KR20210135136A - Adhesive transfer film and bonding method using the same - Google Patents

Abstract

An adhesive transfer film of the present invention comprises: a base film (11); an adhesive layer (12) formed on the base film (11); and an adhesive layer (13) having a multilayer structure which is formed on the adhesive layer. The present invention exhibits high thermal conductivity and high breaking strength, and minimizes defects due to cracks in an adhesive layer by controlling the shape of both ends of the adhesive layer, which is the starting point of cracks, thereby having the advantage of being able to improve product reliability.

Description

Adhesive transfer film and bonding method using same

The present invention relates to an adhesive transfer film, to an adhesive transfer film capable of obtaining excellent bonding strength in bonding power semiconductor chips constituting a power module, and to a bonding method using the same.

The power module changes the voltage used in electric vehicles from direct current to alternating current and supplies it to the motor. Due to the high performance of electric vehicles, semiconductor chips mounted on power modules are changing from silicon (Si) to silicon carbide (SiC) with excellent performance. However, heat dissipation is important because power modules using silicon carbide semiconductors generate high heat due to high voltage.

The power module uses a bonding method using Ag sintering paste to mount a semiconductor chip between two substrates and to improve the heat dissipation characteristics of the semiconductor chip. However, in bonding using Ag sintering paste, it is difficult to uniformly apply Ag sintering paste to semiconductor chips or spacers. There is a problem that requires

In addition, the power module uses a soldering bonding method to prevent damage to the semiconductor chip when bonding each component, but the soldering bonding has a problem in that the bonding is separated due to low bonding strength.

It is an object of the present invention to manufacture Ag sintering paste in a film form in the bonding process for bonding semiconductor chips and spacers to a substrate to enable uniform thickness and void-free bonding, and to secure high thermal conductivity and An object of the present invention is to provide an adhesive transfer film having high breaking strength after sintering and minimizing defects due to cracking, and a bonding method using the same.

According to a feature of the present invention for achieving the above object, the present invention includes a base film, an adhesive layer formed on the base film, and an adhesive layer having a multilayer structure formed on the adhesive layer.

The adhesive layer is an Ag adhesive layer, and the Ag adhesive layer contains 98 to 99 wt% of Ag powder and 1 to 2 wt% of a binder.

Ag powder consists of flaky nanoparticles.

The adhesive layer includes a first adhesive layer laminated on the upper surface of the adhesive layer, a second adhesive layer laminated on the upper surface of the first adhesive layer, and a third adhesive layer laminated on the upper surface of the second adhesive layer, and the first adhesive layer to the third adhesive layer are flaky Including Ag powder made of nanoparticles, the average particle diameter of the Ag powder particles included in the second adhesive layer is relatively smaller than the average particle diameter of the Ag powder particles included in the first adhesive layer and the third adhesive layer.

The adhesive layer includes a first adhesive layer laminated on the upper surface of the adhesive layer, a second adhesive layer laminated on the upper surface of the first adhesive layer, and a third adhesive layer laminated on the upper surface of the second adhesive layer, the first adhesive layer and the third adhesive layer are nanoparticles Ag powder made of, and the second adhesive layer may include Ag powder made of flake-like nanoparticles. In this case, the average particle diameter of the Ag powder included in the second adhesive layer is relatively smaller than the average particle diameter of the Ag powder included in the first adhesive layer and the third adhesive layer.

The thickness of the adhesive layer may be in the range of 40 μm to 60 μm.

The base film is a PET film.

The adhesive layer is OCA.

The adhesive layer has a porosity in the range of 7% to 8% after pressure sintering.

The bonding method using the adhesive transfer film includes a preparation step of preparing an adhesive transfer film, a transfer step of transferring the adhesive layer on the adhesive transfer film to an object, and a temporary bonding step and a temporary bonding step of bonding the object to which the adhesive layer is transferred to the substrate through the adhesive layer Then, it includes a bonding step of bonding the object to the substrate by sintering.

The preparation step includes the steps of preparing a base film, forming an adhesive layer on the base film, and coating the Ag sintering paste on the adhesive layer and drying the adhesive layer three or more times to form an adhesive layer having a multilayer structure. include

The transfer step includes fixing the adhesive transfer film to the die, fixing the object to the upper chuck that adsorbs and fixing the object using vacuum, and heating the upper chuck to a temperature of 100 to 170°C and heating the die to 80-100°C and then transferring the adhesive layer on the adhesive transfer film to the object by heating the object fixed to the upper chuck toward the adhesive transfer film side.

