frame. On the other hand, the side surface 8 has an inclination corresponding to the shape of the V-shaped groove, and forms an inclination angle 10 with the cut surface 9. Therefore, as shown in FIG. 3B, when the cut surface 9 is mounted on the printed circuit board 7, the brazing material 6 such as solder is smoothly smoothed by surface tension from the cut surface 8 to the upper portion of the side surface 8 that is an inclined surface. And can be attached to flow. Therefore, the wettability with the brazing material 6 such as solder at the tip is further improved, and a lead frame with improved reliability of mounting the semiconductor device can be obtained.

  In addition, the mounting by soldering to the printed circuit board 7 can improve reliability by adjusting the inclination angle 10 according to the characteristics such as the viscosity of the brazing material 6 such as solder. The inclination angle 10 can be adjusted by changing the size of the blade, the intensity of the laser, and the focal point in the step of forming the V-shaped groove 5.

  Although the solder has been described as being used as a brazing material, it goes without saying that Pb-containing solder, Pb-free solder containing Su as a main material, and the like can be applied. In addition, plating such as Ag may be used.

It is sectional drawing which shows the manufacturing method of the semiconductor device by this invention. It is an enlarged view of the lead tip part of the semiconductor device manufactured by the method of the present invention. It is a perspective view of the lead tip part of the semiconductor device manufactured by the method of the present invention. It is sectional drawing which shows the manufacturing method of the conventional semiconductor device. It is an enlarged view of a lead tip part of a semiconductor device manufactured by a conventional method. It is a perspective view of a lead tip part of a semiconductor device manufactured by a conventional method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Package 2 Lead frame 3 Brazing material 4 such as solder plating 4 Die or cutting punch 5 V-shaped groove 6 Brazing material 7 such as solder Printed circuit board 8 Side surface of V-shaped groove 9 Cutting surface 10 Inclination angle

Claims (4)

Sealing the island to which the semiconductor element is fixed and the lead electrically connected to the semiconductor element;
Plating the surface of the lead located outside the sealing portion;
Cutting a part of the lead to form a semiconductor device;
In the manufacturing process of a semiconductor device comprising:
A method of manufacturing a semiconductor device, comprising: forming a V-shaped groove on the lead, plating the surface of the lead, and cutting the V-shaped groove from a surface on which the V-shaped groove is formed.   2. The method of manufacturing a semiconductor device according to claim 1, wherein a lead is mounted on an electrode on a printed circuit board so that the V-shaped groove forming surface faces upward.   The method of manufacturing a semiconductor device according to claim 1, wherein the V-shaped groove is configured by laser irradiation. A semiconductor element mounted on the island;
A lead electrically connected to the semiconductor element, plated at a portion located outside the sealing portion, and cut at an end face;
In a semiconductor device comprising:
The end surface of the lead is composed of an inclined region where the plating material is coated by chemical bonding with the material of the lead, and a cut surface cut by mechanical pressure,
The semiconductor device according to claim 1, wherein the cut surface is mechanically coated with a plating material.