CHIP BONDING COMPOSITION FOR POWER SEMUBLER PACKAGE

Abstract

Chip bonding composition, comprehensive: a silver powder; an epoxy resin; a hardening agent; a catalyst; a glycidyl ether-based diluent; and a polysilsesquioxane (PSQ) resin.

Description

[Technical field]

[0001] The embodiments relate to a chip bonding composition for power semiconductor packages with high thermal conductivity, adhesion, high heat dissipation and low modulus. [State of the art]

[0002] Recently, demand for high-power, high-efficiency power semiconductors has increased due to the growth of the markets for environmentally friendly automobiles and renewable energy.

[0003] Accordingly, the demand for wide bandgap (WBG) compound semiconductors based on silicon carbide (SiC), gallium nitride (GaN) or similar materials is increasing.

[0004] Power semiconductors improve energy efficiency and stabilize voltage fluctuations during power transmission and control to ensure system stability and reliability.

[0005] Among wide band gap (WBG) compounds, SiC has an approximately 10 times higher breakdown field strength and an approximately 3 times higher band gap than Si.

[0006] SiC is capable of driving the p- and n-type semiconductors required for the fabrication of electronic components across a wide range. Advantageously, SiC has a thermal conductivity of 4.9 W / mK, which is approximately three times higher than the 1.5 W / mK of silicon (Si).

[0007] Furthermore, SiC has a melting point of 300°C or higher and therefore operates stably even at high operating temperatures.

[0008] It is known that replacing a conventional Si IGBT (Insulated Gate Bipolar Transistor) power semiconductor with a SiC power semiconductor reduces the volume by about 50% or less and increases energy efficiency by about 85% or more.

[0009] Accordingly, it is expected that SiC power semiconductors will be used in the future primarily in place of conventional Si-IGBT power semiconductors in areas requiring high voltages, high currents and high power.

[0010] Power semiconductors are typically used in products in the form of modules containing power semiconductors. A power semiconductor package or module has a configuration where direct bonding copper (DBC), in which copper is directly bonded, is applied to the top and bottom surfaces of a ceramic substrate. A power semiconductor package or module has a configuration where a power semiconductor chip, bonded with solder, is applied to the top surface of the DBC. A metallic base plate is bonded to the bottom surface of the DBC with solder.

[0011] A power semiconductor package using SiC in a power semiconductor chip has a much higher operating temperature than a conventional power semiconductor package using Si. Therefore, there is a need for methods capable of increasing the thermal conductivity within the package, improving its resistance to thermal stress, and maximizing the excellent physical properties of SiC.

[0012] In this context, the bonding material of the power semiconductor chip should ideally exhibit high adhesion, high heat dissipation, and resistance to repeated temperature shocks. Furthermore, the bonding material should not remelt even at high operating temperatures and should be commercially available and competitively priced.

[0013] Compositions such as Ag-Pb and Sn-Ag-Cu (SAC) are mainly used as bonding materials for power semiconductor chips, but these bonding materials have several problems and are therefore not suitable for SiC power semiconductor packages.

[0014] This is because compositions such as Ag-Pb and Sn-Ag-Cu (SAC) remelt at around 180 °C, leading to defects such as cracks and fatigue fractures, and making them unsuitable for use in power semiconductors with high pressure, high currents and high temperatures.

[0015] Furthermore, lead-containing solders or SAC materials cause interface delamination, stress concentrations, and permanent creep deformation in the thin-film layer due to thermal fatigue from repeated current switching. Additionally, the transient liquid-phase (TLP) bonding of Cu / Sn / Cu has a multilayered interface and therefore frequently causes cracking, leading to reliability issues.

[0016] KR 10 2010 0 009 541 A1 further discloses adhesive compositions for bonding semiconductors. The adhesive compositions disclosed therein can contain, among other things, epoxy resins as thermosetting resins and polysiloxanes or polysilsesquioxanes in particulate form as fillers. WO 2015 / 005 371 A1 describes chip bonding compositions with silver particles and an epoxy resin. It also describes a composition comprising silicone resin, for example, polysilsesquioxane resin, for a protective layer encapsulating the semiconductor device.

[0017] Processes that use binders include soldering, eutectic bonding, pressure sintering, and pressureless sintering.

[0018] Sintering metals, such as soldering, produces a solid film of bonding material. Furthermore, metal sintering is known to be the best alternative due to its high adhesion strength, high thermal conductivity of approximately 150 to 300 W / mK, and high melting point.

[0019] Pressure sintering enables sinter bonding at a pressure of approximately 30 MPa and 200 to 250 °C for about 5 minutes. However, due to the significant damage to the chips caused by pressing, pressure sintering is practically unsuitable for mass production and is only used to a limited extent for very expensive power modules in the extended contact area of ​​the metal powder.

[0020] Pressureless sintering is the ideal method, but has the limitation that the sintering process takes more than 200 minutes and mass production is not possible due to the high process temperature.

[0021] Pressureless sintering with copper is disadvantageously unusable due to the difficulty of using an inert gas atmosphere in the bonding process and due to the oxidation problem during use.

[0022] Conventional chip bonding compounds suitable for sintering offer the advantage of high heat dissipation. However, these compounds suffer from the problem that, due to their high modulus, delamination often occurs after temperature cycling between the chip and the bonding material, or between the conductor frame and the substrate.

[0023] Generally, when the silver powder in the chip bonding material is melted and sintered, its modulus increases. However, when the chip bonding material is cooled and repeatedly heated from a low temperature of -40°C or lower to a high temperature of 125°C or higher, it flexes upwards and downwards, adversely leading to cracking and delamination. Accordingly, when applying conventional bonding materials to medium to large chips measuring 4 x 4 mm, the chip bonding material is often too short to be suitable for this application. 2 or more restricted.

