JPH08293576A - Lead frame and manufacture thereof - Google Patents

Abstract

PURPOSE: To enable a chip electrode and the tip of an inner lead to be electrically connected together in a shorter time by a method wherein a fine lead directly connected to the electrode of a semiconductor is provided in the tip of the inner lead. CONSTITUTION: A dry film resist pattern functioning as a plating resist 2 is formed on the one side of a lead frame material 1 so as to enable a part where a fine lead is formed to be exposed. Then, the lead frame material 1 is dipped into electrolytic gold plating solution and plated with gold while the plating resist 2 is left unremoved. Gold plating solution is removed out of a lead frame 10, the lead frame material 1 is dipped into aqueous sodium hydroxide for peeling off the plating resist 2, rinsed, and dried up, and a fine lead 3 of gold is formed on the one side of the lead frame 10. By this setup, the electrode of a chip 20 and the tip of an inner lead can be electrically connected together in a shorter time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame for mounting a semiconductor integrated circuit element (hereinafter referred to as a chip) used in electronic equipment and the like, and particularly to a chip electrode directly without wire bonding. The present invention relates to a lead frame having a structure capable of connecting the inner lead to the inner lead.

[0002]

[Prior art]

(1) Semiconductor device using a lead frame Semiconductor devices using a lead frame (in the form of a package for mounting / connecting a chip and connecting to an external circuit) are widely used. Generally, chips are mounted and connected according to the following procedure.

After the Ag paste is applied to the chip mounting portion (island) of the lead frame and the chip is mounted and fixed, the electrodes on the chip surface are electrically connected to the inner leads by joining an Au wire having a diameter of about 30 μm. (Wire bonding).

In the wire bonding method, a wire bonding apparatus is used in which the bonding points (chip electrode and inner lead tip) are pre-programmed and recognized, and heating / pressurizing (ultrasonic wave) of the Au wire is performed at each bonding point. A series of vibration / cutting processes are performed.

Further, in order to improve the bonding strength of the wire, the tip of the inner lead may be plated with a noble metal (Ag or Au). ) Or a shape is recognized and the above process is performed.

[0006] The wire bonding method has problems to be typified by the following two. Since the connections are made one by one, the time required for the connection becomes longer as the number of connection points increases (when a highly integrated chip is connected to a lead frame having a large number of leads). In narrowing the pitch of the connection points, the pitch is about 3 times the diameter of the wire to be used (about 100 μm), which is the limit, and it is not possible to cope with further narrowing of the pitch.

(2) Semiconductor Device Using Tape Carrier As a method of solving the above problems, there is a method of connecting a chip to a lead frame via a tape carrier (or film carrier). Tape carrier
A chip mounting / connecting element in which a wiring pattern is formed on the surface of an insulating substrate (film).

The wiring pattern of the tape carrier is formed by patterning the foil, patterning the plating, etc., and is therefore thinner than the leads of the lead frame.
Therefore, the pitch can be made narrower than that of the lead frame, and a wiring pattern having the same pitch as the chip electrodes can be formed.

Further, if the wiring pattern is made of a material having good bondability, or if the wiring pattern at the bonding portion is plated (or bumps are formed) having good bondability, the chip electrode (and the lead frame The inner lead tip) and the wiring pattern can be directly connected only by heating and pressurization without using wire bonding.

[0010]

[Problems to be Solved by the Invention] In the above method (2),
In order to connect the chip and the lead frame, a tape carrier must be used as a new joining member,
An additional manufacturing process and materials for the tape carrier are required, which leads to an increase in the cost of the semiconductor device.

The present invention has problems due to the wire bonding method (difficulty in increasing the connection time and narrowing the pitch) and problems due to the tape carrier method (requires a tape carrier as a separate device for connection, It is an object of the present invention to provide a semiconductor device having a configuration capable of solving the problem (device cost increases).

[0012]

In order to achieve the above-mentioned object, the present invention has a structure in which the tip of the inner lead of the lead frame has a minute lead which plays the role of a conventional wire. The minute leads can be connected by aligning the chip electrodes and then applying heat and pressure.

