JP3458907B2 - Lead frame - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame used for manufacturing resin mold type electronic parts.

[0002]

2. Description of the Related Art A lead frame obtained by molding a flat metal plate by etching or pressing is generally used to manufacture a resin mold type electronic component. An example of this will be described with reference to FIG. In the figure, 1 is a set of three leads arranged in parallel at equal intervals in the illustrated example, and a large number of sets of the leads 1 are arranged adjacent to each other at a predetermined interval. Reference numeral 2 denotes a heat radiating plate which is connected to one end of the lead 1a at the center among the leads 1 of each set with a step, and has a mounting hole 2a. A wide portion is formed at one end of each of the other leads 1b and 1c. The middle portion and the other end portion of each lead 1 are respectively connected to each lead 1.
The tie bar 3 and the tie bar 3 which are arranged in parallel with each other are connected and integrated by the connecting piece 4. Reference numeral 5 denotes a protruding portion formed by extending the tie bar 3 and protruding from the lead at the outermost end. A method of manufacturing an electronic component using this lead frame 6 will be described below. First, as shown in FIG. 7, the electronic component body 7 is fixed onto the heat dissipation plate 2. Next, electrodes (not shown) on the electronic component body 7 and the free ends of the leads 1b, 1c are electrically connected by wires. Then, as shown in FIG. 8, the lead frame 6 to which the wire 8 is connected is placed on the lower mold 9 in the resin molding mold, the heat sink 2 is housed in the cavity 10, and the upper mold 11 is mounted. Clamp the lead 1 and clamp the die. In the figure, 12 is a cavity formed in the upper mold 11, 13 is a pin that penetrates the hole 2a in the cavities 10 and 12, 14 is a protrusion that brings the upper and lower molds 9 and 11 close to each other between the heat sink 2 and the tie bar 3, Reference numeral 15 denotes a gate for supplying the resin 16 to the cavities 10 and 12.

The protruding portion 5 of the outermost end lead is shown in FIG.
As shown in FIG. 3, the second protrusion 17 including the protrusion portion having the same shape as the other protrusion 14 and surrounding the protrusion 5 is formed. As shown in FIGS. 10 and 11, the second protrusion 17 has a protrusion 5
Has a crushing portion 17a that crushes the end portion of the. The protrusion 14 closes the gap between the cavities 10 and 12 and the tie bar 3, and the second protrusion 17 crushes and deforms a part of the protruding portion 5 to reduce the distance between the deformed portion and the second protrusion, The resin leaking from the causties respectively is prevented from proceeding toward the lead 1. The electronic component body 7 on the lead frame 6 sandwiched by the molds 9 and 11 is covered with the resin 16 injected into the cavities 10 and 12, and when the resin 16 is in a semi-cured state, the mold 9 and Open 11 and take out the molded product. Then, unnecessary resin such as the gate portion is removed, the tie bar 3 and the connecting piece 4 are cut and removed to be separated into individual electronic components, and the lead 1 is plated with metal for improving solderability as necessary. Further, the lead 1 is bent and formed.

[0004]

By the way, when the resin-molded electronic component is molded with resin, the tie bar 3 prevents the resin 16 injected into the cavities 10 and 12 from leaking to the lead 1 side. However, due to variations in the size and thickness of the lead frame 6, positional deviation of the lead frame 6 on the mold, wear of the mold, etc., the resin 16 crosses the tie bar 3 and adheres to the peripheral surface of the lead 1 to form a thin burr. Could occur.
Therefore, after molding the resin, the resin burr is removed by means such as sandblasting. However, if an oxide film is formed on the surface of the lead frame 6, the resin burr becomes firmly adhered and it is difficult to completely remove it, resulting in an increase in the number of working steps. There was a problem of doing. Further, if the resin burr remains, the metal plating on the lead 1 becomes uncertain and the solderability is deteriorated.