[0024] Therefore, there is a need for a chip bonding composition to replace conventional chip bonding materials that exhibits high thermal conductivity, heat resistance, high heat dissipation properties and a low modulus, and can be used for medium to large chips. [Revelation][Technical Problem]

[0025] One embodiment provides a chip bonding composition for power semiconductor packages with excellent thermal conductivity and adhesion.

[0026] Another embodiment offers a chip bonding composition for power semiconductor packages with excellent heat dissipation properties and low module characteristics.

[0027] Another embodiment offers a chip bonding composition for power semiconductor packages suitable for medium to large high-power SiC and GaN chips.

[0028] Another embodiment offers a chip bonding composition for power semiconductor packages that is suitable for pressure-free sintering and can drastically reduce processing time and temperature.

[0029] The objectives of this disclosure are not limited to those mentioned above, and other objectives and benefits not mentioned here will be understood with the help of the following description and better understood through the examples in this disclosure. Furthermore, it will become apparent that the objectives and benefits of this disclosure can be achieved through the means and combinations thereof defined in the claims. [Technical solution]

[0030] In one embodiment, a chip bonding composition comprises a silver powder, an epoxy resin, a curing agent, a catalyst, a glycidyl ether-based diluent, and a polysilsesquioxane resin (PSQ).

[0031] The silver powder can provide high thermal conductivity.

[0032] The epoxy resin may contain a resin that is a mixture of a glycidylamine-based epoxy resin and a bisphenol-A epoxy resin in order to achieve a low modulus.

[0033] The chip bonding composition may contain 1 to 7 parts by weight of epoxy resin, 0.01 to 5 parts by weight of catalyst, 0.2 to 3 parts by weight of glycidyl ether-based thinner, and 1 to 6 parts by weight of polysilsesquioxane (PSQ) resin, based on 100 parts by weight of silver powder, and the mixing ratio of epoxy resin and curing agent may be a weight ratio of 1:1 to 1:2. [Beneficial effects]

[0034] The chip bonding composition for power semiconductor packages according to the present disclosure exhibits excellent thermal conductivity, adhesion and heat dissipation, as well as a low modulus.

[0035] Furthermore, the chip bonding composition for power semiconductor packages according to the present disclosure reduces the mechanical stress of the power semiconductor package caused by thermal shocks, thus ensuring excellent durability and reliability even at high operating temperatures of power semiconductor chips.

[0036] Furthermore, the chip bonding composition for power semiconductor packages according to the present disclosure advantageously increases the operating temperature of SiC and GaN semiconductor packages, since it does not melt again after completion of the heat treatment (reflow), even at temperatures of 300 °C or more, despite low operating temperatures.

[0037] Furthermore, the chip bonding composition for power semiconductor packages of the present disclosure exhibits a high adhesion strength, regardless of the type of metal present at the interface between the power semiconductor chip and the conductor frame or between the power semiconductor chip and the substrate, such as DBC (direct bonding copper).

[0038] The chip bonding composition for power semiconductor packages according to the present disclosure is suitable for medium to large high-power SiC and GaN chips.

[0039] The chip bonding composition for power semiconductor packages according to the present disclosure is suitable for pressureless sintering, which can drastically reduce the processing time and temperature.

[0040] Detailed effects of the present disclosure, which go beyond the effects described above, are described below together with details on the implementation of the invention. [Brief description of the drawings] Fig. Figure 1 shows the structuring of a chip bonding composition from Example 1 of the present disclosure on a DBC substrate using a dispenser. Fig. Figure 2 shows the result of the processability test of the chip bonding composition from Example 1 according to the present disclosure over time. Fig. Figure 3 is a cross-sectional image showing the chip bonding composition of Example 1 according to the present disclosure, which was applied and sintered between a substrate and a SiC chip. Fig.Figure 4 shows DST (surface) after the adhesion strength test depending on the type of metal applied to the DBC substrate, as well as an SEM image and the porosity of the sintered composition. [Best Design]

[0041] The items, features, and advantages described above are described in detail with reference to the accompanying drawings. Those skilled in the art of the present disclosure will be able to easily implement the technical idea of ​​the present disclosure. In the following description of the present disclosure, detailed descriptions of the prior art to which the present disclosure relates are omitted if they would make the subject matter of the present disclosure unclear. Preferred embodiments according to the present disclosure are described in detail below with reference to the accompanying drawings. Throughout the description of the drawings, identical numbers refer to identical elements.

[0042] When an element is described as being "above" (or "below") or "on" (or "under") another element, it may be in direct contact with the top (or bottom) of the other element, or there may be an element in between.

[0043] When an element is described as "bound", "linked", or "connected" to another element, the elements may be directly bound or connected to each other, or they may be "bound", "linked", or "connected" via the other element.

[0044] The following describes the chip bonding composition for power semiconductor packages according to some embodiments of the present disclosure.

[0045] The chip bonding composition for power semiconductor packages according to the present disclosure is a material that can replace conventional solder pastes such as Sn-Ag-Cu (SAC) and exhibits high thermal conductivity and adhesion, as well as high heat dissipation and a low modulus.

[0046] Advantageously, the chip bonding composition is applicable to SiC and GaN-based power semiconductor packages, semiconductor packages such as modules, communication modules, CPUs and GPUs, high-performance LED packages and similar, and is suitable for medium to large chips.

