TW202328378A - Connection structure and method of forming connection structure - Google Patents

Abstract

A connection structure includes a first electronic component, a buffer layer, an anisotropic conductive film, and a second electronic component. The first electronic component includes a first substrate and a first conductive element on the first substrate. The buffer layer is disposed on the upper surface of the first conductive element. The anisotropic conductive adhesive film contains insulating adhesive layer and a first conductive particle in the insulating adhesive layer, and the insulating adhesive layer is disposed on the buffer layer. The second electronic component is disposed over the first electronic component and on the anisotropic conductive film and includes a second substrate and a second conductive element under the second substrate, and the first conductive particle electrically connects the first conductive element and the second conductive element. The thermal expansion coefficient of the buffer layer is between that of the first conductive element and that of the insulating adhesive layer. A method of forming the connection structure is also provided herein.

Description

Connection structure and method of forming connection structure

The present disclosure relates to a connection structure with an anisotropic conductive adhesive film and a method for forming the same.

Anisotropic Conductive Film (ACF) is widely used in processes that are not suitable for high-temperature soldering, such as integrated circuits (IC) and liquid crystal displays (LCD), flexible printed circuit boards (FPC) and LCD, IC and thin films The press-fit joint between them is used to realize signal transmission and screen display. Anisotropic conductive adhesive film is a transparent polymer connecting material with three characteristics of adhesion, conductivity and insulation at the same time. Its remarkable feature is that it conducts in the Z direction (vertical direction) and insulates in the XY direction (horizontal direction), which can solve some problems. Subtle wire connection issues that the connector cannot handle.

The lamination integrity and reliability of the anisotropic conductive adhesive film are especially important. However, after the connection structure of the known anisotropic conductive adhesive film is used for a period of time, or when a reliability test such as a pressure cooking test is performed, it is found that cracks are prone to occur at the interface of the anisotropic conductive adhesive film, resulting in electrical invalidated.

Some embodiments of the present disclosure provide a connection structure including a first electronic component, a buffer layer, an anisotropic conductive adhesive film, and a second electronic component. The first electronic assembly includes a first substrate and a first conductive element on the first substrate. The buffer layer is disposed on the upper surface of the first conductive device of the first electronic component. The anisotropic conductive adhesive film includes an insulating adhesive layer and first conductive particles in the insulating adhesive layer, wherein the insulating adhesive layer is disposed above the first substrate and the first conductive element of the first electronic component and on the buffer layer . The second electronic component is disposed on the anisotropic conductive adhesive film, the second electronic component includes a second substrate and a second conductive element under the second substrate, and the second conductive element contacts the first conductive particles. The thermal expansion coefficient of the buffer layer is between the thermal expansion coefficient of the first conductive element and the thermal expansion coefficient of the insulating adhesive layer of the anisotropic conductive adhesive film.

In some embodiments, in the joint structure, the buffer layer has a coefficient of thermal expansion of about 20 ppm/K to about 50 ppm/K.

In some embodiments, in the connection structure, the buffer layer includes an organic thin film, a metal plating layer, or a combination thereof.

In some embodiments, in the connection structure, the buffer layer includes an organic film, and the first conductive particles pass through the buffer layer to electrically connect the first conductive element.

In some embodiments, in the connection structure, the buffer layer includes an organic film, and the material of the organic film is rosin (Rosin), active resin (Active Resin), azole (Azole), polyether ether ketone, polyamide imine, or acrylic resin.

In some embodiments, in the connection structure, the anisotropic conductive adhesive film further includes second conductive particles in the insulating adhesive layer, the second conductive particles do not contact the first conductive element and the second conductive element, and the buffer layer The thickness is about 1/20 to about 1/5 of the height of the second conductive particles.

In some embodiments, the connection structure includes a metal coating, and the material of the metal coating is zinc, aluminum, magnesium, lead, cadmium, or a combination thereof.

In some embodiments, in the connection structure, the buffer layer includes a metal plating layer and an organic thin film disposed on the metal plating layer.

In some embodiments, in the connection structure, the buffer layer is also disposed on the side surface of the first conductive element.

In some embodiments, the buffer layer is also disposed on the side surface of the first conductive device and on the first substrate.

In some embodiments, in the connection structure, the coefficient of thermal expansion of the first substrate is smaller than the coefficient of thermal expansion of the second substrate.

In some embodiments, in the connection structure, the coefficient of thermal expansion of the first conductive element is smaller than the coefficient of thermal expansion of the second conductive element.

In some embodiments, in the connecting structure, the horizontal dimension of the first conductive particles is between about 5 microns and about 40 microns.

Some embodiments of the present disclosure provide a method of forming a connection structure, comprising: providing a first electronic assembly, wherein the first electronic assembly includes a first substrate and a first conductive element on the first substrate. A buffer layer is arranged on the upper surface of the first conductive element of the first electronic component; an anisotropic conductive adhesive film is arranged above the buffer layer, wherein the anisotropic conductive adhesive film includes an insulating adhesive layer and a first insulating adhesive layer in the insulating adhesive layer. Conductive particles; a second electronic component is set above the anisotropic conductive adhesive film, wherein the second electronic component includes a second substrate and a second conductive element under the second substrate, and the thermal expansion coefficient of the buffer layer is between the first conductive element Between the coefficient of thermal expansion and the thermal expansion coefficient of the insulating adhesive layer of the anisotropic conductive adhesive film; and pressing the first electronic component, buffer layer, anisotropic conductive adhesive film, and the second electronic component, wherein the anisotropic conductive adhesive The first conductive particles of the film are electrically connected to the first conductive element and the second conductive element.

In some embodiments, in the method of forming the connection structure, the buffer layer is provided through soft-to-hard bonding technology or organic solder protection film technology.

In some embodiments, in the method for forming the connection structure, the buffer layer includes an organic thin film, and when the first electronic component, the buffer layer, the anisotropic conductive adhesive film, and the second electronic component are laminated, the anisotropic The first conductive particles of the conductive adhesive film pass through the organic film and are electrically connected to the first conductive element.

