JPH02263447A - Bonding wire for semiconductor element - Google Patents

Abstract

PURPOSE:To effectively prolong the fatigue life of a gold wire by making germa nium and calcium of a specified weight % act with each other and together with high purity gold in a synergistic manner. CONSTITUTION:Outer terminals 2C of a semiconductor chip 2 are mutually and electrically connected by an inner lead 3B of a lead 3 and a conductive wire; a covered wire 5 is used as the conductive wire. Material of a gold wire 6A of the covered wire 5 is high purity gold (Au) of, e.g. 99.99wt.% or more, which contains 0.03-0.3wt.% germanium (Ge) and 0.0005-0.01wt.% calcium (Ca). As a result, germanium and calcium mutually act with each other and together with high purity gold in a synergistic manner, so that the fatigue life of the gold wire can be effectively prolonged. Thereby the fatigue life of the gold wire is prolonged, and so-called neck-cut can be prevented.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a bonding wire for semiconductor devices, particularly a bonding wire used to connect a chip bridge and a lead of a semiconductor device, The present invention relates to a bonding wire particularly suitable for bonding methods.

[Conventional technology]

Gold (Au) is used as a bonding wire for semiconductor devices.
Those made from are widely used. In particular, so-called pole bonding technology is widely used to electrically connect electrodes of a semiconductor chip and inner leads in resin-sealed semiconductor devices. This technology forms a gold ball at the tip of the supply side of the gold wire, uses thermocompression bonding or thermocompression bonding in combination with ultrasonic vibration to bond the gold ball to the electrode of the semiconductor chip, and then heats the rear end of the gold wire. This is a technology that uses ultrasonic vibration in combination with crimping or thermocompression bonding to bond to the inner lead and make an electrical connection.

By the way, the gold wire used in resin-sealed semiconductor devices has a total of 99.99% by weight or more of high-purity gold (Au), intentionally added elements, and unavoidable elements after gold refining.
．． 0.01% by weight or less. The purpose of intentionally adding elements to gold wire is mainly to improve mechanical properties such as breaking load and elongation, heat resistance, and bonding properties.

Nao, conventionally, germanium (Ge) was intentionally added to gold wire.
Examples of modifying and improving gold wire by incorporating calcium (Ca) include, for example, Japanese Patent Laid-Open No. 56-76556 and Japanese Patent Laid-Open No. 56-96844.

[Problem to be solved by the invention]

The above-mentioned conventional technology reduces mechanical strength deterioration and disconnection caused by coarsening of crystal grains in the neck directly above the ball due to thermal effects during the formation of gold wire balls, or decreases the lifespan and fatigue disconnection of the neck in temperature cycle tests. Or, it is a means to solve problems such as short circuits caused by contact between adjacent wires, short circuits caused by contact between wires and the edges of semiconductor chips, etc. caused by instability of the bond loop shape of gold wires due to insufficient mechanical strength. However, no satisfactory and effective improvement has yet been achieved.

Therefore, the inventors of the present invention conducted further intensive research and found the following.

One of them is the issue of fatigue life of gold wire.

That is, when a resin-sealed semiconductor device is subjected to a temperature change, the gold wire is pulled and subjected to strong stress due to the difference in thermal expansion coefficient between the gold wire and the resin, which are in close contact with each other inside the device. It has been discovered that by repeatedly undergoing these temperature changes (temperature cycles), stress is concentrated in the neck part directly above the ball when ball bonding is performed in conventional gold wires, making fatigue wire breakage more likely. This means that when a ball is formed at the tip of a gold wire using a method such as arc discharge or hydrogen flame, the neck part is affected by heat and the crystal grains in that part become coarse.
The biggest factor is thought to be the difference in crystal grain size between the neck and the subsequent part.

However, in the above-mentioned conventional technology, the content of elements such as germanium and calcium contained in the gold wire was not optimal, so it cannot be said that the prevention of neck breakage has always been successful.

The second problem is ensuring mechanical properties such as breaking load and elongation rate of the gold wire.

That is, in conventional gold wires, heat treatment is applied to increase the elongation rate of the gold wire and remove stress at the neck portion. However, by increasing the elongation rate of the gold wire, the breaking load This results in a significant decrease in the bonding process, resulting in a problem that makes the bonding work less practical.

Thirdly, there are problems associated with long-distance bonding and thinning of wires.

In other words, due to the recent increase in the density of semiconductor devices, the distance between adjacent bonding wires has been shortened, and the distance between external terminals and inner leads of semiconductor chips has become longer. Short circuits are likely to occur due to contact between adjacent wires, or short circuits due to contact between wires and the ends of the semiconductor chip, which occur due to the flow of the resin material.

In addition, since it is necessary to perform long-distance bonding in a multi-bin semiconductor device, thinning of the wire and use of small gold balls are desired.

One object of the present invention is to increase the fatigue life of gold wire and
The object of the present invention is to provide a technology that can prevent so-called neck breakage.

Another object of the present invention is to provide a technique that can ensure mechanical properties such as breaking load and elongation rate of gold wire.

Still another object of the present invention is to provide a technique suitable for long-distance bonding.

Still another object of the present invention is to provide a technique suitable for realizing line thinning.

Still another object of the present invention is to provide a technique suitable for performing ball bonding of gold wire.

Still another object of the present invention is to provide a technique suitable for realizing a small ball portion when performing ball bonding of gold wire.

Still another object of the present invention is to provide a technique that can improve the reliability of wire bonding.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the bonding wire for semiconductor devices of the present invention has a high purity gold of 99.99% by weight or more, and a bonding wire of 0.03 to 0.
．． 3% by weight germanium and 0.0005-0.01
% by weight of calcium.

The content of germanium and calcium is 0.05 each.
~0.15% by weight and 0.001-0.003% by weight
It can be done.

The bonding wire for a semiconductor device according to the present invention can be a coated wire coated with an insulating material.

Moreover, heat-resistant polyurethane resin can be used as this insulating material.

Furthermore, the bonding wire for semiconductor devices of the present invention includes:
Breaking load of 15-30 kg/mm' and 10-30 kg/mm'
It may have an elongation rate of 25%.

[Effect]

The above-described bonding wire for semiconductor devices of the present invention includes:
0.03-0.3% by weight germanium and 0,000
5 to 0.01% by weight of calcium and each other and 9
By working synergistically with high-purity gold of 9.99% by weight or more, it can effectively extend the fatigue life of the gold wire and also prevent coarsening of crystal grains in the neck part during ball formation. This makes it possible to prevent neck breakage.

In addition, by covering the semiconductor device ball of the present invention with an insulating material, it is possible to prevent wire-to-wire shorts due to contact between wires or chip shorts due to contact with chip ends.
Furthermore, it eliminates problems such as tab shorts caused by contact with tabs, and enables long-distance bonding and thinning of wires.

Furthermore, the bonding wire for semiconductor devices of the present invention includes:
By having a breaking load of 15 to 30 kg/2 kg and an elongation rate of 10 to 25%, mechanical properties are improved and excellent bonding performance can be exhibited.

In addition, the heat-resistant polyurethane used to cover the gold wire in the present invention can be bonded by decomposing the urethane bonds even at the bonding temperature or ultrasonic vibration energy during normal wire bonding, so Combination of crimping and ultrasonic vibration or ultrasonic P! Reliable bonding can be achieved through vibration. In that case, if local heating of the bonding site is also used, more reliable wire bonding becomes possible.

Next, to further explain the heat-resistant polyurethane used for the coating film of the coated wire in the present invention, this heat-resistant polyurethane is made by reacting a polyol component with incyanate, and has a structural unit derived from terephthalic acid in its molecular skeleton. This heat-resistant polyurethane is obtained using a polymer component whose main component is a terephthalic acid polyol containing active hydrogen and an isocyanate. Here, "consisting of the main component" includes the case where the whole consists of only the main component.

The above terephthalic acid polyol containing active hydrogen is
Kano/C0O using terephthalic acid and polyhydric alcohol
H=1.2-30, reaction temperature 70-250℃
It can be obtained by a conventional esterification reaction. Generally, those having an average molecular weight of 30 to 10,000 and about 100 to 500 hydroxyl groups, and having hydroxyl groups at both ends of the molecular difference, are used.

Ethylene glycol, diethylene glycol,
Propylene glycol, dipropylene glycol, hexane glycol, butane glycol, chrycerin, trimethylolpropane.

Examples include aliphatic glycols such as hexanetriol and pentaerythritol. In addition, 1.4
- Polyhydric alcohols such as dimethylolbenzene. In particular, it is preferable to use ethylene glycol, propylene glycol, and chrycerin.

Terephthalic acid is used as the dicarboxylic acid, but amic acid and imide acid can be used in combination, if necessary.

The structural formula of imide acid is as follows.

[Structural formula of imide acid]

In addition, to the extent that the heat resistance does not decrease, we can also use two substances such as isophthalic acid, orthophthalic acid, succinic acid, adipic acid, and sebacic acid.
Basic acids, 1,2,3,4-butanetetracarboxylic acid,
There is no problem in using polybasic acids such as cyclobenkunetetracarboxylic acid, ethylenetetracarboxylic acid, pyromellitic acid, and trimellitic acid in combination.

As the incyanate to be reacted with the above terephthalic acid polyol, at least 2 in one molecule such as tolylene diisocyanate and xylylene diisocyanate can be
Examples include those in which the isocyanate group of a polyvalent incyanate having 2 incyanate groups is blocked with a compound having active hydrogen, such as phenols, caprolactam, and methyl ethyl ketone oxime.

Such incyanates are stabilized. Also included are those obtained by reacting the polyvalent incyanate compound with a polyhydric alcohol such as trimethylolpropane, hexanetriol, butanediol, and blocking the resulting product with a compound having active hydrogen.

Examples of the above incyanate compounds include Millionate MS-50 and Coronate 250 manufactured by Nippon Polyurethane Co., Ltd.
1.2503,2505. Examples include Coronate AP-St and Desmodule CT-3t. And, as the polyvalent incyanate, molecules! 300～
It is preferable to use a number of about 20,000.

The present invention creates a coating composition using the above-mentioned raw materials and coats the gold wire of the wire body to form a coating with a thickness of several micrometers, thereby creating an insulating coating for the gold wire of the wire body. Semiconductor devices are manufactured using wire.

The coating composition used in the present invention has 0.4 to 4.0 equivalents of incyanate groups in the stabilized incyanate, preferably 0.9 to 2.0 equivalents, per 1 equivalent of hydroxyl groups in the polyol component.
It can be obtained by adding an equivalent and required amount of a curing accelerating catalyst and further adding an appropriate amount of an organic solvent (phenols, glycol ethers, naphtha, etc.) to obtain a solid content of usually 10 to 30% by weight. can. At this time, appropriate amounts of additives such as appearance improvers and dyes may be added as necessary.