[0047] The chip bonding composition for power semiconductor packages according to the present disclosure contains a silver powder as the main component and may contain a silver powder, an epoxy resin, a curing agent, a catalyst, a glycidyl ether-based diluent, and a polysilsesquioxane resin (PSQ).

[0048] The silver powder comprising the chip bonding composition for power semiconductor packages according to the present disclosure serves to ensure high thermal conductivity. The chip bonding composition preferably contains a large amount of silver powder.

[0049] The silver powder is not spherical, but rather flocculent or plate-shaped.

[0050] The thickness of the silver powder in the form of a scale or platelet can range from 0.1 to 200 nm, in particular from 1 to 150 nm, 1 to 100 nm and especially from 10 to 100 nm.

[0051] The silver powder, with a nanoscale thickness, is advantageously sintered at low temperatures when combined with an organic material, which will be described later.

[0052] In addition to the large quantity of silver powder, the chip bonding composition preferably contains an epoxy resin mixture of a glycidylamine-based epoxy resin and a bisphenol-A epoxy resin to ensure sufficient flowability.

[0053] Epoxy resins have been used primarily as chip bonding compounds in conventional semiconductor packages. Bisphenol A (BPA) epoxy resins, in particular, have a large free volume and therefore a high coefficient of thermal expansion of 55 to 75 ppm / °C. Although BPA epoxy resins are highly impregnated with thermally conductive powder, their coefficient of thermal expansion can only be reduced to a limited extent. Furthermore, due to the high viscosity of BPA epoxy resin, it is only possible to impregnate it with a large quantity of thermally conductive powder to a limited degree.

[0054] The coefficient of thermal expansion is a crucial requirement for ensuring the reliability of power semiconductor packages. If the coefficient of thermal expansion of one component of the power semiconductor package differs significantly from that of another component, or if the coefficient of thermal expansion of one component is very high, the component with the high coefficient of thermal expansion or the component with the large difference in coefficients of thermal expansion can cause fatal problems such as cracking during temperature cycling.

[0055] Furthermore, the melting of the silver powder in the binder causes constriction or sintering, which increases the modulus and leads to problems such as cracking and delamination due to vertical bending. Therefore, there is a problem with applying bonding materials to medium to large chips.

[0056] To solve these problems, a mixed epoxy resin containing a glycidylamine-based epoxy resin and a bisphenol-A epoxy resin was used in the present disclosure.

[0057] Despite the high silver powder content, the chip bonding composition exhibits sufficient flowability because it contains a combination of a glycidylamine-based epoxy resin and a bisphenol-A epoxy resin, and is therefore a low-viscosity liquid.

[0058] In particular, an epoxy resin mixture consisting of a glycidylamine-based epoxy resin and a bisphenol-A epoxy resin provides a low modulus and mitigates the mechanical stress on the power semiconductor packages due to temperature shocks. Accordingly, a chip bonding composition containing an epoxy resin exhibits sufficient durability and reliability even at the high operating temperatures of power semiconductor chips.

[0059] The glycidylamine-based epoxy resin contains at least one nitrogen atom and lone pairs of electrons. The glycidylamine-based epoxy resin exhibits lone pairs of electrons on both the oxygen and nitrogen atoms.

[0060] The glycidylamine-based epoxy resin comprises at least one of the following materials: triglycidyl p-aminophenol (TGPAP), tetraglycidyl diaminodiphenylmethane (TGDDM), triglycidyl m-aminophenol (TGMAP), tetraglycidyl diaminodiphenylsulfone (TGDDS), diglycidylaniline or diglycidyl o-toluidine.

[0061] The chip bonding composition preferably contains the mixed epoxy resin in an amount of 1.0 to 7.0 parts by weight, and more preferably 1.9 to 6.7 parts by weight, based on 100 parts by weight of the silver powder.

[0062] The glycidylamine-based epoxy resin may be present in an amount of 0.1 to 6.0 parts by weight, and the bisphenol-A epoxy resin in an amount of 0.1 to 6.0 parts by weight. Preferably, the glycidylamine-based epoxy resin may be present in an amount of 1.0 to 3.0 parts by weight, and the bisphenol-A-type epoxy resin in an amount of 0.2 to 5.0 parts by weight.

[0063] The chip bonding composition contains 1 to 7 parts by weight of the mixed epoxy resin, resulting in high thermal conductivity and allowing the silver powder to be sintered smoothly.

[0064] If the proportion of the mixed epoxy resin is less than 1 part by weight, it may not be sufficient to reduce the mechanical stress on the power semiconductor package and to ensure the durability and reliability of the power semiconductor package.

[0065] However, if the proportion of the mixed epoxy resin exceeds 7 parts by weight, the resin acts as an obstacle with increasing resin content, preventing the sintering of the silver powder and thus causing the problem of impaired heat dissipation.

[0066] The chip bonding composition contains a combination of two types of epoxy resins as well as a curing agent.

[0067] The curing agent slows down the curing rate and increases work stability. Furthermore, the curing agent ensures a high curing density and forms a continuous weld layer of silver powder.

[0068] In particular, curing can occur at a low temperature of 250 °C or less, as the curing reaction and the externally applied heat generate exothermic heat of reaction. Simultaneously, welding between the silver powder particles can be effectively achieved. Consequently, a high curing density and a continuous welding phase of the silver powder can be formed, leading to an increase in thermal conductivity. Furthermore, the processing time and temperature can be drastically reduced, making it suitable for pressureless sintering.

[0069] The curing agent can be an acid anhydride-based curing agent.

