JPH0636416B2 - Conductive adhesive film for fixing semiconductor elements - Google Patents

Description

The present invention relates to a so-called adhesive film for die bonding for fixing a semiconductor element on a substrate such as a stem or a lead frame.

Die bonding is a method of adhesively fixing a semiconductor element to a semiconductor substrate such as a stem or a lead frame. Conventionally, as a material for die bonding for this adhesive fixation,
Au- that also has an electrical connection function between the substrate and the element
Si eutectic and conductive silver paste compositions are known.

The Au-Si eutectic is to form a metal adhesion layer made of Au-Si eutectic alloy by applying Au plating on the substrate in advance and crimping a silicon chip as a semiconductor element on it at a high temperature. Further, the conductive silver paste composition is one in which silver powder as a conductive material is kneaded into a solution of a precursor of an epoxy resin or a polyimide resin to form a paste, which is intercalated and coated between a substrate and an element and then heat-cured. Is.

However, the Au-Si eutectic bonding described above can achieve highly reliable bonding in a short time, but is expensive because it requires expensive Au.

On the other hand, in the case of the conductive silver paste composition, since the precursor of the epoxy resin or the polyimide resin is used as the binder of the silver powder, it takes a long time to cure, and the die is more difficult than the Au-Si eutectic. In addition to the disadvantage of poor workability in bonding, the epoxy resin, in particular, lacked moisture resistance at high temperatures, causing the wiring pattern of the element to corrode over time. Further, this kind of paste composition has a drawback that it is difficult to apply it to a uniform thickness on a substrate, which causes a tilt of a semiconductor element, which hinders wire bonding and causes uneven distortion of the element. .

All of these drawbacks are based on the characteristics of the binder resin and the liquid (paste) coating method.

From the above viewpoints, the inventors of the present invention have conducted extensive studies to find a suitable die bonding material for a semiconductor element that does not require backside metallization, and as a result, have fused a thermoplastic resin on both sides of a heat resistant film. It was found that a film-like material coated as an agent is extremely useful as the above-mentioned material, and it has been already proposed as Japanese Patent Application No. 58-111286.

According to this adhesive film, by thermocompressing the substrate and the semiconductor element via this film, it is possible to die-bond in an instant due to the thermal fusion property of the fusion agent of the film. The workability of die bonding can be greatly improved as compared with the one using a thermosetting resin such as the epoxy resin or the precursor of the polyimide resin. Moreover, since expensive Au is not used, the cost of the semiconductor device can be reduced.

Further, according to the above-mentioned film, there is no fear that the moisture resistance characteristic of the conventional silver paste composition using an epoxy resin is deteriorated. In particular, when a fluorine-based polymer is used as the fusing agent, a drastic improvement in the above moisture resistance property can be expected.

Furthermore, since die bonding with this type of film does not cause the unevenness of the adhesive layer thickness as seen in the conventional paste-like material coating method, it may interfere with the subsequent wire bonding or cause a semiconductor device failure. A highly reliable semiconductor device can be obtained from this point as well, without the problem of causing non-uniform distortion.

As described above, according to the adhesive film, it is possible to obtain a highly reliable semiconductor device with good productivity and economical efficiency.

However, the above-mentioned adhesive film that has been already proposed can be applied only to a semiconductor device or device in which the metallization on the back surface is unnecessary and the sub-electrode can be pulled out from the bonding pad on the semiconductor device.

Therefore, the present inventors have intended to provide the adhesive film with conductivity for the purpose of obtaining a conductive adhesive film that can be applied to a semiconductor element that requires metallization on the back surface while keeping the advantages of the adhesive film. As a result of intensive studies, the present invention has been completed.

That is, according to the present invention, a mixture of a thermoplastic resin and a conductive filler is applied to both sides of a conductive film as a fusing agent, and the melting point of the thermoplastic resin is 170 to 320 ° C. The melting point of one thermoplastic resin on both sides of the film is 15 ° C. or more higher than the melting point of the other thermoplastic resin, and the decomposition temperature of both thermoplastic resins is 30 higher than the melting point of the higher thermoplastic resin.
The present invention relates to a conductive adhesive film for fixing a semiconductor element, which is characterized by having a temperature of not less than ° C.