In the present invention, the inocyanate group of the stabilizing isocyanate is from 0.4 to 1 hydroxyl group equivalent of the polyol component.
The reason for adding 4.0 equivalents is that if the amount is less than 0.4 equivalents, the crazing properties of the resulting insulated wire will deteriorate;
This is because if the amount exceeds the equivalent amount, the abrasion resistance of the coating film will be poor. The curing accelerating catalyst added when preparing the coating composition is preferably 0.1 to 100 parts by weight per 100 parts by weight of the polyol component.
It is 10 parts by weight. When this amount is less than 0.1 part by weight, the curing accelerating effect tends to decrease and the coating film forming ability tends to deteriorate.On the other hand, when it exceeds 10 parts by weight, the heat deterioration characteristics of the resulting heat-resistant polyurethane bonding wire deteriorate. This is because a decrease will be seen.

Examples of the curing accelerating catalyst include metal carboxylic acids, amino acids, and phenols, and specifically, zinc salts, iron salts, copper salts, manganese salts, cobalt salts such as naphthenic acid, octenoic acid, and versatic acid; Tin salt, 1,8 diazabicyclo(5,4゜0) undecene-7,2,4,6
) Lis(dimethylaminomethyl)phenol is used.

The insulating coated bonding wire used in the present invention is
It can be obtained by applying the coating composition as described above onto the surface of the gold wire of the wire body and then baking it using a commonly used baking coating device.

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

In the thus obtained insulating coated bonding wire, an insulating coating film made of heat-resistant polyurethane is formed around the outer periphery of the gold wire of the wire body made of gold, copper, or aluminum.

Further, in this case, a composite coating structure may be used in which the above-mentioned insulating coating film and another insulating coating film are used together.

This composite coating film is obtained by forming the above-described insulating coating film of the present invention and then further forming a second insulating coating film on the insulating coating film. In this case, it is suitable that the thickness of the second insulating coating film is set to be 2 times or less, preferably 0.5 times or less, that of the insulating coating film of the present invention. Examples of the material for forming the second insulating coating include polyamide resin, special polyester resin, and special epoxy resin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of the present invention will be described below along with examples in which the present invention is applied to semiconductor manufacturing technology used in resin-sealed semiconductor devices.

In addition, in an attempt to explain the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof will be omitted.

[Example 1] Fig. 1 is a half-sectional view of a resin-sealed semiconductor device using a bonding wire, which is an embodiment of the present invention, Fig. 2 is a schematic enlarged sectional view of a wire bonding part, and Fig. 3 4 is a schematic configuration diagram of a wire bonding apparatus that can be used in the present invention, FIG. 4 is a perspective view of the main parts thereof, FIG. 5 is a partial sectional view showing a specific structure of the main parts of the wire bonding apparatus, and FIG. The figure is a plan view seen from the direction of the arrow ■ in Figure 5, Figure 7 is a sectional view taken along the line ■-■ in Figure 6, Figure 8 is a reproduction configuration diagram showing the principle of ball formation, and Figure 9 10 is an enlarged perspective view of the main part of the spool, FIG. 11 is a schematic plan view of a local heating section for wire bonding, and FIG. 12 is a schematic plan view of a local heating section for wire bonding. FIG. 13 is a plan view showing an example of bonding; FIG.
Figure 4 is an enlarged partial sectional view showing the chip shorted state.
FIG. 15 is a partial sectional view showing a tab touch state of the covered wire, FIG. 16 is an enlarged partial sectional view showing a tab short state, and FIG. 17 shows the short circuit rate between the semiconductor chip and the covered wire with respect to temperature cycles in the present invention. Graph, No. 18
The figure is also a graph showing the short circuit rate between the tab and the covered wire with respect to temperature cycles in the present invention.

The semiconductor device of this embodiment is an example of a resin-sealed 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, a MOS logic, or the like.

This semiconductor chip 2 includes a substrate 2A made of silicon (S), for example, a passivation film 2B on the top thereof, and external terminals (ponding pads) 2G exposed from openings in the passivation film 2B. are doing. This semiconductor chip 2 is made of silver (Ag), for example.
) The tab 3A of the lead 3 is
is joined to.

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, and in this embodiment, coated wires 5 are used as the conductive wires.

This coated wire 5 has a structure in which an insulating coating film 5B is coated on the surface of a gold wire 5A.

The material of the gold wire 5A of the coated wire 5 is, for example, 99.
Gold (Au) with high purity of 99% by weight or more, 0.03
~0.3 wt% germanium (Ge) and O,(l
OO contains calcium (Ca) in an amount of 5 to 0.01% by weight, and contains impurities other than these in a range of 0.0001 to 0.01% by weight.

The contents of germanium and calcium are each 0.
Better results can be obtained by setting the content to 05 to 0.15% by weight and 0.001 to 0.003% by weight.

The germanium has the elongation rate and breaking load of the gold wire 5A,
It is a useful element that can increase the yield strength, and its high elongation rate can prevent stress concentration at the neck. However, if the content is less than 0.03% by weight, the effect of improving the elongation rate etc. is Small (not practical)

On the other hand, if the germanium content exceeds 0.03% by weight, the ball shape during bonding will not be stable and the ball hardness will become too large, causing connection failure and chip cracking, which is not practical.

However, the germanium has a useful range (0.03~
0.3% by weight) lowers the recrystallization temperature of the gold wire 5A, resulting in coarsening of crystal grains in the neck portion during pole formation, which has an adverse effect on preventing neck breakage.

Therefore, in the present invention, calcium is contained in combination with the germanium.

Calcium is a useful element for increasing the recrystallization temperature of the gold wire 5A to improve heat resistance, suppressing coarsening of crystal grains, and increasing breaking load.

However, if the calcium content is less than 5% by weight of O, OOO, the above-mentioned usefulness will be low, and if it exceeds 0,01% by weight, the ball shape will not be stable during bonding and the ball will be hard, resulting in chip cracking, etc. This also causes a decrease in the elongation rate of the gold wire 5A, and further causes a decrease in wire drawability, resulting in poor practicality.

Therefore, the content of germanium and calcium is preferably within the above range.

The coating film 5B of the coated wire 5 is made of a heat-resistant polyurethane made by reacting a polyol component with incyanate and containing a structural unit derived from terephthalic acid in its molecular skeleton, as mentioned above and explained in detail later. It is more than that.

The coated wire 5 of this embodiment has its first (first=I)
St) The bonding side, that is, the connection side between the external terminal 2C of the semiconductor chip 2 and one end of the coated wire 5 is the ball 5.
Conductive connection is made by ball bonding by forming Al, while the second (2nd) bonding side, that is, the connection between the inner lead 3B of the lead 3 and the other end of the covered wire 5 is made by thermocompression bonding and ultrasonic vibration. By so-called thermosonic bonding using
A conductive connection is made as Δ2.

In this way, the pellet-bonded and wire-bonded semiconductor chip 2 and the tabs 3 of the leads 3 are bonded to each other.
A, the inner lead 3B, and the covered wire 5 are sealed with a resin material 6 such as epoxy resin, and only the outer lead 3C of the lead 3 protrudes outside the resin material 6.

Next, the structure and operation of the wire bonding apparatus for bonding the coated wire 5 in this embodiment are shown in FIGS.
The explanation will be centered on FIG. 11.

This wire bonding device is configured as a so-called ball bonding device 5, and as shown in FIG. It is composed of

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

In the bonding portion 12, a resin-sealed semiconductor device 1, which is configured as shown in FIGS. 3 and 4, is placed before resin-sealing. As shown in FIG. 3, the resin-sealed semiconductor device 1 before being resin-sealed is mounted on a semiconductor device support stand (semiconductor device mounting table) 1 of a bonding device.
It is supported by 7.

A coated wire 5 is connected to the external terminal 2C of the semiconductor chip 2.
The gold wire 5 is exposed after the coating film 5B on one end side is removed.
The ball 5Al formed by A is connected. The ball 5A is, for example, 2 mm in diameter compared to the gold wire 5A.
It is now constructed with a diameter that is approximately three times larger.

The inner lead 3B of the lead 3 is connected to a gold wire 5A on the other end of the covered wire 5, which is exposed by breaking the coating film 5B on the other end of the covered wire 5 at the connecting portion. That is, on the other end side of the covered wire 5, substantially only the coating film 5B at the connection portion with the lead 3 is removed, and the other coating film 5B remains. The coating film 5B on the other end side of the coated wire 5 can be destroyed by ultrasonic vibrations applied by the bonding tool 16, appropriate pressure, and appropriate heating (energy), as will be described later.

In this way, in the resin-sealed semiconductor device 1 using the covered wire 5, the ball 5A formed of the gold wire 5A at one end of the covered wire 5 is connected to the external terminal 2C of the semiconductor chip 2, and the lead is connected to the external terminal 2C of the semiconductor chip 2. Ball 5A+
Since the size of is large, the external terminal 2C of the semiconductor chip 2
and increasing the contact area of the coated wire 5 with the gold wire 5A,
The bondability between the two can be improved, and the other end side of the covered wire 5 other than the part connected to the inner lead part 3B of the lead 3 is covered with the coating film 5B, and the other end side of the covered wire 5 and the other end side of the covered wire 5 are covered with the coating film 5B. Since it is possible to reduce short circuits with the other end side of other adjacent coated wires 5, the interval between the leads 3 can be reduced, and the resin-sealed semiconductor device 1 can have multiple terminals (so-called multi-pins). be able to.

As shown in the right side of FIG. 3 and FIG. It is composed of The covering member 18A is configured to rotate in six directions shown by arrows in FIG. In other words, the covering member 18
A is configured such that when forming the ball 5A, the bonding tool 16 is inserted through the tool insertion opening 18B by rotational movement in six directions of arrows, and the bonding tool 16 is covered.

This covering member 18A is shown in FIG. It is constructed as shown in FIG. 7 (a cross-sectional view taken along the section line XX in FIG. 6). As will be described later, the coating member 18A is a coating film 5B that melts when forming the balls 5A.
The coating film 5B is configured to prevent the coating film 5B from being scattered onto the bonding portion 12 due to the blow-off. Furthermore, when the gold wire 5A of the covered wire 5 is made of a material that is easily oxidized such as Cu or Aβ, the covering member 18A is configured to easily maintain an oxidation-preventing coating gas atmosphere (shielding gas atmosphere). There is. The covering member 18Δ is made of stainless steel, for example. Further, the covering member 18A may be formed of a transparent glass material so that the operator can check the state of formation of the ball 5A of the covered wire 5.

As shown in FIGS. 3, 4, and 5, an electric torch (arc electrode) 18 is provided at the bottom of the covering member 18A.
D is provided. The electric torch 18D, as shown in FIG. 8 (reproduction diagram explaining the principle of ball formation),
It is arranged so that it is brought close to the gold wire 5A on the supply side tip side of the coated wire 5, and an arc Ac is generated between the two to form a ball 5A+. Electric torch 18D is
For example, it is made of tungsten (W), which can withstand high temperatures.

The electric torch 18D connects the arc generator 2 with a suction pipe 18E to the suction device 19 made of a conductive material.
Connected to 0. The suction pipe 18E is made of stainless steel, for example, and has the electric torch 18D fixed thereto with an adhesive metal layer such as Ag-Cu brazing material interposed therebetween. This suction tube 18E is fixed to the covering member 18A with a clamping member 18F interposed therebetween. In other words, electric torch 18D
The suction tube 18E and the covering member 18A are integrally constructed.