[0070] The acid anhydride-based curing agent may comprise at least one of the following substances: norbornene maleic anhydride (nadic maleic anhydride), dodecyl succinic anhydride, maleic anhydride, succinic anhydride, methyl tetrahydrophthalic anhydride, hexahydrophthalic anhydride (HHPA), tetrahydrophthalic anhydride, pyromellitic dianhydride, cyclohexanedicarboxylic anhydride, methyl tetrahydrophthalic anhydride (MeTHPA), methyl hexahydrophthalic anhydride (MeHHPA), methyl 5-norbornene-2,3-dicarboxylic anhydride (nadic methyl anhydride, NMA), hydrolyzed methyl 5-norbornene-2,3-dicarboxylic anhydride, phthalic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride (nadic anhydride).

[0071] The mixing ratio between the mixed epoxy resin and the curing agent is preferably a weight ratio of 1:1 to 1:2. The mixing ratio can, for example, be a weight ratio of 1:1 or a weight ratio of 1:2.4.

[0072] In other words, if the mixed epoxy resin is present in an amount of 1.0 to 7.0 parts by weight, the curing agent may be present in an amount of 2.0 to 8.0 parts by weight, and preferably 3.0 to 7.0 parts by weight.

[0073] If the mixing ratio of the mixed epoxy resin and the curing agent does not fall within the weight ratio range of 1:1 to 1:2, the exothermic reaction will not proceed normally due to the curing reaction, resulting in insufficient curing at low temperatures and insufficient welding between the silver powder particles.

[0074] The chip bonding composition contains a catalyst that facilitates the curing reaction between the epoxy resin, which contains a nitrogen atom and a free electron pair, and the acid anhydride-based curing agent.

[0075] The catalyst may contain an imidazole-based catalyst.

[0076] Der Katalysator auf Imidazolbasis kann mindestens einen der folgenden Stoffe enthalten: 2-Methylimidazol (2MZ), 2-Undecylimidazol (C11-Z), 2-Heptadecylimidazol (C17Z), 1,2-Dimethylimidazol (1.2DMZ), 2-Ethyl-4-methylimidazol (2E4MZ), 2-Phenylimidazol (2PZ), 2-Phenyl-4-methylimidazol (2P4MZ), 1-Benzyl-2-methylimidazol (1B2MZ), 1-Benzyl-2-phenylimidazol (1B2PZ), 1-Cyanoethyl-2-methylimidazol (2MZ-CN), 1-Cyanoethyl-2-ethyl-4-methylimidazol (2E4MZ-CN), 1-Cyanoethyl-2-undecylimidazol (C11Z-CN), 1-Cyanoethyl-2-phenylimidazoliumtrimellitat (2PZCNS-PW), 2,4-Diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazin (2MZ-A), 2,4-Diamino-6-[2'-Undecylimidazolyl-(1')]-ethyl-s-triazin (C11Z-A), 2,4-Diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazin (2E4MZ-A), 2,4-Diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazin-Isocyanursäure-Addukt (2MA-OK), 2-Phenyl-4,5-dihydroxymethylimidazol (2PHZ-PW) oder 2-Phenyl-4-methyl-5-hydroxymethylimidazol (2P4MHZ-PW).

[0077] The chip bonding composition preferably contains the catalyst in an amount of 0.01 to 5 parts by weight, more preferably 0.01 to 2.0 parts by weight and even more preferably 0.05 to 1.0 parts by weight, based on 100 parts by weight of the silver powder.

[0078] If the catalyst content is in the range of 0.01 to 5 parts by weight, the catalyst can activate the curing agent without delaying the curing reaction time.

[0079] When an imidazole catalyst is added to the chip bonding composition, it primarily causes esterification between the epoxy resin and the curing agent by activating the acid anhydride curing agent.

[0080] Furthermore, curing occurs through competing esterification and etherification (ROR') reactions of the hydroxyl groups of the epoxy resin and homopolymerization of the remaining epoxy resin.

[0081] With increasing imidazole catalyst content, the esterification peaks gradually shifted to lower temperatures. The etherification peaks were observed at a nearly constant temperature, independent of the catalyst content.

[0082] Furthermore, the heat of reaction (total heat) generated during the curing reaction decreases with increasing catalyst content. This means that the conversion rate decreases with increasing catalyst content.

[0083] Considering that the heat of reaction is preferably as high as possible because the chip bonding composition according to the present disclosure utilizes the heat generated by the reaction between the epoxy resin and the curing agent and the external heat, the catalyst content is preferably 5 parts by weight or less, and more preferably 2 parts by weight or less.

[0084] The chip bonding composition contains a glycidyl ether-based thinner to increase flexibility after curing.

[0085] The glycidyl ether-based diluent is inserted between the main chains of the cured epoxy material through a chemical reaction to loosen the overall three-dimensional network structure of the composition. In other words, the glycidyl ether-based diluent is distributed between the three-dimensional network structures by reacting with the epoxy main chain, thereby increasing the flexibility of the chip bonding composition and reducing the modulus after curing.

[0086] Furthermore, the glycidyl ether-based diluent has a mono- or bifunctional group and lowers the viscosity of the chip bonding composition, allowing the silver powder to be added in a large quantity.

[0087] The glycidyl ether-based diluent comprises at least one of the following substances: lauryl alcohol glycidyl ether (LGE), butyl glycidyl ether (BGE), 2-ethylhexyl glycidyl ether, allyl glycidyl ether (AGE), polypropylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether or 1,6-hexanediol diglycidyl ether.

[0088] The chip bonding composition preferably contains the glycidyl ether-based diluent in an amount of 0.2 to 3.0 parts by weight, and more preferably 0.4 to 3.0 parts by weight, based on 100 parts by weight of the silver powder.