The conductive adhesive film for fixing a semiconductor element of the present invention has the advantages of the above-mentioned adhesive film already proposed, namely,
Die bonding workability can be greatly improved compared to the conventional one using a thermosetting resin such as a precursor of epoxy resin or polyimide resin, and since expensive Au is not used, semiconductor device Can contribute to cost reduction,
There is no possibility of causing deterioration of moisture resistance characteristics such as a silver paste composition using a conventional epoxy resin, and further, there is an advantage that there is no defect found in a conventional pasty material coating method, and Au-Si Since it has an electrical connection function comparable to that of a eutectic or a conductive silver paste composition, this conductive adhesive film can be applied to a semiconductor element that requires backside metallization, A highly reliable semiconductor device can be obtained with good productivity and economy.

The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a conductive adhesive film for fixing a semiconductor element according to the present invention. This adhesive film 1
Is a conductive film composed of a metal thin film such as Al or Cu, a film obtained by mixing a heat-resistant resin such as polyimide resin or polytetrafluoroethylene with a conductor such as silver particles to form a thin film, and the like 2. And a fusion agent 3,3 'formed by applying a mixture of a thermoplastic resin and a conductive filler such as carbon or silver particles by solution coating or melt coating. There is.

The heat-resistant resin in the conductive film 2 usually has heat resistance higher than the fusing temperature of the fusing agents 3 and 3 '. On the other hand, as the thermoplastic resin in the fusing agents 3 and 3 ', resins having different melting points from each other on both sides of the film are used. Such a thermoplastic resin has a melting point of 17
It is in the range of 0 to 320 ° C., the melting point of one thermoplastic resin is 15 ° C. or more higher than the melting point of the other thermoplastic resin, and the thermal decomposition temperature of both resins is 3 higher than the melting point of the resin on the high melting point side.
It is preferably as high as 0 ° C or higher. According to the conductive adhesive film obtained in this case, the adhesive film is pre-fused to the back surface of the silicon wafer through a fusion agent containing a thermoplastic resin having a lower melting point to form a wafer with a conductive adhesive film. This wafer can be scribed in full cut to form a semiconductor device with a conductive adhesive film, and this semiconductor device is diced to a stem or lead frame via a fusion agent containing a thermoplastic resin with a higher melting point. Since the bonding can be performed, it is not necessary to cut the conductive adhesive film in accordance with the size of the semiconductor element, and the workability of die bonding can be further improved.

On the other hand, if the melting point of the thermoplastic resin in the fusing agent 3, 3'is too low, the heat resistance of the semiconductor device is likely to cause a problem, and if it is too high, a high temperature is required during die bonding, which is not preferable. . If the melting points of the thermoplastic resins having different melting points are too small, the melting point of the high melting point side when the adhesive film is fused to the back surface of the silicon wafer via the fusion agent containing the thermoplastic resin of the low melting point side. It is not preferable because the resin-containing fusing agent becomes sticky and dust or the like adheres to it. Furthermore, if the difference between the melting point of the resin on the high melting point side and the thermal decomposition temperature of one or both of the resins is too small, a thermoplastic resin is used when die-bonding with a fusion agent containing the resin on the high melting point side. Is not preferable because it thermally decomposes.

Further, as the thermoplastic resin, a fluorine-based polymer is preferable, and in some cases, a polyester having a melting point similar to the above,
Other thermoplastic resins such as nylon 6.6 and polyparaphenylene sulfide may be used.

The fluorine-based polymer usually has a fluorine content of 20.
An amount of at least 50% by weight, preferably 50 to 76% by weight is used. In particular, a homopolymer or copolymer of perfluoroalkene or perfluorovinyl ether is suitable, and a typical example thereof is tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter referred to as FEP), a structural formula; (However, in the formula, Rf has 7 or less carbon atoms, preferably 1 to 3 carbon atoms.
A tetrafluoroethylene-perfluorovinyl ether copolymer (hereinafter referred to as PFA). Above P
Commercially available products of FA include NEOFLON PFA manufactured by Daikin Industries, Ltd. and Teflon PFA manufactured by Dyupon Co.

As the other fluorine-based polymer, one in which a part of fluorine of PFA represented by the above structural formula is replaced with hydrogen, polychlorotrifluoroethylene (hereinafter referred to as PCTF)
E), ethylene-tetrafluoroethylene copolymer (hereinafter referred to as ETFE), ethylene-chlorotrifluoroethylene copolymer and the like can also be used.