Said electric torch 18. D is ball 5A+ as mentioned above.
It is configured so that it can move in the direction of the arrow shown in FIG. 4 so that it can be moved in the direction of the arrow shown in FIG. 4 so that it can be moved in the direction of the arrow shown in FIG. .

The moving device that moves this electric torch 18D is mainly
Support member 18G1 supporting electric torch 18D with suction pipe 18E and insulating member 18H interposed
The crankshaft 1811 rotates the crankshaft 8G in the direction indicated by the arrow, and the drive source 18 rotates the crankshaft 18I. The rotation of the crankshaft 18I is performed by the movement of the shaft 18J connected to the crank portion and driven by the drive source 18 in the direction of arrow B. The drive source 18 includes, for example, an electromagnetic solenoid. The crankshaft 18I is
Although not shown, it is rotatably supported by the bonding device main body. Note that the movement of the electric torch 18D and the movement of the covering member 18A are substantially the same since both are integrally constructed.

As shown in FIG. 4, the arc generating device 20 mainly includes an arc generating thyristor D operated by a capacitor C+ and a storage capacitor C2.

It consists of a resistor R. The DC power source C is configured to supply a negative polarity voltage of about -1000 to -3000 (V), for example.

A DC power source C is connected to an electric torch 18D via a thyristor D, a resistor R, and the like. The reference potential GND is
For example, it is a ground potential (=Of:V)). ■ is a voltmeter, and A is an ammeter.

As will be described in detail later, the end of the gold wire 5A of the covered wire 5 wound around the spool 11 is connected to the reference potential GND. As a result, when forming the ball 5A at the tip of the covered wire 5 with the electric torch 18D, as shown in FIGS. Gold wire 5 at the tip in the feeding direction of 5
A can be set to a positive potential (10).

In this way, in a bonding apparatus that generates an arc Ac between the gold wire 5A at the tip of the covered wire 5 and the arc electrode 18D and forms a ball 5A+ at the tip of the covered wire 5, the gold wire of the covered wire 5 5A to a positive potential (+) and the electric torch 18b to a negative potential (-), the position of the arc Ac generated between the gold wire 5A of the coated wire 5 and the electric torch 18D can be determined. Since the polarity can be stabilized compared to the case of the opposite polarity, it is possible to reduce the arc Ac creeping up toward the rear end side of the gold wire 5A of the coated wire 5. The reduction in creeping up of the arc Ac reduces the melting up of the coating film 5B of the coated wire 5, and can prevent the occurrence of balls in the insulating coating film.

Note that the present invention connects the gold wire 5A of the covered wire 5 to a voltage higher or lower than the reference potential GND so that the gold wire 5A of the covered wire 5 has a positive potential with respect to the electric torch 18D. It's okay.

The spool 11 around which the covered wire 5 is wound is
It is constructed as shown in FIGS. 4 and 9 (disassembled perspective view of essential parts). The spool 11 is made of, for example, a cylindrical aluminum metal whose surface is subjected to alumite treatment. Alumite treatment is performed to improve mechanical strength and prevent scratches. As described above, this spool 11 is anodized and has insulation properties.

The spool 11 is attached to a spool holder 21, and attached to the bonding apparatus main body 10 by a rotating shaft 21A of the spool holder 210.

The spool holder 21 is made of, for example, stainless steel so that at least a portion thereof is electrically conductive.

The spool 11 is provided with a connecting terminal 11A, as shown in FIGS. 9 and 10 (enlarged perspective views of main parts). The connection terminal 11A is provided in a dot pattern on the side surface (flange) of the spool 11 that contacts the conductive portion of the spool holder 21.

The connection terminal 11A is connected to the insulator 11 as shown in FIG.
A conductor 11Ab is provided above Aa, and this conductor 11A
A connecting metal part 11Ac is provided on the upper part of b. The insulator 11Aa is made of polyimide resin, for example, so as to ensure electrical separation between the conductor 11Ab and the spool 11 and to have appropriate elasticity to ensure that the connection metal part 11Ac contacts the spool holder 21. Form.

The conductor 11Ab is formed of, for example, Cu foil so that the connection metal part 11Ac that connects the gold wire 5A of the coated wire 5 and the connection metal part 11A'C that contacts the spool holder 21 can be reliably connected. do. Connection metal part 11
Ac is formed using conductive paste, solder, or the like.

This connection terminal 11A has a side surface (flange) of the spool 11.
The gold wire 5 at the end of the coated wire 5 on the opposite side to the side supplied to the bonding part 12 is inserted through the notch formed in the
A, that is, gold wire 5 at the winding start end of coated wire 5
It is configured to connect A. This gold wire 5A
is connected to the connection terminal 11A by the connection metal part 11Ac. The coating film 5B on the surface of the gold wire 5A at the beginning of winding of the coated wire 5 is removed by heating or chemically. The connection terminal 11A, that is, the gold wire 5A of the coated wire 5, is
It is connected to base potentials GN and D through the spool holder 21, its rotating shaft 21A, and the bonding device main body 10. The reference potential GND is the same potential as the reference potential GND of the arc generating device 20.

In this way, the connection terminal 11A for connecting to the reference potential GND is provided on the spool 11, and the gold wire 5A at the start end of the winding of the coated wire 50 is connected to this connection terminal. Potential GND
Therefore, the gold wire 5A of the covered wire 5 can be reliably connected to the reference potential GND.

Further, the gold wire 5A of the covered wire 5 is at the reference potential GN.
By being connected to D, when forming the ball 5A, the electric torch 18D and the gold wire 5A of the covered wire 5 on the supply side
Since a sufficient potential difference can be secured between the two and the arc Ac can be generated well, the ball 5Al can be formed reliably.

As shown in FIGS. 3 and 4, the bonding tool 16 is connected to a bonding head (digital bonding head) 22 with a bonding arm 16A interposed therebetween.
is supported by 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 connected to the XY table 2
It is supported by a base 24 with 3 interposed therebetween. The bonding head 22 is provided with a moving device that can move the bonding arm 16A in the vertical direction (in the direction of arrow C) so that the bonding tool 16 can approach and move away from the bonding section 12. The moving device mainly includes a guide member 22A, an arm moving member 22B, and a female screw member 22C1.
It is composed of a male screw member 22D and a motor 22E. The guide member 22A moves the arm moving member 22B in the direction of arrow C.
is configured to move. The motor 22E
is configured to rotate the male threaded member 22D, and this rotation moves the female threaded member 22C that fits into the male threaded member 22D in the direction of arrow C, and this movement moves the arm moving member 22B in the direction of arrow C. .

The bonding arm 16A supported by the arm moving member 22B is configured to rotate around a rotating shaft 22F. The rotation of the bonding arm 16A about the rotation axis 22F is controlled by the elastic member 22G.

The rotation of the elastic member 22G is controlled to prevent the bonding part 12 from being pressurized more than necessary when the bonding tool 16 comes into contact with the bonding part 12, and to prevent damage or destruction of the bonding part 12. It is composed of

The wire clamper 15 is configured to be able to clamp the covered wire 5 and to control the supply of the covered wire 5. The wire clamper 15 is a clamper arm 15
A is provided on the bonding arm 16A with A interposed therebetween.

The wire guide member 14 is configured to guide the coated wire 5 supplied from the spool 11 to the bonding section 12. The wire guide member 14 is connected to the clamper arm 1
It is installed at 5A.

Near the tip of the covered wire 5 in the supply direction,
As shown in FIGS. 3 and 8, a fluid spray nozzle 18C of a fluid spray device 25 is located near the supply path of the coated wire 5 between the bonding tool 16 and the bonding part 12.
is provided.

When the fluid spray nozzle 18C forms the ball 5A with the gold wire 5A at the tip of the coated wire 5 in the supply direction,
It is configured to spray the fluid GS from the fluid spray device 25 onto the formed portions (gold wire 5Ai and coating film 5B). As shown in FIG. 8, the fluid Gs blown out from the fluid spray nozzle 18C is melted by the heat generated by the arc Ac when forming the ball 5A+ with the gold wire 5A at the tip of the covered wire 5. It is configured to blow away the covering film 5B (5Ba).

Basically, the fluid spray nozzle 18C only needs to spray the fluid Gs onto the tip of the bonding tool 16, that is, the tip of the coated wire 5 as described above, and in this embodiment, the fluid spray nozzle 18C is provided on the coating member 18A. ing. As shown in FIGS. 4 to 7, the fluid spray nozzle 18C is arranged in a direction from the rear end of the coated wire 5 to the front end in order to reduce melting of the coating film 5B. Fluid Gs
It is designed to spray. Note that it is preferable that the fluid spray nozzle 18C not be attached to the bonding tool 16. When the fluid spray nozzle 18C is attached to the bonding tool 16, the bonding tool 16
As the weight of the connector increases and the load of its ultrasonic vibration increases, the bondability of the connection part decreases.

The fluid Gs uses a gas such as N2, H2, He, Ar, or air, and as shown in FIG. 25C and is supplied to the fluid spray nozzle 18C.

The cooling device 25A is configured to actively cool the fluid Gs to a temperature lower than normal temperature. The cooling device 25A is composed of, for example, an electronic cooling device that utilizes the Peltier effect. Although the fluid conveying pipe 25C is shown in a simplified manner in FIG.
The space between the supply port 8C and the supply port is covered with a heat insulating material 25D. In other words, the heat insulating material 25D is the cooling device 25A.
The temperature of the cooled fluid Gs is not changed during movement of the fluid transport pipe 25C (to improve cooling efficiency).

Further, the suction device 19 is located near the tip of the coated wire 5 in the supply direction and at a position facing the fluid spray nozzle 18C with the melted part of the coating film 5B of the coated wire 5 at its center. A suction pipe 18E connected to is provided. As described above, this suction tube 18E is also used as a conductor to connect the electric torch 18D and the arc generator 20, but it is mainly used to melt the coated wire 5 blown off by the fluid spray nozzle 18C. The raised coating film 5B
It is configured to attract a. The coating film 5Ba sucked by the suction tube 18E is sucked by the suction device 19.

In addition, in this embodiment, in order to bond the other end of the covered wire 5 to the inner lead 3B of the lead 3 more reliably (second bonding), only the inner lead 3B of the lead 3 is higher than the other part. A ceramic heater 26 for local heating is provided in the shape of a rectangular ring as shown in FIGS. 2 and 11. Incidentally, the reference numeral 26A is a power supply line to the rectangular ring-shaped heater 26 for local heating.

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

First, as shown in Figures 3, 4, 5, and 8,
The tip portion of the bonding tool 16 and the feeding direction of the covered wire 5 protruding from its pressurizing surface side is attached to the covering member 18A.
Cover with This coating is performed by moving the coating member 18A in the direction of the arrow by a moving device operated by the drive source 18. In addition, this covering member 18A
By performing the coating, the electric torch 18D and the fluid spray nozzle 18C can be placed near the tip of the coated wire 5.

Next, as shown in FIG. 8, an arc Ac is generated between the gold wire 5A at the tip of the coated wire 5 in the feeding direction and the electric torch 18D, and the gold wire 5A causes the ball 5A,
form. Arc Ac forming this ball 5A1
The heat melts the insulating coating film 5B at the tip of the covered wire 5 in the feeding direction. That is, the coating film 5B at the tip of the coated wire 5 in the feeding direction is removed, and the gold wire 5
A is exposed.

