Method for manufacturing bonded body, and bonded body

Abstract

In this method for manufacturing a bonded body, a bonded body comprising a first member, a second member, and a bonding part that includes a sintered body of a metal paste containing metal particles and that joins the first member and the second member is manufactured. The surface shape on the joining side of the second member is a quadrilateral having two pairs of parallel sides X and Y with all corners being right angles. The first member has a main surface that is wider than the quadrilateral. The method comprises: a step A for providing a metal paste coating in a predetermined pattern in a region corresponding to the quadrilateral on the main surface of the first member; a step B for placing the second member on the first member having the coating so as to align with the region to obtain a laminate; and a step C for forming the bonding part by sintering the coating of the laminate. In the step A, the pattern is a honeycomb arrangement of hexagons having three pairs of parallel sides a, b, and c at a predetermined interval, and the coating is provided in the region so as to satisfy the following conditions (i) and (ii). Condition (i): The side X and the side a of a hexagon are parallel to each other. Condition (ii): The side X does not overlap a gap between adjacent hexagons in a direction orthogonal to the side X.

Description

Method for manufacturing a bonded body and a bonded body

[0001] The present invention relates to a method for manufacturing a bonded body and the bonded body.

[0002] When manufacturing semiconductor devices, various bonding materials are used to form a bonding layer that bonds a semiconductor element to a lead frame or other supporting member. Recently, a method of forming a bonding layer using a metal sintered body formed by sintering metal particles has been utilized. In this method, a metal paste containing metal particles and organic substances such as a reducing agent and a dispersant is used, and bonding is achieved by heating the metal particles to decompose the organic substances and sinter them together.

[0003] Furthermore, Patent Document 1 below proposes a method of providing a film-forming region where a film of the metal paste is formed and a film-free region that continues to the edge of the joining region when applying the metal paste to the joining region. When the joining area is large, it becomes difficult for gas generated during sintering of the metal paste to escape, but with the above method, the film-free region allows the gas to efficiently escape outside the joining region, thereby suppressing the occurrence of voids and peeling due to the gas generated during sintering.

[0004] Japanese Patent Application Laid-Open No. 2021-127505

[0005] When applying a metal paste to a support member, patterning the coating film formation areas into hexagons and arranging them in a honeycomb pattern at predetermined intervals can increase the total area of ​​the coating film formation areas while ensuring a degassing path, making it easier to obtain bonding strength. On the other hand, when applying a metal paste to a support member, it is desirable to provide a coating film only in the area corresponding to the bonding surface of the semiconductor element from the perspective of reducing loss of bonding material. However, if the above patterning is not sufficiently controlled, there may be a large area where the metal paste does not contact the edge of the semiconductor element. In this case, the bonding strength between the semiconductor element and the support member may decrease, and chip cracks may occur when excessive stress is applied to the semiconductor element, potentially compromising the reliability of the semiconductor element. In addition to the semiconductor element and support member described above, bonding using metal pastes has also been considered for various other components, such as bonding an insulating heat dissipation circuit board such as a DCB (Direct Copper Bonding) board to a power semiconductor element such as a power MOSFET or a cooler such as a cooling plate. Even in such cases, the above-mentioned problems may arise. In an assembly of an insulating heat dissipation circuit board and a cooler, each component repeatedly expands and contracts due to, for example, heat generation and cooling cycles caused by repeated on-off switching during device operation, and thermal cycles caused by rising and falling environmental temperatures. In this case, if there is a large area at the edge of the insulating heat dissipation circuit board where the metal paste does not come into contact, peeling and cracking are likely to occur starting from that area, leading to reduced reliability.

[0006] Therefore, an object of the present invention is to provide a method for manufacturing a bonded body using a metal paste, which can sufficiently suppress the occurrence of voids and peeling even in components with a large bonding area, and which can achieve both reduced loss of bonding material and bonding strength and reliability of the components.

[0007] In some aspects, the present invention provides the following [1] to [5].