In the bonding step, sintering is performed for 2 to 5 minutes while heating and pressurizing the temporary bonding body of the object and the substrate at 240 ~ 300 ℃.

The temporary bonding step and the main bonding step may be performed at the same time.

The object may include a semiconductor chip and a spacer.

The present invention prepares an adhesive transfer film in which Ag sintering paste is coated on a base film three times or more and dried to form an Ag adhesive layer having a multilayer structure on the base film, and the adhesive transfer film is applied to a semiconductor chip and a spacer on a substrate Used for bonding.

The Ag adhesive layer has a small shrinkage during sintering because the Ag powder particles have a flake shape, and since the Ag adhesive layer is composed of a multi-layer structure and different powder particles, there is an advantage in removing residual stress that is the starting point of cracks. Defects are minimized, and high breaking strength (tensile strength) of 50 MPa or more can be secured.

In addition, the above-described Ag adhesive layer can secure high thermal conductivity by minimizing pores when bonding semiconductor chips and spacers to a substrate by applying a pressure sintering method, and can shorten the sintering time to increase process efficiency there is

1 is a cross-sectional view showing an adhesive transfer film according to an embodiment of the present invention.
2 is a cross-sectional view showing the structure of the adhesive layer of the adhesive transfer film according to an embodiment of the present invention and a state in which the adhesive layer is sintered.
Figure 3 is a cross-sectional view showing the microstructure of the adhesive layer of the adhesive transfer film according to an embodiment of the present invention.
4 is a view for explaining a bonding method using an adhesive transfer film according to an embodiment of the present invention.
5 is a view for explaining the shrinkage state after sintering of the adhesive layer bonded to the substrate in the embodiment of the present invention.
6 is a semiconductor and its SME photograph comparing the crack characteristics by applying the Ag adhesive layer (Example) and Sn Solder (Comparative Example) of the present invention to a power module.
7 is a SEM photograph and graph showing the microstructure according to the binder content of the Ag adhesive layer of the present invention.
8 is a SEM photograph showing the microstructure of the Ag adhesive layer of the present invention in a sintered state without pressure at 250° C. for 30 minutes.
9 is a photograph of the structure of the Ag adhesive layer (Ag sintered layer) sintered after press-sintering the Si semiconductor chip to which the Ag adhesive layer of the present invention is transferred.
10 is a graph comparing the adhesive strength of the Ag adhesive layer of the present invention with a product of another company (comparative example).
11 is a general photograph and SEM photograph of the fracture surface of the Example and Comparative Example of FIG. 10 .
12 is a photograph comparing the shrinkage rate, warpage occurrence, and microstructure of the Ag adhesive layer of an embodiment of the present invention and a comparative example (manufactured by another company).
13 is a graph comparing the weight loss (weightloss) of the Ag adhesive layer of an embodiment of the present invention and a comparative example (manufactured by a third party).
14 is a graph of measuring the calorimetric of the Ag adhesive layer of an embodiment of the present invention and a comparative example (manufactured by another company).

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The adhesive transfer film of the present invention may be used for bonding an object such as a power semiconductor chip or a spacer to a substrate.

As shown in FIG. 1 , the adhesive transfer film 10 has a base film 11 , a sticky layer 12 formed on the base film 11 , and a multilayer structure formed on the adhesive layer 12 . and an adhesive layer 13 . The adhesive transfer film 10 is made of Ag sintering paste in the form of a film. The base film 11 is a PET film, the adhesive layer 12 is an OCA film, and the adhesive layer 13 is an Ag adhesive layer. The Ag adhesive layer 13 is used for good heat dissipation properties.

The Ag adhesive layer includes 98 to 99% by weight of Ag powder and 1 to 2% by weight of a binder. The Ag adhesive layer increases the content of Ag powder to increase thermal conductivity.

Ag has good heat dissipation properties due to its high thermal conductivity, and allows the adhesive layer to have conductivity. The binder ensures that Ag has high adhesion and is uniformly applied. The Ag adhesive layer enables low-temperature sintering by maximizing the content of Ag powder and minimizing the content of the binder in the range that can be applied uniformly. The low temperature sintering temperature may be in the range of 240 ~ 300 ℃.