In some embodiments, in the method for forming the connection structure, the buffer layer includes a metal plating layer, and when the first electronic component, the buffer layer, the anisotropic conductive adhesive film, and the second electronic component are laminated, the anisotropic The first conductive particles of the conductive adhesive film are electrically connected to the first conductive element by contacting the metal plating layer.

In some embodiments, in the method for forming the connection structure, the buffer layer is an organic thin film, and the thickness of the buffer layer is between about 1 micron and about 4 microns.

In order to make the description of the present disclosure more detailed and complete, the following provides an illustrative description of the implementation and specific embodiments of the present disclosure; but this is not the only way to implement or use the specific embodiments of the present disclosure. The various embodiments disclosed below can be combined or replaced with each other when beneficial, and other embodiments can also be added to one embodiment, without further description or illustration.

In the following description, numerous specific details will be set forth in order to enable readers to fully understand the following embodiments. However, embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known structures and devices are only schematically shown in order to simplify the drawings.

In addition, the present disclosure may repeat element symbols and/or letters in various embodiments. This repetition is for the purpose of simplicity and clarity and does not in itself indicate a relationship between the various implementations and/or configurations discussed. In addition, in subsequent disclosures, a feature formed on another feature, connected to and/or coupled to another feature may include implementations in which these features are in direct contact, and may also include that another feature may be formed and/or coupled to another feature. An embodiment in which the features are interposed such that the features may not be in direct contact.

In addition, spatially relative terms such as "upper", "lower", "above", "below" and similar terms are used herein to facilitate describing the relationship between one element or feature and another element or feature in the drawings. . These spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device can also be transformed into other orientations (rotated 90 degrees or other orientations), and thus the spatially relative descriptions used herein should be interpreted similarly.

In a conventional connection structure with an anisotropic conductive adhesive film, the anisotropic conductive adhesive film is placed between two electronic components and directly contacts the substrates and circuits of the two electronic components. After the process of attaching the anisotropic conductive film is completed, reliability testing will be carried out, such as pressure cooking test (Pressure Cooker Test, PCT) (or saturated steam test), where the device under test is placed under severe temperature, Saturated humidity (saturated water vapor) and high-pressure environmental conditions are tested to evaluate the impact of the device under test on the interface of sealants or electronic components under high temperature, high humidity, and high pressure conditions. Then check whether the device under test will have electrical failure.

According to some experimental examples of the present disclosure, a conventional connection structure with an anisotropic conductive adhesive film is tested. This connection structure uses an anisotropic conductive adhesive film to connect a rigid substrate and a circuit (that is, a conductive element, or a conductive pad) and another electronic assembly with a flexible circuit board and circuitry. When the known device to be tested with the connection structure of the anisotropic conductive adhesive film was placed in an environment test of a temperature of 121°C, a relative humidity of 100%, and a pressure of 205Kpa for 4 hours, it was found that the A crack occurs at the interface, so the electrical function of the device under test fails. Moreover, it can be found that there are peeling gaps by scanning electron microscope observation, and the peeling gaps are concentrated at the interface between the anisotropic conductive adhesive film and the conductive elements of the electronic assembly.

Since the thermal expansion coefficient of the anisotropic conductive adhesive film has a large difference from the thermal expansion coefficient of the conductive element or substrate material of the electronic component, when multiple materials with different thermal expansion coefficients form a device, the temperature changes due to the inconsistent degree of thermal expansion. Stress will be generated. Therefore, at the interface where the difference in thermal expansion coefficient is relatively high, it is easy to cause the problem of interface peeling due to the stress generated by the temperature rise.

This disclosure relates to a method for improving the bonding process of the anisotropic conductive adhesive film. By adding a buffer layer between the anisotropic conductive adhesive film and the first electronic component at the interface where the stress is concentrated, the coefficient of thermal expansion is between the different between the thermal expansion coefficient of the anisotropic conductive adhesive film and the thermal expansion coefficient of the conductive element of the first electronic component, so as to buffer the strain effect between different interfaces, and share the stress-strain gradient between the anisotropic conductive adhesive film and the buffer between layers, and between buffer layers and conductive elements. Therefore, the problem of interfacial peeling caused by temperature rise is reduced.

Please refer to FIG. 1 , which illustrates a cross-sectional view of a connection structure according to some embodiments. The connection structure 100 includes a first electronic component 110 , a buffer layer 120 , an anisotropic conductive adhesive film 130 , and a second electronic component 140 .

The first electronic component 110 includes a first substrate 112 and a plurality of first conductive elements 114 on the first substrate 112 . In some embodiments, the first conductive element 114 covers a portion of the surface of the first substrate 112 . The buffer layer 120 is disposed on the first electronic component 110 and covers the first substrate 112 and the plurality of first conductive elements 114 . The anisotropic conductive adhesive film 130 includes an insulating adhesive layer 132 and first conductive particles 134 and second conductive particles 136 in the insulating adhesive layer 132 . The height _H1 of the first conductive particles 134 is reduced by pressing, and configured to electrically connect the first conductive element 114 of the first electronic component 110 and the conductive component of the second electronic component 140 . The first conductive particles 134 pass through the buffer layer 120 to physically and electrically connect the first conductive element 114 of the first electronic component 110 . The second conductive particles 136 are located in a region that does not overlap with the first conductive element 114 of the first electronic component 110 and the conductive component of the second electronic component 140 in the vertical direction (ie, the Z direction) and is surrounded by the insulating glue layer 132 . That is to say, the second conductive particle 136 does not overlap with the vertical projection area of the first conductive element 114 of the first electronic component 110 on the first substrate 112 in the area vertically projected on the first substrate 112, nor overlaps with the area of the second electronic component 110. Areas of the second conductive element 144 of 140 perpendicular to the first substrate 112 do not overlap. In other words, the second conductive particles 136 are located between the first substrate 112 and the second substrate 142 and are not deformed and reduced in height due to the pressing effect. As shown in FIG. 1 , the second conductive particles 136 have a height H ₂ , and the height H ₁ of the first conductive particles is smaller than the height H ₂ of the second conductive particles 136 . The second electronic component 140 is disposed on the anisotropic conductive adhesive film 130 and includes a second substrate 142 and a plurality of second conductive elements 144 under the second substrate 142 . In some embodiments, the second conductive element 144 covers a portion of the surface of the second substrate 142 . The first conductive element 114 and the second conductive element 144 overlap vertically, and the second conductive element 144 is physically and electrically connected to the first conductive particle 134 . That is to say, the second conductive element 144 overlaps with the first conductive particles 134 and the first conductive element 114 in the vertical projection area of the first substrate 112 . In some embodiments, the size of the first conductive element 114 may be smaller than, approximately equal to, or larger than the size of the second conductive element 144 . As shown in FIG. 1 , the first conductive element 114 and the second conductive element 144 are electrically connected via the first conductive particles 134 .

