JP2651205B2 - Method of manufacturing semiconductor device and semiconductor device obtained thereby - Google Patents

Abstract

PURPOSE:To prevent film breakage caused by the thermal degradation of a coating film, by making the coating film of wire that connects the external terminals of a chip with leads from heat-resistant polyurethane containing in the molecular skeleton a constituent unit induced from terephthalic acid, making a polyol component react on isocyanate. CONSTITUTION:The insulating coating film of coated wire is made from heat- resistant polyurethane containing a constituent unit induced from terephthalic acid, in the molecular skeleton, making polyol component react on isocyanate. After the polyurethane is applied on the surface of metal wire of the wire body, it is finished by baking with an ordinary used baking finish device. Then, one end sides of the coated wires are connected to the external terminals of a semiconductor chip, and the other end sides are connected to leads. As joining can be performed by resolving the urethane bond even with ultrasonic wave vibrational energy or joining temperature in time of usual wire bonding, secure bonding can be obtained with the simultaneous use of both ultrasonic wave vibration and thermocompressing bonding by usual heating, or with ultrasonic wave vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a semiconductor device manufacturing technique, and more particularly, to an external terminal and a lead of a semiconductor chip by a coated wire in which the surface of a metal wire is coated with an insulating coating film. And a technology effective when applied to a semiconductor device obtained thereby.

[Conventional technology]

Generally, a wire made of, for example, gold (Au), aluminum (Al), or copper (Cu) is used to electrically connect external terminals (bonding pads) of semiconductor chips and leads (inner leads) in a semiconductor device. Used.

Conventionally, as this kind of wire, a so-called bare wire consisting only of a metal wire of the above-mentioned material has been used, but recently, in order to prevent a short circuit between the wires, a surface of the metal wire is coated with an insulating film. It is contemplated to use a coated wire coated with.

Regarding the use of such a coated wire, for example, JP-A-57-152137, JP-A-57-162438, JP-A-60-224237,
Nos. 61-194735 and 61-186239.

According to these known techniques, urethane resin or nylon resin (JP-A-57-152137), polyimide resin, polyurethane resin, or fluorine-based resin (JP-A-57-162438) is used as a material of a coating insulating film of a coating wire. No.),
Polyethylene resin, polyimide resin or urethane resin (Japanese Patent Application Laid-Open No. 60-224237), urethane resin, polyvinyl chloride resin or polyimide resin (Japanese Patent Application Laid-Open No. 61-194735), and insulating varnishes such as enamel, formal, and polyester Resin or polyurethane resin
No. 61-186239).

[Problems to be solved by the invention]

However, the present inventor has found that all of the above-mentioned known techniques have the following problems.

That is, the present inventors have conducted intensive studies and found that among the materials of the insulating coating film disclosed in the above-described known technology,
Polyester resin cannot be used because the rigidity of the film is too large and the bonding property is poor, which may cause poor bonding.

In addition, including polyester resin, polyimide resin (nylon resin), fluorine resin, polyethylene resin,
Polyvinyl chloride resin and enamel are not sufficiently satisfactory in the following points. That is, these materials
For example, since carbonization occurs without being decomposed at the heating temperature at the time of forming the metal ball, carbide attached to the coated wire at the time of wire bonding to the external terminal of the semiconductor chip is caught by the capillary and hinders the supply of the wire,
Carbide, which is a conductive material, falls on the circuit forming surface of the semiconductor chip to cause a short circuit.In addition, the bonding property is poor due to poor peeling of the coating film during wire bonding to the lead. Attempting to remove it results in carbonization by heating, which makes it difficult to remove the carbide and hinders bonding.

Furthermore, although polyurethane (or urethane) resin and formal have generally better properties than the other materials described above, according to experiments performed by the present inventors, particularly due to insufficient heat resistance, It has been found that a problem of thermal deterioration occurs. That is, when the semiconductor device is used after being mounted, the wires also receive a considerably large thermal shock due to the heat generated by the semiconductor element. Therefore, even if it is a coated wire, if a general polyurethane resin or formal is used as the coating film, if the wire has a tab touch state, a touch state on the silicon region of the chip, and a touch state between the wires, It has been confirmed by the present inventors that the temperature cycle test and high-temperature storage test of MIL-883B conducted by polyurethane and formal cause thermal degradation, and eventually cause tab shorts, chip shorts, and even shorts between wires due to film destruction. It was done.

Regarding this, in any of the above-mentioned known techniques, no consideration has been given to the problem of thermal deterioration in the polyurethane resin coating film. Cannot be used under the conditions of use and the test conditions of MIL-883B, so that there is a problem that short-circuit failure occurs as described above.

One object of the present invention is to provide a technology that can prevent a tab short, a chip short, or a short between wires due to film destruction due to thermal deterioration of a coating film in a semiconductor manufacturing technology using a coated wire. It is in.

It is another object of the present invention to provide a semiconductor manufacturing technology using a covered wire, which can ensure the bonding property of the covered wire, particularly the bonding strength between the covered wire and the lead.

It is another object of the present invention to provide a technique in a semiconductor manufacturing technique using a covered wire, which can perform bonding without causing a bonding failure by a normal wire bonding technique.

Another object of the present invention is to provide a technology that can improve the reliability of a semiconductor device in a semiconductor technology using a covered wire.

Still another object of the present invention is to provide a technique capable of realizing a multi-terminal semiconductor device in a semiconductor technique using a covered wire.

The above and other objects and novel features of the present invention are as follows.
It will be apparent from the description of this specification and the accompanying drawings.

[Means for solving the problem]

The outline of a representative invention among the inventions disclosed in the present application will be briefly described as follows.

In the semiconductor device manufacturing technology of the present invention and the semiconductor device obtained thereby, the insulating coating film of the coated wire, the polyol component and isocyanate react,
It is made of a heat-resistant polyurethane containing a structural unit derived from terephthalic acid in its molecular skeleton. One end of the covering wire is connected to an external terminal of the semiconductor chip, and the other end is connected to a lead.

The coating film on the one end side of the coating wire is removed at the time of forming the metal ball, or is connected to the external terminal of the semiconductor chip without forming the metal ball.

[Action]

According to the above-described means, the coating film made of heat-resistant polyurethane is prevented from causing film destruction due to thermal deterioration.
Alternatively, it is possible to prevent an electrical short failure such as a short between wires.

In addition, the heat-resistant polyurethane as the insulating coating film of the wire can be bonded by decomposing the urethane bond even at the bonding temperature or ultrasonic vibration energy at the time of normal wire bonding. Reliable bonding can be obtained in combination with ultrasonic vibration or ultrasonic vibration. In this case, if local heating of the bonding site is used together, more reliable wire bonding can be performed.

Next, the heat-resistant polyurethane used for the coating film of the coated wire in the present invention will be further described. The heat-resistant polyurethane is obtained by reacting a polyol component and an isocyanate, and has a structural unit derived from terephthalic acid in a molecular skeleton. This heat-resistant polyurethane is obtained by using a polymer component mainly composed of a terephthalic acid-based polyol containing active hydrogen, and isocyanate. Here, “consists of a main component” is intended to include a case where the whole is composed only of a main component.

Terephthalic acid-based polyol containing the active hydrogen, terephthalic acid and polyhydric alcohol, using OH / COO
It can be obtained by a usual esterification reaction by setting the reaction temperature to 70 to 250 ° C. in the range of H = 1.2 to 30. In general,
Those having an average molecular weight of 30 to 10,000 and having about 100 to 500 hydroxyl groups, and having hydroxyl groups at both ends of the molecular difference are used.

Raw materials constituting such a terephthalic acid-based polyol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol,
Hexane glycol, butane glycol, glycerin,
Aliphatic glycols such as trimethylolpropane, hexanetriol and pentaerythritol;
In addition, polyhydric alcohols such as 1,4-dimethylolbenzene can be mentioned. In particular, it is preferable to use ethylene glycol, propylene glycol, and glycerin.