When the content of the binder is lowered to 1 to 2 wt%, the organic content is lowered, so that the thermal decomposition and sintering temperature of the Ag adhesive layer can be lowered by about 60 to 100°C. The low sintering temperature enables fast sintering of the Ag adhesive layer. The rapid sintering of the Ag adhesive layer reduces the shrinkage during sintering and prevents cracking of the sintered layer, thereby lowering the defect rate.

The Ag adhesive layer contains Ag powder in the form of nanoparticles. Ag powder has a liquid phase temperature of 900° C. or higher, so it can be sintered in a range of 240 to 300° C., and Ag solder cannot be sintered in a range of 240 to 300° C. because a liquid phase temperature is 200° C. or higher. Therefore, the Ag adhesive layer should contain Ag powder, not Ag solder, in the form of nanoparticles.

The Ag adhesive layer has high thermal conductivity with a thermal conductivity of 200 to 300 W/mK, a shear strength of 50 MPa or more, and a viscosity of 40 to 100 kcps, so it has high adhesion to various surfaces. It is also possible to use Au instead of Ag, but it is preferable to use Ag in view of cost.

The adhesive transfer film 10 may be formed by attaching an OCA film on the base film 11 , applying or printing Ag sintering paste on the OCA film, and drying. Alternatively, the adhesive transfer film 10 may be formed by applying or printing Ag sintering paste on the base film 11 and drying it. Printing may be screen printing or stencil printing.

The adhesive layer 12 improves the releasability of the adhesive layer 13 to the base film 11 . The Ag sintering paste contains 97 to 99% by weight of Ag powder and 1 to 3% by weight of the binder in the same manner as the Ag adhesive layer.

The adhesive transfer film 10 manufactured in the form of a film can make the height of the adhesive layer 13 very uniform. When bonding an object between two substrates, the height of the adhesive layer 13 must be uniform so that a tolerance does not occur between the two substrates and a problem does not occur in the final product.

In addition, when the adhesive transfer film 10 is used when bonding an object between two substrates, compared to a paste process of applying a paste to a conventional object and bonding to a substrate, void and stand-off defects can be reduced. A void refers to the occurrence of pores in the adhesive layer 13 after sintering, and a stand-off defect means that the object is inclined to one side without being flatly bonded to the substrate.

In the adhesive transfer film 10 , the thickness of the base film 11 may be 75 to 100 μm. The thickness of the adhesive layer 13 may be 40 to 60 μm, preferably 50 μm. The adhesive transfer film 10 can control the thickness and voids of the adhesive layer 13 .

As such, the adhesive transfer film 10 is an Ag coated dry film dried by coating Ag sintering paste on a PET film.

As shown in FIG. 2 , the adhesive transfer film 10 has a multilayered adhesive layer 13 . The adhesive layer 13 may be three or more layers. The adhesive layer 13 is a first adhesive layer 13a laminated on the upper surface of the adhesive layer 12, a second adhesive layer 13b laminated on the upper surface of the first adhesive layer 13a, and the second adhesive layer 13b. and a third adhesive layer 13c laminated thereon.

The average particle diameter of the Ag powder particles included in the first adhesive layer 13a and the third adhesive layer 13c is different from the average particle diameter of the Ag powder particles included in the second adhesive layer 13b. Preferably, the average particle diameter of the Ag powder particles included in the second adhesive layer 13b is relatively smaller than the average particle diameter of the Ag powder particles included in the first adhesive layer 13a and the third adhesive layer 13c. When the adhesive layer 13 is formed in a multi-layered structure and the average particle diameter of Ag powder particles included in each layer is different, the shrinkage rate during sintering occurs differently.

As in the embodiment, the average particle diameter of the Ag powder particles included in the second adhesive layer 13b, which is the intermediate layer, is the average particle diameter of the Ag included in the third adhesive layer 13c and the first adhesive layer 13a, which are the upper and lower layers of the second adhesive layer 13b. When a relatively small particle diameter is applied compared to the average particle diameter of the powder particles, the shrinkage rate of the second adhesive layer 13b having a relatively small average particle diameter during sintering is greater than that of the first adhesive layer 13a and the third adhesive layer 13c, so that the adhesive layer ( 13) can control the shape of both ends to be concave. When the shape of both ends of the adhesive layer 13 is controlled to be concave, stress in the central portion of the adhesive layer 13 can be relieved to increase the breaking strength (tensile strength).

In addition, the adhesive layer 13 may enable dense sintering even if the adhesive layer 13 having a thick overall thickness is applied by applying Ag powder particles having a small average particle diameter to the center.