These fluorine-based polymers are non-adhesive at room temperature, but have the property of easily adhering to metals etc. when heated above the melting point, and the polymer flow during melting is small. is doing.

Particles of carbon, silver or the like are preferable as the conductive filler to be blended with the thermoplastic resin as described above, but other metal particles can also be used. The conductive filler may be different depending on the surface of the conductive film. Regarding the use ratio of these conductive fillers, the ratio of the conductive filler and the thermoplastic resin in the total amount is usually 3 to 5% by weight for carbon, and usually 70 to 85% by weight for silver. It is good to say If the proportion is too low, the electroconductivity of the electroconductive adhesive film will be insufficient, and if it is too high, it will be difficult to disperse uniformly and the adhesiveness will be lowered, such being undesirable.

The combination of the conductive filler and the thermoplastic resin is not particularly limited. However, with this combination, the conductivity of the resulting conductive adhesive film may be slightly reduced, but in such a case, sufficient electrical conductivity can be obtained by etching the adhesive film surface of the adhesive film using a method such as spatula etching. Sex is obtained.

The thickness of the conductive adhesive film 1 having the above structure is generally 7 to 150 μm, preferably 20 to 11 μm.
0 μm, and the thickness of the conductive film 2 is 5 to 5 μm.
90 μm, preferably 10 to 70 μm, and the thickness of each of the fusion agents composed of the thermoplastic resin and the conductive filler applied to both surfaces of the film 2 is 1 to 30 μm,
It is preferably 5 to 20 μm.

2 and 3 show an example of a semiconductor device in which a semiconductor element is die-bonded using the conductive adhesive film 1 of the present invention. Reference numeral 4 denotes a lead frame 5a as a semiconductor substrate. The semiconductor element die-bonded, that is, fixed and adhered by the film 1,
6 is a bonding wire that connects the electrodes 7 and 7 formed on the element 4 to the other lead frames 5b and 5c, and 8 is a sealing resin that integrally encloses each of the above components.

In the die bonding of the element 4 with the conductive adhesive film 1, the conductive adhesive film 1 is first bonded to the back surface of the silicon wafer to prepare a wafer with a conductive adhesive film. FIG. 4 shows an example of the wafer with a conductive adhesive film, 9 is a silicon wafer, and 10 is a wafer with a conductive adhesive film formed by bonding the conductive film 1 to the wafer 9. The melting point of the thermoplastic resin contained in the fusing agent 3 in the conductive adhesive film 1 is lower than the melting point of the resin contained in the fusing agent 3 '.

The wafer 9 with a conductive adhesive film is scribed in a full cut to form a semiconductor element with a conductive adhesive film, and a fusion agent 3'containing a resin on the high melting point side of the film 1 is formed on a lead frame as a semiconductor substrate. Die bonding is performed by hot pressing under the temperature of melting and softening.

Thus, in the semiconductor device obtained by using the conductive adhesive film of the present invention as a material for die bonding, the substrate and the element are electrically connected by this adhesive film, and the substrate at this time is The resistance between the device and the device depends on the thickness of the adhesive film, etc., but is usually 10 ⁻³ to 2 × 1.
It is about 0 ² Ω, which is comparable to the conductivity of the Au—Si eutectic and the conductive silver paste composition.

Examples of the present invention will be described below for more specific description. In the following,% means% by weight.

Examples 1 to 5 For each side of a conductive film as shown in Table 1 below, 10 μm of a fusion agent containing a conductive filler (powder) in a thermoplastic resin having different melting points shown in the same table ( However, in Example 5, a conductive coating film for fixing a semiconductor element of the present invention was obtained by melt coating with a coating thickness of 20 μm.

In the table, the term "conductive polyimide" means a conductive polyimide film obtained by curing a paste (trade name JR10000) made of a Nitto Denki Kogyo polyimide resin precursor and silver powder into a film. .

The conductive adhesive film obtained as described above was applied to the back surface of a silicon wafer by using a roll on a hot plate at 290 ° C. with the surface containing the resin having the lower melting point among the thermoplastic resins as a fusion agent. A wafer with an adhesive film was obtained by fusion. The obtained wafer with an adhesive film was scribed to obtain semiconductor elements with an adhesive film each having a size of 3 mm × 3 mm.