[0008] [1] A method for producing a joined body comprising a first member, a second member, and a joint portion that joins the first member and the second member and includes a sintered body of a metal paste containing metal particles, wherein the surface shape of the joining side of the second member is a rectangle having two sets of parallel sides X and Y and all right angles, and the first member has a main surface that is wider than the rectangle, the method comprising: step A of providing a coating film of the metal paste in a predetermined pattern on the main surface of the first member in an area corresponding to the rectangle; step B of arranging the second member on the first member on which the coating film is provided, so as to match the area, to obtain a laminate; and step C of forming the joint portion by sintering the coating film of the laminate, wherein in step A, the pattern is a hexagon having three sets of parallel sides a, b, and c arranged in a honeycomb shape at predetermined intervals, and the coating film is provided in the area so as to satisfy the following conditions A and B. Condition A: Side X and side a of the hexagon are parallel. Condition B: Side X does not overlap a gap between adjacent hexagons in a direction perpendicular to side X. [2] The method for producing a bonded body according to [1], wherein the pattern is such that the hexagons are arranged so that their centers are aligned on the same line perpendicular to side a, and the sides a of the hexagons in alternate rows overlap on the same line. [3] The method for producing a bonded body according to [2], wherein in step A, the coating film is provided in the region so as to further satisfy the following condition C: Condition C: Side Y intersects with side a of the hexagon [4] A joined body comprising a first member, a second member, and a joint including a metal sintered body that joins the first member and the second member, wherein the surface shape of the joined side of the second member is a rectangle having two sets of parallel sides X and Y and all right angles, the first member has a main surface wider than the rectangle, the joint is provided in an area on the main surface of the first member corresponding to the rectangle, the joint includes hexagonal metal sintered bodies having three sets of parallel sides a, b, and c arranged at predetermined intervals in a honeycomb pattern, the side X and the side a of the hexagonal metal sintered bodies are parallel, and the length of the side X that is not in continuous contact with the metal sintered body does not exceed the length of the side a. [5] The joined body according to [4], wherein the second member is a semiconductor element.

[0009] According to the present invention, in manufacturing a bonded body using a metal paste, it is possible to provide a manufacturing method for a bonded body and a bonded body that can sufficiently suppress the occurrence of voids and peeling even in components with a large bonding area, and that can achieve both reduced loss of bonding material and bonding strength and reliability of the components.

[0010] Fig. 1 is a diagram showing an example of a bonded body manufactured by the method for manufacturing a bonded body of the present embodiment; Fig. 2 is a diagram showing an example of a pattern of a metal paste coating; Fig. 3 is a diagram for explaining the relationship between the pattern of a metal paste coating and an area where the metal paste coating is provided; Fig. 4 is a schematic cross-sectional view showing an example of a metal paste coating; Fig. 5 is a diagram for explaining the relationship between the pattern of a metal paste coating and an area where the metal paste coating is provided;

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes in detail an embodiment of the present invention (hereinafter referred to as the "present embodiment"). The present invention is not limited to the following embodiment.

[0012] <Method for manufacturing a bonded body> The method for manufacturing a bonded body of the present embodiment is a method for manufacturing a bonded body including a first member, a second member, and a bonding portion that bonds the first member and the second member and includes a sintered body of a metal paste containing metal particles.

[0013] Fig. 1 is a diagram showing an example of a bonded body manufactured by the bonded body manufacturing method of the present embodiment. The bonded body 100 shown in Fig. 1 includes a first member 1, a second member 2, and a bonding portion 3 that bonds the first member 1 and the second member 2. Fig. 1(a) is a diagram showing the bonded body 100 as viewed from above on the second member 2 side, and Fig. 1(b) is a cross-sectional view taken along line II of Fig. 1(a).

[0014] The second member may have a surface shape on the joining side that is a rectangle having two pairs of parallel sides X and Y and all corners being right angles. The corners of the rectangle may have a predetermined radius.

[0015] The quadrangle may be a square or a rectangle.

[0016] Examples of the second member include semiconductor elements, power supply members such as metal ribbons, metal blocks, and terminals, and insulating heat dissipation circuit substrates such as metal plate-attached ceramic substrates (e.g., DCB substrates). Examples of the semiconductor element include power modules including diodes, rectifiers, thyristors, MOS gate drivers, power switches, power MOSFETs, IGBTs, Schottky diodes, and fast recovery diodes, as well as transmitters, amplifiers, LED modules, temperature sensors, and current sensors.

[0017] The area of ​​the joining surface of the second member is 400 mm ２ Over 1600mm ２ or more, or 3600 mm ２ It may be more than that.

[0018] The first member may have a main surface that is larger than the quadrangle that is the joining surface of the second member.

[0019] Examples of the first member include lead frames, metal plate-attached ceramic substrates (for example, DCB substrates), substrates for mounting semiconductor elements such as LED packages, and coolers such as heat sinks, water-cooled plates, and cooling plates.

[0020] Examples of metal particles contained in the metal paste include copper particles, silver particles, gold particles, platinum group particles (platinum, palladium, rhodium, iridium), magnetic particles (iron, cobalt, nickel), light metal particles (aluminum, beryllium, magnesium, titanium, alkali metals, alkaline earth metals), low-melting point particles (tin, indium, lead, germanium), other common transition metal particles, and semi-metal particles, as well as alloy particles that combine two or more of these.

[0021] The shape of the metal particles may be, for example, spherical, blocky, needle-like, flat (flake-like), or approximately spherical.

