JP3058754B2 - Lead frame plating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of plating a lead frame, and more particularly to a method of plating a lead frame formed by plating a semiconductor chip with a die.

[0002]

2. Description of the Related Art In a lead frame used in a semiconductor device or the like, a bonding portion at the tip of an inner lead is plated to improve the wire bonding property of the inner lead, and the die attaching property of the semiconductor chip is improved. Plating is applied to die pads.
Since these platings improve wire bonding and die attachability, they need only be applied to one side to be wire-bonded or die-attached.Conventionally, the back side of the lead frame is covered with a plating jig, The surface side of the lead frame is covered with a mask having a predetermined plating pattern, and is partially plated.

[0003]

However, when the above-described partial plating is performed, the conventional lead frame is clamped and plated with a mask having a predetermined pattern and a plating jig. In addition to the need for plating on the wire bonding surface or die attaching surface, when the back surface of the inner lead comes into contact with the heater block during wire bonding, plating is transferred from the inner lead to the heater block, and this is used in the assembly process. Because of the cause of defects and poor adhesion between the plating and the mold resin, if the plating adheres to the back side of the lead frame, it may cause package cracks. This is to prevent the plating solution from flowing around the back side and causing the plating to adhere. .

In recent years, the die pad of a lead frame tends to increase in size as the semiconductor chip increases in size due to an increase in storage capacity and the like. As a result, according to the plating method as described above, there is a problem that the plating solution easily leaks to the rear surface of the die pad portion. In other words, when plating is performed on the front side of the die pad, the mask is open at the die pad portion. Therefore, if the plating jig on the back side of the die pad is not sufficiently pressed, the plating solution flows from the peripheral portion of the die pad to the die pad. The plating goes around the back side and the plating adheres to the back side of the die pad. In a product having such a large die pad, the occurrence of a package crack or the like is greatly affected by the die pad, and it is important to prevent the plating solution from flowing to the back surface of the die pad in order to enhance the reliability of the product. Therefore, the present invention has been made to solve the above problems, and the purpose thereof is to
It is an object of the present invention to provide a plating method for a lead frame, which prevents a plating solution from flowing to the back side of a die pad during partial plating, thereby enabling a suitable assembly and obtaining a highly reliable product.

[0005]

The present invention has the following arrangement to achieve the above object. That is, the lead frame having a die pad, the entire surface of the back side of the lead frame
Sandwiched between a plating jig that covers over and a mask on which a predetermined plating pattern is formed, and exposed from the mask.
In the plating method of the lead frame is subjected at least plating on the surface of the die pad of the lead frame,
A tip portion of the inner lead; and a tip portion inside the tip portion.
And a die pad whose peripheral portion is spaced apart.
Formed by exposing the area inside the tip of the knurled lead
With pressing the inner leads by the mask, characterized in that plating by pressing a good site even without performing the plating of the periphery of the O Ri said die pad of the surface covering portion provided in said Ma <br/> disk And Also, due to the covering part,
Of the two parallel sides of the die pad
Each of them is pressed. In addition, the coating portion
And pressing multiple points on one side of the die pad.
Features.

[0006]

[Function] When partial plating is applied to a lead frame, a portion of the peripheral portion of the die pad that does not need to be plated is clamped by a plating jig and a covering portion provided on a mask , so that the die pad and the plating jig adhere to each other. The plating solution is prevented from flowing around the back surface of the die pad. This prevents plating from adhering to the back surface of the die pad, and prevents occurrence of package cracks and failures in assembly processes such as wire bonding.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an explanatory view showing a method of performing partial plating on a lead frame according to a lead frame plating method according to the present invention. The method of plating a lead frame according to the present invention is common to the conventional method in that the back surface of the lead frame is entirely covered with a plating jig to prevent the plating solution from flowing around the back surface of the lead frame. It is characterized in that the surface side is covered with a mask having a predetermined plating pattern formed thereon and plating is performed by providing a covering portion for pressing a part of the peripheral portion of the die pad.