In some embodiments, the first substrate 112 of the first electronic component 110 is a rigid substrate, and the second substrate 142 of the second electronic component 140 is a flexible substrate; but the present disclosure is not limited thereto, the buffer of the present disclosure Layers can be applied to interfaces with large differences in thermal expansion coefficients.

In some embodiments, the thermal expansion coefficients of the first conductive element 114 of the first electronic component 110 and the second conductive component 144 of the second electronic component 140 are smaller than the thermal expansion coefficient of the insulating adhesive layer 132 of the anisotropic conductive adhesive film 130 . In some embodiments, the thermal expansion coefficient of the first conductive element 114 of the first electronic component 110 is smaller than the thermal expansion coefficient of the second conductive component 144 of the second electronic component 140; The difference of the coefficient of thermal expansion of the element 114 is greater than the difference of the coefficient of thermal expansion between the insulating glue layer 132 and the second conductive element 144 .

In some embodiments, the thermal expansion coefficients of the first substrate 112 of the first electronic component 110 and the second substrate 142 of the second electronic component 140 are both smaller than the thermal expansion coefficient of the insulating adhesive layer 132 of the anisotropic conductive adhesive film 130, and the second The thermal expansion coefficient of the first substrate 112 of an electronic component 110 is smaller than the thermal expansion coefficient of the second substrate 142 of the second electronic component 140 . That is to say, the difference of the thermal expansion coefficient between the insulating glue layer 132 and the first substrate 112 is greater than the difference of the thermal expansion coefficient between the insulating glue layer 132 and the second substrate 142 .

The buffer layer 120 is disposed between the first conductive element 114 and the insulating glue layer 132 having a large difference in thermal expansion coefficient, and the thermal expansion coefficient of the buffer layer 120 is between the thermal expansion coefficient of the first conductive element 114 and that of the insulating glue layer 132 between the coefficients of thermal expansion, so the strain gradient of the stress caused by the temperature rise can be shared between the interface between the first conductive element 114 and the buffer layer 120, and the interface between the buffer layer 120 and the insulating adhesive layer 132 interface.

In addition, the buffer layer 120 is also disposed between the first substrate 112 and the insulating adhesive layer 132 having a large difference in thermal expansion coefficient, and the thermal expansion coefficient of the buffer layer 120 is between the thermal expansion coefficient of the first substrate 112 and the insulating adhesive layer 132. Between the coefficients of thermal expansion, the strain gradient of the stress caused by the temperature rise can be shared between the interface between the first substrate 112 and the buffer layer 120, and the interface between the buffer layer 120 and the insulating glue layer 132. interface.

It should be noted that although the buffer layer 120 is shown in FIG. The layer 120 may cover only the upper surface of the first conductive element 114 , or only cover the upper surface and the side surfaces of the first conductive element 114 . Since once peeling occurs between the insulating adhesive layer and the first conductive element, the electrical function of the device will fail. Therefore, the buffer layer 120 is preferably disposed between the insulating adhesive layer 132 and the first conductive element 114, especially Between the insulating glue layer 132 and the upper surface of the first conductive element 114 .

Some examples are described below to illustrate that the connection structure of the present disclosure can reduce the peeling phenomenon between the anisotropic conductive adhesive film and the substrate through the arrangement of the buffer layer.

Referring to Table 1 below, the minimum peel strengths of three different anisotropic conductive adhesive films at different bonding temperatures were obtained through the peel test. In the peel test, three different anisotropic conductive adhesive films were sample (1), sample (2), and sample (3). Each sample to be tested has a length of 1.168 cm and a width of 0.716 cm. During the peel test, a part of the sample is peeled off along the length direction of the sample, and then the peel strength of the sample is tested. Table 1 below shows the minimum peel strength obtained under different test conditions.

Table I Test Conditions Bonding temperature (°C) Bonding force Anisotropic conductive film samples The median of the minimum peel strength (kgf/cm) Group 1 140 25N Sample (1) 1.23 Group 2 160 25N Sample (1) 1.57 Group 3 180 25N Sample (1) 1.6 Group 4 140 25N Sample (2) 1.06 Group 5 160 25N Sample (2) 1.19 Group 6 180 25N Sample (2) 1.51 Group 7 180 25N Sample (3) 1.38

According to the maximum normal stress criterion (also known as the first strength theory or the maximum tensile stress theory), the fracture of the material is caused by the maximum tensile stress, that is, when the maximum tensile stress reaches a certain limit value, the material will fracture. According to the above peel strength test under different conditions, use the median of the measured maximum and minimum peel strength, that is, 1.6 kgf/cm, to calculate the maximum normal stress that causes the destruction (peeling) of the anisotropic conductive adhesive film . That is, the failure condition σ ₁ =σ _bt = 1.6*9.81/0.716 = 21.92 N/cm.