In most of the fracture phenomena due to bending due to thermal stress, fracture proceeds as cracks occur along the junctions of heterogeneous interfaces. However, if the adhesive layer 13 has a multi-layer structure, the bonding strength becomes higher during sintering of a single material, so that the center of the sintered adhesive layer 13 is more likely to be the starting point of cracks than the bonding surface of the heterogeneous interface.

Therefore, the adhesive layer 13 having a multilayer structure is formed using an Ag sintering paste in which Ag particle sizes are clearly distinguished, thereby preventing cracks at heterogeneous interfaces. In addition, the shape of both ends of the adhesive layer 13 is controlled by configuring each layer differently to prevent the occurrence of cracks in the center of the adhesive layer 13 so that the shrinkage rate is different depending on the Ag particle size. This relieves the stress in the center of the adhesive layer 13 to increase the breaking strength.

As shown in FIG. 2 , the adhesive layer 13 having a multilayer structure on the adhesive transfer film 10 is transferred to the object 40 , and then the upper chuck 3 holding the object 40 is applied to the substrate 40 . By heating and pressing to the (20) side, the object 40 and the substrate 20 are sintered together. The shape of both ends of the sintered adhesive layer 13 "is a concave shape by the second adhesive layer 13b, which shrinks more relative to the first adhesive layer 13a and the third adhesive layer 13c, and relieves stress in the center. In addition, the sintered adhesive layer 13" has a higher thermal conductivity because the sintered density is higher at the center than the others. Thermal conductivity is high at the minimum pore condition.

As shown in FIG. 3 , the Ag powder particles included in the adhesive layer 13 are made of flake-like nanoparticles. Specifically, the first adhesive layer 13a to the third adhesive layer 13c include Ag powder particles made of flake-like nanoparticles, and the average particle diameter of the Ag powder particles included in the second adhesive layer 13b is the first adhesive layer. The average particle diameter of Ag powder particles included in (13a) and the third adhesive layer (13c) is relatively small.

Ag powder particles in the form of flakes improve sinterability while minimizing the amount of the organic binder. Moreover, the Ag powder particles in the form of flakes have less shrinkage during sintering, better bonding strength, and higher shear strength than those in nano-sized spheres. If the amount of the organic binder in the adhesive layer 13 is large, gas may be generated when the temperature rises to 350 to 400° C. due to overvoltage, and cracks in the adhesive layer may occur. Accordingly, the embodiment includes Ag powder particles made of flake-like nanoparticles so that the content of the organic binder is minimized and the content of Ag powder particles is maximized. In an embodiment, the flake shape has a flat elliptical shape with a thickness of several nanometers.

As described above, the adhesive transfer film 10 is an Ag coated dry film in which Ag sintering paste is coated on a PET film three times or more and dried to form an Ag adhesive layer having a multilayer structure on a base film.

The adhesive transfer film 10 may be applied for bonding an object 40 such as a semiconductor chip or a spacer to a power module substrate.

As shown in FIG. 4, in the bonding method using the adhesive transfer film, the adhesive layer 13 is transferred to the object 40 using the adhesive transfer film 10, and the adhesive layer 13' is transferred to the object 40. may be bonded to the upper surface of the substrate 20 .

Specifically, the bonding method using the adhesive transfer film includes a preparation step (s1) of preparing the adhesive transfer film 10, and a transfer step of transferring the adhesive layer 13 on the adhesive transfer film 10 to the object 40 (s1). , s2, s3) and the temporary bonding step (s4, s5, s6) of temporarily bonding the object 40 to which the adhesive layer 13' has been transferred to the substrate 20 via the adhesive layer 13" (s4, s5, s6), and after the temporary bonding step , including a bonding step of bonding the object 40 to the substrate 20 by sintering.

The preparation step is a step of pre-coating the adhesive layer 13 on the base film 11 .

The preparation step includes the steps of preparing the base film 11 , forming the adhesive layer 12 on the base film 11 , and coating and drying the Ag sintering paste on the adhesive layer 12 . and forming the adhesive layer 13 having a multilayer structure by performing it more than once.

For example, the preparation step includes the steps of attaching an OCA film on a PET film, applying or printing an Ag sintering paste on the OCA film, and performing drying three times to form an Ag adhesive layer composed of three layers. do.

