JPH0845978A - Method of manufacturing package without wire defect - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent wire defects such as wire sweeping or short circuit from occurring during the molding process. A step of mounting a semiconductor chip on a die pad, a step of wire bonding the chip to an internal lead of a lead frame having an internal lead and an external lead, and a step of bonding the semiconductor chip, the bonded wire and the lead frame to each other. A step 23 of coating with a non-conductive coating agent, a step 24 of molding the coated package with a resin, and a step of removing the coating agent from outer leads of the coated lead frame. Stage 25 of deflashing the package
And having.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor package having no wire defects, and more particularly to a non-conductive coating agent for a package obtained after wire bonding during a normal semiconductor manufacturing process. For example, by coating with para-xylene,
The present invention relates to a method of manufacturing a semiconductor package that prevents an electrical short circuit from occurring due to a wire defect such as sweeping or sagging during a subsequent molding process.

[0002]

2. Description of the Related Art Generally, in a semiconductor package, a process of cutting a wafer into individual chips, a process of mounting this chip on a die pad (a "die bonding" process), and an electrical connection of this chip to an internal lead of a lead frame. It includes a step of connecting (“wire bonding” step) and a step of sealing the chip and internal leads with a thermosetting resin (“molding”) step. Next, the dam bar of the external lead of this lead frame is removed, deflash of chemical substances, etc. is performed, and this chip is mounted on the substrate of the printed circuit to form the final semiconductor chip package. Obtainable.

In recent years, electronic products have been required to have miniaturization, high density and high performance. Therefore, development of packaging or mounting technology for high density or high pin count semiconductor chips has been required. Has been done.

[0004]

By the way, the above-mentioned highly integrated semiconductor chip having a high density or a large number of pins has a large number of leads, and these leads are not only input / output terminals but also wires on this chip. Are electrically connected through. In the case of a center pad package having a bus bar, which is one type of LOC (Lead On Chip), an electrical short circuit between the wire and the bus bar is taken up as an important problem.

Particularly, in a high-density package having a large number of pins, since the distance between adjacent wires is extremely small and the length of the wires is considerably long, wire sweeping, short circuit between wires, or wire sagging may occur. Frequent wire defects frequently occur during the molding process.

Such wire defects are usually caused by the wire bonding package, the physical properties and diameters of the wires used, the conditions of the capillaries, the operating conditions and environmental factors, and the density of the packages. The higher the value becomes, the more difficult it becomes to suppress the occurrence of the factors.

On the other hand, the wire is 4.06 mm (60 mi
If the length is l) or more, it is difficult to form a stable wire loop. Especially when the number of leads to be bonded through the wire is small and the distance between the adjacent wires is small, it becomes more difficult to form a stable wire loop, and the wire is swept even a little. May also cause a wire short circuit.

As a countermeasure against such a problem, TAB (Tape automated bon) is used instead of wire bonding.
Ding) or mounting technology using bumps has been proposed, and technology using coated gold wires has also been developed.

However, since the use of the TAB and the bumps significantly increases the production cost as compared with the wire bonding technique, it is difficult to put them into practical use. In addition, coated gold wire is still in the development stage,
It has not been put to practical use.

Therefore, there has been an urgent need to provide a method for forming a stable wire loop or a method capable of preventing the occurrence of wire defects such as wire sweeping and sagging during the molding process.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to mount a package by preventing a wire defect such as wire sweeping or a short circuit from occurring during a molding process. To provide a method of manufacturing a package without wire defects, which increases efficiency and eases restrictions on circuit design due to interference between adjacent wires, while preventing moisture from penetrating inside the package. It is in.

[0012]

In order to achieve the above object, a first invention according to claim 1 is to mount a semiconductor chip on a die pad, and to use an inner lead of a lead frame having an inner lead and an outer lead. Wire bonding the semiconductor chip, a step of coating the semiconductor chip, the bonded wires and the lead frame with a non-conductive coating agent, and a step of molding the coated package with a resin, Removing the coating agent from the outer leads of the lead frame in the coated step to deflash the package.

The second aspect of the present invention is summarized in that the non-conductive coating agent is para-xylene.

A third aspect of the present invention is summarized in that the coating step is performed using para-xylene gas.

[0015]

According to the first aspect of the present invention, in the ordinary semiconductor packaging process, the wire sweeping is performed by adding a step of coating the entire package with a non-conductive coating agent after the wire bonding process. It is possible to prevent wire defects such as dripping or short circuit.

[0016] In a second aspect of the invention, the coating step is a non-conductive coating agent such as perylene.
Since e), that is, paraxylene is used, the perylene applied to the portion of the lead where soldering is required can be easily removed during the deflash process.

According to the third aspect of the invention, since the coating step is performed by using paraxylene gas, it is not necessary to use a mask or a protective means when coating the package with perylene.

[0018]

An embodiment of the present invention will be described below with reference to the drawings.

One example of a device that can be used from the present invention is illustrated in FIG. The coating apparatus 10 in FIG. 1 includes a vaporization chamber 11, a thermal decomposition chamber 12, a coating chamber 13 and a control unit 14. The vaporization chamber 11 has an inlet 15 to which a coating agent, for example, perylene dimer, is supplied, and a line L3.
Is connected to the thermal decomposition chamber 12 through. The vaporization chamber 1
1 is heating means 1 for vaporizing perylene dimer
1a is provided.

The thermal decomposition chamber 12 is equipped with a heating means 12a for thermally decomposing the perylene gas supplied from the vaporization chamber 11 through the line L3.

