JP2520610Y2 - Lead frame - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a lead frame used in a semiconductor package.

[Summary of the Invention] In the present invention, in a lead frame used for a semiconductor package in which a semiconductor chip is covered with a molding material such as resin, the inner surface of the guide hole is plated with a material having a lower dynamic friction coefficient than the frame body, By providing lubricity to the holes, it is possible to prevent galling of the positioning pins or feed pins inserted into the guide holes when positioning or feeding the lead frame during the semiconductor package manufacturing process. Is.

[Prior Art] FIG. 4 is a plan view showing a conventional lead frame.
In the figure, 1 is a lead frame, which is
The frame body 2 made of a thin metal plate such as stainless steel or copper (copper content of 98% or more) or 42Alloy (Fe-Ni) is cut and etched to form the die pad 3 as the semiconductor chip placement portion. A lead finger 4 and a guide hole 5 are formed on the outer side thereof so as to be spaced apart from each other in a comb shape. Normally, one frame body 2 has one die pad 3, lead fingers 4, and guide holes 5.
The unit part is formed from dozens to dozens of sets. Further, in order to maintain the bonding strength between the bonding fingers (not shown) and the lead fingers 4 in the wire bonding step of the semiconductor package manufacturing process, after forming the die pad 3, the lead fingers 4, the guide holes 5, etc. on the frame body 2. The inner lead portions of the lead fingers 4 are plated with silver to a thickness of, for example, 3 to 5 μm. This silver-plated area is indicated by reference numeral 6 surrounded by an imaginary line in FIG.

By the way, in a die bonding process, a wire bonding process, a molding process, a trimming form process and the like in the semiconductor package manufacturing process, a lead pin (not shown) is inserted into the guide hole 5 of the frame body 2 to move the lead frame 1. At the end of this movement, a positioning pin (not shown) is inserted into the guide hole 5 to position the lead frame 1.

[Problems to be Solved by the Invention] In the lead frame 1 described above, the hole diameter of the guide hole 5 and the outer diameters of the feed pin and the positioning pin in the semiconductor package manufacturing process are set to be substantially the same, and If the fitting gap (clearance) with the feed pin or the positioning pin to be inserted into this is made extremely small to improve the feeding and positioning accuracy, the frame body 2 is still penetrating the guide hole 5, so that it is caused by friction. Too much resistance may lead to galling of the feed and locating pins. To prevent this, a lubricant such as oil or fat may be used, but it is not possible to use a lubricant such as oil or fat because it is extremely disliked by dust and dirt in the semiconductor package manufacturing process. From such a thing,
In the mechanism including the feed pin, the frame feed is set to a high precision with a tolerance of, for example, ± 10 to 50 μm, or the fitting gap between the guide hole 5 and the feed pin or the positioning pin is set so that no galling occurs. Measures such as expansion were taken.

However, the equipment cost is high, and the adjustment work with high difficulty and maintenance and inspection with short adjustment intervals are required.
Regarding the trend of high-density mounting on semiconductor chips,
It has been pointed out that manufacturing of a fine-pitch semiconductor package in which the pitches of the adjacent lead fingers 4 are narrow requires extremely high feed and positioning accuracy, which makes manufacturing difficult.

[Means for Solving the Problem] Therefore, in the present invention, the inner surface of the guide hole formed in the frame body is plated with a material having a lower dynamic friction coefficient than the frame body.

[Operation] After forming the semiconductor chip arrangement portion, the lead fingers, the guide holes, etc. in the frame body, for example, after covering the surface of the frame body other than the inner surfaces of the lead fingers and the guide holes with the mask pattern, Perform a plating treatment such as silver plating. After that, the plating solution is washed, dried, and the mask pattern is sequentially removed to obtain a lead frame in which at least the inner lead portions of the lead fingers and the inner surfaces of the guide holes are plated with the same plating. In this lead frame, the friction of the guide hole with respect to the feed pin and the positioning pin is reduced by the plating.

[Embodiment] Hereinafter, an embodiment of the present invention will be described in detail by giving the same reference numerals to the same portions as those of the conventional structure described above with reference to the drawings.

In FIG. 1, 1A is a lead frame, 2 is a frame body, 3 is a die pad, 4 is a lead finger, 5A is a guide hole, 6 is a plated area of the lead finger 4 including the die pad 3, and 7 is a plated area of the guide hole 5A. Is.

Here, in order to make the lead frame 1A, first, the frame body 2 made of a strip-shaped metal plate such as a copper-based material having a thin copper content of 98% or more or 42 Alloy made of Fe-Ni is subjected to cutting and etching, The die pad 3, the lead finger 4 arranged outside the die pad 3 and the guide hole 5A are formed.

Next, as shown in FIG. 2, one surface of the frame main body 2 as a semi-finished product on which the die pad 3, the lead fingers 4 and the guide holes 5A have been formed is formed on the surface of the plating area 6 with a material having a plating solution resistance. After forming the mask pattern 8 having the openings 8a in the portions corresponding to the electrodes 7 and 7, the surface of the frame body 2 on the side where the mask pattern 8 is not formed is attached in close contact with the pad and the electrode 9 of the plating system. The mask pattern 8 is obtained by immersing in a plating solution 10 such as a plating solution and energizing the frame body 2 from the electrode 9.
Using the mask as a mask, the inner surface of the die pad 3 and the lead fingers 4 exposed in the plating areas 6 and 7 of the frame body 2 and the inner surface (hole wall surface) of the guide hole 5A are provided with a plating 11 such as silver plating. To the thickness of.