Terephthalic acid is used as the dicarboxylic acid. If necessary, amic acid and imidic acid can be used in combination.

 The structural formula of the imidic acid is as follows.

Also, dibasic acids such as isophthalic acid, orthophthalic acid, succinic acid, avidisoic acid, sebacic acid, and 1,2,3,4-butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, ethylene Polybasic acids such as tetracarboxylic acid, pyromellitic acid and trimellitic acid may be used in combination.

As the isocyanate to be reacted with the terephthalic acid-based polyol, the isocyanate group of a polyvalent isocyanate having at least two isocyanate groups in one molecule such as toluylene diisocyanate and xylylene diisocyanate is converted into a compound having active hydrogen, for example, phenol. , Caprolactam and those blocked with methyl ethyl ketone oxime.
Such isocyanates are stabilized. Further, a compound obtained by reacting the above polyvalent isocyanate compound with a polyhydric alcohol such as trimethylolpropane, hexanetriol, or betandiol, and blocking with a compound having active hydrogen is also used.

Examples of the isocyanate compound, manufactured by Nippon Polyurethane Co., Millionate MS-50, Coronate 2501,250
3,2505, Coronate AP-St, Death Module CT-St and the like. It is preferable to use a polyisocyanate having a molecular weight of about 300 to 10,000.

The present invention provides a coating composition in which the metal wire of the wire main body is insulated by forming a coating composition using the above-described raw materials, coating the coating composition on the metal wire of the wire main body, and forming a coating having a thickness of several μm. A semiconductor device is manufactured using wires.

The coating composition used in the present invention is prepared by adding an isocyanate group of the stabilized isocyanate of 0.4 to 4.0 equivalents, preferably 0.9 to 2.0 equivalents and a required amount of a curing acceleration catalyst per equivalent of the hydroxyl group of the polyol component, and further adding an appropriate amount of an organic compound. It can be obtained by adding a solvent (phenols, glycol ethers, naphtha, etc.) to make the solid content usually 10 to 30% by weight. At this time, if necessary, an appropriate amount of an additive such as an appearance improving agent and a dye can be blended.

In the present invention, the isocyanate group of the stabilized isocyanate is 0.4 to 0.4 per hydroxyl equivalent of the polyol component.
The reason for adding 4.0 equivalents is that if it is less than 0.4 equivalents, the crazing characteristics of the resulting insulated wire will decrease, while the wear resistance of the coating film exceeding 4.0 equivalents will be inferior. The curing acceleration catalyst added at the time of preparing the coating composition is preferably 0.1 to 10 parts by weight per 100 parts by weight of the polyol component. When this is less than 0.1 part by weight, the tendency to deteriorate the film-forming ability as well as the curing promoting effect is reduced,
Conversely, if the amount exceeds 10 parts by weight, the heat-resistant urethane bonding wire obtained will have reduced thermal degradation characteristics.

Examples of the curing acceleration catalyst include metal carboxylic acids, amino acids, and phenols.Specifically, naphthenic acid, octenoic acid, zinc acids such as persatic acid, iron salts, copper salts, manganese salts, cobalt salts, A tin salt, 1,8 diazabicyclo (5,4,0) undecene-7,2,4,6 tris (dimethylaminomethyl) phenol is used.

The insulated coated bonding wire used in the present invention can be obtained by applying the above-described coating composition on the surface of the metal wire of the wire main body and baking it with a conventional baking coating device.

The coating and baking conditions vary depending on the amounts of the polyol component, the stabilized isocyanate, the polymerization initiator and the curing accelerator, but are usually about 200 to 300 ° C. for about 4 to 100 seconds. In short, baking is performed at a temperature and for a time sufficient to substantially complete the curing reaction of the coating composition.

The insulating coated bonding wire thus obtained has an insulating coating film made of heat-resistant polyurethane formed on the outer periphery of a metal wire of a wire body made of gold, copper or aluminum.

In this case, a composite coating film structure using the insulating coating film and another insulating coating film in combination may be used. This composite coating film, after forming the insulating coating film of the present invention described above,
It is obtained by further forming a second insulating coating film on the insulating coating film. In this case, the thickness of the second insulating coating film is not more than twice the thickness of the insulating coating film of the present invention,
Preferably, it is set to 0.5 times or less. Examples of the material for forming the second insulating coating film include a polyamide resin, a special polyester resin, and a special epoxy resin.

Hereinafter, the configuration and operation of the present invention will be described together with an example in which the present invention is applied to a semiconductor manufacturing technique used for a resin-encapsulated semiconductor device.

In all the drawings for describing the embodiments, components having the same function are denoted by the same reference numerals, and redundant description thereof will be omitted.

Embodiment 1 FIG. 1 is a half sectional view of a resin-sealed semiconductor device according to an embodiment of the present invention, FIG. 2 is a schematic enlarged sectional view of a wire bonding portion, and FIG. 3 is used in the present invention. FIG. 4 is a perspective view of a main part of the wire bonding apparatus, FIG. 5 is a partial sectional view showing a specific structure of a main part of the wire bonding apparatus, and FIG. Arrow VI
FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 6, FIG. 8 is a schematic diagram showing the principle of forming metal balls, and FIG. 9 is a view of the wire bonding apparatus. FIG. 10 is an exploded perspective view of a main part of the spool, FIG. 10 is an enlarged perspective view of a main part of the spool, FIG. 11 is a schematic plan view of a local heating unit for wire bonding, and FIG. 12 is a plan view showing an example of wire bonding. , FIG. 13 is a partial cross-sectional view showing a chip touch state of the coated wire, FIG. 14 is an enlarged partial cross-sectional view showing a chip short state thereof, FIG. 15 is a partial cross-sectional view showing a tab touch state of the coated wire, FIG. Is an enlarged partial cross-sectional view showing a tab short-circuit state, FIG. 17 is a graph showing a short-circuit rate between a semiconductor chip and a coated wire with respect to a temperature cycle in the present invention, and FIG. 18 is a tab and a coated wire with respect to a temperature cycle in the present invention. Is a graph showing the short-circuit rate.

The semiconductor device of this embodiment is an example of a resin-encapsulated semiconductor device 1, and its semiconductor chip 2 can be configured as a semiconductor integrated circuit element such as a memory, a gate array, a microprocessor, and a MOS logic.

The semiconductor chip 2 includes a substrate 2A made of, for example, silicon (Si) and a passivation film 2B on the top thereof.
And an external terminal (bonding pad) 2C exposed from the opening of the passivation film 2B. The semiconductor chip 2 is joined to the tab 3A of the lead 3 by a joining material 4 such as a silver (Ag) paste.

On the other hand, the external terminals 2C of the semiconductor chip 2 are electrically connected to the inner leads 3B of the leads 3 by conductive wires. In this embodiment, the covering wires 5 are used as the conductive wires. This coated wire 5 is a metal wire 5A
And a structure in which an insulating coating film 5B is applied to the surface of the substrate.

The material of the metal wire 5A of the covered wire 5 is, for example, gold (A
u), copper (Cu) or aluminum (Al) can be used.

The coating film 5B of the coating wire 5 is obtained by reacting a polyol component with an isocyanate, as described above and in detail later, and is made of a heat-resistant polyurethane having a molecular skeleton containing a structural unit derived from terephthalic acid. It becomes.

The coated wire 5 of the present embodiment has its first (first =
1st) The bonding side, that is, the connection side between the external terminal 2C of the semiconductor chip 2 and one end of the covering wire 5 is a metal ball
While being conductively connected by ball bonding by the formation of 5A _1, second (first 2 = 2nd) bonding side, i.e. the connection is thermocompression and ultrasonic vibration to the other end of the inner lead 3B and the coated wire 5 of the lead 3 the so-called thermo-sonic bonding using are conductively connected as second bonding portion 5A ₂ without prior removal of the coating film 5B.

The semiconductor chip 2 thus pellet-bonded and wire-bonded and the tab of the lead 3 are formed.
3A, the inner lead 3B, and the covering wire 5 are sealed with a resin material 6 such as an epoxy resin, for example.
Only the outer leads 3C protrude outside the resin material 6.