The base film 11 may be a PC (Polycarbonate) film in addition to a PET (Polyester) film. However, compared to the PC film, the PET film is advantageous in maintaining the flatness of the lower surface of the adhesive layer 13 . The flatness of the upper surface of the adhesive layer 13 may be maintained by the pressing force of the upper chuck 3 . If the flatness of the adhesive layer 13 is not good, there is a problem in that the adhesive layer is bent during sintering. In the Ag adhesive layer, the average particle diameter of the Ag powder particles of the second adhesive layer 13 constituting the intermediate layer is relatively compared to the average particle diameter of the Ag powder particles of the third adhesive layer 13 and the second adhesive layer 13 formed on the upper and lower parts of the intermediate layer. By adopting a small one, the shape of both ends of the Ag adhesive layer during sintering is controlled in a direction to remove the stress of the intermediate layer. In addition, the Ag adhesive layer uses a thing in which Ag powder particle|grains are flake shape.

In the transfer step (s1, s2, s3), the adhesive transfer film 10 is fixed to the die 1, and the object 40 is fixed to the upper chuck 3 for adsorbing and fixing the object 40 using a vacuum. step (s1), while heating the upper chuck 3 and the die 1, respectively, pressing the object 40 fixed to the upper chuck 3 toward the adhesive transfer film 10 to the adhesive transfer film 10 The step (s2) of transferring the adhesive layer 13 to the object 40, and the step of raising the upper chuck 3 while maintaining the vacuum to raise the object 40 to which the adhesive layer 13' is attached (s3) include

The temporary welding step (s4, s5, s6) is a step (s4) of transferring the upper chuck 3 to the upper portion of the substrate 20, and pressing the object 40 fixed to the upper chuck 3 toward the substrate 20 and temporarily bonding the object 40 to the substrate 20 (s5), and releasing the vacuum of the upper chuck 3 and raising the upper chuck 3 (s6). Steps (s1) to (s3) are steps of transferring the adhesive layer 13 from the adhesive transfer film 10 to the object 40, and steps (s4) to (s6) are the steps to which the adhesive layer 13' is transferred ( 40) is a step of temporarily bonding the substrate 20.

Step (s1) is a step in which the upper chuck 3 picks up the object 40 in a vacuum.

Step (s2) is a step of transferring the adhesive layer 13 to the lower surface of the object 40. In step (s2), the die 1 is heated to a temperature of 80 ~ 100 ℃, the upper chuck 3 is heated to a temperature of 100 ~ 170 ℃. Preferably, the die is heated to a temperature of 80 to 100°C, and the upper chuck 3 is heated to a temperature of 160°C. Pressurization may be performed at 1-4 MPa. When the heating temperature of the upper chuck 3 is higher than the heating temperature of the die 1 , the adhesive layer 13 can be strongly adhered to the object 40 having a higher temperature.

Step (s3) is a step of picking up the adhesive layer 13 ′ by attaching it to the object 40 . In step (s3), the adhesive layer 13 ′ is attached to the lower surface of the object 40 by transfer and is separated from the base film 11 . At this time, since the adhesive layer 12 is not separated from the base film 11 , the adhesive layer 13 ′ can be separated cleanly.

Step (s4) is a step of transferring the object 40 to the upper portion of the substrate 20 in order to temporarily bond the object 40 on the substrate 20 . The substrate 20 may be an AMB substrate or a DBC substrate. The AMB substrate is a ceramic substrate including a ceramic substrate 21 and a metal layer 22 brazed to at least one surface of the ceramic substrate 21 to increase heat dissipation efficiency of heat generated from the semiconductor chip.

Step (s5) is a step of temporarily bonding the object 40 on the substrate 20 by pressing the object 40 fixed to the upper chuck 3 toward the substrate 20 .

In step (s5), the die 1 is heated to a temperature of 80 ~ 100 ℃, the upper chuck 3 is heated to a temperature of 100 ~ 170 ℃. Preferably, the die 1 is heated to a temperature of 80 to 100°C, and the upper chuck 3 is heated to a temperature of 160°C. Pressurization may be performed in the range of 1 to 4 MPa.

Step (s6) is a step of releasing the vacuum and raising the upper chuck 3 to complete the temporary welding. In this way, the adhesive transfer film 10 is heated using the die 1 heated to a temperature of 80 to 100° C., and the object 40 is heated using the upper chuck 3 heated to a temperature of 100 to 170° C. After heating, when the upper chuck 3 is lowered so that the object 40 is pressed toward the adhesive transfer film 10, the adhesive layer 13 on the adhesive transfer film 10 is on the lower surface of the object 40 with a higher temperature. can be transcribed.