As the material of the minute lead, Au or A which is a noble metal having good bonding property as in the conventional wire is used.
An alloy containing u as a main component is preferable. The size of the micro lead is 20 to 50 μm in width and 10 to 50 μm in thickness.
Then, the length of the portion protruding from the tip of the inner lead is preferably about 0.5 to 5 mm.

In manufacturing the lead frame having the above-described structure, a step of forming a resist pattern functioning as a plating resist on one surface of the lead frame material before molding so that a portion for forming minute leads is exposed, and a lead frame. It is preferable that a series of steps including a step of plating the exposed portion of the material with a metal and a step of forming the lead frame into a predetermined shape from the other surface (or both surfaces) of the lead frame material.

In this case, in order to increase the number of pins and the pitch of the leads, the side etching has an influence.
Etching molding from both sides is effective.

[0016]

[Function] The material of the fine lead has good bondability,
By making the size suitable for the bondability, it is possible to connect to the chip electrode without using wire bonding.

After the chip electrodes and the lead frame are aligned, heating and pressurization are collectively performed, so that the bonding is completed at all the bonding points at the same time. Is reduced.

Regarding the pitch reduction, unlike the wire bonding method, there is no restriction of up to 3 times the wire diameter.

In the wire bonding method, the Au wire has a loop shape from the chip electrode to the tip of the inner lead. However, in this method, the inductance of the lead is lower than that of the Au wire, so that when a high frequency electric signal is used. The transfer characteristics are improved.

By providing the groove portion in the portion where the minute lead is formed by half etching or the like, the fixing of the minute lead to the inner lead is further strengthened.

[0021]

Embodiments Embodiments will be described below with reference to the drawings. (1) Lead frame material An iron-nickel alloy plate having a thickness of about 150 μm is used as the lead frame material 1, immersed in an alkaline degreasing solution at 70 ° C. for about 10 minutes, then washed with hot water at about 50 ° C. After repeating the operation, it is immersed in 5% hydrochloric acid for 30 to 60 seconds. It is again washed with water, and finally, dry air is blown to completely remove water drops on the surface, and the surface is dried by placing it in an oven at about 90 ° C. for 10 minutes. (Not shown)

(2) Formation of Plating Resist A sheet-shaped dry film resist is laminated on the lead frame material 1 at the same time on both sides by rollers heated to about 100 ° C., and left as it is until the temperature cools. Next, the pattern masks where the portions corresponding to the formation of the micro leads become the light-shielding portions are overlapped, set on a double-sided exposure machine, irradiated with ultraviolet rays, and the resist of the irradiated portion (the portion where the micro leads are not formed) is developed. Change to insoluble state. Then
A sodium carbonate solution is sprayed onto the lead frame material 1 to dissolve and remove the dry film resist in a portion not irradiated with ultraviolet rays. Through the above steps, a dry film resist pattern functioning as the plating resist 2 is formed on one surface of the lead frame material 1 so that the portions where the fine leads are formed are exposed. (See Fig. 1)

(3) Formation of Micro Leads The ferric chloride solution is sprayed onto the lead frame material 1 to deeply remove the iron-nickel alloy in the portions not covered with the plating resist 2 (locations where the micro leads are formed). About 10μ
Etching (forming a groove portion) was performed so as to be m. The leadframe material 1 is washed with water for several minutes to completely remove the ferric chloride solution. Then, while leaving the plating resist 2 as it is, the lead frame material 1 is dipped in an electrolytic gold plating solution, plated at a current density of ² to 5 A / dm ² for about 30 minutes, and the thickness of the portion is about 30 μm. Then, gold plating (micro lead 3) is performed. After thoroughly washing with water to completely remove the gold plating solution, the lead frame material 1 is dipped in a 5% sodium hydroxide solution to remove the plating resist 2 and then rinsed and dried. As described above, the minute lead 3 made of gold and having a thickness of about 30 μm is provided on one surface of the lead frame material 1.
To form.