The ball 5A is formed in as short a time as possible. When the ball 5A+ is formed in a short time and with high energy (in a region where both current and voltage are high), the amount of melting of the coating film 5B of the covered wire 5 is reduced. In this way, forming the ball 5A in a short time and with high energy means that
As described above, this can be achieved by stabilizing the generation of the arc Ac, that is, by setting the electric torch D to a negative potential (-) and the gold wire 5A of the covered wire 5 to a positive potential (+).

When forming this ball 5A, the covering member 1
Fluid Gs is sprayed from the fluid spray device 25 onto the coating film 5B of the coated wire 5 by the fluid spray nozzle 18C whose position is set with 8A, and the coating film 5B is blown off as shown in FIG.

The blown coating film 5Ba is sucked into the suction device 19 through the suction pipe 18E and removed from the system.

The fluid Gs from this fluid spray nozzle 18C is cooled by a cooling device 25A shown in FIG.
℃]. The lower the temperature of the fluid Gs from the fluid spray nozzle 18C, the lower the coating film 5B of the coated wire 5.
The amount of melting is small. That is, the fluid GS cooled by the cooling device 25A is the gold wire 5A of the covered wire 5 and the coating film 5B.

Since the bonding tool 16 and the like can be actively cooled, the coating film 5B only in the area where the arc Ac occurs is melted, and the coating film 5B in other parts is not melted, and as a result, the coating film 5B is melted. The amount of melting can be reduced.

Next, the covering member 18A, together with the electric torch 18D and the fluid spray nozzle 18C, are each moved in the direction indicated by the arrow (in the opposite direction to the above).

Next, a ball 5Al formed at the tip of the coated wire 5 in the supply direction is placed on the pressurizing surface of the bonding tool 16.
Attract.

Next, in this state, the bonding tool 16 is brought closer to the bonding part 12, and as shown by the broken line in FIG. Connect to external terminal 2C of chip 2 (first bonding: 1st). This connection of the ball 5A+ is performed by ultrasonic vibration of the bonding tool 16 and/or thermocompression bonding (either one may be used).

Next, as shown in FIG.
(Second bonding: 2nd). The connection on the rear end side of the covered wire 5 is performed by ultrasonic vibration of the bonding tool 16 and thermocompression bonding (only the former may be used). As a result, the rear end of the covered wire 5 is separated from the inner lead 3B by the second bonding portion 5A2.
At this point, the wedge bond is strongly inked.

In connection with the rear end side of the coated wire 5, the coated wire 5 at the connection portion is covered with a coating film 5B in advance, but by ultrasonically vibrating the bonding tool 16, the coating film 5B only at the connection portion is removed. It is destroyed and the gold wire 5A is exposed.

The thickness of the coating film 5B of the covered wire 5 is preferably about 0.2 to 3 [μm], for example, although it varies slightly depending on the energy of the ultrasonic vibration of the bonding tool 16 and the thermocompression bonding force. If the thickness of the coating film 5B of the covered wire 5 is too small, the dielectric strength voltage as an insulating coating film is small. Furthermore, if the thickness of the coating film 5B of the covered wire 5 is too thick, the coating film 5B will be difficult to be destroyed by the ultrasonic vibration of the bonding tool 16, and the thickness of the coating film 5B will not reach a predetermined value. If it exceeds the limit, the coating film 5B will not be destroyed, resulting in a poor connection between the gold wire 5A of the coating wire 5 and the inner lead 3B of the lead 3.

In this embodiment, the material of the gold wire 5A of the coated wire 5 is, for example, gold (Au) having a high purity of 99.99% by weight or more, and germanium (Ge) of 0.03 to 0.3% by weight. Since we use a material containing 0.0005 to 0.01% by weight of calcium (Ca), germanium and calcium interact synergistically with each other and with high-purity gold. The fatigue life of the gold wire 5A can be effectively extended, and the crystal grains in the neck portion can be prevented from becoming coarser during ball formation, thereby preventing neck breakage.

In this embodiment, when bonding the other end of the covered wire 5 (second bonding), only the inner lead 3B of the lead 3 is locally heated to a temperature higher than other parts by the heater 26, so that the inner lead 3B of the lead 3 is heated locally to a temperature higher than other parts. Covering film 5
Since the heating and decomposition of B is further promoted, the bondability of second bonding can be improved, and strong wire bonding becomes possible.

Thereafter, by separating the bonding tool 16 (at this time, the covered wire 5 is cut), one bonding process for the covered wire 5 is completed, as shown in FIG. 2.

In this way, in the bonding technique of forming the ball 5A1 at the tip of the covered wire 5, the fluid Gs is placed near the tip of the covered wire 5.
Fluid spray nozzle 18C (fluid spray device 25
By providing a part of the insulating coating film 5B on the coated wire 5, it is possible to blow off the coating film 5B that melts the coated wire 5, thereby preventing the formation of balls of the insulating coating film 5B on the coated wire 5. can. As a result, it is possible to prevent the covered wire 5 from being caught on the bonding tool 16 due to the balls of the insulating coating film 5B, and to draw the covered wire 5 to the pressurizing surface of the bonding tool 16, thereby performing ball bonding. This makes it possible to prevent bonding defects.

Further, a bonding technique in which a ball 5A+ is formed at the tip of the coated wire 5, and the fluid spray nozzle 18
C (a part of the fluid spray device 25) is provided near the tip of the coated wire 5, and includes a suction tube that sucks the coating film 5B of the coated wire 5 that is blown away by the spray of the fluid Gs from the fluid spray nozzle 18C. By providing 18E (suction device 19), the coating film 5B increases the melting of the coated wire 5.
By blowing off the coating film 5B, it is possible to prevent the formation of balls of the coating film 5B on the coated wire 5, thereby preventing bonding defects as described above, and also to prevent the coating film 5B from being blown off.
Since the coating film 5Ba is not scattered to the bonding portion 12, bonding defects caused by the scattered coating film 5Ba can be prevented. The bonding failure caused by the scattered coating film 5Ba is, for example, when 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 gold wire 5A of the covered wire 5. However, there is a case where there is poor conduction between the two.

Further, the bonding technique forms a ball 5A at the tip of the coated wire 5, and the fluid spray nozzle 18C
(fluid spray device 25) is provided, and this fluid spray nozzle 18
By providing the cooling device 25A that cools the fluid Gs of C, the melting of the insulating coating film 5B of the covered wire 5 is significantly reduced, and even if the melting rises, the coating film 5B is not blown away. Therefore, the coating film 5 is applied to the coated wire 5.
It is possible to prevent the formation of the ball B, and to prevent bonding defects as described above.

In addition, in the bonding technique using the coated wire 5, foil 5A+ is placed on the tip side of the coated wire 5 in the supply direction.
This ball 5A+ is connected to the external terminal 2C of the semiconductor chip 2, and the rear end side of the covered wire 5 in the supply direction is brought into contact with the inner lead 3B of the lead 3.
By destroying the coating film 5B at this contact portion and connecting the gold wire 5A on the other end side of the covered wire 5 to the inner lead 3B of the lead 3, the coating film 5B on the rear end side of the covered wire 5 is removed. Since the coating film 5B can be removed without using the coating film removal torch, the need for the coating film removal torch, its moving device, control device, etc. can be reduced. As a result, the structure of the bonding device can be simplified.

In particular, in the semiconductor device 1 of this embodiment, the insulating coating film 5B of the covered wire 5 is made of heat-resistant polyurethane whose molecular skeleton contains a structural unit derived from terephthalic acid by reacting a polyol component with incyanate. By using this, it is possible to reliably prevent tab shorts, chip shorts, or wire-to-wire shorts due to film destruction caused by thermal differentiation of the coating film for 5 days.

That is, after bonding the covered wire 5 as described above, a resin molding operation is performed using the resin material 6 to manufacture the resin-sealed semiconductor device 1. For example, as shown in FIG. Chip 2 external terminal 2C
When the distance between the wire 5 and the bonding site of the inner IJ-domain 3B of the lead 3 is long, the covered wire 5 and the silicon region of the semiconductor chip 2 come into contact with each other, as shown in FIG.
In the so-called chip touch state, as shown in Fig. 15,
A so-called tab touch state in which the covered wire 5 and the tab 3A contact each other, and a so-called wire-to-wire touch state in which the covered wires 5 contact each other may occur. Such a wire touch phenomenon is particularly likely to occur when the wire length is 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 covered wire 5 is destroyed due to thermal deterioration caused by heat generation from the semiconductor chip 2, etc.
The gold wire 5A may come into direct contact with the semiconductor chip 2, causing a chip short between the semiconductor chip 2 and the tab 3A as shown in FIG. A short circuit may occur between the wires.

However, in the semiconductor device 1 of this embodiment, since the coating film 5B of the coated wire 5 is made of special heat-resistant polyurethane as described above, even if the chip touch, tab touch, or inter-wire contact occurs as described above, 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 neck breakage and preventing short circuit defects obtained by the bonding wire for semiconductor devices according to the present invention, the results of experiments conducted by the present inventors on semiconductor devices after resin encapsulation will be used as an experimental example. This will be explained below. Note that parts in the experimental examples indicate parts by weight.

Experimental Example 1 Germanium (Ge) was added to 99.99% by weight gold (Au).
) and calcium (Ca) were added, melted and cast, and subjected to wire drawing to produce a gold wire for bonding with a wire diameter of 25 μm, and the mechanical properties of the gold wire such as elongation rate and breaking load were measured. At the same time, bonding work was performed using it.

The various bonding properties obtained as a result, along with the mechanical properties, are shown in Table 1 in terms of germanium and calcium content.

(Left below) As is clear from Table 1, 99.99% by weight of gold
0.03-0.3% by weight germanium, 00005
By containing ~0.01% calcium, the mechanical properties such as the breaking load of the gold wire are improved, and the neck and arch parts (loop-like tension from the neck part to the second bonding side) during bonding are improved. It was confirmed that the uniformity of the crystal grains with respect to the part being passed was ensured, preventing neck breakage and improving the bonding characteristics.

In particular, the contents of germanium and calcium are each reduced to 0.
．． 05-0.15% by weight and 0.001-0°003
Even better results can be obtained by setting it as % by weight.

Experimental Example 2 Using the gold wire obtained in Experimental Example 1, its breaking load (kg/s') and elongation rate [%] were measured in order to confirm its fatigue strength. The wire diameter of the gold wire is 25 [μ
m].

As a result, the fatigue strength of the gold wire itself, regardless of the formation of the gold ball, was as shown in FIG. 45, and the fatigue strength of the neck portion after the formation of the gold ball was as shown in FIG. 46.

As is clear from FIG. 45, the gold wire of the present invention has superior fatigue strength compared to the conventional one, especially when the germanium content (■) is 0.1% by weight and the calcium content is 0. The best breaking load and elongation were obtained at .002% by weight. And the breaking load is 15-30kg/ml
112, particularly good results were obtained with gold wires with an elongation of 10-25%.