[0089] If the glycidyl ether-based diluent content is in the range of 0.2 to 3.0 parts by weight, excellent flexibility of the chip bonding composition can be ensured.

[0090] If the concentration of the glycidyl ether-based diluent is not within the range of 0.2 to 3.0 parts by weight, the curing reaction is delayed and the glass transition temperature is lowered. Conversely, if the concentration of the glycidyl ether-based diluent is too high, bubbles may form. This has the disadvantage of potentially reducing the adhesion strength of the chip bonding compound.

[0091] The chip bonding composition contains a polysilsesquioxane (PSQ) resin to stimulate the sintering of the silver powder even at low temperatures of 250 °C or less.

[0092] The polysilsesquioxane resin is evenly distributed in the matrix of the chip bonding composition to reduce the module size.

[0093] Furthermore, the polysilsesquioxane resin occupies a large volume fraction compared to its weight and thus has the effect of reducing the distance between the silver powder particles. As from Fig. As can be seen in Figure 3(b), the black spherical polysilsesquioxane resin causes a reduction in the volume of the matrix, with the exception of the silver powder. The polysilsesquioxane resin does not react chemically or physically to curing and sintering, so it retains its original shape even after curing and sintering.

[0094] Accordingly, the polysilsesquioxane resin has the effect of stimulating the sintering of silver powder even at low temperatures of 250°C or less, without the addition of substances to stimulate low-temperature sintering, such as metal complexes.

[0095] The polysilsesquioxane resin may contain at least one of polypropylene silsesquioxane, polyphenylsilsesquioxane or polymethylene silsesquioxane.

[0096] The chip bonding composition preferably contains the polysilsesquioxane (PSQ) resin in an amount of 1.0 to 6.0 parts by weight, and more preferably 1.0 to 5.8 parts by weight, based on 100 parts by weight of the silver powder.

[0097] If the polysilsesquioxane resin content is less than 1.0 part by weight, the polysilsesquioxane resin may have almost no effect on reducing the modulus and improving the sintering properties.

[0098] If, however, the proportion of polysilsesquioxane resin exceeds 6.0 parts by weight, the dispersibility of the composition decreases and the viscosity increases, leading to a deterioration of the physical properties of the chip bonding composition and making it unsuitable for dosing or screen printing.

[0099] Thus, the chip bonding composition of the present disclosure contains a glycidyl ether-based diluent and a polysilsesquioxane (PSQ) resin, resulting in low modulus properties.

[0100] Accordingly, the chip bonding composition can ensure stable adhesion in low and high temperature cycle tests on medium to large power semiconductor packages.

[0101] Depending on the processing conditions, the chip bonding composition may also contain at least one of the following dispersants: a butadiene-based dispersant, a phosphoric acid-based dispersant, or an ester-based dispersant.

[0102] The dispersing agent serves to maintain or improve the dispersibility of the chip bonding composition.

[0103] The chip bonding composition may also contain the dispersing agent in an amount of 0.1 to 3 parts by weight, based on 100 parts by weight of the silver powder.

[0104] Furthermore, the chip bonding composition may contain an organic solvent depending on the processing conditions.

[0105] The organic solvent comprises at least one of the following substances: diethylene glycol monobutyl ether (BC), diethylene glycol monoethyl ether acetate (CA), dipropylene glycol methyl ether (DPM) or dipropylene glycol n-butyl ether (DPNB).

[0106] The chip bonding composition may, but is not limited to, contain the organic solvent in an amount of 0.01 to 100 parts by weight, based on 100 parts by weight of the silver powder.

[0107] The process for producing the chip bonding composition for power semiconductor packages according to the present disclosure is as follows.

[0108] First, an epoxy resin, including a glycidylamine-based epoxy resin and a bisphenol-A type epoxy resin, a curing agent, a dispersing agent, a thinning agent and a PSQ resin were weighed out and a homogeneous mixture was prepared using a planetary mixer or a rotary mixer.

[0109] The silver powder was then weighed, added to the resulting mixture, and stirred with a planetary mixer for about 30 minutes to 3 hours.

[0110] Finally, a catalyst was added and the mixture was stirred using a 3-roll mill with a cooler until it was fully dispersed to produce a chip bonding composition.

[0111] As described above, the chip bonding composition for power semiconductor packages, as disclosed herein, exhibits high thermal conductivity, high adhesion, high heat dissipation, low modulus, and excellent resistance to repeated temperature shocks. Furthermore, the chip bonding composition does not remelt even at high operating temperatures of 300 °C or more, thereby increasing the operating temperature of the power semiconductor package and making it commercially viable.

[0112] Furthermore, the chip bonding composition exhibits high adhesion strength, regardless of the type of metal present at the interface between the power semiconductor chip and the conductor frame or at the interface between the power semiconductor chip and the DBC.

[0113] Because of this effect, the chip bonding composition can be used in high-power, medium to large-dimension power semiconductor packages and pressure-free sintering.

[0114] Analysis of the FT-IR spectrum prior to curing with the chip bonding composition according to the present disclosure revealed characteristic peaks of the -C=O acid anhydride hardener at 1856.34 cm⁻¹. -1 and 1777.82 cm -1 observed.

[0115] -CO Oxirane peaks were measured at 983.74 cm -1 , 912.55 cm - 1 and 897.87 cm -1 , and characteristic -COC oxirane peaks at 808.07 cm -1observed.

[0116] A C=O ester peak associated with the dispersant was observed at 1721.02 cm -1 observed.

[0117] The catalyst-associated -C=NH₄ amine peak was measured at 1634.48 cm⁻¹ -1 observed.