The coating chamber 13 is connected to the thermal decomposition chamber 12 through a line L1, and the cooling means 16 is also provided.
It is also connected to. The cooling means 16 liquefies the excess perylene gas supplied from the coating chamber 13, and the liquefied perylene is recirculated to the vaporization chamber 11.

The control unit 14 controls the operation of each chamber and the coating thickness.

The coating process is as follows.
For example, the injection port 1 for the coating agent of perylene dimer
5 and then through line L4 to vaporization chamber 1
Feed to 1. From the vaporization chamber 11, the perylene dimer is heated by the heating means 11a at a temperature of about 150 ° C. and a pressure of about 1 to.
Heated to rr. Subsequently, the perylene dimer gas is transported to the thermal decomposition chamber 12 through the line L3, and heated from the thermal decomposition chamber 12 to a higher temperature, for example, about 690 ° C. and a pressure of about 0.5 torr by the heating means 12a. The pyrolyzed perylene monomer gas is transported to the coating chamber 13 and the coating chamber 1
Package obtained after wire bonding from 3 (=
It is sprayed onto a lead frame strip to form a conformal coating film. The coating conditions are a temperature of about 35 ° C. and a pressure of about 0.1 torr.
The perylene monomer applied to the package is polymerized in the coating chamber 13.

The surplus perylene is recycled to the vaporization chamber 11 through the line L6. Control unit 1 for all operations of the device
Controlled by 4.

The overall semiconductor fabrication process, including the coating process, is illustrated in FIG. Referring to FIG. 2, in a die bonding step 21, a semiconductor chip is bonded to a die pad using an adhesive. Then, the gold wire is used to electrically connect the inner lead of the lead frame to a bonding pad formed on the chip (wire bonding step 22).

Subsequently, the coating step 23 is carried out in the box indicated by the broken line in the figure. The coating process 23 is performed in three stages: a non-conductive coating agent such as perylene dimer is vaporized in the vaporization chamber 1.
Vaporization step 23-1 of vaporizing from 1; thermal decomposition step 23 of pyrolyzing vaporized perylene to form perylene monomer
-2; and a precipitation step 23-3 for conformally coating the package obtained after the wire bonding step 22 with perylene. The perylene gas is sprayed onto the package.

The thickness of the coating film varies depending on the surface area to be coated and the coating time, but is preferably 0.5 to 2.0 μm, more preferably about 1.0 μm.

All coating processes are automatically controlled by the controller 14.

As the automated perylene coating device, a commercially available one can be used. Products from NOVA TRAN, located in clear Lake, can be used.

The coating device is a chamber fixer (chamber fixtur) that is hung before the lead frame strip after the wire bonding process in a normal semiconductor package manufacturing line is sent to the molding process.
It can be applied to the semiconductor package manufacturing line by mounting it on e). The lead frame strip is directly transferred to the coating chamber 13 for coating without passing through other parts of the coating apparatus.

The coated package is then processed into a final package through a molding process 24, a deflash process 25 and a trimming process 26, as shown in FIG. Here, the deflash process 25
It was confirmed that an electrical contact point, for example, perylene applied to a portion of the lead where soldering was required was easily removed. That is, the coating material is removed from the outer leads of the lead frame at the coated stage. Then, the package is deflashed with a chemical substance or the like. Therefore, no special masks or protective means need to be used when coating the package with perylene.

FIG. 3 is a view showing a package coated according to the present invention. In FIG. 3, numeral 31 is a chip, numeral 32 is a wire, numeral 30 is a die pad, and numeral 33 is a coating film. There is.

[0033]

As described above, the first aspect of the present invention includes the step of conformally coating the entire surface of the package, for which the wire bonding step has been completed, with a non-conductive coating agent before molding the package. The package manufactured by the method of the present invention has the following advantages. First, it prevents wire defects such as wire sweeping, sagging or short circuit during the molding process to increase the packaging efficiency of the package and alleviates the limitation on circuit design due to interference between adjacent wires. Since the perylene forms a water-insoluble film, the humus of the bonding pad and the permeation of water in the package can be effectively prevented. Further, by forming a plastic perylene film on the gold wire, it is possible to improve the physical properties of the gold wire, such as ductility, and increase its reliability in reliability tests such as the temperature cycle test.

In a second aspect of the present invention, the coating step is a non-conductive coating agent such as perylene.
Since e), that is, paraxylene is used, the perylene applied to the portion of the lead where soldering is required can be easily removed during the deflash process.

In the third aspect of the invention, since the coating step is performed using para-xylene gas, it is not necessary to use a mask or a protective means when coating the package with perylene.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus used to perform a coating process of a method for manufacturing a package without defect of wire according to the present invention.

FIG. 2 is a diagram showing a manufacturing process according to the manufacturing method of the present invention.

FIG. 3 is a cross-sectional view of a semiconductor package coated according to the present invention.

[Explanation of symbols]

 10 coating device 11 vaporization chambers 11a, 12a heating means 12 thermal decomposition chamber 13 coating chamber 14 control chamber 16 cooling means 31 chip 32 wire 33 coating film

Claims (3)

[Claims] 1. Mounting a semiconductor chip on a die pad, wire bonding the semiconductor chip to an inner lead of a lead frame having an inner lead and an outer lead, the semiconductor chip, the bonded wire and the lead frame. With a non-conductive coating agent, molding the coated package with a resin, and removing the coating agent from the outer leads of the coated lead frame to remove the package. A method of manufacturing a semiconductor package having no wire defects, comprising: a step of deflashing the semiconductor package. 2. The non-conductive coating agent is a para
The method according to claim 1, wherein the package is xylene (para-xylene). 3. The method according to claim 1, wherein the coating step is performed by using para-xylene gas.