Next, the configuration and operation of the wire bonding apparatus for bonding the covered wire 5 in the present embodiment will be described mainly with reference to FIGS.

The wire bonding apparatus is configured as a so-called ball bonding apparatus. The ball bonding apparatus is configured to supply the covering wire 5 wound around the spool 11 to the bonding section 12 as shown in FIG. Have been.

That is, the supply of the covering wire 5 from the spool 11 to the bonding section 12 is performed through the tensioner 13, the wire guide member 14, the wire clamper 15, and the bonding tool (capillary) 16.

The resin-sealed semiconductor device 1 before resin sealing, which is configured as shown in FIG. 3 and FIG. Then, as shown in FIG. 3, the resin-encapsulated semiconductor device 1 before resin encapsulation is mounted on a semiconductor device support base (semiconductor device mounting table) 17 of a bonding apparatus.
It is supported by.

An external terminal 2C of the semiconductor chip 2 has a coating wire 5
Coating film 5B at one end is connected to the metal balls 5A ₁ formed by the exposed metal lines 5A been removed. Metal ball 5A ₁
Is configured to have a diameter that is, for example, about twice as large as the diameter of the metal wire 5A. The inner lead 3B of the lead 3 is connected to a metal wire 5A on the other end of the covered wire 5 that is exposed by breaking the covering film 5B on the other end of the covered wire 5 in the connection portion. That is, the other end side of the covering wire 5 is configured so that substantially only the covering film 5B at the connection portion with the lead 3 is removed, and the other covering film 5B remains. The coating film 5B on the other end side of the coating wire 5
As will be described later, the destruction can be performed by ultrasonic vibration, appropriate pressurization, and appropriate heating (energy) provided by the bonding tool 16.

As described above, in the resin-encapsulated semiconductor device 1 using the covering wire 5, the metal terminal 5 </ b> A formed on the one end side of the covering wire 5 is attached to the external terminal 2 </ b> C of the semiconductor chip 2.
5A ₁ is connected to the inner lead 3B of the lead 3, and the metal wire at the other end of the coated wire 5 in which the coating film 5B at the contact portion is broken.
By connecting 5A, the size of the metal balls 5 ₁ is large, that increases the contact area between the external terminals 2C of the semiconductor chip 2 and the metal wire 5A of the covered wire 5, to improve the bondability between the two The other end of the covered wire 5 other than the portion connected to the inner lead portion 3B of the lead 3 is covered with a covering film 5B, and the other end of the covered wire 5 adjacent to the other end of the covered wire 5 Since the short-circuit with the side can be reduced, the interval between the leads 3 can be reduced, and the number of terminals of the resin-encapsulated semiconductor device 1 (so-called multi-pin) can be increased.

Feed direction of the distal end portion of the bonding tool 16 and the insulated wire 5 (metal balls 5A ₁ forming portion), as shown in the FIGS. 3 and 4, during the formation of metal balls 5A _1, covering the covering member 18A It is configured to be. The covering member 18A is configured to rotate in the direction of arrow A shown in FIG. That is, the covering member 18A
, Upon formation of the metal balls 5A _1, and insert the bonding tool 16 from the tool insertion opening 18B by the rotation operation direction of the arrow A, and is configured so as to cover it.

This covering member 18A is shown in FIG. 5 (partial sectional view showing a specific configuration, corresponding to a section taken along the line VV in FIG. 6), FIG. 6 (from the direction of arrow VI in FIG. 5). FIG. 7 (a cross-sectional view taken along the line VII-VII in FIG. 6).
It is configured as shown by. As will be described later, the coating member 18A is a coating film 5B that melts when the metal ball 5A ₁ is formed.
It is configured such that the coating film 5B does not scatter to the bonding portion 12 by blowing away. When the metal wire 5A of the coated wire 5 is formed of an easily oxidizable material such as Cu or Al, the coating member 18A is configured to easily hold the coating gas atmosphere for preventing oxidation (shield gas atmosphere). I have. Covering member
18a is formed of, for example, stainless steel. Further, the covering member 18A is a state of formation of the metal balls 5A _1, etc. coated wire 5 so the operator can confirm, it may be formed of a glass material having transparency.

As shown in FIGS. 3, 4 and 5, an electric torch (arc electrode) 18D is provided on the bottom of the covering member 18A.
Is provided. The electric torch 18D is, as shown in FIG. 8 (a schematic configuration diagram illustrating the principle of forming a metal ball),
Close to the metal wire 5A on the tip side on the supply side of the coated wire 5,
It is configured to generate an arc Ac to form a metal ball 5A ₁ in between them. The electric torch 18D is formed of, for example, tungsten (W) that can withstand high temperatures.

Electric torch 18D is a suction device 1 made of conductive material
It is connected to the arc generator 20 via a suction pipe 18E to the pipe 9. The suction tube 18E is made of, for example, stainless steel, and fixes the electric torch 18D with an adhesive metal layer such as an Ag-Cu brazing material interposed therebetween. The suction tube 18E is fixed to the covering member 18A with the holding member 18F interposed therebetween.
That is, the electric torch 18D, the suction tube 18E and the covering member 18A
And are integrally formed.

The electric torch 18D is proximate the distal end of the supply side of the coated wire 5 when forming the metal balls 5A ₁ as described above,
It is configured to be movable in the direction of arrow A shown in FIG. 4 so that it can be separated from the supply path of the covering wire 5 during the bonding step. The moving device for moving the electric torch 18D mainly includes a support member 18G for supporting the electric torch 18D with the suction tube 18E and the insulating member 18H interposed therebetween, a crankshaft 18I for rotating the support member 18G in the direction of arrow A, A drive source 18K for rotating the crankshaft 18I is provided. The rotation of the crankshaft 18I is performed by the movement of the shaft 18J of the drive source 18K in the direction of the arrow B connected to the crank portion. Drive source 18K is formed of, for example, an electromagnetic solenoid. Although not shown, the crankshaft 18I is rotatably supported by the bonding apparatus main body. Note that the movement of the electric torch 18D and the movement of the covering member 18A are substantially the same because they are integrally formed.

As shown in FIG. 4, the arc generator 20 is mainly composed of a capacitor C ₁ , a storage capacitor C ₂ , a thyristor D for generating an arc activated by a trigger, and a resistor R. The DC power supply DC is configured to supply a negative polarity voltage of, for example, about -1000 to -3000 [V]. DC power supply DC is an electric torch 18D via thyristor D, resistor R, etc.
It is connected to the. The reference potential GND is, for example, a ground potential (= 0 [V]). V is a voltmeter and A is an ammeter.

As will be described in detail later, the metal wire 5A of the covering wire 5 is a spool.
The end wound around 11 is connected to the reference potential GND. As a result, when forming a metal ball 5A ₁ to the distal end portion of the covered wire 5 with electric torch 18D, FIG. 3, as shown in FIG. 4 and FIG. 8, an electric torch 18D negative potential (-), the coating The metal wire 5A at the distal end in the supply direction of the wire 5 can be set to a positive potential (+).

Thus, the arc Ac is generated between the metal wire 5A at the tip of the covered wire 5 and the arc electrode 18D, and the covered wire 5
In bonding apparatus for forming a metal ball 5A ₁ at the tip of the metal wire 5A of the covered wire 5 is connected to a positive potential (+), an electric torch 18D negative potential (-) by connecting to the coated wire The position of the arc Ac generated between the metal wire 5A and the electric torch 18D can be stabilized as compared with the case of the opposite polarity, so that the arc Ac is located behind the metal wire 5A of the coated wire 5. Crawling up to the end side can be reduced. The reduction of the crawling of the arc Ac reduces the melting of the coating film 5B of the coating wire 5,
The generation of spheres of the insulating coating film can be prevented.

Note that the present invention connects the metal wire 5A of the coated wire 5 to a voltage higher or lower than the reference potential GND so that the metal wire 5A of the coated wire 5 has a positive potential with respect to the electric torch 18D. You may.