Figure 2 shows a comparative example. The connection structure 300 includes a rigid substrate 310 , an anisotropic conductive adhesive film 320 on the rigid substrate 310 , and a flexible substrate 330 on the anisotropic conductive adhesive film 320 . Wherein, the material of the rigid substrate 310 is alumina ceramics, and the coefficient of thermal expansion is 7.1 ppm/K. The material of the insulating adhesive layer in the anisotropic conductive adhesive film 320 is acrylic, and the thermal expansion coefficient of the anisotropic conductive adhesive film 320 is 169 ppm/K. Flexible substrate 330 includes DuPont Kapton ^® black polyimide film and DuPont Pyralux ^® black flexible circuit board material, and the thermal expansion coefficient of DuPont Kapton ^® black polyimide film is 10 ppm/K, and DuPont Pyralux ^® black flexible circuit board material The thermal expansion coefficient of the board material is 25 ppm/K; in the test of this comparative example, the DuPont Pyralux ^® black flexible circuit board material is the part in contact with the anisotropic conductive adhesive film 320 . Therefore, the difference in the coefficient of thermal expansion between the rigid substrate 310 and the anisotropic conductive adhesive film 320 is a difference of 22.8 times, while the difference in the coefficient of thermal expansion between the anisotropic conductive adhesive film 320 and the flexible substrate 330 is a difference of 22.8 times. 5.76 times.

Afterwards, a variety of physical quantity coupling analysis software (COMOSOL Multiphysics ^® ) was used to simulate the temperature change, and it was obtained that when the temperature of the device rises from 25°C to 121°C, the temperature between the rigid substrate 310 and the anisotropic conductive adhesive film 320 The normal stress between them is 26.59 N/cm, and the normal stress between the anisotropic conductive adhesive film 320 and the flexible substrate 330 is 22.60. Referring to FIG. 3 , it shows that when the temperature is 121° C., the normal stress between the rigid substrate 310 and the anisotropic conductive adhesive film 320 is 26.59 N/cm. In addition, the simulation test shows that the shear force between the rigid substrate 310 and the anisotropic conductive adhesive film 320 is -15.38 N/cm.

That is to say, on the side of the anisotropic conductive adhesive film 320 close to the rigid substrate 310 , the normal stress is 26.59 N/cm, which is significantly higher than the failure condition σ _bt (ie, 21.92 N/cm). Therefore, when the temperature rises, the stress generated by the temperature change easily causes peeling on the side of the anisotropic conductive adhesive film 320 close to the rigid substrate 310 .

Figure 4 shows an experimental example. The connection structure 500 includes a rigid substrate 510 , a buffer layer 520 on the rigid substrate 510 , an anisotropic conductive adhesive film 530 on the buffer layer 520 , and a flexible substrate 540 on the anisotropic conductive adhesive film 530 . Wherein, the material of the rigid substrate 510 is alumina ceramics, and the coefficient of thermal expansion is 7.1 ppm/K. The buffer layer 520 is made of acrylic resin with a thermal expansion coefficient of 34.6 ppm/K. The material of the insulating adhesive layer in the anisotropic conductive adhesive film 530 is acrylic, and the thermal expansion coefficient of the anisotropic conductive adhesive film 530 is 169 ppm/K. Flexible substrate 540 includes DuPont Kapton ^® black polyimide film and DuPont Pyralux ^® black flexible circuit board material, and the thermal expansion coefficient of DuPont Kapton ^® black polyimide film is 10 ppm/K, and DuPont Pyralux ^® black flexible circuit board material The thermal expansion coefficient of the board material is 25 ppm/K; in the test of this experimental example, the DuPont Pyralux ^® black flexible circuit board material is the part in contact with the anisotropic conductive adhesive film 530 . Therefore, the difference between the thermal expansion coefficient between the rigid substrate 510 and the buffer layer 520 is 4.87 times, and the difference between the thermal expansion coefficient between the buffer layer 520 and the anisotropic conductive adhesive film 530 is 4.88 times. The difference in thermal expansion coefficient between the anisotropic conductive adhesive film 530 and the flexible substrate 540 is 5.76 times.

Afterwards, a variety of physical quantity coupling analysis software (COMOSOL Multiphysics ^® ) was used to simulate the temperature change, and it was obtained that when the temperature of the device rises from 25°C to 121°C, the temperature between the buffer layer 520 and the anisotropic conductive adhesive film 530 The normal stress between them is -0.65 N/cm. Referring to FIG. 5, it is shown that when the temperature is 121°C, the normal stress between the rigid substrate 510 and the buffer layer 520 is -0.65 N/cm. In addition, the simulation test shows that the shear force between the rigid substrate 510 and the buffer layer 520 is 6.48 N/cm. That is to say, through the arrangement of the buffer layer 520, the normal stress on the side of the anisotropic conductive adhesive film 530 closer to the rigid substrate 510 is significantly reduced, which is much smaller than the failure condition _σbt (that is, 21.92 N/cm ), and less than the normal stress of the side of the anisotropic conductive adhesive film 530 close to the flexible substrate 540 . Therefore, the phenomenon of peeling damage concentrated on the side of the anisotropic conductive adhesive film 530 close to the rigid substrate 510 can be improved.

6A-6E illustrate cross-sectional views of various intermediate stages of forming a connection structure according to some embodiments.

Please refer to FIG. 6A, which illustrates providing the first electronic component in this step. The first electronic component 710 includes a first substrate 712 and a plurality of first conductive elements 714 on the first substrate 712 .

In some embodiments, the first substrate 712 can be a rigid substrate, such as a paper substrate, a glass fiber cloth substrate, a synthetic fiber cloth substrate, a non-woven fabric substrate, a composite substrate, and the like.

In some embodiments, the material of the first conductive element 714 may include conductive materials such as gold, silver, copper, aluminum, and indium tin oxide.

Please refer to FIG. 6B , which shows a buffer layer disposed on the first electronic component. The buffer layer 720 is disposed on the first substrate 712 and the first conductive element 714 of the first electronic component 710 . The buffer layer 720 is an organic thin film, and its thermal expansion coefficient is between the thermal expansion coefficient of the first substrate 712 and the thermal expansion coefficient of the insulating adhesive layer formed later, for example, about 20 to about 50 ppm/K. In some embodiments, the buffer layer 720 is made of Rosin, Active Resin, Azole, PEEK, polyimide, or acrylic resin.