After the temporary bonding step, bonding and sintering an upper substrate (not shown) on the upper portion of the object 40 temporarily bonded on the substrate 20 to bond the object 40 between the substrate 20 and the upper substrate. can be done Sintering can be performed for 2 minutes to 5 minutes while heating and pressing at 240 ~ 300 ℃. Pressurization may be performed in the range of 8 to 15 MPa.

The pressurization is to prevent the occurrence of voids. When the pressure sintering is performed, the adhesive layer 13 becomes dense without holes, thereby increasing heat conduction and excellent heat dissipation properties. Pressurization also enables fast sintering.

The sintering temperature and time at the time of main bonding can be adjusted within the above-mentioned range in order to shorten the mass production time. For example, for sintering during main bonding, it is preferable to pressurize at 250°C for 5 minutes, but pressurization may be performed at 300°C for 2 minutes to improve mass productivity. Sintering is intended to improve bonding strength.

The temporary bonding step and the main bonding step may be performed separately or may be performed simultaneously. At the same time, the meaning of progress means that the temporary bonding is omitted from the temporary bonding step and the main bonding step can be performed. For example, in step (s5), the object 40 fixed to the upper chuck 3 is heated and pressed toward the substrate 20 at a temperature of 240 to 300° C. and a pressure of 8 to 15 MPa for 2 minutes to 5 minutes. (40) may be bonded to the substrate 20 without the provisional bonding.

As shown in Fig. 5, the sintered adhesive layer 13" has a shrinkage rate, but is as small as about 6%. Moreover, the adhesive layer 13 does not shrink well up and down and small shrinkage occurs on both sides, which is the adhesive layer 13 This is because Ag constituting the ) is in the form of flakes. The form of flakes increases the bonding strength of the adhesive layer 13" to improve the breaking strength.

Hereinafter, the present invention will be described by way of Examples and Comparative Examples.

Table 1 below shows the characteristics of the Ag adhesive layer (Example) and the Sn-Ag solder layer (Comparative Example) obtained by sintering the adhesive layer of the present invention compared to pure Ag. The Ag adhesive layer of the embodiment includes 98 to 99% by weight of Ag powder and 1 to 2% by weight of a binder.

division Pure Ag Ag sintered layer (adhesive layer) Sn-Ag solder layer Liquidus (℃) 961 961 221 Electrical Conductivity (MS/m) 68 41 7.8 Thermal Conductivity (W/mK) 429 200 70 Density (g/cm3)
10.5 8.2 8.4 CTE (ppm/℃)
19.3 19 28 Tensile strength (MPa) 139 55 30

According to Table 1, the Ag adhesive layer of the present invention has a high thermal conductivity with a thermal conductivity of 200 W/mK, and a tensile strength of 50 MPa or more, which is higher than that of the Sn-Ag solder layer. From this, it can be seen that the thermal conductivity and tensile strength of the Ag adhesive layer are superior to those of the Sn-Ag solder layer.

6 is a comparison of cracking properties by applying the Ag adhesive layer (Example) and Sn Solder (Comparative Example) of the present invention to a power module.

As shown in FIG. 6 , the operating temperature of the semiconductor chip of the power module is 150 to 250° C., and bending (indicated in red) occurs while cooling and heating are repeated. However, when the semiconductor chip was bonded to the substrate with Sn Solder, as a result of 800 tests at an operating temperature of -40 to 125°C, cracks occurred in the Sn Solder bonding surface confirmed in the SEM photograph.

On the other hand, the Ag adhesive layer of Example was tested 800 times at an operating temperature of -40 ~ 125 ℃, cracks were not confirmed.

7 is an SEM photograph and graph for explaining the microstructure according to the binder content of the Ag adhesive layer.

As shown in FIG. 7 , it can be confirmed that the pores are minimized as the content of the binder, which is an organic material, is minimized. Through this, it can be seen that by minimizing unnecessary organic matter, excellent sintering properties can be secured and cracks of the sintered layer can be secured. However, for uniform diffusion of the Ag powder particles, the content of the binder, which is an organic material, is preferably 1 to 2% by weight. The uniform adhesive layer 13 can be formed only when the Ag powder particles are uniformly diffused.

8 is a sintering of the Ag adhesive layer of the present invention at 250° C. for 30 minutes without pressure.