[0118] Furthermore, aromatic rings were detected at 1513.77 cm -1 , 1464.76 cm -1 and 1406 cm -1 observed.

[0119] Specific examples of chip bonding composition for power semiconductor packages are the following. 1. Production of a chip bonding composition for power semiconductor packages

[0120] First, an epoxy resin, including a glycidylamine-based epoxy resin and a bisphenol A-type epoxy resin, a curing agent, a dispersant, a thinning agent, and a PSQ resin were weighed out in the parts by weight specified in Tables 1, 3, and 5, based on 100 parts by weight of the silver powder. Then, a homogeneous mixture was prepared using a planetary or rotary mixer.

[0121] Then, 100 parts by weight of a silver powder were weighed out, added to the resulting mixture, and stirred with a planetary mixer for about 1 hour.

[0122] Finally, a catalyst was added and the mixture was then stirred using a 3-roll mill with a cooler until it was fully dispersed to produce a chip bonding composition. 2. Procedures for testing the physical properties and their results

[0123] 1) Specific resistance: The prepared chip bonding composition was screen-printed in a 3 cm × 3 cm size. The composition was then cured at 170°C for 30 minutes and at 220°C for 60 minutes. The layer resistance was measured with a 4-pole probe using Loresta-GX, the sample thickness was measured, and the specific resistance was calculated.

[0124] 2) Thermal conductivity: The prepared chip bonding composition was poured into a specimen with a diameter of 12.5 mm and a thickness of 2 mm, which was then coated with graphite to obtain a sample for measuring thermal conductivity.

[0125] The thermal diffusivity was measured using an LFA (Laser Flash Analysis) device and calculated according to the equation λ (thermal conductivity) = a (thermal diffusivity) × Cp (specific heat capacity) × ρ (density).

[0126] 3) Chip adhesion strength: The prepared chip bonding composition was applied to a silver-plated copper substrate, and then a 5 mm × 5 mm SiC chip was placed on top. The chip was then subjected to heat treatment at 240°C to prepare a sample for measurement.

[0127] The shear strength was measured at room temperature (25±1°C) using a die shear tester.

[0128] 4) Memory module: The prepared chip bonding composition was cast to create a sample for DMA measurement. The elastic modulus of the DAP bonding material was measured at room temperature and 200°C using a dynamic mechanical analyzer (DMA). A static force of 110 mN and a dynamic force of 100 mN were applied to the sample at a frequency of 1 Hz and measured at a temperature increase rate of 5°C / min.

[0129] 5) Thermal cycle testing: The thermal cycle testing of the package sample with a 4.5 mm × 4 mm SiC chip attached to it was measured under test condition G according to JEDEC.

[0130] The sample was taken after 1,000 cycles and tested for X-ray CT scans, changes in packaging resistance, adhesion strength, etc., to determine whether it had passed or not. [Table 1] Test conditions Minimum temperature (°C) Maximum temperature (°C) G -40 (+10, -10) +125 (+15, -0) [Table 2] component Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 epoxy resin Triglycidyl-ρ-aminophenol (TGPAP) 1.7 1.7 1.7 Tetraglycidyldiaminodiphenylmethane (TGDDM) 2.3 2.0 2.1 2.1 Diglycidyl of aniline Diglycidyl of toluidine Bisphenol-A epoxy 1.9 5.0 0.2 1.9 1.8 1.9 1.9 Urethane-modified epoxy Curing agent Methyltetrahydrophthalic anhydride (MeTHPA) 4.5 6.7 4.5 4.7 4.6 4.9 4.9 Methylhexahydrophthalic anhydride (MeHHBA) Methyl 5-norbornene-2,3-dicarboxylic anhydride (NMA) catalyst 2E4MMZ 0.06 0.06 0.06 0.06 0.05 0.06 0.06 silver powder 100 100 100 100 100 100 100 PSQ resin PMSQ 2.2 4.6 2.2 4.7 1 4.7 5.8 Polybutadiene dispersant 1.2 1.2 PPGDE diluent Polypropylene glycol diglycidyl ether 2.0 0.4 BGE (Butyl Glycidyl Ether) 2.0 2.0 1.2 0.4 3.0 1.6 Characteristic Unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Specific resistance x 10 -6 Ωcm 5.67 6.58 4.68 6.78 4.12 7.22 6.81 Thermal conductivity W / mK 152 154 168 148 178 157 138 Chip adhesion strength MPa(kgf / mm 2 ) 45.1(4.6) 66.7(6.8) 53.0(5.4) 77.5(7.9) 47.1(4.8) 80.4(8.2) 90.2(9.2) Storage module at 25°C GPa 14.5 13.2 15.1 12.7 18.7 12.4 13.8 Storage module at 200°C GPa 4.8 3.6 4.9 3.2 6.8 3.1 3.8 Thermal Cycle Test (JEDECG Class) Passed Passed Passed Passed Passed Passed Passed Passed

[0131] The results of examples 1 to 7 were analyzed. The results show that all chip bonding compositions of examples 1 to 7 have a specific resistance of 1 x 10⁻⁵. -6 up to 10x10 -6 Ωcm, a thermal conductivity of 100 to 200 W / mK, a chip adhesion strength of 39.2 to 98.1 MPa (4.0 to 10.0 kgf / mm²) 2), have a storage module of 1 to 20 GPa at room temperature and a storage module of 1 to 10 GPa at 200°C.

[0132] In particular, all chip bonding assemblies of Examples 1 to 7 have a memory modulus of 12 to 19 GPa at room temperature and a memory modulus of 3 to 7 GPa at 200°C.