(4) Formation of etching resist The lead frame material 1 was immersed in an alkaline degreasing solution at 70 ° C.
After soaking for 0 minute, it was washed with hot water at about 50 ° C., washed with water several times, and then soaked in 5% hydrochloric acid for 30 to 60 seconds. It is again washed with water, and finally, dry air is blown to completely remove water drops on the surface, and the surface is dried by placing it in an oven at about 90 ° C. for 10 minutes. Next, the lead frame material 1 is slowly dipped in a photosensitive liquid resist, left standing for about 10 seconds, and then slowly pulled up at a speed of about 5 to 10 mm per second to form a liquid resist film of about 10 μm on the surface. Form. Then, after leaving it at room temperature for a while, 70
Place in an oven at ℃ for about 30 minutes to dry well. Next, on the surface of the lead frame material 1, a glass mask having a light-shielding pattern formed on a portion other than the shape of the lead frame to be molded is overlaid and irradiated with ultraviolet rays. The developing solution is sprayed by spraying to dissolve and remove the portion not exposed to the ultraviolet rays to form an etching resist pattern in which the surface of the lead frame material 1 is exposed in a lead frame shape. Rinse and dry in an oven at 110 ° C for approx. 30
Allow for a minute to cure the etching resist.

(5) Formation of Lead Frame The lead frame material 1 is sprayed with ferric chloride solution to etch the iron-nickel alloy in the portion not covered with the etching resist to form a lead of a predetermined shape. The frame 10 is formed. Lead frame 10
Is thoroughly washed with water to completely remove the ferric chloride solution, then immersed in a 5% sodium hydroxide solution to remove the resist, followed by washing with water and drying. As described above, the lead frame 10 having a structure in which the inner leads have minute leads is manufactured. (See Fig. 2)

(6) Mounting / Connecting Chip After that, the chip is mounted / connected to the produced lead frame 10. The lead frame 10 is set in the existing bonding device, and the electrodes of the chip 20 and the lead frame 1
0 minute lead is aligned and brought into intimate contact.
Bonding is performed by applying ultrasonic vibration while heating each side of the 0 electrode. As the bonding device, T
A gang bonding device for AB (film carrier) and a system that does not apply ultrasonic vibration can also be used. In addition, do not heat the entire surface of the joint
It is also possible to apply pressure and perform the joining process all at once. Finally, a resin is applied to the joint to firmly fix the chip 20 and the lead frame 10. (See Figure 3)

In the present embodiment, the lead frame has a shape without a chip mounting portion (island), but the present invention is not limited to this, and may be appropriately changed within a range not departing from the gist. Needless to say. That is, in a lead frame having an island, the upper surface of the chip and the upper surface of the inner lead (bonding surface of the chip electrode and the micro lead) are made flush with each other by lowering the tab (displacement of the island downward). , Chips may be connected.

[0028]

The remarkable effects of the present invention are listed below. (A) The time required for electrical connection between the chip electrode and the tip of the inner lead is dramatically reduced as compared with the wire bonding method. (B) The pitch reduction required when mounting and connecting a highly integrated chip on a lead frame having a large number of pins is easier than the wire bonding method. (C) The cost of the semiconductor device is lower than that of the tape carrier system.

[0029]

[Brief description of drawings]

FIG. 1 is an explanatory view showing a lead frame material on which a plating resist is formed.

FIG. 2 is an explanatory view showing a lead frame of the present invention.

FIG. 3 is an explanatory diagram showing a state in which a chip is mounted and connected to a lead frame.

[Explanation of symbols]

 1 ... Lead frame material 2 ... Plating resist 3 ... Micro lead 10 ... Lead frame 20 ... Chip

Claims (4)

[Claims] 1. A lead frame having a structure in which minute leads for directly connecting to electrodes of a semiconductor integrated circuit element are provided at the tips of the inner leads. 2. The lead frame according to claim 1, wherein a groove portion narrower than the lead width is formed at the tip of the inner lead in the length direction of the lead, and the groove portion has a minute lead. 3. The fine lead is made of Au or an alloy containing Au as a main component, and has a width of 20 to 50 μm and a thickness of 10 to 50 μm, and the length of the portion protruding from the tip of the inner lead is 0.
It is 5-5 mm, The lead frame of Claim 1 or Claim 2 characterized by the above-mentioned. 4. A step of forming a resist pattern which functions as a plating resist on one surface of a lead frame material before molding so that a portion for forming minute leads is exposed, and metal plating is applied to an exposed portion of the lead frame material. The method of manufacturing a lead frame according to claim 1, further comprising: a step of applying the lead frame and a step of molding the lead frame into a predetermined shape.