As for the fatigue strength of the neck part, as shown in Figure 46,
Good results were obtained with the invention. In addition, in measuring the fatigue strength of the neck part, the gold wire was connected to the positive electrode, the torch electrode was connected to the negative electrode, the distance between the gold wire and the torch electrode was 0.5 teeth, and a gold ball was attached to the tip of the gold wire. The formed one was used. Then, the breaking load and elongation rate of this sample gold wire were measured using a Tensilon tensile tester under the measurement conditions that the sample wire length was 13 navy blue and the bowing speed was 2 m+n/min.

Moreover, as is clear from FIG. 46, the breaking load and elongation rate of the neck portion are hardly affected by the heat treatment temperature of the gold wire.

Experimental Example 3 In order to test the fatigue strength of a gold wire, especially its neck part, the gold wire after forming a gold ball was bonded to a fixed part only at the gold ball part (1st bonding side), and the other end of the gold wire was bonded to a fixed part using mercury. At the same time, the gold wire is clamped with a clamper at a predetermined length from the bonding part, and the clamper is moved to a predetermined displacement! (amplitude) to detect fractures due to fatigue of the gold wire.

The results of this fatigue test are as shown in FIG. 47, and it was confirmed that the gold wire of the present invention has extremely excellent fatigue strength.

Experimental Example 4 Changes in fatigue strength of gold wire due to differences in polarity of discharge during ball formation of gold wire were measured.

There were two types of discharge in this test: a positive electrode discharge in which the wire was negative (-) and the torch electrode positive (+), and a negative electrode discharge in which the wire was positive and the torch electrode was negative. .

The discharge conditions for positive electrode discharge and negative electrode discharge were set so that the ball diameter was 60 μm, the respective discharge currents were 3 (mA) and 15 [mA], and the discharge time was 6. O
Cmsec] and 6.5 (msec), and the discharge voltage was 1200 (V).

The fatigue test after forming the ball was conducted in the same manner as in Experimental Example 3 above.

The experiments were conducted on two types of gold wire, and the results for each are shown in FIGS. 48 and 49.

As is clear from these figures, in either type, by changing from positive electrode discharge to negative electrode discharge,
The wire fatigue strength is approximately doubled. Furthermore, in negative electrode discharge, there is almost no difference in fatigue strength between the two types.

As described above, it was found that the difference in the polarity of the discharge during the formation of a gold wire ball has a large effect on the fatigue strength, and that the fatigue life of the neck portion of the gold pole is approximately twice as long when the negative electrode discharge is used.

It was also discovered that negative electrode discharge has the advantage that the shape of the gold ball is more stable.

Experimental Example 5 First, the raw materials shown in Table 2 below were mixed in the proportions shown in the same table, put into a 500 cc flask, attached a thermometer and a steam condenser, and allowed to react. Types of terephthalic acid polyols P-1, P-2, P-
I got 3. The ratio of terephthalic acid to ethylene glycol, reaction time, etc. at this time are also shown in Table 2. The end point of the above synthesis reaction is the theoretical reaction water and acid value 5.
The decision was made based on the following. In this case, a reduced pressure reaction was also carried out if necessary.

(Left below) Using the three types of terephthalic acid polyols P-1, P-2, and P-3 obtained as described above and a commercially available polyol, these polyol components and isocyanate components were added as described below. A coating composition was prepared by blending the ingredients in the proportions shown in Table 3. The coating composition thus obtained was diluted to a concentration of 10% using a solvent, and applied to the outer peripheral surface of the wire body two or more times, then heated at 175°C for 21 minutes, and then heated at 170°C for 2 hours. After curing, an insulating film made of heat-resistant polyurethane was formed, and wire was manufactured.

The composition and coating properties in this case are shown in Table 3 below.

(Blank 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 as shown in Fig. 13 (chip touching state) and Fig. 15. (Tab touch state) A semiconductor device corresponding to the touch state shown in FIG.
A 3B temperature cycle test was conducted to compare the short circuit rate with a semiconductor device using a commercially available polyurethane coated wire, and the degree of improvement of the present invention was evaluated.

The results of this comparative experiment were as shown in FIGS. 17 and 18. 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. The device was confirmed to have a significant short circuit rate, that is, a chip short prevention effect, compared to semiconductor devices using commercially available polyurethane-coated wires.

Further, FIG. 18 shows the short circuit rate between the tab and the coated wire in the tab chip state as shown in FIG. It was confirmed that the tab short-circuit prevention effect can be obtained.

Next, the inventors conducted a comparative experiment on the heat-resistant polyurethane-coated wire according to the present invention and a commercially available polyurethane-coated wire in the wire state before resin sealing under the test conditions described below.
The wear strength and deterioration rate of the coating film were evaluated. The results of these experiments and other various experiments are shown below in Experimental Examples 6 to 1.
19 to 25 will be explained with reference to FIGS.

Experimental Example 6 The experimental conditions were as shown in the model diagram shown in FIG. That is, a fixed load (1 g) is suspended from the lower end of the coated wire 5 whose outer surface is coated with an insulating coating film (heat-resistant polyurethane of the present invention or commercially available polyurethane) 5B, so as to suspend it in a vertical direction. The tab 3A of the lead frame is brought into contact with the covered wire 5 at its edge at a contact angle α=45 degrees, and pressed against the covered wire 5 with a load Wl (0.65 g) in the horizontal direction from the opposite side of the tab edge contact portion. Abrasion of the coating film 5B was evaluated by applying force and vibrating the tab 3A vertically by 20 μm.

Here, the amplitude (
The number of vibrations (Nf) was defined as the wear strength for evaluation.

In addition, the heat resistance of the coating film 5B is as follows:
Evaluation was made by measuring Nf after 0 to 1000 hours at 0°C.

As a result, it has been found that in the case of polyurethane, thermal deterioration can be significantly suppressed by imidizing it, and temperature cycle life Tcy3 can also be significantly improved.

Below, these experimental results will be specifically explained.

First, Figures 20 and 21 show temperatures of 150°C and 1°C, respectively.
Thermal deterioration of abrasion strength of coating film 5B at 75°C (10
This shows the reduction in the number of times the coating film breaks down after 0 hours. As is clear from these figures, in the case of the coating film using the heat-resistant polyurethane of the present invention, the decrease in the abrasion strength Nf is small even after the elapse of high temperature storage time, and there is very little deterioration of the coating film. It has been found. In particular, 150-175℃, 10
It has been found that the fact that the deterioration rate of the coating film 5B in reducing the number of times the coating film breaks down after 0 hours (Hrs) is within 20% is an extremely advantageous characteristic for the coated wire.

Experimental Example 7 Next, FIG. 22 shows temperature (horizontal axis) and deterioration rate, that is, deterioration rate [ΔNf/100Hrs) (-N.

It shows the experimental results of the relationship with N10°/100Hrs) (vertical axis). It can also be seen from this figure that the deterioration rate of the heat-resistant polyurethane coated wire of the present invention is much lower than that of commercially available polyurethane.

Experimental Example 8 Next, Fig. 23 shows the imidization rate (horizontal axis) of the coating film, the deterioration rate, that is, the deterioration rate (vertical axis on the left), and the peeling strength of the coated wire (2nd> bonding peeling strength (vertical axis on the right)). These are experimental results showing the relationship between

Regarding the peeling strength of the 2nd bonding, the present inventors conducted an experiment using a wire coated with heat-resistant polyurethane with a diameter of φ-25 μm and bonding it to the inner lead 3B without peeling off the coating film 5B in advance as shown in FIG. This is the result of doing this.

As is clear from FIG. 23, it is preferable for the imidization rate of the coating film to be about 1/3 in terms of both the deterioration rate (deterioration rate) and peel strength.

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

Experimental Example 9 Furthermore, FIG. 24 shows the temperature cycle amplitude of the coated wire (
-55 to 150°C) and the experimental results regarding temperature cycle life. As is clear from the figure, the lifespan T of the coating film made of commercially available polyurethane is approximately 400, whereas that of the heat-resistant polyurethane of the present invention is approximately 4000.
This was significantly improved with Hayabusa.

Experimental Example 10 Further, FIG. 25 is a diagram showing the results of an experiment on the influence of the presence or absence of addition of a colorant to the coating film of a covered wire on the deterioration rate (deterioration rate).

According to the findings of the present inventors, when performing bonding using the coated wire 5, for example, when forming a ball, the thickness of the coating film 5B is very thin, so it is necessary to check whether the coating film 5B melts or peels off. It is very difficult to confirm
It can be said that it is impossible, at least with the naked eye. Therefore, the present inventors have discovered that adding a coloring agent, such as oil scarlet, to the coating film 5B is extremely useful, as it is possible to visually check for dissolution and peeling (for example, by using an electron microscope). It was.

However, if the amount of colorant added is too large, the rate of deterioration (deterioration rate) of the coating film will increase, so the inventors have conducted various experiments to determine the appropriateness of this. The results are shown in FIG.

As is clear from the experimental results shown in Figure 25, if the amount of colorant added is too large, the rate of deterioration of the coating film (
If the amount added is too small, the above-mentioned merits of adding the colorant will be lost. Therefore, in view of these two conflicting demands, the present inventors conducted intensive research and found that the colorant (in this example,
It has been found that the optimum amount of the oil (scarlet) added is 2.0% by weight or less, particularly 0.5% to 2.0% by weight. By adding a coloring agent to the coating film within this range, the properties of the coating film can be prevented from being impaired.
There is an advantage that melting or peeling of the coating film from the coated wire can be visually confirmed.

The present inventors obtained the following knowledge through Experimental Example 5, Experimental Examples 6 to 10, and various other experiments, studies, examinations, and confirmations.

That is, as described above, the use of the heat-resistant polyurethane of the above composition of the present invention as the coating film of the coated wire is extremely useful for improving the thermal deterioration of the coating film, bonding properties, and furthermore, the peel strength of bonding. .

Furthermore, as is clear from Experimental Example 6, in addition to this, thermal deterioration (deterioration rate) of the coating film, i.e., through a temperature cycle test of the coating film and an abrasion test under the experimental conditions shown in It is extremely important to use a material that can reduce the rate of deterioration of the coating film within 20% after 100 hours at 150° C. to 175° C. as the constituent material of the coating film.

In addition, it is very important that the coating film has properties that do not cause problems in bonding properties when the coated wire is used in wire bonding work. The inventors have conducted intensive research on this point and have found that it is important that the coating film be made of a material that exhibits non-carbonizing properties, for example, when forming balls in ball bonding or when removing the coating film by heating. There was found.

The reason is as follows. In other words, when the ball is formed or the coating film is removed by heating, the coating film melts directly above the ball, but if the coating film is carbonizable, it will be decomposed by the high heating temperature, for example, 1060°C. Instead, it carbonizes. As a result, the carbonized coating film remains attached to the ball, wrapping it around the gold wire.
When performing bonding with a bonding tool, the deposited carbonized coating film becomes an obstruction that prevents the coated wire from being fed through the capillary, making it difficult or impossible for the coated wire to pass through the capillary.

On the other hand, if the adhered carbonized coating film falls for some reason onto the integrated circuit forming surface of the semiconductor chip, since carbide has conductivity, the falling object may cause an electrical short-circuit in the integrated circuit. It is. Moreover, the coated wire with carbide adhered to it, for example, the second wire to the inner lead.
It has been found that this also causes bonding defects during nd bonding.