[0133] It is shown that with increasing content of reactive diluent based on glycidyl ether and PSQ resin, the storage module decreases at room temperature and at 200 °C.

[0134] Example 6 has a high proportion of PSQ resin and glycidyl ether-based reactive diluent and exhibits the lowest storage modulus.

[0135] As in Fig. As shown in Figure 1, the chip bonding composition from Example 1 was applied to the DBC substrate using a dispenser.

[0136] Changes were observed over time. The results show that stable patterns without tailing or clogging form for up to 16 hours, as in Fig. 2 shown.

[0137] Here, "tailing" refers to a phenomenon where, during the application of the chip-bonding composition with a dispenser, tail-like, defective patterns form on the surface of the droplet due to problems with rheology and surface tension. "Clogging" refers to a phenomenon where a nozzle becomes blocked due to the surface hardening of the chip-bonding composition inside the dispenser nozzle.

[0138] Fig. Figure 3 is a cross-sectional image showing the chip bonding composition of Example 1, which was applied and sintered between a substrate and a SiC chip according to the present disclosure.

[0139] As from Fig.As can be seen in Figure 3, the chip bonding composition of Example 1 was sintered under heat treatment conditions at 220°C. This shows that sintering without the use of a silver complex compound for low-temperature sintering is possible.

[0140] The silver powder used in Example 1 is not spherical, but has a flake or plate shape and has a diameter and thickness that depend on the flake or plate shape.

[0141] The silver powder used in Example 1 has a large diameter (D50) of 4 µm or less and a small thickness of 100 nm or less.

[0142] If the diameter of the silver powder is large, sintering usually does not take place at low temperatures, so sintering does not occur at 250 °C.

[0143] Since the thickness of the silver powder used in Example 1 is 100 nm or less, the silver powder does not melt at a relatively low temperature. However, the silver powder does not melt at 220 °C unless it is combined with an organic material. In other words, even if the thickness of the silver powder is only 100 nm or less, sintering at a low temperature is possible through internal heat of reaction when combined with organic materials.

[0144] The results of examples 2 to 7 show, in addition to the results of example 1, that the sintering at a low temperature occurs due to the heat of the curing reaction of the epoxy resin and the reactive glycidyl ether, as well as the reduction of the distance between the silver powder particles by the silsesquioxane polymer resin.

[0145] Fig.Figure 4 shows the surface image (DST) after the adhesion strength test depending on the type of metal applied to the DBC substrate, as well as the SEM image and the porosity of the sintered composition.

[0146] As from Fig. As can be seen in Figure 4, which shows the SEM image of the adhesive layer according to the chip bonding composition, the chip bonding composition has been sufficiently sintered.

[0147] Furthermore, the adhesion strength was so high when measuring the shear strength of the chips that the adhesion strength was representative of the degree of chip breakage.

[0148] It is shown that with a chip size of 5 mm, the original adhesion strength is maintained even after thermal cycle testing at a pressure of 15 GPa or less at room temperature and at a pressure of 7 GPa or less at 200 °C without cracking or delamination. [Table 3] component Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 Comparative example 7 epoxy resin Triglycidyl-ρ-aminophenol (TGPAP) 1.7 1.7 3.0 6.3 Tetraglycidyldiaminodiphenylmethane (TGDDM) 3.1 3.0 Diglycidyl of aniline Diglycidyl of toluidine Bisphenol-A epoxy 1.9 1.9 3.0 3.1 6.1 3.0 Urethane-modified epoxy Curing agent Methyltetrahydrophthalic anhydride (MeTHPA) 4.5 4.5 6.1 6.3 6.1 6.3 6.3 Methylhexahydrophthalic anhydride (MeHHBA) Methyl 5-norbornene-2,3-dicarboxylic anhydride (NMA) catalyst 2E4MMZ 0.06 0.06 0.06 0.06 0.06 0.06 0.06 silver powder 100 100 100 100 100 100 100 PSQ resin PMSQ 4.2 0.5 1.1 2.3 2.3 Polybutadiene dispersant PPGDE thinner Polypropylene glycol diglycidyl ether BGE (Butyl Glycidyl Ether) 3.0 3.0 0.2 0.1 1.3 [Table 4] Characteristic Unit Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 Comparative example 7 Specific resistance x 10 -6 Ωcm 9.78 12.32 10.51 19.87 9.64 14.21 13.2 Thermal conductivity W / mK 33 28 29 12 22 27 31 Adhesion strength of the chips MPa(kgf / mm 2 ) 37.3(3.8) 24.5(2.5) 28.4(2.9) 63.7(6.5) 41.2(4.2) 47.1(4.8) 54.9(5.6) Storage module at 25°C GPa 22.2 19.2 25.9 16.8 17.2 13.4 15.8 Storage module at 200°C GPa 9.2 8.5 7.8 7.8 6.2 5.8 6.1 Thermal Cycle Test (JEDECG Class) Passed Failed Failed Failed Failed Failed Failed Failed

[0149] In Table 4, Comparison Example 1 has almost the same composition as Example 1, except that the PMSQ content was increased without the addition of BGE diluent. As can be seen from Table 4, Comparison Example 1 exhibits a significantly higher storage modulus and lower thermal conductivity than Example 1. These results indicate that the silver powder was not sufficiently sintered.

[0150] Although not listed in the table, the production of a sample in comparison example 1 was not good.

[0151] Comparison example 2 is a sample that does not contain PSQ resin, and comparison example 3 is a sample that contains neither PSQ resin nor thinner. Comparison example 4 is a sample that has a PSQ resin content outside the range defined above, comparison examples 5 and 7 are samples that contain a single epoxy resin, and comparison example 6 is a sample that has a PSQ resin content outside the range defined above.