As shown in FIG. 8 , as a result of sintering the Ag adhesive layer at 250° C. for 30 minutes without pressure, adhesive strength of 60 MPa or more was secured. In addition, it can be confirmed that the Ag adhesive layer is sintered without pressure, and the organic matter is minimized, so that thermal conductivity of about 150 W/mK or more is secured.

9 shows the structure of the sintered Ag adhesive layer (Ag sintered layer) after press-sintering the Si semiconductor chip to which the Ag adhesive layer has been transferred. Here, the Ag adhesive layer has a thickness of 200 μm and is formed by mask stencil printing on a base film.

The Ag adhesive layer shown in FIG. 9 was pressure sintered at 240° C. for 4 minutes at 15 MPa. After pressure sintering, a dense bonding layer with a porosity of 7-8% was confirmed. In the case of FIG. 9, sufficient bonding was possible even if the sintering time was short, adhesive strength of 50 MPa or more, and thermal conductivity of about 300 W/mK were secured. The porosity is confirmed to be secured at 7-8% by minimizing organic matter after sintering, and it is confirmed that the thermal conductivity is increased due to the minimum pore condition.

In FIG. 9, pores are minimized by sintering the adhesive layer under pressure, and in FIG. 8, many pores are confirmed by sintering without pressure. Through this, it can be seen that the pressure sintering has the effect of increasing the thermal conductivity by minimizing the pores.

10 is a comparison of the adhesive strength of the Ag adhesive layer according to an embodiment of the present invention with a product of another company (comparative example).

A third-party product is Semipowerrex (Korea). In both Examples and Comparative Examples, sintering was performed at 290° C. for 150 sec.

As can be seen in FIG. 10 , it can be seen that the embodiment can obtain sufficient bonding strength within a short time of about 2 minutes at a temperature of 290° C., and the bonding strength is very high at 65 MPa or more.

11 is a general photograph and SEM photograph of the fracture surface of the Example and Comparative Example of FIG. 10 .

11 , in the Example, a portion of the Ag adhesive layer was separated and separated, whereas in the Comparative Example, the bonding surface between the adhesive layer and the substrate was broken.

Comparing the shape of the fractured surface in the SEM photograph, the Ag adhesive layer was ruptured in the middle of the Ag adhesive layer, and in Comparative Example (manufactured by another company), the entire adhesive layer was separated from the substrate. This phenomenon is confirmed because, in the case of Examples, the central portion of the Ag adhesive layer has a higher sintering density than other portions and the Ag powder particles are flaky. In the comparative example, the Ag powder particles are close to spherical. Moreover, the Example ruptures at about 65 MPa and the Comparative Example ruptures at about 23 MPa.

12 is a comparison of the shrinkage rate, warpage occurrence, and microstructure of the Ag adhesive layer of Example and Comparative Example (manufactured by another company).

Examples and Comparative Examples were sintered at a temperature of 270° C. for 60 minutes in a non-pressurized state.

As shown in FIG. 12 , in the Example, about 6% shrinkage occurred, and in the Comparative Example, about 24% shrinkage occurred. In addition, the Example did not cause warpage after sintering, while the Comparative Example showed warpage after sintering. In addition, in the Example, a flake phase was confirmed in the microstructure measured by SEM, whereas in the Comparative Example, a sphere phase was confirmed.

From the above results, it can be seen that the shrinkage rate of the Ag adhesive layer of the embodiment is 20% lower than that of the comparative example, and can contribute to reducing defects due to jig tolerance after bonding the semiconductor chip.

13 is a graph comparing the weight loss of the Ag adhesive layer of the Example and the comparative example (manufactured by another company), and FIG.

It is confirmed that the Ag adhesive layer of the example has a thermal decomposition and sintering temperature of 60-100° C. lower at an organic content of 1 to 2 wt % compared to the comparative example (product of another company). Through this, it can be expected that the low sintering temperature enables fast sintering.

The above-described Ag adhesive layer of the embodiment of the present invention can secure thermal conductivity of 150W/mK in pressureless sintering, 280W/mK or more when pressure sintering using test equipment, and 300W/mK or more when using official pressurization equipment. have.