In some embodiments, the thickness of the buffer layer 720 is about 1 micron to about 4 microns, preferably about 1.5 microns to about 3 microns, more preferably about 1.8 microns to about 2.2 microns, for example about 2 microns. In some embodiments, the thickness of the buffer layer 720 is about 1/20 to about 1/5, preferably about 1/10, of the height of the conductive particles (before lamination) of the subsequently disposed anisotropic conductive adhesive film, In order to provide a proper stress buffering effect and allow the conductive particles to penetrate the buffer layer 720 during pressing. In some embodiments, the material of the buffer layer 720 can be disposed on the first substrate 712 and the first conductive element 714 of the first electronic component 710 by coating. In some embodiments, the organic thin film can be pasted on the first electronic component 710 through a soft-to-hard (STH) technique.

In an embodiment where the organic thin film is bonded via soft-to-hard technology, a polyether ether ketone film with a thermal expansion coefficient of about 20 to 50 ppm/K can be bonded to the first electronic component 710; or a thermal expansion coefficient of A polyimide film or acrylic resin film of about 30 to 40 ppm/K (eg, about 34.6 ppm/K) is pasted on the first electronic component 710 .

Please refer to FIG. 6C , which shows disposing the anisotropic conductive adhesive film on the buffer layer. The anisotropic conductive adhesive film 730 includes an insulating adhesive layer 732 and first conductive particles 734 and second conductive particles 736 distributed in the insulating adhesive layer 732 . The insulating adhesive layer 732 has the functions of bonding, heat resistance, insulation, fixing the relative positions of multiple conductive elements, and maintaining the contact area between the conductive elements and the conductive particles in contact. In some embodiments, the material of the insulating adhesive layer 732 may include a thermosetting epoxy resin, such as acrylic, or various bisphenol A epoxy resins, such as E-44, E-20, E-51, etc., but This disclosure is not limited thereto. In some embodiments, the insulating glue layer 732 further includes additives, such as curing agent, cross-linking agent, diluent, photoinitiator, coupling agent and the like.

In some embodiments, the first conductive particles 734 and the second conductive particles 736 are polymer microspheres coated with conductive metal. The material of the polymer microspheres can be, for example but not limited to: polyethylene, polypropylene, polyester, polystyrene, polyvinyl alcohol, or polymethylmethacrylate. The conductive metal can be, for example, nickel, gold, copper, silver, tin, lead, aluminum, tungsten, iron, the like, or combinations thereof. In some embodiments, the diameter of the first conductive particles 734 and the second conductive particles 736 may be about 5 microns to 40 microns, such as about 5 microns, 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, 35 microns microns, or 40 microns.

In some embodiments, the insulating adhesive layer 732 in the anisotropic conductive adhesive film 730 is made of acrylic with a thickness of about 25 microns. The first conductive particles 734 and the second conductive particles 736 are polymer microspheres coated with nickel and gold, with a size of about 20 microns and a density of 300 Pcs/mm ² .

Please refer to FIG. 6D , which illustrates disposing the second electronic component on the anisotropic conductive adhesive film. The second electronic assembly 740 includes a second substrate 742 and a second conductive element 744 on the second substrate 742 . In the vertical direction, the second conductive element 744 overlaps with the first conductive element 714 of the first electronic component 710 . Specifically, the area of the second conductive element 744 vertically projected on the first substrate 712 at least partially overlaps the area of the first conductive element 714 vertically projected on the first substrate 712 .

In some embodiments, the second substrate 742 can be a flexible substrate, and its material can include but not limited to polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyethylene, polycarbonate, Resin such as polyimide or acrylic resin, or the like. In some embodiments, the material of the second conductive element 744 may include gold, silver, copper, aluminum, indium tin oxide, composite conductive polymer material, or the like.

Please refer to FIG. 6E , which shows the connection structure 700 formed by pressing each element. Pressing the second electronic component 740, the anisotropic conductive adhesive film 730, the buffer layer 720, and the first electronic component 710, so that the first substrate 712 of the first electronic component 710 and the second substrate 742 of the second electronic component 740 Connected via the insulating adhesive layer 732, and the first conductive particles 734 between the first conductive element 714 and the second conductive element 744 are compressed and physically contact and electrically connect the first conductive element 714 and the second conductive element 714. Conductive element 744 . During pressing, the resin in the insulating adhesive layer 732 is hardened by heating, and the second electronic component 740 is fixed on the first electronic component 710 .

Under the external vertical pressing force _P1 , the first conductive particles 734 sandwiched between the first conductive element 714 and the second conductive element 744 are squeezed and deformed, thus forming It has the effect of electrical conduction. When the insulating adhesive layer 732 is cured for a period of time, the first conductive particles 734 are no longer moved by external force and form an electrically conductive structure, thus electrically connecting the first conductive element 714 and the second conductive element 744 . Furthermore, the second conductive particles 736 are located in a region not overlapping the first conductive element 714 and the second conductive element 744 in the vertical direction, so they are not deformed by extrusion, and are kept surrounded and insulated by the insulating glue layer 732 .

In other embodiments, when the anisotropic conductive adhesive film 730 is placed on the buffer layer 720, a pre-lamination step can be performed, and the anisotropic conductive adhesive film 730 is laminated to the buffer layer 720 and the buffer layer 720 through a laminating device. On the first electronic component 710 , the pre-lamination temperature may be, for example, about 95°C to 110°C. Next, the second electronic component 740 is pressed onto the anisotropic conductive adhesive film 730, the buffer layer 720, and the first electronic component 710 through a pressing device, and the temperature of the pressing can be, for example, about 160°C to 220°C .

Please refer to FIG. 7A and FIG. 7B, which show partial enlarged views of the connection structure before and after applying the pressing force. FIG. 7A shows the first conductive particles 734 interposed between the buffer layer 720 and the second conductive element 744 before lamination. FIG. 7B shows that when lamination is performed, the height of the first conductive particles 734 is reduced due to lamination, and the buffer layer 720 is pushed away to contact the first conductive element 714, while other parts of the anisotropic conductive adhesive film 730 connectivity is not affected. In one embodiment, the diameter of the first conductive particles 734 is 20 microns before lamination, and the diameter of the first conductive particles 734 becomes larger after lamination to about 30 microns, and the thickness of the buffer layer 720 is about 2 microns.