The spool 11 around which the coating wire 5 is wound,
It is configured as shown in FIGS. 4 and 9 (an exploded perspective view of a main part). The spool 11 is formed by, for example, performing alumite treatment on a surface of a cylindrical aluminum metal. The alumite treatment is performed to improve mechanical strength and prevent scratches. As described above, the spool 11 has an insulating property because it is anodized.

The spool 11 is attached to a spool holder 21,
The spool holder 21 is attached to the bonding apparatus main body 10 by a rotation shaft 21A.

The spool holder 21 is made of, for example, stainless steel so that at least a part thereof has conductivity.

The spool 11 is provided with a connection terminal 11A as shown in FIGS. 9 and 11 (an enlarged perspective view of a main part). The connection terminal 11A is provided in a dotted shape on a side surface portion (flange) of the spool 11 that comes into contact with a conductive portion of the spool holder 21.

As shown in FIG. 10, the connection terminal 11A is configured such that a conductor 11Ab is provided on an insulator 11Aa, and a connection metal part 11Ac is provided on the conductor 11Ab. The insulator 11Aa is electrically separated from the conductor 11Ab and the spool 11 reliably, and furthermore, is made of, for example, a polyimide resin so as to have an appropriate elasticity so that the connection metal portion 11Ac can be reliably brought into contact with the spool holder 21. Form. The conductor 11Ab includes a connection metal part 11Ac for connecting the metal wire 5A of the covered wire 5 and a spool holder 21A.
It is formed of, for example, a Cu foil so that the connection metal portion 11Ac that comes into contact with the contact can be reliably connected. The connecting metal part 11ac is formed of a conductive paste, solder, or the like.

The connection terminal 11A passes through a notch formed in the side surface (flange) of the spool 11, and the metal wire 5A at the end of the sheath wire 5 opposite to the side supplied to the bonding portion 12, ie, the sheath wire 5A. Is configured to connect the metal wire 5A at the start end of the winding. This metal wire 5A is a metal part for connection.
Connected to the connection terminal 11A by 11Ac. Insulated wire 5
The coating film 5B on the surface of the metal wire 5A at the beginning of winding is heated or chemically removed. The connection terminal 11A, that is, the metal wire 5A of the covering wire 5 is connected to the reference potential GND through the spool holder 21, its rotating shaft 21A and the bonding apparatus main body 10. The reference potential GND is the arc generator 20.
Is the same as the reference potential GND.

Thus, by providing the spool 11 with the connection terminal 11A for connecting to the reference potential GND, and connecting the metal wire 5A at the winding start end of the covering wire 5 to this connection terminal,
Since the connection can be made to the reference potential GND through the spool holder 21 or the like, the metal wire 5A of the covering wire 5 can be reliably connected to the reference potential GND.

Further, the by metal wire 5A of coated wire 5 is connected to the reference potential GND, and during the formation of metal balls 5A _1, sufficient potential difference between the electric torch 18D and the metal wire 5A of coated wire 5 on the supply side reserved, since arcing Ac can be improved, it is possible to reliably form the metal ball 5A _1.

As shown in FIGS. 3 and 4, the bonding tool 16 is supported by a bonding head (digital bonding head) 22 with a bonding arm 16A interposed therebetween. Although not shown, the bonding arm 16A has a built-in ultrasonic vibration device, and is configured to ultrasonically vibrate the bonding tool 16. The bonding head 22 is supported by a base 24 with an XY table 23 interposed. The bonding head 22
A moving device capable of moving the bonding arm 16A in the vertical direction (the direction of arrow C) is provided so that the bonding tool 16 can be moved toward and away from the bonding section 12. The moving device mainly includes a guide member 22A, an arm moving member
22B, a female screw member 22C, a male screw member 22D, and a motor 22E. The guide member 22A is configured to move the arm moving member 22B in the direction of arrow C. The motor E is configured to rotate the male screw member 22D, move the female screw member 22C fitted with the male screw member 22D in the direction of arrow C by this rotation, and move the arm moving member 22B in the direction of arrow C by this movement. Have been.

Bonding arm 1 supported by arm moving member 22B
6A is configured to rotate around a rotation shaft 22F. The rotation of the bonding arm 16A about the rotation axis 22F is controlled by the elastic member 22G. This elastic member 22G
The rotation control is configured to prevent the bonding unit 12 from being pressed more than necessary when the bonding tool 16 comes into contact with the bonding unit 12, and to prevent damage or destruction of the bonding unit 12. I have.

The wire clamper 15 can hold the covering wire 5 and is configured to control the supply of the covering wire 5. The wire clamper 15 is provided on the bonding arm 16A with the clamper arm 15A interposed.

The wire guide member 14 is configured to guide the covered wire 5 supplied from the spool 11 to the bonding section 12. The wire guide member 14 is provided on the clapper arm 15A.

As shown in FIGS. 3 and 8, in the vicinity of the leading end of the covering wire 5 in the supply direction and in the vicinity of the supply path of the covering wire 5 between the bonding tool 16 and the bonding portion 12, as shown in FIGS. A fluid spray nozzle 18C of the fluid spray device 25 is provided. Fluid spray nozzles 18C, when forming the metal balls 5A ₁ with metal wire 5A of the distal end portion of the supply direction of coated wire 5, fluid from the fluid spray device 25 to the forming portion (metal lines 5A and coating film 5B) It is configured to spray Gs. Fluid Gs blown out from fluid spray nozzle 18C
As shown in FIG. 8, when forming a metal ball 5A ₁ with metal wire 5A of the distal end portion of the covered wire 5, blow coating film 5B rising melted by heat generated by the arc Ac (5Ba) so Is configured.

The fluid spray nozzle 18C may basically spray the fluid Gs on the tip portion of the bonding tool 16, that is, the tip portion of the coating wire 5 as described above. In the present embodiment, the fluid spray nozzle 18C is provided on the coating member 18A. ing. As shown in FIG. 4 to FIG. 7, the fluid spray nozzle 18C is provided with a fluid from the rear end side to the front end side of the coated wire 5 to reduce the melting of the coating film 5B. It is configured to spray Gs. The fluid spray nozzle 18C
Is preferably not attached to the bonding tool 16. When the fluid spray nozzle 18C is attached to the bonding tool 16, the weight of the bonding tool 16 increases, and the load of the ultrasonic vibration increases, so that the bondability of the connection portion decreases.

The fluid Gs uses a gas such as N ₂ , H ₂ , He, Ar, air,
As shown in FIG. 8, the fluid is supplied from a fluid spraying device (fluid source) 25 to a fluid spraying nozzle 18C via a cooling device 25A, a flow meter 25B, and a fluid transfer pipe 25C.

The cooling device 25A is configured to actively cool the fluid Gs below normal temperature. The cooling device 25A is configured by, for example, an electronic cooling device using the Peltier effect. The fluid transfer pipe 25C is shown in a simplified form in FIG. 8, but is configured to cover at least the space between the cooling device 25A and the supply port of the fluid spray nozzle 18C with a heat insulating material 25D. That is, the heat insulating material 25D is the fluid cooled by the cooling device 25A.
It is configured not to change the temperature of Gs during the movement of the fluid transport pipe 25C (to increase the cooling efficiency).

Further, in the vicinity of the leading end of the coating wire 5 in the supply direction, and at a position facing the fluid spray nozzle 18C around the melted portion of the coating film 5B of the coating wire 5,
A suction tube 18E connected to the suction device 19 is provided. As described above, the suction pipe 18E is also used as a conductor for connecting the electric torch 18D and the arc generator 20, but mainly the melting of the coated wire 5 blown off by the fluid spray nozzle 18C. It is configured to suck the coated film 5Ba. The coating film 5Ba sucked by the suction tube 18E is
The suction is performed by the suction device 19.

Further, in the present embodiment, only the inner lead 3B of the lead 3 is higher than the other parts in order to more securely bond (second bond) the other end of the covered wire 5 to the inner lead 3B of the lead 3. As shown in FIGS. 2 and 11, a ceramic heater 26 for locally heating to a temperature is provided in a square ring shape. Reference numeral 26A denotes this square ring-shaped heater 2 for local heating.
This is the feed line to 6.