In addition, the Ag adhesive layer of the embodiment of the present invention has a small shrinkage rate because the Ag powder particles have a flake shape, and the Ag adhesive layer has a multi-layer structure and heterogeneous powder particles, so it has an advantage in removing residual stress. It is minimized, and high breaking strength (tensile strength) of 50 MPa or more can be secured.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is disclosed in the drawings and in the specification with preferred embodiments. Here, although specific terms have been used, they are used only for the purpose of describing the present invention and are not used to limit the meaning or the scope of the present invention described in the claims. Therefore, it will be understood by those skilled in the art that various modifications and equivalent other embodiments of the present invention are possible therefrom. Accordingly, the true technical scope of the present invention should be defined by the technical spirit of the appended claims.

10: adhesive transfer film 11: base film
12: adhesive 13: adhesive layer
13a: first adhesive layer 13b: second adhesive layer
13c: third adhesive layer 13': transferred adhesive layer
13": glued adhesive layer or sintered layer
20: substrate 21: ceramic substrate
22: metal layer 40: object
1: Die 3: Upper chuck

Claims (15)

base film;
an adhesive layer formed on the base film; and
an adhesive layer having a multilayer structure formed on the adhesive layer;
Adhesive transfer film comprising a. According to claim 1,
The adhesive layer is an Ag adhesive layer,
The Ag adhesive layer is an adhesive transfer film comprising 98 to 99% by weight of Ag powder and 1 to 2% by weight of a binder. 3. The method of claim 2,
The Ag powder is an adhesive transfer film made of flaky nanoparticles. According to claim 1,
The adhesive layer is
a first adhesive layer laminated on an upper surface of the adhesive layer;
a second adhesive layer laminated on an upper surface of the first adhesive layer; and
A third adhesive layer laminated on the upper surface of the second adhesive layer,
The first adhesive layer to the third adhesive layer include Ag powder consisting of flaky nanoparticles,
The average particle diameter of the Ag powder included in the second adhesive layer is relatively small compared to the average particle diameter of the Ag powder included in the first adhesive layer and the third adhesive layer. According to claim 1,
The adhesive layer is
a first adhesive layer laminated on an upper surface of the adhesive layer;
a second adhesive layer laminated on an upper surface of the first adhesive layer; and
A third adhesive layer laminated on the upper surface of the second adhesive layer,
The first adhesive layer and the third adhesive layer include Ag powder made of nanoparticles, and the second adhesive layer includes Ag powder made of flaky nanoparticles,
The average particle diameter of the Ag powder included in the second adhesive layer is relatively small compared to the average particle diameter of the Ag powder included in the first adhesive layer and the third adhesive layer. According to claim 1,
The thickness of the adhesive layer is an adhesive transfer film of 40㎛ ~ 60㎛. According to claim 1,
The base film is an adhesive transfer film that is a PET film. According to claim 1,
The adhesive layer is an adhesive transfer film of OCA. According to claim 1,
The adhesive layer is an adhesive transfer film having a porosity of 7% to 8% after sintering under pressure. A preparation step of preparing an adhesive transfer film;
a transfer step of transferring the adhesive layer on the adhesive transfer film to an object;
a temporary bonding step of bonding the object to which the adhesive layer is transferred to a substrate via the adhesive layer; and
After the temporary bonding step, the main bonding step of sintering the main bonding of the object to the substrate;
A bonding method using an adhesive transfer film comprising a. 11. The method of claim 10,
The preparation step is
preparing a base film;
forming an adhesive layer on the base film; and
forming an adhesive layer having a multilayer structure by coating the Ag sintering paste on the adhesive layer and drying the adhesive layer three or more times;
A bonding method using an adhesive transfer film comprising a. 11. The method of claim 10,
The transfer step is
fixing the adhesive transfer film to a die and fixing the object to an upper chuck for adsorbing and fixing the object using a vacuum; and
The upper chuck is heated to a temperature of 100 to 170° C. and the die is heated to a temperature of 80 to 100° C., and then the object fixed to the upper chuck is pressed toward the adhesive transfer film to form an adhesive layer on the adhesive transfer film. transferring to the object;
A bonding method using an adhesive transfer film comprising a. 11. The method of claim 10,
The bonding step is
The sintering is a bonding method using an adhesive transfer film that is performed for 2 minutes to 5 minutes while pressurizing and heating the temporary bonding body of the object and the substrate at 240 ~ 300 ℃. 11. The method of claim 10,
A bonding method using an adhesive transfer film in which the temporary bonding step and the bonding step are performed simultaneously. 11. The method of claim 10,
The object is a bonding method using an adhesive transfer film including a semiconductor chip and a spacer.

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