Figure 8 shows an alternative embodiment. In this embodiment, the buffer layer 820 of the connection structure 800 is an organic thin film formed by Organic Solderability Preservative (OSP) technology, also known as an organic solderability preservative film. The buffer layer 820 includes a first portion 820A in contact with the first substrate 712 and a second portion 820B in contact with the first conductive element 714 . The other components of the connection structure 800 are similar to the connection structure 100 discussed above with reference to FIG. 1 or the connection structure 700 discussed above with reference to FIGS. 6A-6E , and thus will not be described again here.

In the embodiment where the buffer layer is formed by organic soldering technology, the material of the first conductive element 714 is copper, and the coating film on the copper surface may include rosin, reactive resin, or azole, for example. In some embodiments, the organic film of azoles can be, for example, polybenzimidazole (PBI), benzotriazole (BTA), alkylimidazole (IA), benzimidazole (Benzimidazole, BIA), substituent benzo Imidazole (Substituted Benzimidazole, SBA), or alkyl phenyl imidazole (Aryl Phonylimidazole, APA). The organic copper compound film can be formed on the first conductive element 714 through organic soldering technology. Since the organic solder protection film is easy to be scratched and scratched, the organic solder protection film will be damaged due to high temperature and high pressure during the pressing process, so the part of the first conductive element 714 is exposed so that the first conductive particles 734 can be electrically connected to the first conductive element 734. A conductive element 714 .

Please refer to FIG. 9 , which illustrates the flow of the method for forming the organic solder protection film. In the method 900 , first in step 902 , the first conductive element 714 of the first electronic component 710 is degreased. Next in step 904, water washing is performed. Then in step 906, the copper surface of the first conductive element 714 is micro-etched. After microetching, in step 908, a secondary water wash is performed. Then in step 910, the copper surface of the first conductive element 714 is micro-etched again. Next in step 912, the first conductive element 714 is washed with ultrapure water. Then in step 914, the OSP solution is brushed on the first electronic component 710 or the first electronic component 710 is immersed in the OSP solution, and then an organic solder protection film is formed and air-dried. Then in step 916 , the first electronic component 710 coated with the organic solder protection film is cleaned with ultrapure water. Then in step 918, the cleaned first electronic component 710 is dried.

Referring to FIG. 8 again, the buffer layer 820 is an organic thin film formed by organic soldering technology, wherein the first portion 820A of the buffer layer 820 contacts the upper surface of the first substrate 712 of the first electronic component 710 . The first portion 820A of the buffer layer 820 is an organic thin film comprising the organic materials described above. The second portion 820B of the buffer layer 820 is in contact with portions of the upper surface and the side surface of the first conductive element 714, and is an organic thin film containing copper complex. In some embodiments, the thickness of the first part 820A and the second part 820B of the buffer layer 820 is about 1/20 to about 1/5 of the height of the conductive particles (before lamination) of the anisotropic conductive adhesive film, preferably The ratio is about 1/10, so as to provide proper stress buffering effect and enable the first conductive particles 734 to penetrate through the second portion 820B of the buffer layer during pressing.

Figure 10 shows an alternative embodiment. In this embodiment, the buffer layer 1020 of the connection structure 1000 includes a first portion 1020A in contact with the first substrate 712 and a second portion 1020B in contact with the first conductive element 714 . Other components of the connection structure 1000 are similar to the connection structure 100 discussed above with reference to FIG. 1 or the connection structure 700 discussed above with reference to FIGS. 6A-6E , and therefore, will not be described again here.

In the connecting structure 1000, the second portion 1020B of the buffer layer 1020 is an organic thin film formed by organic soldering technology. The first part 1020A of the buffer layer 1020 is an organic thin film, and its thermal expansion coefficient is between that of the first substrate 712 and that of the insulating adhesive layer 732, for example, between about 20 ppm/K and about 50 ppm/K. between. The material of the first portion 1020A of the buffer layer 1020 can be, for example, rosin, reactive resin, azole, polyether ether ketone, polyimide, acrylic resin, or the like.

In some embodiments, the method for forming the second portion 1020B of the buffer layer 1020 may be similar to the method 900 for the organic solder protection film process described in FIG. The part of the first substrate 712 that is not covered by the first conductive element 714 is covered with a protective layer; after that, when the organic solder protection film is formed on the upper surface and the side surface of the first conductive element 714 (that is, the buffer layer 1020 After the second part 1020B), the protective film on the first substrate 712 is removed, and the above-mentioned organic material is disposed on the first substrate 712, for example, by coating, thus forming the second layer of the buffer layer 1020 Part 1020A.

Figure 11 is an alternative embodiment. In this embodiment, the upper surface of the first conductive element 714 of the connection structure 1100 is provided with a buffer layer 1120 . In some embodiments, the material of the first conductive element 714 is gold, silver, copper, or a combination thereof, and the buffer layer 1120 is a metal plating layer, and the material is zinc, aluminum, lead, cadmium, magnesium, or a combination thereof. Since the thermal expansion coefficient of gold is 14.2, the thermal expansion coefficient of silver is 19.5, and the thermal expansion coefficient of copper is 16.5ppm/K, these values are significantly lower than the thermal expansion coefficient of the insulating adhesive layer 732, so between the insulating adhesive layer 732 and the first Delamination may easily occur between conductive elements 714 . By disposing the buffer layer 1120 formed by the metal plating layer on the first conductive element 714, and the thermal expansion coefficient of the metal plating layer is between the thermal expansion coefficient of the first conductive element 714 and the thermal expansion coefficient of the insulating adhesive layer 732, it can provide a considerable The function of the buffer layer reduces peeling between the insulating adhesive layer 732 and the first conductive element 714 . Since once peeling occurs between the insulating adhesive layer 732 and the first conductive element 714, the electrical function of the device will fail. Therefore, the buffer layer 1120 formed by the metal plating layer is preferably arranged between the insulating adhesive layer 732 and the first conductive element 714. Between the conductive elements 714 , especially between the insulating glue layer 732 and the upper surface of the first conductive element 714 . Optionally, the buffer layer may also include other parts, for example, disposed between the insulating adhesive layer 732 and the side surface of the first conductive element 714 , or disposed between the insulating adhesive layer 732 and the first substrate 712 .