Next, the wire bonding method of this embodiment will be briefly described.

First, as shown in FIG. 3, FIG. 4, FIG. 5, and FIG. 8, the bonding tool 16 and the leading end portion of the coating wire 5 protruding toward the pressing surface thereof in the supply direction are coated with a coating member 18A.
Cover with. This coating is performed by moving the coating member 18A in the direction of arrow A by the moving device operated by the driving source 18K. Further, by performing the coating with the coating member 18A, the electric torch 18D, the fluid spray nozzle
Each of the 18Cs can be placed near the tip of the coated wire 5.

Next, as shown in FIG. 8, an arc A is provided between the metal wire 5A at the end of the coating wire 5 in the supply direction and the electric torch 18D.
c is generated to form a metal ball 5A ₁ by the metal wire 5A. By arc Ac heat to form a metal ball 5A _1, the insulating coating film 5B of the supply direction of the distal end portion of the covered wire 5
Melts up. That is, the coating film 5B at the tip in the supply direction of the coating wire 5 is removed, and the metal wire 5A is exposed.

Formation of metal balls 5A ₁ is carried out in the shortest possible time.
Short, yet high energy to form a metal ball 5A ₁ in (current, each of the higher voltage region), the covered wire 5
Of the coating film 5B is reduced. in this way,
Short time formation of the metal balls 5A _1, be carried out at high energy, as described above, to stabilize arcing Ac, that is, the electric torch D negative potential (-) to the metal wire coated wire 5
This can be achieved by setting 5A to a positive potential (+).

When forming the metal ball 5A _1, sprayed fluid Gs from the fluid spray device 25 in the fluid spray nozzle 18C which position is set with the covering member 18A to dissolve up the coating film 5B covering the wire 5, 8 As shown in the figure, the coating film 5B is blown off. The blown coating film 5Ba is sucked by the suction device 19 through the suction pipe 18E, and is removed out of the system.

The fluid Gs from the fluid spray nozzle 18C is cooled to, for example, about 0 to -10 [° C.] by the cooling device 25A shown in FIG. Fluid Gs from fluid spray nozzle 18C
The lower the temperature is, the smaller the melting amount of the coating film 5B of the coating wire 5 is. That is, the fluid Gs cooled by the cooling device 25A
Since the metal wire 5A, the coating film 5B, the bonding tool 16 and the like of the coating wire 5 can be actively cooled,
Melt the coating film 5B only on the Ac generating part, and
5B is not melted, and as a result, the amount of melting of the coating film 5B can be reduced.

Next, the covering member 18A and the electric torch 1
8D, and each of the fluid spray nozzles 18C is moved in the direction of arrow A (the direction opposite to the above).

Next, a metal ball 5A ₁ formed on the pressing surface of the bonding tool 16 at the tip end in the supply direction of the covering wire 5 is formed.
Attraction.

Next, in this state, the bonding tool 16 is moved closer to the bonding portion 12, and as shown by the broken line in FIG. 2, the metal ball 5A ₁ formed at the tip of the covering wire 5 in the supply direction. To the external terminal 2C of the semiconductor chip 2 (fast bonding: 1s
t). This metal ball 5A ₁ connection is a bonding tool
16 ultrasonic vibrations and / or thermocompression bonding (one or the other).

Next, as shown in FIG. 2, the metal wire 5A at the rear end of the covered wire 5 is connected to the inner lead 3B of the lead 3 by a bonding tool 16 (second bonding: 2n).
d). The connection on the rear end side of the covered wire 5 is performed by ultrasonic vibration and thermocompression bonding of the bonding tool 16 (the former may be used alone).
Do with. Thus, the rear end of the insulated wire 5 and the inner leads 3B at second bonding portion 5A _2, are firmly wedge Bonn Dink.

The connection at the rear end side of the coated wire 5 is such that the coated wire 5 at the connection portion is coated in advance with the coating film 5B, but the coating film 5B only at the connection portion is formed by ultrasonic vibration of the bonding tool 16. It is destroyed, and the metal wire 5A is exposed. Although there is a slight change depending on the energy of the ultrasonic vibration of the bonding tool 16 and the thermocompression force, the coating film 5B of the coating wire 5 is preferably, for example, about 0.2 to 3 [μm] thick. When the thickness of the coating film 5B of the coating wire 5 is too small, the withstand voltage as the insulating coating film is small. If the thickness of the coating film 5B of the coating wire 5 is too large, the coating film 5B is less likely to be broken by the ultrasonic vibration of the bonding tool 16, and the coating film 5B has a predetermined value. If it exceeds, the coating film 5B will not be destroyed, resulting in poor connection between the metal wire 5A of the coating wire 5 and the inner lead 3B of the lead 3.

In this embodiment, when the other end of the covered wire 5 is bonded (second bonding), only the inner lead 3B of the lead 3 is locally heated by the heater 26 to a temperature which is particularly higher than the other portions. Since the heating / decomposition of the covering film 5B is further promoted, the bondability of the second bonding can be improved, and strong wire bonding can be performed.

Thereafter, the bonding tool 16 is separated (at this time, the covering wire 5 is cut), thereby completing one bonding step of the covering wire 5 as shown in FIG.

Thus, the metal ball 5A ₁
In the bonding technique for forming a wire, fluid Gs is applied to the tip of the covered wire 5 near the tip of the covered wire 5.
By providing a fluid spray nozzle 18C (a part of the fluid spray device 25) for spraying the coating wire 5B, the coating film 5B that melts the coating wire 5 can be blown off. Can be prevented from being formed. As a result, the coated wire 5 is prevented from being caught by the bonding tool 16 due to the sphere of the insulating coating film 5B, and the coated wire 5 can be drawn to the pressing surface of the bonding tool 16, so that ball bonding is performed. And bonding defects can be prevented.

Further, a bonding technique to form a metal ball 5A ₁ to the distal end portion of the covered wire 5, wherein the fluid spray nozzle 18
C (a part of the fluid spraying device 25) is provided, and a suction pipe for sucking a coating film 5B of the coated wire 5 blown off by spraying the fluid Gs from the fluid spray nozzle 18C near the tip of the coated wire 5. By providing 18E (suction device 19)
Blow off the coating film 5B, which melts the coating wire 5,
The sphere of the coating film 5B is prevented from being formed on the coating wire 5 and the bonding failure can be prevented as described above, and the blown coating film 5Ba is not scattered to the bonding portion 12, so that the scatter is prevented. It is possible to prevent bonding failure caused by the applied coating film 5Ba. The bonding failure caused by the scattered coating film 5Ba is, for example, that the coating film 5Ba is scattered between the external terminal 2C of the semiconductor chip 2 or the inner lead 3B of the lead 3 and the metal wire 5A of the coating wire 5. However, this is the case where conduction failure occurs between the two.

Further, a bonding technique to form a metal ball 5A ₁ to the distal end portion of the covered wire 5, wherein the fluid spray nozzle 18
By providing C (fluid spray device 25) and cooling device 25A for cooling the fluid Gs of the fluid spray nozzle 18C, melting of the insulating coating film 5B of the coated wire 5 is significantly reduced, and Even in this case, since the coating film 5B can be blown off, it is possible to prevent the sphere of the coating film 5B from being formed on the coating wire 5 and prevent the bonding failure as described above.

In the bonding technique using the covered wire 5, a metal ball 5A
_Then , the metal ball 5A ₁ is connected to the external terminal 2C of the semiconductor chip 2, the rear end side of the covering wire 5 in the supply direction is brought into contact with the inner lead 3B of the lead 3, and the contact portion is covered. A covering film for removing the covering film 5B on the rear end side of the covering wire 5 by breaking the covering film 5B and connecting the metal wire 5A on the other end side of the covering wire 5 to the inner lead 3B of the lead 3. Since the coating film 5B can be removed without using a removing torch, it is possible to reduce the coating film removing torch, its moving device, control device, and the like. As a result, the structure of the bonding apparatus can be simplified.