[0152] It turns out that when using a single epoxy resin, a PMSQ resin, or a reactive glycidyl ether diluent alone, sufficient sintering is not achieved, resulting in low thermal conductivity and relatively low adhesion. [Table 5] component Comparative example 8 Comparative example 9 Comparative example 10 epoxy resin Triglycidyl-ρ-aminophenol (TGPAP) 6.0 1.7 1.7 Tetraglycidyldiaminodiphenylmethane (TGDDM) Diglycidyl of aniline Diglycidyl of toluidine Bisphenol-A epoxy 2.4 2.0 2.0 Urethane-modified epoxy Curing agent Methyltetrahydrophthalic anhydride (MeTHPA) 8.3 4.7 4.6 Methylhexahydrophthalic acid anhydride (ΜeHHPΑ) Methyl 5-norbornene-2,3-dicarboxylic anhydride (NMA) catalyst 2E4MMZ 0.06 0.06 0.06 silver powder 100 100 100 PSQ resin PMSQ 2.4 7.0 2.3 Polybutadiene dispersant PPGDE diluent Polypropylene glycol diglycidyl ether 4.0 BGE (Butyl Glycidyl Ether) 0.9 [Table 6] Characteristic Unit Comparative example 8 Comparative example 9 Comparative example 10 Specific resistance x 10 -6 Ωcm 24.55 8.52 17.90 Thermal conductivity W / mK 7.8 62 18 Adhesion strength of the chips MPa(kgf / mm 2 ) 11.8 (1.2) 16.7 (1.7) 24.5 (2.5) Storage module at 25°C GPa 13.9 10.6 12.2 Storage module at 200°C GPa 4.1 3.5 4.3 Thermal Cycle Test (JEDECG Class) Passed Failed Failed Failed

[0153] As can be seen from Table 5, comparison example 8 is a sample with a total epoxy resin content outside the range defined above, comparison example 9 is a sample with a PSQ resin content outside the range defined above, and comparison example 10 is a sample with a diluent content outside the range defined above.

[0154] Example 8 contained a high proportion of binder (epoxy resin) compared to the silver powder, leading to the formation of an excessively hardened matrix. Consequently, the binder hinders the constriction of the silver powder and impairs the sintering properties, resulting in low thermal conductivity and adhesion strength.

[0155] Comparison example 9 exhibited a low modulus value but showed poor processability for chip bonding due to its poor dispersibility and high viscosity. Furthermore, comparison example 9 shows poor wettability between the interface between the chip and the compound (bond layer) and the interface between the substrate and the compound (bond layer), leading to reduced adhesion strength and reliability failure.

[0156] Example 10 has a relatively low modulus value, but requires high-temperature heat treatment due to the delayed curing rate and the lower heat generation of the curing reaction. It can be seen that the adhesion was insufficient and the thermal conductivity was low under low-temperature conditions.

[0157] All chip bonding compositions in comparison examples 1 to 10 exhibit high modulus or significantly low thermal conductivity and adhesion. This leads to cracking and delamination during the thermal cycle (TC) testing of the power semiconductor package, resulting in poor reliability.

Claims

[1] Chip bonding composition, comprising: a silver powder; an epoxy resin; a hardening agent; a catalyst; a glycidyl ether-based diluent; and a polysilsesquioxane (PSQ) resin. [2] Chip bonding composition according to claim 1, wherein the epoxy resin comprises a glycidylamine-based epoxy resin and a bisphenol A epoxy resin. [3] Chip bonding composition according to claim 1, wherein the chip bonding composition comprises 1 to 7 parts by weight of the epoxy resin, 0.01 to 5 parts by weight of the catalyst, 0.2 to 3 parts by weight of the glycidyl ether-based diluent and 1 to 6 parts by weight of the polysilsesquioxane (PSQ) resin, based on 100 parts by weight of the silver powder, and the mixing ratio of the epoxy resin to the curing agent is a weight ratio of 1:1 to 1:

2. [4] Chip bonding composition according to claim 1, wherein the curing agent comprises an acid anhydride-based curing agent. [5] Chip bonding composition according to claim 1, wherein the catalyst comprises an imidazole-based catalyst. [6] Chip bonding composition according to claim 1, wherein the glycidyl ether-based diluent comprises at least one of the following components: lauryl alcohol glycidyl ether (LGE), butyl glycidyl ether (BGE), 2-ethylhexyl glycidyl ether, allyl glycidyl ether (AGE), polypropylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether or 1,6-hexanediol diglycidyl ether. [7] Chip bonding composition according to claim 1, wherein the polysilsesquioxane resin comprises at least one of polypropylene silsesquioxane, polyphenyl silsesquioxane or polymethylene silsesquioxane. [8] Chip bonding composition according to claim 1, further comprising at least one of the following dispersing agents: a butadiene-based dispersing agent, a phosphoric acid-based dispersing agent or an ester-based dispersing agent. [9] Chip bonding composition according to claim 1, wherein the chip bonding composition has a chip bonding strength of 39.2 to 98.1 MPa (4.0 to 10.0 kgf / mm²). 2 ) exhibits, wherein the chip bonding strength is measured at room temperature using a shear tester after the chip bonding composition has been applied to a substrate, a 5 mm × 5 mm chip has been placed on the substrate and the chip has been heat-treated at 240°C. [10] Chip bonding composition according to claim 1, wherein the chip bonding composition has a memory module of 3 to 7 GPa, wherein the memory module is measured at 200°C and a frequency of 1 Hz using a dynamic mechanical analyzer (DMA).

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