Considering these facts comprehensively, the deterioration rate of the coating film of the coated wire under the above-mentioned predetermined conditions,
In other words, the deterioration rate in reducing the number of times the coating film breaks after 100 hours at 150°C to 175°C must be within 20%, and the material must be non-carbonizable when forming the ball or removing the coating film by heating. The inventors have determined that two requirements are extremely important and that materials that meet these two requirements provide very satisfactory results as coated wires.

According to the study results of the present inventors, the heat-resistant polyurethane with the above composition naturally satisfies these two requirements, but the only material that satisfies these two requirements is the heat-resistant polyurethane with the above composition. Without limitation, heat-resistant polyurethanes of other compositions, and even materials other than heat-resistant polyurethanes, can be used as the preferred material for the coating film.

Regarding this, among polyurethanes, commercially available polyurethanes and formals meet the non-carbonization requirement, but
Since the above-mentioned deterioration rate exceeds 20%, it is unsuitable as a coating film.

On the other hand, polyimide, polyamide, nylon, polyester, polyamideimide, polyesterimide, etc. exhibit carbonization during ball formation or when the coating is removed by heating, so they are unsuitable for use as coatings for coated wires. It became clear.

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

[Embodiment 2] In the embodiment shown in FIG. 26, as an example of another wire bonding method included in the present invention, the first (I S t) bonding side of the covered wire 5 is bonded with a ball 5A+ as in the above embodiment 1. Although this is a bonding method, on the second (2nd) bonding side, as shown in the figure as a second bonding part 5A2□, the coating film 5B is removed in advance before the 2nd bonding, and the 2nd bonding is performed by thermocompression bonding and/or ultrasonic vibration method. It is something to do.

[Example 3] Next, in the example shown in FIG. 27, the second bonding part 5A2 is bonded without removing the coating film 5B as in Example 1, and the first bonding side is also bonded to the ball. Instead of ball bonding, thermocompression bonding and/or bonding without removing the coating film 5B in advance
Alternatively, first bonding is performed using an ultrasonic vibration method to form a first bonding portion 5Az.

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

[Example 4] Furthermore, in the example shown in FIG. 28, the first bonding part 5Az is the same as in Example 3, but the second bonding part 5A22 is bonded by removing the coating film 5B in advance, as in Example 2. This is what we are doing.

[Embodiment 5] Furthermore, in the embodiment shown in FIG. 29, the bonding method in which the coating film 5B is removed in advance is used as the first bonding portions 5A and □, and the second bonding portion 5A2 is the same as in the embodiment 1. Similarly to 3 and 3, bonding was performed without removing the coating film 5B.

[Embodiment 6] Furthermore, in the embodiment shown in FIG. 30, the first bonding part 5Al□ and the second bonding part 5A
22 are examples in which the gold wire 5A is bonded by a non-pole forming method with the coating film 5B removed in advance.

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

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

As mentioned above, the material of the second coating film 5C is polyamide resin or special polyester resin.

Special epoxy resin etc. can be used. A second coating film made of nylon or the like may be applied in order to improve the slipperiness of the coated wire inside the capillary.

Further, the thickness of the second coating film 5C is 2 of the thickness of the coating film 5B.
It can be reduced to less than 0.5 times, preferably 0.5 times or less.

[Embodiment 8] Fig. 32 is an explanatory diagram showing the route of the covered wire from the wire spool to the bonding tool in a wire bonding device as an assembly device used in another embodiment of the present invention, and Fig. 33 is an explanatory diagram showing the path of the covered wire from the wire spool to the bonding tool. FIG. 34 is a side view showing the shape of the inner peripheral surface of the airbag tensioner, FIG. 35 is a schematic sectional view showing the clamper, and FIG. 36 is the clamper. FIG. 37 is a schematic plan view showing the drive mechanism of the clamper, FIG. 38 is a schematic sectional view of the clamper in the prior art for comparison with FIG. 35, and FIG. 39 is the present embodiment. FIG. 40 is an explanatory plan view of the lead frame showing the wire bonding state according to this example, and FIG. 41 is a resin-sealed semiconductor device 33 obtained according to this example.
FIG.

In this embodiment, the structure of the wire bonding apparatus itself is almost the same as that shown in FIG. The feature is that the static eliminating means is different.

That is, the coated wire 5 supplied from the wire spool 11 is connected to the airbag tensioner 31 and the sprocket 14.
and is inserted into the bonding tool 16 via the clamper 32.

The airbag tensioner 31 has a pair of guide plates 31A, as shown in FIG. 33. The guide plate 31A may be made of an aluminum alloy and subjected to alumite treatment, but by forming at least the contact surface with the coated wire 5 with a conductive metal, charging of the coated wire 5 during contact can be prevented. It has a structure. Furthermore, not only the contact surface but also the entire guide plate 31A may be made of stainless steel or the like.

Wire passage space 31G of the guide plate 31A of this embodiment
As shown in FIG. 34, a plurality of protrusions 31B are formed on the side surface parallel to the long side direction in the figure. As a technique for obtaining such a structure of the protrusion 31B, the inner circumferential surface of the guide plate 31A may be processed into a protrusion shape using a processing technique such as pressing, or the guide plate 31 formed flat may be used.
A rod-shaped member may be fixed to the inner circumferential surface of A using means such as bonding or adhesion.

As described above, in this embodiment, by providing the protrusion 31B extending substantially perpendicularly to the passing direction of the covered wire 5 on the inner circumferential surface of the guide plate 31A, the covering wire 5 can be easily covered when passing through the airbag tensioner 31. The contact between the outer circumferential surface of the wire 5 and the inner circumferential surface of the guide plate 31A is almost in a point contact state, and by narrowing the contact area, friction can be suppressed and charging of the outer circumferential surface of the covered wire 5 can be prevented.

A metal adapter 31D connected to a fluid supply pipe 31C is attached to one longitudinal end of both guide plates 31A, and a fluid outlet 31 is attached to an end surface of the adapter 31D.
E has been established. A flat spacer 31F is formed protruding from the periphery of the fluid outlet 31E, and the width of the wire passage space 31G is determined by the thickness of the spacer 31F. The width of the wire passage space 31G varies depending on the diameter of the covered wire 5 used or the height of the protrusion 31B from the inner surface of the guide plate 31A, but in this embodiment, it is approximately 1 + am.

The fluid supply pipe 31C connected to the adapter 31D is
It is connected to a fluid supply source 31H. This fluid supply source 3
1H has a built-in corona discharge means 31HI, for example, and the ion gas separated by this is supplied as a current eliminating body GS2 to the wire passage space 31G from the outlet 31E of the adapter 31D.

Therefore, according to this embodiment, by supplying the current eliminating body Gs2 to the wire passage space 31G, it is possible to apply back tension to the covered wire 5, which is the original purpose of the air bag tensioner 31, and at the same time, it is possible to apply back tension to the covered wire 5, which is the original purpose of the air bag tensioner 31. It is also possible to remove static electricity. Further, as described above, due to the structure of the protrusion 31B on the inner circumferential surface of the guide plate 31A, the contact between the covered wire 5 and the air bag tensioner 31 is almost a point contact. Recharging of the outer circumferential surface of is also suppressed.

The clamper 32 located below the airbag tensioner 31 has a pair of clamper arms 32A as shown in FIGS. The front end can be opened and closed by the operation of a cam mechanism 32C that is engaged at the rear end (FIG. 37). In addition, in a normal state, the pair of clamper arms 32A1 and 32A2 are biased in a direction in which their tips are closed by a spring 32D, etc., and from this state, the cam mechanism 32C is operated to close the clamper arms. 32A1, 32
The tips of A2 move away from each other and clamper 3
2 can be placed in an open state.

Inside the tip of one clamper arm 32A1 (fixed side) is a first clamper chip 32E that is made of hard metal such as stainless steel and has a mirror-finished surface with chrome plating or the like.
1 is fixed. 35 and 3 are located approximately in the center of the chip surface of the first clamper chip 32E1.
A blowout port 32F of the current eliminating body Gs2 as shown in FIG. It is possible to spray the current eliminating body Gs2. The fluid supply source 31H has a built-in corona discharge means 31H1 as described in the description of the air bag tensioner 31 above.

A sub-arm 32G having a predetermined elasticity like a leaf spring is attached to the tip of the other clamper arm 32A2 (movable side) with its base fixed by a screw 32H, etc. A second clamper chip 32E2 made of ruby or the like is fixed. The second clamper chip 32E2 is removable from the clamper arm 32A2 in units of sub-arms 32G, and can be replaced in units of sub-arms 32G if it becomes worn due to a predetermined number of clamping operations. There is. Such a leaf spring-like sub-arm 32
The structure G controls the load force applied to the side surface of the covered wire 5 when the covered wire 5 is clamped, thereby preventing damage to the covered wire 5.

Note that a chip-shaped stopper 32J is fixed to the back side of the second clamper chip 32E2, that is, to the inner end of the movable clamper arm 32A2.

The positional relationship between the clamper 32 and the covered wire 5 is
As shown in FIGS. 5 and 36, the covered wire 5 from the sprocket 14 to the bonding sole 16 is connected to the first and second clamper F-7'32E1.
32E2 is arranged so that it passes approximately through the center between the opposing chip surfaces.

Here, as shown in FIG. 35, a current eliminating body GS2 is constantly blown out from an outlet 32F provided on the chip surface of the first clamper chip 32E1, and this current eliminating body Gs2, for example, As the ion gas passes through the chip surfaces of the coated wire 5 and the second clamper chip 32E2, static electricity charged on the chip surfaces of the coated wire 5 and the second clamper chip 32E2 is removed. According to experiments conducted by the present inventors, it has been confirmed that, in addition to the above-mentioned ion gas, the static eliminating effect can be obtained by spraying N2 gas or the like as the current eliminating body GS2.

Note that if static electricity is to be removed only from the chip surface of the clamper chip 32E2, it is not necessary to arrange the air outlet 32F at the center of the clamper chip surface of the first clamper chip 32E1, but it is possible to wire 5
It becomes possible to blow the current eliminating body Gs2 also to the side surface of the holder.

As a result, static electricity can be removed from the coated wire 5 and adsorbed foreign matter 5D such as small pieces attached to the side surface of the coated wire 5 can be scattered and removed.
The coated wire 5 can be cleaned. Therefore, in this embodiment, it is possible to effectively prevent clogging in the bonding tool 16 caused by the adsorbed foreign matter 5D adsorbed on the coated wire 5, and as a result, the maintenance cycle of the bonding tool 16 is extended, resulting in efficient It is also possible to manufacture a resin-sealed semiconductor device 33. In the eighth embodiment, as described above, since static electricity is effectively prevented on the damper chip 32E2 made of ruby and attached to the tip of the sub-arm 32G, the coated wire 5 can be prevented from being attracted to the damper chip 32E2 and curled. That is, in the prior art, as shown in FIG.
The coated wire 5 was attracted to the wire 2, and the coated wire 5 remained curled even when the clamper 32 was opened. When this is inserted into the bonding tool 16 and wire bonding is performed,
The curl shape also affects the loop shape of wire bonding, reducing the bonding strength between the external terminal 2G (bonding pad) or inner lead 33B and the covered wire 5, and causing wire flow during resin molding due to loop abnormality. That was the result. In addition, since the covered wire 5 is attracted to the charged clamper chip 32E2, the bonding tool 1
The feeding of the coated wire 5 from the wire 6 is not performed smoothly,
This results in extra resistance being applied to the bonding tool 16 when the bonding tool 16 is lowered. There was a possibility that the wire 5 would be broken or a loop abnormality would occur.