In particular, in the semiconductor device 1 of the present embodiment, a heat-resistant polyurethane containing a structural unit derived from terephthalic acid in the molecular skeleton is used as the insulating coating film 5B of the coating wire 5 by reacting a polyol component with an isocyanate. As a result, it is possible to reliably prevent a tab short, a chip short, or a short between wires due to film destruction caused by thermal differentiation of the coating film 5B.

That is, after bonding the covering wire 5 as described above, a range molding operation is performed with the resin material 6 to manufacture the resin-sealed semiconductor device 1. For example, as shown in FIG. When the distance between the external terminal 2C of the chip 2 and the bonding portion of the inner lead 3B of the lead 3 is long, as shown in FIG.
A so-called chip touch state in which the silicon wire of the semiconductor chip 2 contacts with the so-called chip touch state, or a so-called tab touch state in which the covering wire 5 and the tab 3A contact each other as shown in FIG.
Further, a so-called wire-to-wire touch state where the coated wires 5 come into contact with each other may occur. Such a wire touch phenomenon tends to occur particularly when the wire length becomes 2.5 mm or more, or when the size of the tab 3A is larger than the size of the semiconductor chip 2.

When such a wire touch phenomenon occurs, for example, as shown in FIG. 14, the coating film 5B of the coating wire 5 is broken by thermal deterioration caused by heat generation from the semiconductor chip 2, and the metal wire 5A is 2 is in direct contact with the semiconductor chip 2
In some cases, a short-circuit between the wires may occur, or as shown in FIG. 16, a short-circuit between the tabs 3A may occur, and a short-circuit between the wires may occur.

However, in the semiconductor device 1 of the present embodiment, as described above, since the coating film 5B of the coating wire 5 is made of a special heat-resistant polyurethane, it is temporarily assumed that the chip touch, the tab touch or the wire Even if a touch state occurs, it is possible to reliably prevent a short circuit from occurring.

In order to confirm the effect of preventing short-circuit failure according to the present invention, the results of an experiment performed by the present inventors on a semiconductor device after resin sealing will be described below as Experimental Example 1. Parts in the experimental examples indicate parts by weight.

Experimental Example 1 First, raw materials as shown in Table 1 below were blended in a ratio as shown in the table, and this was put into a 500 cc flask.
A thermometer and a steam condenser were attached and reacted to obtain three types of terephthalic acid-based polyols P-1, P-2 and P-3. Table 1 also shows the ratio of terephthalic acid and ethylene glycol and the reaction time at this time. The end point of the above synthesis reaction was determined based on theoretical reaction water and an acid value of 5 or less. In this case, a reduced pressure reaction was performed as needed.

Using the three types of terephthalic acid-based polyols P-1, P-2, P-3 obtained as described above and commercially available polyols, these polyol components and isocyanate components are shown in Table 2 below. A coating composition was prepared by blending at such a ratio. Then, the coating composition thus obtained was diluted to a concentration of 10% using a solvent, and 2 μm
Apply at least 175 ° C for 21 minutes, then 170 ° C
For 2 hours to form an insulating film made of heat-resistant polyurethane, followed by wire drawing. The composition and coating film properties in this case are shown in Table 2 below.

Next, using the heat-resistant polyurethane-coated wire obtained as described above, the semiconductor chip wire-bonded as described above is molded with a resin material, and FIG. 13 (chip touch state) and FIG. 15 (tab touch state). A semiconductor device corresponding to the touch state shown in Fig. 1 was manufactured, a temperature cycle test of MIL-883B was performed, and a short-circuit rate with a semiconductor device using a commercially available polyurethane-coated wire was compared to evaluate the improvement of the present invention. did.

The results of this comparative experiment were as shown in FIG. 17 and FIG. That is, FIG. 17 shows the short-circuit rate between the semiconductor chip and the coated wire in the chip touch state as shown in FIG. 13. As is clear from FIG. 17, the semiconductor using the heat-resistant polyurethane-coated wire of the present invention was used. In the device, a remarkable short-circuit rate, that is, a chip short-circuit preventing effect was confirmed as compared with a semiconductor device using a commercially available polyurethane-coated wire.

FIG. 18 shows the short-circuit rate between the tab and the coated wire in the tab chip state as shown in FIG. 15, but also in this case, the semiconductor device using the heat-resistant polyurethane-coated wire of the present invention has a remarkable short-circuit. Rate, that is, a tab short prevention effect was obtained.

Next, the present inventors compared the heat-resistant polyurethane-coated wire according to the present invention and a commercially available polyurethane-coated wire in a wire state before resin sealing under the test conditions described below,
The wear strength and the deterioration rate of the coating film were evaluated. The results of these experiments and other various experiments are described below in Experimental Examples 2 to 5.
19 to 25 will be described.

Experimental Example 2 Experimental conditions were represented by a model diagram shown in FIG. That is, a constant load (1 g) is hung on the lower edge of the insulated wire 5 whose outer surface is coated with the insulating coating film (heat-resistant polyurethane of the present invention or commercially available polyurethane) 5B to make a vertically suspended state. Then, the tab 3A of the lead frame is brought into contact with the coated wire 5 at the edge thereof at a contact angle α = 45 degrees, and the load is applied to the coated wire 5 in the horizontal direction from the side opposite to the tab edge contact portion with a load W ₁ (0.65 g). By applying a pressing force and vibrating the tab 3A vertically by 20 μm,
The wear of the coating film 5B was evaluated.

Here, the amplitude (vibration) frequency Nf until the coating film 5B wears and breaks is defined as a wear strength and evaluated.

In addition, the heat resistance of the coating film 5B is high temperature storage (150-200 ° C,
(0 to 1000 hours).

As a result, it has been found that, in the case of polyurethane, thermal degradation can be greatly suppressed by imidizing the polyurethane, and the temperature cycle life T∞ can be significantly improved.

 Hereinafter, these experimental results will be specifically described.

First, FIGS. 20 and 21 show the thermal deterioration of the wear strength of the coating film 5B at 150 ° C. and 175 ° C., respectively (reduction of the number of coating film breakage after 100 hours). As is apparent from these figures, in the case of the coating film using the heat-resistant polyurethane of the present invention, the wear strength Nf even after the high-temperature leaving time has elapsed.
Was found to be small, and the deterioration of the coating film was very small. In particular, it was found that the fact that the rate of deterioration of the coating film 5B in reducing the number of times the coating film was destroyed after 150 to 175 ° C for 100 hours (Hrs) was within 20% was an extremely advantageous characteristic for the coated wire.

Experimental Example 3 Next, FIG. 22 shows the experimental results of the relationship between the temperature (horizontal axis) and the deterioration rate, that is, the deterioration rate [ΔNf / 100Hrs] (= N ₀ −N ₁₀₀ / 100Hrs) (vertical axis). is there. Also in this figure,
It is understood that the degradation rate of the heat-resistant polyurethane-coated wire of the present invention is much smaller than that of the commercially available polyurethane.

Experimental Example 4 Next, FIG. 23 shows the imidization ratio (horizontal axis) of the coating film, the degradation rate, that is, the deterioration rate (vertical axis on the left), and the peel strength of the second (2nd) bonding of the coated wire (vertical axis on the right). It is an experimental result showing the relationship with.

The peel strength of the 2nd bonding was determined by the inventors of the present invention using a heat-resistant polyurethane-coated wire having a diameter of φ = 25 μm and bonding the inner film 3B to the inner lead 3B without previously peeling the coating film 5B as shown in FIG. This is the result of performing.

As is clear from FIG. 23, the imidization ratio of the coating film is about
1/3 is preferable for both the deterioration rate (deterioration rate) and the peeling strength.

In particular, in the case of the heat-resistant polyurethane-coated wire of the present invention,
Since the peel strength of the 2nd bonding part was large, the reliability of bonding was high and an extremely advantageous result was obtained.