In some embodiments, the metal coating has a coefficient of thermal expansion of about 25 ppm/K to about 50 ppm/K, for example, zinc has a coefficient of thermal expansion of 36 ppm/K, aluminum has a coefficient of thermal expansion of 23.2 ppm/K, and lead has a coefficient of thermal expansion of 29.3 ppm/K, cadmium has a thermal expansion coefficient of 41.0 ppm/K, and magnesium has a thermal expansion coefficient of 26.0 ppm/K. In some embodiments, the thickness of the buffer layer 1120 formed by the metal plating may be 5 to 30 microns, but the disclosure is not limited thereto, and the thickness of the metal plating can be adjusted depending on the process and process parameters used.

As shown in FIG. 11, since the electroplating process used is anisotropic, the buffer layer 1120 formed by the metal plating layer is on the upper surface of the first conductive element 714 and contacts the upper surface of the first conductive element 714. . Other components of the connecting structure 1100 are similar to the connecting structure 100 discussed above with reference to FIG. 1 or the connecting structure 700 discussed above with reference to FIGS. 6A-6E , and therefore, will not be described again here. It should be further noted that, in addition to being disposed on the upper surface of the first conductive element 714, the buffer layer 1120 may also be disposed on the upper surface of the second conductive element 744 in other feasible examples, or on the first Both the upper surface of the conductive element 714 and the upper surface of the second conductive element 744 are provided with a buffer layer 1120 . Figure 12 is an alternative implementation, similar to the connection structure in Figure 11, the difference is that in the connection structure 1200, when the buffer layer 1220 formed by metal plating is formed, the side surface of the first conductive element 714 will also be Metal plating is applied, therefore, between the insulating adhesive layer 732 and the side surface of the first conductive element 714 , the buffer layer 1220 formed by the metal plating is also used to share the stress caused by the difference in thermal expansion coefficient.

Figure 13 is an alternative implementation, similar to the connection structure in Figure 12, in the connection structure 1300, the first buffer layer 1320 formed by metal plating is disposed between the insulating glue layer 732 and the first conductive element 714 between the top and side surfaces. The difference between the connection structure 1300 and the connection structure 1200 in FIG. 12 is that in the connection structure 1300, between the insulating adhesive layer 732 and the first substrate 712, an organic thin film is also used as the second buffer layer 1322 to share the Stresses due to differences in thermal expansion coefficients.

In some embodiments, after the first electronic component 710 is provided, a metal plating layer (ie, the buffer layer 1220 ), such as zinc, aluminum, lead, cadmium, magnesium, or a combination thereof, is plated on the first conductive element 714 . The second buffer layer 1322 formed of an organic thin film can be formed afterwards, for example, by coating. The thermal expansion coefficient of the material of the second buffer layer 1322 is between the thermal expansion coefficient of the first substrate 712 and the thermal expansion coefficient of the insulating adhesive layer 732 , such as about 25 ppm/K to about 50 ppm/K. The material of the second buffer layer 1322 can be, for example, rosin, reactive resin, azole, polyether ether ketone, polyimide, or acrylic resin.

Figure 14 shows an alternative embodiment. In this embodiment, the first buffer layer 1420 formed by metal plating is disposed on the upper surface and the side surface of the first conductive element 714 of the connection structure 1400, and the second buffer layer 1422 formed by an organic film covers the first buffer layer 1422. A substrate 712 and the first buffer layer 1420 , and the first conductive particles 734 break through the second buffer layer 1422 to electrically connect the first buffer layer 1420 and the first conductive element 714 . That is to say, on the first conductive element 714 , the buffer layer may be a composite layer, including a first buffer layer 1420 formed of a metal plating layer and a second buffer layer 1422 formed of an organic thin film thereon. Other components of the connection structure 1400 are similar to the connection structure 100 discussed above with reference to FIG. 1 or the connection structure 700 discussed above with reference to FIGS. 6A-6E , and therefore, will not be described again here.

In some embodiments, after the first electronic component 710 is provided, a metal plating layer (ie, the first buffer layer 1420 ), such as zinc, aluminum, lead, cadmium, magnesium, or its combination. Afterwards, the second buffer layer 1422 formed by an organic thin film can be disposed on the first substrate 712 of the first electronic component 710 and the first substrate 712 of the first electronic component 710 through, for example, coating or a soft-to-hard bonding technique. on the first buffer layer 1420 . In some embodiments, the materials and properties of the first buffer layer 1420 and the second buffer layer 1422 may be, for example, those of the first buffer layer 1320 and the second buffer layer 1322 discussed above with reference to FIG. 13 .

In the connection structure provided by the present disclosure, a buffer layer is added at the interface where the stress and strain are concentrated (that is, the interface between the anisotropic conductive adhesive film and the first conductive structure), and its thermal expansion coefficient is lower than that of the anisotropic conductive adhesive. The coefficient of thermal expansion of the film and the substrate, therefore, distributes the stress-strain gradient across the two interfaces (ie, the conductive element and the buffer layer, and the buffer layer and the anisotropic conductive adhesive film). Therefore, the peeling problem of the anisotropic conductive adhesive film caused by the difference in thermal expansion coefficient is improved. In addition, it can be extended to other bonding processes, and the position of the buffer layer can be flexibly selected between interfaces with large differences in thermal expansion coefficients, such as between the anisotropic conductive adhesive film and the substrate.

Although the content of this disclosure has been disclosed above in terms of implementation, it is not intended to limit the content of this disclosure. Anyone who is skilled in this art can make various changes and modifications without departing from the spirit and scope of this disclosure. Therefore, this The scope of protection of the disclosed content shall be subject to the definition of the appended patent application scope.