Regarding this point, according to Embodiments 8 and 1, since the power is removed (reliably) from the clamper chip 32E2, adsorption of the covered wire 5 to the clamping chip surface is prevented, and as a result, the covered wire 5 As shown in FIGS. 35 and 36, it is inserted straightly and smoothly into the bonding tool 161.

Therefore, bonding failure force due to loop abnormality due to disconnection or curling of the coated wire 5 is effectively prevented.According to research by the present inventors, it has been found that 5 (FIG. 38) is a phenomenon that occurs significantly in the coated wire 5 having the same structure as that described in Example 1. A
It has been found that this phenomenon is highly likely to occur when a wire made of aluminum (Aj) or copper (Cu) is used as a bonding wire.

Next, the structure of the resin-sealed semiconductor device 33 assembled in Example 8 will be briefly described.

In this embodiment 8, the resin-sealed semiconductor device 33
is provided in an unassembled state, that is, in a lead frame 33A state. Figure 40 (showing the state in which wire bonding has already been completed). For convenience, the inner leads of the lead frame 33A are
This will be explained in section B).

As shown in the same figure, the lead frame 33A is extended in four directions on the plane without contacting the tab 33D, centered on the tab 33D supported by the tab suspension lead 33C. Each inner lead 33B is connected to each other by a frame (not shown) at the outer periphery as shown in the figure. Such a frame 33A is made of, for example, Kovar, 42
The alloy 0 is obtained by processing a plate-like member made of nickel alloy or the like with a thickness of about O.L 5 s into the shape shown in FIG. 40 through pressing or etching.

The tab 33D has a thickness of 30 mm as shown in FIG.
The semiconductor chip 2 is fixed via a bonding material 4 such as silver paste, silicon paste, or gold foil, which is deposited to a thickness of approximately μm. Although detailed illustrations are omitted, a microprocessor, a logic circuit, etc. are formed on the upper layer of this semiconductor chip 2 through an oxidation/diffusion process using photoresist technology. To briefly explain the schematic structure of each layer inside the semiconductor chip 2, the thickness is 400 μm.
A silicon oxide film 2A2 with a thickness of about 0.45 μm is formed on the upper layer of the chip substrate 2AI made of silicon (Sl), which is formed at a thickness of about 1.5 μm. It is formed with a thickness. A passivation film 2B as a protective film is deposited on the uppermost layer to a thickness of about 1 to 2 μm, and a part of the passivation film 2B is opened, and a layer of aluminum (Aβ) with a thickness of 0 is partially provided in the lower layer. , 8 μm, and the upper surface of the external terminal 2C is exposed to the outside.

Next, the wire bonding procedure according to this embodiment will be explained. In the following description, it is assumed that the structure of the wire bonding apparatus other than that shown in FIG. 32 is the same as that shown in FIG. 3 described in the first embodiment.

First, when the lead frame 33A is fixed at a predetermined position on the stage surface of the bonding tool 17, the heat of the heater 26 built in the bonding stage 17 is transferred to the lead frame 33A, and the lead frame 33A and the semiconductor The chip 2 is heated to a predetermined bonding condition temperature.

Subsequently, the XY child table 3 is operated to move the bonding head 22 by a predetermined amount, and the bonding tool 16 is stopped at a position directly above the semiconductor chip 2 on the lead frame 33A.

At this time, the clamper 32 is in a state where the covered wire 5 is clamped from the side, and the covered wire 5 is thereby in a state where its position is fixed.

Subsequently, as shown in FIG. 8, using an electric torch 18D,
As shown in FIG. 8 (reproduction diagram illustrating the formation principle of the ball 5A1), the ball 5A1 is formed by placing the coated wire 5 close to the gold wire 5A on the supply side tip side and generating an arc Ac between the two. It is formed. Subsequently, ultrasonic vibration is applied to the bonding tool 16 so that the tip of the bonding tool 16 touches the external terminal 2 of the semiconductor chip 2.
By being pressed by C, the ball 5A1 is bonded onto the external terminal 2C due to the synergistic effect of the heating of the heater 26 and the ultrasonic vibration (1st bonding).

Next, when the cam mechanism 32C in the clamper 32 is activated, each clamper arm 32 Al, 32A2
is in an open state, and the covered wire 5 is released from the clamper 32.

At this time, in this embodiment, the static electricity charged on the other clamper chip 32E2 is reliably removed by blowing the current removing body Gs2 from the outlet 32F of one clamper chip 32E1.
It is possible to insert the covered wire 5 into the bonding tool I6 in a substantially straight state without causing the covered wire 5 to curl as shown in the figure.

In this state, when the vertical movement block 22B and the XY child table 3 in the bonding head 22 are moved by a predetermined amount in their respective directions, the bonding tool 16 feeds out the covered wire 5 from its tip and removes the covered wire 5. It moves in a loop and stops right above a predetermined inner lead 33B (see FIG. 39). At this time, the coated wire 5 fed out from the tip of the bonding tool 16 is supplied from the wire spool 11, passes through the air pack tensioner 31 and the clamper 32, and reaches the bonding tool 16.
gJ, as shown in Figure 35, air pack tensioner 3
1 and the clamper 32. During this time, the current removing body Gs is being blown.
Now, the bonding tool 16 as described in Example 1
The application of ultrasonic vibrations may be continued, or the application of ultrasonic vibrations may be stopped except during bonding.

Next, when the vertically movable block 22B is moved downward again, the tip of the bonding tool 16 lands on the surface of the inner lead 33B with the coated wire 5 led out from the tip.

Subsequently, when the vertical movement block 22B is moved downward again, the tip of the bonding tool 16 reaches the inner lead 33B with the coated wire 5 pulled out from the tip.
land on the surface of Here, when the ultrasonic oscillation mechanism 22H is activated and ultrasonic vibration is again applied to the tip of the bonding 7-rule 16, the coated wire 5 is bonded at the abdomen of the coated wire 5 led out from the punch 7-rule 16. The portion of the coating film 5B rubbed against the surface of the inner lead 33B is exposed to y! by this ultrasonic energy. A part of M5B is destroyed and removed, and the gold wire 5A inside comes into contact with the surface of the inner lead 33B.

By continuing to apply ultrasonic vibration in this state, the gold wire 5A and the inner lead 33B are bonded to each other as shown in FIG. 39 (second bonding).
.

Next, the clamper 32 is closed and the bonding tool 1
When the covered wire 5 is held above the bonding tool 6 and the vertical movement block 22B is moved upward, the covered wire 5 is cut between the bonding portion of the covered wire 5 and the bonding tool 16, and one cycle is completed. wire bonding work is completed.

The wire bonding process of this embodiment is completed by repeating the above wire bonding operation in a predetermined cycle between all the external terminals 2C (bonding pads) on the semiconductor chip 2 and the corresponding inner leads 33B. .

In this way, in the eighth embodiment, the air pack tensioner 3
static elimination of the covered wire 5 by the current elimination body Gs2 from 1;
In addition, the covered wire 5 is attracted and the adsorbed foreign matter 5D is removed through the neutralization of the clamper chip 32E2, so that breakage of the covered wire 5, loop abnormality, clogging of the bonding tool, etc. during wire bonding are reliably prevented. Prevented.

In this way, in the eighth embodiment, wire bonding using the coated wire 5 can be practically realized.
Cross-bonding, etc. at the part indicated by a in the figure is also possible, making it possible to realize highly functional and highly integrated microprocessors or logic elements.

In addition, at the location indicated by b in FIG. 40, wire bonding is performed with the covered wire 5 straddling the tab suspension lead 33C, so there is a possibility that the covered wire 5 and the tab suspension lead 33C come into contact with each other at 1g. expensive. but,
Even if the coated wire 5 comes into contact with the tab suspension lead 33C, in the eighth embodiment, the coating film 5B only comes into contact with the tab suspension lead 33C, thereby preventing an electrical short circuit.

In this manner, in the eighth embodiment, wire bonding, which has been difficult with conventional bare gold wires, can be achieved.

After completing the wire bonding process as described above, the lead frame 33Δ is placed in a mold (not shown),
The package body 33 of the resin-sealed semiconductor device 33 is injected into the mold at high pressure by injecting molten synthetic resin into the mold.
E (see FIG. 41) is formed. At this time, if there is an abnormality such as curl in the loop shape of the bonded covered wire 5, the injection pressure of the synthetic resin may cause contact between the covered wires 5 (wire loop) or contact between the covered wire 5 and the tab 33D. There is a high possibility that defects such as contact (tabunyoto) will occur. However, according to this embodiment, in the wire bonding process, as described above, the air pack tensioner 31 removes the static electricity from the covered wire 5 and the clamper chip 32E2, so that when each part of the clamper 32 etc. passes through the Since adsorption of the covered wire 5 and adhesion of foreign matter are effectively prevented, bonding defects such as wire breakage and abnormalities in the shape of the wire loop due to these are prevented, and highly reliable wire bonding is realized.

After the injected synthetic resin is cooled and hardened as described above, the lead frame 33A on which the package body 33E is formed is taken out from the mold.

Next, the outer leads 33G protruding from the package body 33E are processed to be electrically separated and independent, and the outer leads 33G are further bent at a predetermined angle to form a resin-sealed type as shown in FIG. A semiconductor device 33 is obtained.

Although the invention made by the present inventor has been specifically explained based on Examples 1 to 8 above, the present invention is not limited to the above-mentioned Examples, and various changes can be made without departing from the gist thereof. Needless to say.

For example, the present invention is not limited to coated wires, but can also be applied to bonding wires consisting only of bare wires, and in either case, the bonding temperature is, for example, 160 to 300°C.

Furthermore, the semiconductor devices to which the present invention can be applied are not limited to the examples shown in FIGS. 11, 12, 40, and 41, but are, for example, as shown in FIGS. It can also be widely applied to semiconductor devices.

In the examples of these various semiconductor devices, not only the memory type semiconductor devices shown in FIGS. 12, 42, and 43 but also the logic type semiconductor devices shown in FIGS. Both wire and ring wire are available.

Further, in the logic type semiconductor devices shown in FIGS. 11 and 44, coated wires are advantageous in order to prevent wire shorts, but bare wires can of course also be used.

In addition, when a bare wire is used as the bonding wire, the fluid supply pipe 31C for blowing off the covering material in the above embodiment can be omitted.

In addition, the blow of the current eliminating body GS2 from the air outlet 32F is as follows:
I explained that it is always done during wire bonding, but
The blowing cycle may be controlled and performed at predetermined time intervals. It goes without saying that when the coated wire 5 is reinserted into the bonding tool 16 during maintenance of the apparatus, the blowing of the current eliminating body Gs2 from the air outlet 32F is stopped.