Next, these semiconductor elements with an adhesive film were each placed on a 42 alloy plate, which is a lead frame material, through a fusion agent containing a resin having a higher melting point of the adhesive film, at 350 ° C., respectively.
It was thermocompression bonded under the conditions of 5 kg / cm ² and 5 seconds. After the bonding, it was cooled to room temperature and the shear adhesive force was measured using a push-pull gauge, but in both cases, the adhesive strength was large and the element was broken. Further, when the respective shear adhesive strengths were measured at the measurement temperatures shown in Table 2 below, the adhesive strengths as shown in Table 2 below were exhibited, and all values were equal to or higher than the adhesive strength required during wire bonding. It was

Further, the resistance between the semiconductor element and the 42 alloy plate at the time of adhesion was measured, and the results are also shown in Table 4 below.

Next, using the above-mentioned adhesive film, a model element for measuring aluminum corrosiveness was die-bonded to a 16-pin DIP lead frame in the same manner as described above, and predetermined wire bonding was performed. A semiconductor device was produced by molding and sealing with an epoxy molding material MP-10. About this device, 143 ° C, 4 atm, 95% R
An H, 10 volt bias pressure test was performed. The results are as shown in Table 3 below.

Comparative Example 1 A 42 alloy plate was plated with gold and a silicon chip was pressure bonded under the conditions of 350 ° C., 5 kg / cm ² , and 5 seconds for Au—Si.
A eutectic alloy was formed and bonded. At this time, the resistance between the silicon chip and the 42 alloy plate was 1 × 10 ⁻³ Ω. When the shear adhesive strength at 200 ° C. was measured, the chip broke. Further, a required portion of the lead frame of the 16-pin DIP is plated with gold, and a model element for measuring aluminum corrosion is die-bonded by forming an Au-Si eutectic alloy on the lead frame. We conducted a Shark Tuker Bias test. The results are as shown in Table 3 below.

Comparative Example 2 A commercially available epoxy-based silver paste composition was used.
After coating on an alloy plate, a silicon chip was placed on the alloy plate and cured at 180 ° C. for 1 hour to bond the chip to the 42 alloy plate. The resistance between the silicon chip and the 42 alloy plate at this time was 5 × 10 ^-2 Ω. Also, when the shear adhesive strength at 200 ° C. was measured, it was 2
It had a sufficient adhesive strength of 0 kg / cm ² . Next, a model element for measuring aluminum corrosion was die bonded onto the lead frame of a 16-pin DIP under the curing condition of 180 ° C. for 1 hour using the above silver paste composition. We conducted a Shark Tuker Bias test. The results are as shown in Table 3 below.

As is clear from the above results, according to the conductive adhesive film of the present invention, it is possible to adopt a bonding method using an Au-Si eutectic alloy, which is said to have extremely high workability and high reliability in the past. It can be seen that a semiconductor device having good moisture resistance reliability and conductivity comparable to that of the semiconductor device can be obtained.

[Brief description of drawings]

FIG. 1 is an adhesive film for fixing a semiconductor element of the present invention, FIG. 2 is a sectional view showing an example of a semiconductor device produced by using the above film, FIG. 3 is a plan view of the same, and FIG. 4 is a conductive adhesive film. Attached wafer. 2 ... Heat-resistant film, 3, 3 '... Fusing agent composed of thermoplastic resin and conductive filler.

Front Page Continuation (72) Inventor Haruo Tabata 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denki Kogyo Co., Ltd. (56) Reference JP-A-58-77273 (JP, A) JP-A-56- 45060 (JP, A) JP 57-128933 (JP, A) JP 57-104234 (JP, A) Actually developed 57-102137 (JP, U)

Claims (3)

[Claims] 1. A mixture of a thermoplastic resin and a conductive filler is coated on both sides of a conductive film as a fusing agent, and the melting point of the thermoplastic resin is 170 to 320.
And the melting point of one of the thermoplastic resins on both sides of the film is 15 than the melting point of the other thermoplastic resin.
A conductive adhesive film for fixing a semiconductor element, characterized in that the temperature is higher than 0 ° C and the decomposition temperature of both thermoplastic resins is higher than the melting point of the thermoplastic resin having a higher melting point by 30 ° C or higher. 2. The conductive adhesive film for fixing a semiconductor element according to claim 1, wherein the thermoplastic resin is a fluorine-based polymer. 3. The conductive adhesive film for fixing a semiconductor element according to claim (2), wherein the fluorine-based polymer is a homopolymer or copolymer of perfluoroalkene or perfluorovinyl ether.