FIG. 1 shows a state in which a lead frame is clamped by a plating jig and a mask when viewed from the mask side.
In the figure, 10 is a die pad, 12 is a stage support bar,
14 is an inner lead. The mask 16 is arranged so as to expose a tip portion which is a wire bonding portion of the inner lead 14 and cover an outer portion thereof. Reference numeral 18 denotes a covering portion that clamps each peripheral edge of the long side of the die pad 10 formed in a rectangular shape. The covering portion 18 is arranged so as to slightly cover the periphery of the die pad 10 as shown in the figure. The coating portion 18 is fixedly supported on the mask 16, and is arranged so as to simultaneously press the die pad 10 when the lead frame is clamped to the plating jig by the mask 16.

An elastic body such as rubber is provided on the clamp surface of the covering portion 18 to prevent the plating solution from flowing to the back surface of the die pad 10 when the die pad 10 is clamped, and to be provided on the surface of the peripheral portion of the die pad 10. So that the plating solution does not flow around. When plating, use a mask 16
Then, the lead frame is clamped to the plating jig by the covering portion 18 and plated. The die pad 10 has the coating 1
By pressing the peripheral portion at 8, the adhesion to the plating jig is improved, and the plating solution is effectively prevented from flowing around the back surface of the die pad 10.

Note that, in FIG.
The plating solution does not flow around the portion (hatched portion in the figure) corresponding to (1), and plating is not performed. Therefore, when the die pad 10 is clamped by the covering portion 18, it is necessary to set the covering portion so as not to hinder the die attachment of the semiconductor chip. In the embodiment, the periphery of the die pad outside the die attachment range of the semiconductor chip is clamped so as not to hinder the die attachment. The covering portion of the die pad 10 by the covering portion 18 may be appropriately set to an effective position according to the shape of the die pad and the mounting position of the stage support bar 12, and the corner portion may be pressed in addition to the method of pressing the side of the die pad. A suitable method such as a method or a method of pressing at a plurality of positions on the side can be selected.

When plating is performed by pressing the die pad 10 with the covering portion 18 according to the method of the present embodiment, the die pad 10 is effectively pressed down even if the die pad 10 becomes large, so that the plating solution is prevented from flowing around. Thus, it is possible to prevent the plating from adhering to the back surface of the die pad 10. As a result, the adhesion between the die pad 10 and the mold resin is improved, and it is possible to effectively prevent the occurrence of package cracks after molding. According to the method of the embodiment, since the plating does not adhere to the surface of the peripheral portion of the die pad 10, the adhesion between the mold resin and the die pad 10 is further improved. Further, the problem that plating is transferred to the heater block at the time of assembly such as wire bonding can be solved, and the occurrence of defects in the assembly process can be solved.

[0012]

According to the method for plating a lead frame according to the present invention, as described above, it is possible to preferably prevent the plating from adhering to the back surface of the die pad during the partial plating. In addition, it is possible to prevent the occurrence of defects and to prevent the occurrence of defects in the assembly process.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a state of plating a lead frame.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Die pad 12 Stage support bar 14 Inner lead 16 Mask 18 Covering part

Claims (3)

(57) [Claims] 1. A lead frame provided with a die pad ,
The lead frame sandwiched between a plating jig that covers the entire back surface side of the lead frame and a mask on which a predetermined plating pattern is formed, and exposed from the mask
A plating method for a lead frame, wherein plating is performed on at least the surface of the die pad, wherein the tip portion of the inner lead and the tip portion are provided inside the tip portion.
And a die pad whose peripheral portion is spaced apart.
Formed by exposing the area inside the tip of the knurled lead
With pressing the inner leads by the mask, of the lead frame, characterized in that plating by pressing a good site even without performing the plating of the periphery of the surface of the die pad Ri by the covering portion provided in said mask Plating method. 2. A rectangular shape is formed by said covering portion.
Press the edges of the two parallel sides of the die pad
The plating of a lead frame according to claim 1, wherein
Method. 3. The method according to claim 1, wherein the coating portion forms one of the die pads.
2. The method according to claim 1, wherein a plurality of sides are pressed.
Lead frame plating method.