Then, although not shown, after the energization of the electrode 9 is cut off, the pad including the frame body 2 and the electrode 9 are taken out from the plating solution 10, the frame body 2 is removed from the pad and the electrode 9, and the mask pattern 8 and the plating 11 are formed. Then, the plating liquid 10 adhering to the frame body 2 is washed with water and removed.
Further, when the water content during washing is dried, the mask pattern 8 is formed by an appropriate method so as not to damage the plating 11.
Is removed. As a result, the lead frame 1A plated with the die pad 3 included in the plated regions 6 and 7, the inner lead portions of the lead fingers 4 and the inner surface of the guide hole 5A is completed. As shown in FIG. 3, the diameter L1 of the guide hole 5A before the plating 11 is applied.
Is set based on the thickness t of the plating 11 and the outer diameter D of the pin 12 for feeding and positioning (L1 ≧ D + 2 × t), the hole diameter L2 of the guide hole 5A after the plating 11 is applied.
The dimension (L2 = L1-2 × t) is much larger than the outer diameter D of the pin 12 (L2> D). Symbols in FIG. 3
Reference numeral 13 is a guide member for guiding the pin 12.

According to the structure of the above-described embodiment, when the lead frame 1A is used in the manufacturing process of the semiconductor package, as shown in FIG. 3, when the tips of the pins 12 face each other so that they can enter the guide holes 5A, the pins 12 Is inserted into the guide hole 5A. Then, the slope 12a at the tip of the pin 12 is plated 11
Move with contact with very little friction on the pin 12
Fits into the guide hole 5A. Here, assuming that the pin 12 is a positioning pin, in the process of fitting the pin 12 into the guide hole 5A, the lead frame 1A moves in the direction of the arrow X in FIG. Accurately positioned as a reference. Further, assuming that the pin 12 is a feed pin, although not shown, since the lead frame 1A is fitted to the pin 12 without rattling, the feed movement amount by the pin 12 is accurate.

On the other hand, the plating 11 is silver plated, and the lead frame 1A
When the feed and positioning were performed, the occurrence rate of burrs around the guide hole 5A due to the galling of the feed pin and the positioning pin was 50% or less of the conventional rate.

Further, in this embodiment, since the plating 11 applied to the guide hole 5A is the same as the plating applied to the lead finger 4, the lead finger 4 is plated and the inner surface of the guide hole 5A is also plated 11 at the same time. Therefore, it is possible to easily manufacture the lead frame 1A having lubricity in the guide hole 5A without affecting the manufacturing process of the lead frame 1A.

It should be noted that the present invention is not limited to the above-described embodiment, and various embodiments can be considered without departing from the gist of applying the plating 11 to the inner surface of the guide hole 5A of the present invention.

For example, although not shown, the opening of the mask pattern 8
Make the diameter of 8a larger than the diameter of guide hole 5A,
A small gap may be formed between the pad and the portion of the electrode 9 around the guide hole 5A and the frame body 2, or the above-mentioned opening may be formed.
The plating 11 is continuously deposited from the inner surface of the guide hole 5A to the surface around the guide hole 5A of the frame main body 2 by using a larger hole diameter of 8a and separation from the pad and the electrode 9 and the like.

The plating 11 may be other than silver plating as long as it has a low dynamic friction coefficient with the pin 12 as long as it does not hinder the bonding strength between the bonding finger and the lead finger 4 in the wire bonding process.

The semiconductor chip disposition part has been illustrated and described with respect to the structure composed of the die pad 3 integrated with the frame body 2.
It is also possible to form the die pad 3 with a material different from that of the frame body 2 such as a mold resin of a semiconductor package, or to form a window from which the die pad 3 is removed. When the die pad 3 is removed, the semiconductor chip is arranged in the window, the bonding wire is connected across the bonding pad of the semiconductor chip and the lead finger 4, and this is resin-molded to form a semiconductor package.

[Advantages of the Invention] As described above, according to the present invention, the inner surface of the guide hole is plated with a material having a lower dynamic friction coefficient than the frame body to provide lubricity to the guide hole. It is possible to prevent galling of the positioning pin or the feed pin inserted into the guide hole without causing dust or dirt when the lead frame is positioned and fed. Therefore, the accuracy of the frame feed can be relaxed as compared with the conventional one, and the mechanism including the feed pin can be structured so that the facility cost is low, the adjustment work is easy, and the maintenance and inspection are not required so much. Moreover, the fitting gap between the guide hole and the feed pin or the positioning pin can be set to a very small dimension to perform highly accurate positioning that can be applied to a fine pitch semiconductor package.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention, FIG. 2 is a sectional view showing a state in which a lead frame of the embodiment is plated, and FIG. 3 is a sectional view explaining the operation of the embodiment. FIG. 4 is a plan view showing a conventional lead frame. 1A ... Lead frame, 2 ... Frame body, 3 ... Die pad (semiconductor chip placement part), 4 ... Lead fingers, 5A ... Guide hole, 6,7 ... Plating area, 11 ...
plating.

Claims (1)

(57) [Scope of utility model registration request] 1. A lead frame, wherein an inner surface of a guide hole formed around a semiconductor chip disposition portion of a frame body is plated with a material having a lower dynamic friction coefficient than the frame body.