In each of the embodiments, ion gas separated by corona discharge or N2 gas was used as the current eliminating body GS2 for blowing, but the current eliminating body GS2 is not limited to these. It is known that static electricity can be removed by irradiation with α-rays or β-rays, irradiation with ultraviolet rays, and even by spraying liquid such as water, and static electricity removal methods using these methods may also be used. .

Furthermore, the materials for forming the coating film 5B or 5C, such as the polyol component, isocyanate 5 terephthalic acid 1 and its compound, as well as the types and compositions of additives, are not limited to the examples described above.

In the above explanation, the invention made by the present inventor was mainly applied to the field of application, which is a wire bonding device that combines thermocompression bonding and ultrasonic bonding, but the invention is not limited to this. For example, it can also be applied to an ultrasonic bonding type wire bonding device.

Furthermore, in the above description, the invention made by the present inventor is mainly applied to a resin-encapsulated semiconductor device, which is the field of application of the invention, but the invention is not limited to this, for example, a ceramic-encapsulated semiconductor device. The present invention can be widely applied to various semiconductor devices such as devices and their manufacturing techniques.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

(1) 1 The bonding wire for semiconductor devices of the present invention is:
0.03-0.3% by weight of germanium and o, o
o.

5 to 0.01% by weight of calcium and each other and 9
By working synergistically with gold having a high purity of 9.99% by weight or more, the fatigue life of the gold wire can be effectively extended.

(2) According to (1) above, it is possible to prevent the crystal grains in the neck portion from becoming coarse during ball formation, and thereby to prevent neck breakage.

(3) According to the above (1), the mechanical properties such as the breaking load of the gold wire and the reliability of bonding can be improved.

(4)5. The contents of germanium and calcium are 0.05 to 0.15% by weight and 0.001 to 0.0% by weight, respectively.
By setting the content to 0.003% by weight, it is possible to obtain a better fatigue life extension effect and/or a better effect of preventing neck portion crystal grain coarsening (preventing neck breakage).

(5) Furthermore, by covering the bonding wire for semiconductor devices of the present invention with an insulating material, it is possible to prevent short-circuits between wires due to contact between wires or chip short-circuits due to contact with chip ends, and even short-circuits due to contact with tabs. It is possible to eliminate problems such as tab shorts.

(6) and [5] above enable long-distance bonding, thinning of wires, and formation of small balls.

(7), (5), and (6) above make it possible to increase the number of bins (multiple terminals) and, in turn, increase the degree of integration of semiconductor devices.

(8) Furthermore, the bonding wire for semiconductor devices of the present invention has a breaking load of 15 to 30 kg/am' and an elongation rate of 10 to 25%, which improves mechanical properties and provides excellent bonding. performance.

(9) In addition, the heat-resistant polyurethane used to cover the gold wire in the present invention can be bonded even at the bonding temperature or ultrasonic vibration energy during normal wire bonding because the urethane bond is decomposed and bonding is possible. Reliable bonding can be achieved by a combination of thermocompression bonding by heating and ultrasonic vibration, or by ultrasonic vibration. In that case, if local heating of the bonding site is also used, more reliable wire bonding becomes possible.

[Brief explanation of drawings]

Fig. 1 is a half-sectional view of a resin-sealed semiconductor device using bonding wire, which is an embodiment of the present invention, Fig. 2 is a schematic enlarged sectional view of a wire bonding part, and Fig. 3 is used in the present invention. FIG. 4 is a perspective view of the main parts thereof; FIG. 5 is a partial sectional view showing a specific structure of the main parts of the wire bonding apparatus; FIG. Fig. 7 is a cross-sectional view taken along the cutting line - - in Fig. 6, Fig. 8 is a schematic diagram showing the principle of ball formation, and Fig. 9 is a diagram showing the wire bonding. Fig. 10 is an enlarged perspective view of the main parts of the spool of the device; Fig. 11 is a schematic plan view of a local heating section for wire bonding; Fig. 12 shows an example of wire bonding. 13 is a partial sectional view showing the tip touch state of the covered wire; FIG. 14 is an enlarged partial sectional view showing the tip touch state; FIG. 15 is a partial sectional view showing the tab touch state of the covered wire; FIG. 16 is an enlarged partial sectional view showing the tab short circuit state, FIG. 17 is a diagram showing the short circuit rate between the semiconductor chip and the coated wire with respect to the temperature cycle in the present invention, and FIG. 18 is a diagram showing the short circuit rate between the tab and the coated wire with respect to the temperature cycle in the present invention. 19 is a model diagram showing the experimental conditions used to evaluate the coating film of the covered wire used in the present invention, and FIGS. A diagram showing the results of a comparative experiment on the abrasion strength of the coating film,
Figure 22 is a diagram showing experimental results regarding the relationship between temperature and deterioration rate in the present invention. Figure 23 is a diagram showing the imidization rate of the coating film (horizontal axis), deterioration rate, or deterioration rate (vertical axis on the left). Figure 24 is a diagram showing the experimental results regarding the relationship between the second (2nd) bonding peeling strength (vertical axis on the right) of the coated wire, and Figure 24 is a diagram showing the experimental results regarding the temperature cycle amplitude and temperature cycle life of the coated wire. Figure 25 shows the deterioration rate (
Figures 26 to 31 are partial cross-sectional views for explaining the wire bonding states in Examples 2 to 7 of the present invention, and Figure 32 is according to Example 8 of the present invention. FIG. 33 is an explanatory diagram showing the route of the covered wire from the wire spool to the bonding tool in the wire bonding apparatus; FIG. 33 is a partially cutaway perspective view showing the structure of the airbag tensioner in Example 8; FIG. 34 35 is a schematic sectional view showing the clamper of Embodiment 8, FIG. 36 is an enlarged perspective view showing the vicinity of the clamper, and 37 is the same. 38 is a schematic sectional view of the clamper in the prior art for comparison with FIG. 35, and FIG. 39 is an explanatory sectional view showing the wire bonding state in Example 8. 40 is an explanatory plan view showing a lead frame in a wire bonding state according to Example 8, FIG. 41 is an overall sectional view of a resin-sealed semiconductor device obtained according to Example 8, and FIGS. 42 to 44 45 and 46 are diagrams showing experimental results of breaking load and elongation rate of gold wire in the present invention, and FIGS. 47 to 49 are diagrams showing various embodiments of semiconductor devices to which the present invention can be applied.
The figure is a diagram showing the results of a fatigue strength test of gold wire in the present invention. DESCRIPTION OF SYMBOLS 1...Resin-sealed semiconductor device, 2...Semiconductor chip, 2A...Substrate, 2Δ1...Chip substrate, silicon oxide film 2Δ2 2A3...PSG film, 2B...
Bangbanyon film, 2C...external terminal (bonding pad), 3...lead, 3A...tab, 3B...
... Inner lead, 4 ... Bonding material, 5 ... Covered wire, 5A ... Gold wire, 5A1 ... Ball, 5
A11゜5AI2...1st bonding part, 5A2
．． 5A22=2nd bonding part, 5B, 5Ba...
- Coating film, 5c... Second coating film, 5D... Adsorbed foreign matter, 6... Resin material, 1o... Bonding device main body, 11... Wire spool, 11A... Connection terminal,
11Aa...Insulator, 11Ab...Conductor, 11A
c... Connection metal part, 12... Bonding part, 1
3... Tensioner, 14... Sprocket, 15...
・・Clamper I6・・Punch Ingur (Cow Yapirari), 16A・Bonding arm, 16B・
...Through hole, 16C... Conductive material, 17... Bonding arm, 18A... Covering member, 18B...
Tool insertion port, 18C...Cooling fluid spray nozzle, 18
D... Electric torch (arc electrode), 18E... Suction tube, 18F... Holding member, 18G... Supporting member, 1
8H...Insulating member, 181...Crankshaft, 18J
... Shaft, 18K... Drive source, 19... Suction device, 20... Arc generator, 21... Spool holder, 21A... Rotating shaft, 22... Bonding head (digital bonding head), 22A...
・Guide member, 22B...Vertical movement block, 22C・
... Female thread member, 22D... Male thread member, 22E...
・Motor, 22F... Rotating shaft, 22G... Elastic member, 22H... Ultrasonic oscillation mechanism, 23... XY table, 24... Base, 25... Cooling fluid spray device (fluid source), 25A...cooling device, 25B...flow meter,
25C...Fluid conveyance pipe, 25D...Insulating material, 25E
...Corona discharge means, 26...Heater, 26A...
・Power line, 31... Air pack tensioner, 31A...
・Guide plate, 31B...Protrusion, 31C...Fluid supply pipe, 31D...Adapter, 31E...Fluid outlet,
31F... Spacer, 31G... Wire passage space,
31H... Fluid supply source, 31H1... Corona discharge means, 32... Clamper, 32 Al. 32A2... Clamper arm, 32B... Shaft support, 32C... Cam mechanism, 32D... Spring, 32E1
...First clamper chip, 32E2...Second clamper chip, 32F...Air outlet, 32G...Sub arm, 32H...Screw, 32J...Stopper,
33... Resin-sealed semiconductor device, 33A... Lead frame, 33B... Inner lead, 33C...
Tab suspension lead, 33D...Tab, 33E...Pan cage body, 33G...Outer lead, C1/capacitor, C2...Storage capacitor, D...Silisk for arc generation, R...Resistance , D, C...DC power supply, GND...Reference potential, Gs...Cooling fluid, Gs
2... Current removing body, ■... Voltmeter, A... Ammeter. Agent Patent Attorney Daiwa Tsutsui Figure 19: Suction device diagram ■ 18A: Covering member 18E: Suction pipe Figure 1A Figure 11 Figure 13 Figure 15 Figure 16 Figure 18 Figure Wetness cycle No. 17 Figure Wetness cycle Figure 19 Figure 22 Figure Temperature [℃] (xlooHrs) Figure 24 Temperature cycle amplitude (-55 to 150℃) Id conversion rate Figure 25 Wetness [℃] (XI 0OHrs) Figure 26 Figure 27 Figure 08 Figure 29 Figure 30 et al Figure 32 Figure 31 Figure 34 Figure 35 Figure 38 Figure 40 Figure 33A Figure 42 Figure 45 Gold wire diameter: 25 μm Temperature (1) Figure Temperature (°C) Number of figure repetitions (N)

Claims (1)

[Claims] 1. Gold having a high purity of 99.99% by weight or more, 0.
03-0.3% by weight of germanium and 0.0005-0.0005% by weight of germanium
A bonding wire for a semiconductor device, characterized in that it contains 0.01% by weight of calcium. 2, 0.05-0.15% by weight of germanium;
2. The bonding wire for a semiconductor device according to claim 1, further comprising 0.001 to 0.003% by weight of calcium. 3. The bonding wire for a semiconductor device according to claim 1 or 2, wherein the bonding wire is coated with a coating film made of an insulating material. 4. The bonding wire for a semiconductor device according to claim 3, wherein the insulating material is made of a heat-resistant polyurethane resin. 5. Breaking load of 15~30kg/mm^2 and 10~25
Claims 1, 2, and 3 characterized in that the elongation rate is %.
Or the bonding wire for semiconductor devices according to 4.