Experimental Example 5 FIG. 24 shows the experimental results on the temperature cycle amplitude (−55 to 150 ° C.) and the temperature cycle life of the coated wire. As is clear from the figure, the service life T の of the coating film made of a commercially available polyurethane is about 400, while that of the heat-resistant polyurethane of the present invention is greatly improved to 4000 or more.

Experimental Example 6 FIG. 25 is a diagram showing the results of an experiment on the effect of the presence or absence of a coloring agent on the coating film of a coated wire on the deterioration rate (deterioration rate).

According to the knowledge of the present inventors, when performing bonding using the covered wire 5, for example, when forming a metal ball, since the thickness of the covering film 5B is very thin, it is determined whether or not the coating film 5B melts or peels. It is very difficult to confirm, and at least it is impossible with the naked eye. Therefore,
The present inventors have found that if a coloring agent such as oil scarlet is added to the coating film 5B, the dissolution or peeling thereof can be visually confirmed (for example, by using an electron microscope), and is extremely useful. .

However, if the amount of the coloring agent added is too large, the deterioration rate (deterioration rate) of the coating film increases, and the present inventors conducted various experiments on the appropriate amount, and as a result, Is shown in FIG.

As is clear from the experimental results shown in FIG. 25, when the amount of the colorant added is too large, the deterioration rate (deterioration rate) of the coating film increases, while when the amount is too small, the above-mentioned results are obtained. The merit of adding such a coloring agent is lost. So, in light of these two conflicting requirements,
As a result of extensive studies by the present inventors, the amount of the coloring agent (in this example, oil scarlet) was 2.0% by weight or less,
In particular, it became clear that 0.5% by weight to 2.0% by weight was optimal. By adding a colorant to the coating film in this range, the advantage that the coating film can be visually confirmed as melting or peeling from the coating wire while preventing the characteristics of the coating film from being impaired is obtained. Can be

The present inventors have obtained the following findings through Experimental Example 1, further Experimental Examples 2 to 6, and various other experiments, studies, studies, and confirmations.

That is, as described above, the use of the heat-resistant polyurethane having the above composition of the present invention as the coating film of the coated wire is extremely useful for the thermal deterioration of the coating film, the bonding property, and the improvement of the peeling strength of the bonding.

In addition to this, as is clear from, for example, Experimental Example 2 and the like, the thermal degradation (degradation rate) of the coating film, that is, the abrasion test under the experimental conditions shown in FIG. It is extremely important to use a material that can reduce the degradation rate within 20% in reducing the number of times the coating film is destroyed after 100 hours at 150 ° C. to 175 ° C. as a constituent material of the coating film.

In addition, as a characteristic to be provided as a coating film, it is also very important that the coated wire does not cause a problem in bonding property when the coated wire is put to practical use in a wire bonding operation. The present inventors have conducted intensive studies on this point. As a result, it is important that the coating film is made of a material that exhibits non-carbonization, for example, when forming metal balls in ball bonding or when removing the coating film by heating. It has been found.

The reason is as follows. In other words, the coating film melts immediately above the metal ball when forming the metal ball or removing the coating film by heating, but if the coating film is carbonized, the coating film is decomposed by the heating temperature at that time, for example, a high temperature of 1060 ° C. Instead, it is carbonized. As a result, the carbonized coating film adheres and remains on the metal ball just above the metal ball so as to wrap the metal wire.When bonding with a bonding tool, the carbonized coating film is supplied by the coated wire passing through the capillary. This makes it difficult or impossible for the coated wire to pass through the capillary. On the other hand, if the deposited carbonized coating film falls on the integrated circuit forming surface of the semiconductor chip for some reason, the carbide has conductivity, and the dropped object causes an electrical short-circuit failure of the integrated circuit. It is. In addition, it has been found that the coated wire to which the carbide has adhered causes a bonding failure, for example, also at the time of the second bonding to the inner lead.

Considering such facts comprehensively, as the coating film of the coated wire, the deterioration rate under the above-mentioned predetermined conditions, ie, 150 ° C. to 175 ° C., in reducing the number of times of coating film destruction after 100 hours It is extremely important that the deterioration rate is within 20% and that these two requirements are non-carbonized at the time of forming the metal ball or removing the coating film by heating. It has been confirmed by the inventors that very satisfactory results can be obtained as a coated wire.

According to the study results of the present inventors, the heat-resistant polyurethane having the above-described composition is, of course, one that satisfies these two requirements. However, the material that satisfies these two requirements is only the heat-resistant polyurethane having the above-described composition. The material is not limited, and a heat-resistant polyurethane having another composition, or a material other than the heat-resistant polyurethane, can be used as the material of the preferable coating film.

In this regard, among polyurethanes, commercially available polyurethanes and formals satisfy the requirement of non-carbonization, but are not suitable as coating films because the above-mentioned deterioration rate exceeds 20%.

On the other hand, polyimide, polyamide, nylon, polyester, polyamide imide, polyester imide and the like exhibit carbonization when forming metal balls or when the coating film is removed by heating, so that they are unsuitable for use as a coating film for a coated wire. It turned out that there was.

Next, the present invention will be further described with reference to FIGS. 26 to 30 showing other various embodiments of the wire bonding method which can be used in the present invention.

In the embodiment of Example 2 FIG. 26, as an example of another wire bonding method included in the present invention, the ball also by metal balls 5A ₁ first of the covered wire 5 (1st) bonding side as in Example 1 The bonding method is as follows. On the second (2nd) bonding side, the coating film 5B is removed in advance before the second bonding as shown in the figure as a second bonding portion 5A ₂₂ , and the second bonding is performed by thermocompression bonding and / or ultrasonic vibration. Is what you do.

Then Example 3, in the embodiment of Figure 27, in addition to second bonding portion 5A ₂ are bonded without removing the same coating film 5B to Example 1, also the first bonding side rather than ball bonding by metal balls, the coating film 5B and the first bonding by thermocompression and / or ultrasonic vibration method without prior removal, to form the first bonding portion 5A _11.

Therefore, in the present embodiment, the same bonding method is used for both the first and second bonding.

Example 4 Further, examples of FIG. 28 is first bonding portion 5A ₁₁ are the same as in Example 3, like-second bonding portion 5A ₂₂ Example 2, previously removed covering film 5B Is bonded.

Example 5 In the embodiment of Figure 29, as the first bonding portion 5A _12, the previously removed the bonding method of the coating film 5B, similarly second bonding portion 5A ₂ and Examples 1 and 3, the coating The bonding is performed without removing the film 5B.

Example 6 Further, in the embodiment of Figure 30, bonded in a non-ball formation method of the metal wire 5A the state in which the previously removed covering film 5B of the first bonding portion 5A ₁₂ and second bonding portion 5A ₂₂ Here is an example.

Embodiment 7 FIG. 31 is a partial sectional view showing a wire bonding portion according to another embodiment of the present invention.

In this embodiment, the coating film of the coating wire 5 has a composite coating film structure. That is, the outer surface of the covering wire 5 is covered with the covering film 5B made of the above-described heat-resistant polyurethane, and the outer surface of the covering film 5B is further covered with a second covering film 5C made of another insulating material. This is an example of coating with.

As the material of the second coating film 5C, as described above, a polyamide resin, a special polyester resin, a special epoxy resin, or the like can be used. For the purpose of improving the slipperiness of the coated wire in the capillary using nylon or the like, a second coating film can be applied.

Further, the thickness of the second coating film 5C can be set to twice or less, preferably 0.5 times or less of the thickness of the coating film 5B.

As described above, the invention made by the inventor has been specifically described based on the embodiments. However, the present invention is not limited to the embodiments, and it can be said that various modifications can be made without departing from the gist of the invention. Not even.

For example, the materials for forming the coating film 5B or 5C, such as the polyol component, isocyanate, terephthalic acid, and the compounds thereof, and the types and compositions of the additives are not limited to those described above.

Further, the material of the metal wire 5A of the covered wire and the bonding method thereof are not limited to the examples described above.