In order to avoid such a problem, for example, JP-A-57-52155 and JP-A-62-19785.
Japanese Unexamined Patent Publication No. 2 (1994) discloses a method of previously coating a material, such as wax, to which a resin is unlikely to adhere or a material that can be easily peeled off even if the resin is easily adhered, to a portion where resin burrs are easily generated. However, there is a problem in that the number of man-hours required for the wax application work increases. Further, for example, Japanese Utility Model Publication No. 61-69840 and Japanese Utility Model Publication No. 63-36056.
Japanese Patent Laid-Open Publication No. 2003-187242 discloses that the tie bar 3 is provided with a minute projection that is easily crushed by clamping to improve the adhesion between the die and the lead frame. Even if it can be applied, even if the lead frame 6 and the upper and lower molds 9 and 11 are in close contact with each other, a gap is formed along the peripheral surface of the protruding portion 5, and it cannot be applied to the protruding portion 5 of the outer end lead. Therefore, in the protruding portion 5, a part of the protruding portion 5 is crushed and deformed by the second protrusion 17 of the mold 11 and the deformed portion and the second portion.
The gap with the projection 17 is narrowed to fill the gap and prevent the resin from advancing, thereby eliminating the influence of variations in the thickness of the lead frame and wear of the mold.

However, when the amount of crush deformation of the projecting portion 5 is increased in a state where the space between the gaps is narrow due to the displacement of the lead frame 6 on the mold, the crush deformed portion comes into close contact with the mold and after resin molding. When the lead frame 6 is taken out of the mold, the lead frame is deformed to cause a defect such as bending of the lead, so that the crush cannot be excessively performed, and when the mold is worn, the crush amount is also reduced, and the mold and the protrusion 5 There is a possibility that the gap formed between the lead wire and the resin expands along the peripheral surface of the protruding portion 5 to the side wall of the area that is actually soldered outside the tie bar 3 of the outermost lead. It was Therefore, as shown in FIG. 12, a notch 5a is formed at the end of the protruding portion 5 to facilitate the crushing and to easily release the mold even when the die and the crushing portion are in close contact with each other. Due to the displacement of the frame 6 in the direction of the tie bar 3, the interval between the protrusion 5 and the mold was varied, and it was not possible to completely prevent the resin wrapping around the protrusion 5 from reaching the lead side wall. It is difficult to remove the resin adhered to the side wall of the lead 1 by means such as sandblasting, and the portion where the resin adheres is a portion to be soldered when soldering and mounted on a printed wiring board or the like. The problem of incomplete soldering still remained.

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed for the purpose of solving the above-mentioned problems, in which the middle portions of a large number of leads arranged in parallel are connected and integrated by a tie bar, and the leads at the outermost end are connected. A lead frame formed with a protruding portion protruding in the extension direction of the tie bar, wherein the protrusion is formed by a pair of upper and lower resin molding dies having a cavity formed in a portion adjacent to the tie bar and facing a region including a lead free end. In the lead frame in which the main portion of the lead is resin-molded with the resin injected into the cavity, the cut portion is crushed and sandwiched, and the notch portion is formed on the side wall opposite to the lead free end of the protruding portion. A characteristic lead frame is provided. It is possible to prevent the resin from reaching the lead side wall by smoothly guiding the resin advancing on one of the facing inner walls of the cutout into the cutout. Further, by setting the opening diameter of the cutout portion larger than the facing distance between the opening portion of the cutout portion and the resin molding die, the leaked resin can be guided into the cutout portion. The resin can be prevented from advancing. A single notch may be provided, but a plurality of notches may be formed to further ensure the effect.