100: Connection structure 110: The first electronic component 112: The first substrate 114: the first conductive element 120: buffer layer 130: Anisotropic conductive film 132: insulating adhesive layer 134: The first conductive particle 136: The second conductive particle 140: Second electronic component 142: second substrate 144: second conductive element 300: Connection structure 310: rigid substrate 320: Anisotropic conductive film 330: flexible substrate 500: connection structure 510: rigid substrate 520: buffer layer 530: Anisotropic conductive film 540: flexible substrate 700: Connection structure 710: The first electronic component 712: The first substrate 714: first conductive element 720: buffer layer 730: Anisotropic conductive film 732: insulating adhesive layer 734: The first conductive particle 736:Second Conductive Particles 740: Second electronic component 742: second substrate 744: second conductive element 800: connection structure 820: buffer layer 820A: Part I 820B: Part II 900: method 902, 904, 906, 908, 910, 912, 914, 916, 918: steps 1000: connection structure 1020: buffer layer 1020A: Part I 1020B: Part II 1100: connection structure 1120: buffer layer 1200: connection structure 1220: buffer layer 1300: connection structure 1320: The first buffer layer 1322: Second buffer layer 1400: connection structure 1420: The first buffer layer 1422: Second buffer layer H1: height H2: height P1: Compression force

In order to make the above and other purposes, features, advantages and embodiments of the present disclosure more comprehensible, the accompanying drawings are described as follows: Figure 1 illustrates a cross-sectional view of a connection structure according to some embodiments. Fig. 2 is a cross-sectional view according to a comparative example. FIG. 3 is a stress diagram simulated by multiple physical quantity coupling analysis software according to the comparative example in FIG. 2 . Fig. 4 is a cross-sectional view according to an experimental example. FIG. 5 is a stress diagram simulated by multiple physical quantity coupling analysis software according to the experimental example in FIG. 4 . 6A-6E are cross-sectional views at various intermediate stages of forming a connection structure according to some embodiments. 7A, 7B are enlarged cross-sectional views at various intermediate stages of forming a connection structure according to some embodiments. Figure 8 depicts a cross-sectional view of a connection structure according to some alternative embodiments. FIG. 9 is a flowchart illustrating a method of forming an organic solder repellant film according to some embodiments. Figure 10 depicts a cross-sectional view of a connection structure according to some alternative embodiments. Figure 11 depicts a cross-sectional view of a connection structure according to some alternative embodiments. Figure 12 depicts a cross-sectional view of a connection structure according to some alternative embodiments. Figure 13 depicts a cross-sectional view of a connection structure according to some alternative embodiments. Figure 14 depicts a cross-sectional view of a connection structure according to some alternative embodiments.

Domestic deposit information (please note in order of depositor, date, and number) none Overseas storage information (please note in order of storage country, institution, date, and number) none

100: Connection structure

110: The first electronic component

112: The first substrate

114: the first conductive element

120: buffer layer

130: Anisotropic conductive film

132: insulating adhesive layer

134: The first conductive particle

136: The second conductive particle

140: Second electronic component

142: second substrate

144: second conductive element

H ₁ : height

H ₂ : Height

Claims (10)

A connection structure comprising: A first electronic component comprising a first substrate and a first conductive element on the first substrate; a buffer layer disposed on the upper surface of the first conductive element of the first electronic component; An anisotropic conductive adhesive film, comprising an insulating adhesive layer and a first conductive particle in the insulating adhesive layer, wherein the insulating adhesive layer is disposed on the first substrate of the first electronic component and the first conductive element above and on the buffer layer; and A second electronic component is arranged on the anisotropic conductive adhesive film, the second electronic component includes a second substrate and a second conductive element under the second substrate, wherein the first conductive particles are electrically conductive connecting the first conductive element and the second conductive element; The thermal expansion coefficient of the buffer layer is between the thermal expansion coefficient of the first conductive element and the thermal expansion coefficient of the insulating adhesive layer of the anisotropic conductive adhesive film. The connection structure according to claim 1, wherein the thermal expansion coefficient of the buffer layer is about 20 ppm/K to about 50 ppm/K. The connection structure according to claim 1, wherein the buffer layer comprises an organic thin film, a metal plating layer, or a combination thereof. The connection structure according to claim 1, wherein the buffer layer includes an organic thin film, and the first conductive particles pass through the buffer layer to electrically connect the first conductive element. The connection structure as claimed in item 1, wherein the anisotropic conductive adhesive film further comprises a second conductive particle in the insulating adhesive layer, the second conductive particle does not contact the first conductive element and the second conductive element, and the thickness of the buffer layer is about 1/20 to about 1/5 of the height of the second conductive particles. The connection structure according to claim 1, wherein the material of the buffer layer is zinc, aluminum, magnesium, lead, cadmium, or a combination thereof. The connection structure according to claim 1, wherein the buffer layer is also disposed on the side surface of the first conductive element and on the first substrate. A method of forming a connection structure, comprising: providing a first electronic component, wherein the first electronic component includes a first substrate and a first conductive element on the first substrate; disposing a buffer layer on the upper surface of the first conductive element of the first electronic component; An anisotropic conductive adhesive film is disposed above the first electronic component and the buffer layer, wherein the anisotropic conductive adhesive film includes an insulating adhesive layer and a first conductive particle in the insulating adhesive layer; A second electronic component is arranged above the anisotropic conductive adhesive film, wherein the second electronic component includes a second substrate and a second conductive element under the second substrate, and the coefficient of thermal expansion of the buffer layer is between Between the thermal expansion coefficient of the first conductive element and the thermal expansion coefficient of the insulating adhesive layer of the anisotropic conductive adhesive film; and laminating the first electronic component, the buffer layer, the anisotropic conductive adhesive film, and the second electronic component, wherein the first conductive particles of the anisotropic conductive adhesive film are electrically connected to the first conductive element and the second conductive element. The method for forming a connection structure as claimed in item 8, wherein the buffer layer comprises an organic thin film, and the first electronic component, the buffer layer, the anisotropic conductive adhesive film, and the second In electronic components, the first conductive particles of the anisotropic conductive adhesive film pass through the organic film and connect to the first conductive element. The method for forming a connection structure as claimed in item 8, wherein the buffer layer includes a metal plating layer, and in the lamination process of the first electronic component, the buffer layer, the anisotropic conductive adhesive film, and the second In electronic components, the first conductive particles of the anisotropic conductive adhesive film are electrically connected to the first conductive element by contacting the metal plating layer.

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