Further, the structure of the wire bonding apparatus used for carrying out the present invention is not limited to the above-described example.

In the above description, the case where the invention made by the present inventor is applied to a resin-encapsulated semiconductor device as a field of application has been mainly described. However, the present invention is not limited to this. Can be widely applied to various semiconductor devices and their manufacturing techniques.

〔The invention's effect〕

The effects obtained by the representative inventions among the inventions disclosed in the present application will be briefly described as follows.

(1). A method for manufacturing a semiconductor device, comprising connecting a lead and an external terminal of a semiconductor chip by a covered wire in which a surface of a metal wire is covered with an insulating covering film, wherein the covering film of the covered wire is a polyol component. Is reacted with isocyanate, and is made of heat-resistant polyurethane containing a structural unit derived from terephthalic acid in a molecular skeleton. One end of the coated wire is connected to the external terminal of the semiconductor chip, and the other end is connected to a lead. By doing so, it is possible to prevent the coating film from being destroyed due to thermal deterioration, so that it is possible to reliably prevent the occurrence of electrical short-circuit defects such as tab shorts, chip shorts, and short-circuits between the wires. Can be.

(2). Even if the coated wire bends, the coating film does not crack or peel off, and a highly reliable semiconductor device without wire failure can be obtained.

(3). Since the urethane bond of the heat-resistant polyurethane constituting the coating film is decomposed at the bonding temperature during normal wire bonding or at the ultrasonic vibration energy to enable bonding, thermocompression bonding by normal heating and / or ultrasonic vibration is performed. A strong bonding can be performed.

(4). According to the above (3), since the coating film is not carbonized,
It is possible to prevent carbide from hindering the passage of the coated wire to the capillary, to prevent the coated wire from dropping on the integrated circuit and cause an electrical short circuit, and to prevent the carbide from deteriorating the wire bonding property.

(5). According to the above (3), reliable wire bonding can be performed even with an ordinary wire bonding apparatus. In particular, if the wire bonding apparatus shown in the above embodiment is used, extremely reliable wire bonding can be performed.

(6). According to the above (1), it is possible to realize a multi-terminal (multi-pin) semiconductor device using a covered wire.

(7). A semiconductor device comprising an external terminal of a semiconductor chip and a lead connected by a coated wire in which the surface of a metal wire is coated with an insulating coating film, wherein the coating film of the coated wire comprises a polyol component and an isocyanate. React
By using a heat-resistant polyurethane containing a structural unit derived from terephthalic acid in the molecular skeleton, it is possible to obtain a semiconductor device free from electrical short-circuit failure due to thermal deterioration of the coating film.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a resin-sealed semiconductor device according to an embodiment of the present invention, FIG. 2 is a schematic enlarged sectional view of a wire bonding portion, and FIG. 3 is wire bonding which can be used in the present invention. FIG. 4 is a perspective view of a main part of the apparatus, FIG. 5 is a partial sectional view showing a specific structure of a main part of the wire bonding apparatus, and FIG. 6 is a view from the direction of arrow VI in FIG. FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 6, FIG. 8 is a schematic configuration view showing the principle of forming metal balls, and FIG. 9 is a spool of the wire bonding apparatus. FIG. 10 is an enlarged perspective view of a main part of the spool, FIG. 11 is a schematic plan view of a local heating unit for wire bonding, FIG. 12 is a plan view showing an example of wire bonding, FIG. Fig. 13 is a partial cross section showing the tip of the coated wire FIG. 14, FIG. 14 is an enlarged partial cross-sectional view showing a chip short state, FIG. 15 is a partial cross-sectional view showing a tab touch state of the coated wire, FIG. 16 is an enlarged partial cross-sectional view showing a tab short state, FIG. FIG. 18 is a diagram showing a short-circuit rate between a semiconductor chip and a coated wire with respect to a temperature cycle in the present invention. FIG. 18 is a diagram showing a short-circuit rate between a tab and a coated wire with respect to a temperature cycle in the present invention. FIG. 20 is a model diagram showing the experimental conditions used in the evaluation of the coating film of the coated wire to be used, FIG. 20 and FIG. 21 are diagrams respectively showing the results of a comparative experiment of the wear strength of the coating film in the present invention, FIG. FIG. 23 is a diagram showing experimental results on the relationship between temperature and deterioration rate in the present invention, and FIG. Second (2n d) Diagram showing the experimental results on the relationship with the peel strength of bonding (vertical axis on the right), FIG. 24 shows the experimental results on the temperature cycle amplitude and temperature cycle life of the coated wire, and FIG. 25 shows the coating FIG. 26 is a diagram showing the effect of the presence or absence of a coloring agent on the wire coating film on the deterioration rate (deterioration rate). FIGS. 26 to 30 show other various embodiments of the wire bonding method that can be used in the present invention. FIG. 31 is a partial sectional view of a wire bonding portion showing a composite coating film structure according to another embodiment of the present invention. 1 ... semiconductor device, 2 ... semiconductor chip, 2A ... substrate,
2B: Passivation film, 2C: External terminal (bonding pad), 3: Lead, 3A: Tab, 3B: Inner lead, 4: Bonding material, 5: Coated wire, 5A:
Metal wire, 5A ₁ … Metal ball, 5A ₁₁ , 5A ₁₂ … First bonding part, 5A ₂ , 5A ₂₂ … Second bonding part, 5B, 5Ba… Coating film, 5C… Second coating film , 6 ... resin material, 10 ... bonding device body, 11 ... spool,
11A Connection terminal, 11Aa Insulator, 11Ab Conductor, 1
1Ac ... Connection metal part, 12 ... Bonding part, 13 ...
Tensioner, 14 Wire guide member, 15 Wire clamper, 16 Bonding tool (capillary), 16A
…… Bonding arm, 17… Support base (semiconductor device mounting table), 18A… Coating member, 18B… Tool insertion port, 18C …… Fluid spray nozzle, 18D …… Electric torch (arc electrode), 18E …… Suction tube, 18F …… Nipping member, 18G…
… Supporting member, 18H …… Insulating member, 18I …… Crankshaft, 18
J …… Shaft, 18K …… Drive source, 19 …… Suction device, 20…
... Arc generator, 21 ... Spool holder, 21A ... Rotary shaft, 22 ... Bonding head (digital bonding head), 22A ... Guide member, 22B ... Arm moving member, 22C ... Female screw member, 22D ... Male thread member, 22E ……
Motor, 22F ... rotary shaft, 22G ... elastic member, 23 ... XY table, 24 ... base, 25 ... fluid spray device (fluid source),
25A …… Cooling device, 25B …… Flow meter, 25C …… Fluid transport pipe, 25D …… Insulation material, 26 …… Heater, 26A …… Power supply line, C ₁
…… Capacitor, C ₂ …… Storage capacitor, D …… Arc thyristor, R …… Resistance, DC …… DC power supply, G
ND: Reference potential, V: Voltmeter, A: Ammeter.

Claims (3)

(57) [Claims] 1. A method of manufacturing a semiconductor device, comprising connecting a lead to an external terminal of a semiconductor chip by a covered wire in which a surface of a metal wire is covered with an insulating covering film. The covering film is made of a heat-resistant polyurethane containing a structural unit derived from terephthalic acid in a molecular skeleton by reacting a polyol component and an isocyanate, and connecting one end of the covering wire to the external terminal of the semiconductor chip; A method for manufacturing a semiconductor device, comprising connecting an end to the lead. 2. The semiconductor device according to claim 1, wherein said coating film on said one end side of said coating wire is removed when a metal ball is formed, and said metal ball is connected to said external terminal of said semiconductor chip. A method for manufacturing a semiconductor device. 3. A semiconductor device in which external terminals of a semiconductor chip and leads are connected by a covering wire in which the surface of a metal wire is covered with an insulating covering film, wherein the covering film of the covering wire is A semiconductor device comprising a heat-resistant polyurethane containing a structural unit derived from terephthalic acid in a molecular skeleton by reacting a polyol component with an isocyanate.