[0008]

According to the present invention, the resin leaked out along the side wall of the protrusion is caught because the notch formed at the end of the lead frame is insufficiently crushed by the mold.
It prevents the lead from reaching the side wall and prevents the generation of resin paris.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. In the figure, the same reference numerals as those in FIG. The only difference in the figure is the protruding portion 18 protruding from the side wall of the lead at the outermost end in the extension direction of the tie bar 3, and this protruding portion 18 is provided on the side opposite to the free end of the lead 1, that is, the side of the heat sink 2. The difference is that a notch 19 that opens to the side wall is formed. As shown in FIG. 2, in this lead frame, a part of the protruding portion 18 is crushed on the resin molding die 9, but in that state, a gap is formed between the protrusion 17 of the die 9 and the protruding portion 18. Even if the resin 16 advances along the peripheral surface of the protruding portion 18, the resin 16 along the peripheral surface of the protruding portion 18 is guided by the cutout portion 19 and is captured in the cutout portion 19, and Do not move forward. During this time, the thermosetting of the resin 16 progresses and the fluidity decreases, so that even if the resin 16 fills the inside of the cutout portion 19 and overflows, it cannot advance to the front of the cutout portion 19 and the occurrence of resin burr can be prevented.

Although the notch portion 19 of the present invention is formed in a shape having parallel opposing walls in FIG. 1, it is not only inclined to be arranged in the longitudinal direction of the tie bar 3 as in the illustrated example, but also in this longitudinal direction. Alternatively, they may be arranged orthogonally. 3 to 5
As shown in, the planar shape may be a substantially trapezoidal shape, a triangular shape, or a circular shape. Further, the width of the protruding portion 18 may be set such that the gap between the opening end of the cutout portion 19 and the resin molding die is wide on the resin inflow side and narrow on the resin outflow side. The cutout portion 19 has a diameter of an opening thereof set to be larger than a facing distance between the protruding portion 18 and the resin molding die.
The flow resistance toward the notch portion 19 can be made smaller than the flow resistance of the resin toward the front of the notch portion 19, so that the notch portion 1
It is possible to make the resin flow into 9 smoothly. Furthermore, the effect can be enhanced by forming a plurality of the notches 19 along the peripheral surface of the protrusion 18.

[0011]

As described above, according to the present invention, it is possible to prevent the resin from leaking from the end portion of the tie bar of the lead frame and prevent the resin from adhering to the lead side wall at the outermost end.

[Brief description of drawings]

FIG. 1 is a partial plan view of a lead frame showing an embodiment of the present invention.

FIG. 2 is a plan sectional view of an essential part for explaining a resin molding die state of an electronic component using a lead frame.

FIG. 3 is a partial plan view of a lead frame showing a modified example of the present invention.

FIG. 4 is a partial plan view of a lead frame showing another modification of the present invention.

FIG. 5 is a partial plan view of a lead frame showing another modification of the present invention.

FIG. 6 is a partial plan view of a lead frame which is a premise of the present invention.

FIG. 7 is a side sectional view of the lead frame shown in FIG.

FIG. 8 is a side sectional view of an essential part for explaining resin molding of an electronic component using a lead frame.

9 is a plan sectional view of a main part of FIG.

10 is a sectional view taken along line AA of FIG.

11 is a sectional view taken along line BB of FIG.

FIG. 12 is a partial plan view showing a modified example of the protruding portion of the lead frame shown in FIG. 9;

[Explanation of symbols]

1 lead 3 Divers 18 Projection 19 Notch

Claims (4)

(57) [Claims] 1. A lead frame in which a plurality of lead-intermediate portions arranged in parallel are connected and integrated by a tie bar, and a projecting portion projecting in the extension direction of the tie bar from the outermost lead is formed. The protrusion is crushed and sandwiched by a pair of upper and lower resin molding dies having a cavity formed in a portion adjacent to the area including the lead free end portion, and the main portion of the lead is made of resin injected into the cavity. A lead frame resin-molded with a lead frame, wherein a notch is formed on a side wall of the protruding portion opposite to a free end of the lead. 2. The lead frame according to claim 1, wherein the cutout portion is formed so as to guide the inflow of the resin. 3. The lead frame according to claim 1, wherein the opening diameter of the notch exposed on the side wall of the protrusion is set to be larger than the facing distance between the protrusion and the resin molding die. 4. The lead frame according to claim 1, wherein a plurality of cutouts are formed.