[0022] The average particle size of the metal particles may be from 10 nm to 50 μm, from 50 nm to 40 μm, or from 100 nm to 30 μm.

[0023] The content of the metal particles in the metal paste may be 70 to 95 mass %, or may be 75 to 90 mass %, based on the total mass of the metal paste.

[0024] The metal paste may contain an organic solvent as a dispersant for the metal particles.

[0025] Examples of organic solvents include monohydric and polyhydric alcohols such as pentanol, hexanol, heptanol, octanol, decanol, dihydroterpineol, terpineol, isobornylcyclohexanol (MTPH), 1,5-pentanediol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, tetraethylene glycol, α-terpineol (α-terpineol), dihydroterpineol (dihydroterpineol), and geraniol; ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, diethylene glycol hexyl ether, triethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, diethylene glycol isopropyl methyl ether, and triethylene glycol di ethers such as methyl ether, triethylene glycol butyl methyl ether, propylene glycol propyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, and tripropylene glycol dimethyl ether; esters such as ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), ethyl lactate, butyl lactate, γ-butyrolactone, and propylene carbonate; acid amides such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide; aliphatic hydrocarbons such as cyclohexanone, octane, nonane, decane, and undecane; aromatic hydrocarbons such as benzene, toluene, xylene, and 1-methylnaphthalene; mercaptans having an alkyl group having 1 to 18 carbon atoms;Examples of mercaptans having a cycloalkyl group having 5 to 7 carbon atoms include mercaptans having an alkyl group having 1 to 18 carbon atoms include ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, i-butyl mercaptan, t-butyl mercaptan, pentyl mercaptan, hexyl mercaptan, and dodecyl mercaptan. Examples of mercaptans having a cycloalkyl group having 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan.

[0026] The metal paste may contain, as additives, wetting improvers such as nonionic surfactants and fluorine-based surfactants; surface tension adjusters; dispersants such as alkylamines and alkylcarboxylic acids; antifoaming agents such as silicone oils; and ion trapping agents such as inorganic ion exchangers.

[0027] The Casson viscosity of the metal paste at 25°C may be 10 Pa·s or more, or 20 Pa·s or more, and may be 40 Pa·s or less, or 30 Pa·s or less.

[0028] The method for manufacturing a bonded body of this embodiment includes the following steps A, B, and C. Step A: On the main surface of the first member, a coating film of metal paste is provided in a predetermined pattern in an area (hereinafter, sometimes referred to as a "bonding area") corresponding to the above-mentioned rectangle (i.e., the surface shape of the side to be bonded of the second member). Step B: A laminate is obtained by arranging a second member on the first member on which the coating film is provided, in accordance with the above-mentioned area. Step C: A bonded portion is formed by sintering the coating film of the laminate.

[0029] (Step A) In step A, a coating of metal paste can be provided in the joining region in a honeycomb pattern of hexagons each having three sets of parallel sides a, b, and c arranged at predetermined intervals, so as to satisfy the following conditions A and B. Condition A: Side X and side a of the hexagon are parallel. Condition B: Side X does not overlap with the gap between adjacent hexagons in the direction perpendicular to side X.

[0030] In this specification, unless otherwise specified, the shape and arrangement of the metal paste coating or metal sintered body refer to the shape and arrangement when viewed from a direction perpendicular to the main surface of the first member.

[0031] In step A, the section of side X where the metal paste coating is not continuous (the section without coating) can be set so as not to exceed the length of side a. In other words, the section without coating on side X can be set to be equal to or shorter than the length of side a. By positioning the side of the second member where reliability needs to be ensured as side X, the area where the metal paste does not come into contact with the end of the member can be reduced. This makes it possible to prevent defects such as cracks from occurring when excessive stress is applied to the second member.

[0032] 2 is a diagram showing an example of a pattern of a metal paste coating. The pattern shown in FIG. 2 is a pattern in which a hexagonal coating formation region 10 having three pairs of parallel sides a, b, and c is spaced apart at a predetermined interval D １ are arranged in a honeycomb pattern.

[0033] The lengths of sides a, b, and c of the hexagon may all be the same (a = b = c), or any one of them may be different, or they may all be different. From the viewpoint of increasing the total area of ​​the coating film-forming region while ensuring a degassing path, when the length of side a is 1, the lengths of sides b and c may each be 0.2 to 5, or even 1.

[0034] From the viewpoint of increasing the total area of ​​the coating film formation region while ensuring a degassing path, the predetermined distance D1 may be 0.1 to 50, 1 to 30, or 2 to 10, when the length of side a is 100.

[0035] As shown in FIG. 2, the pattern is such that the hexagons are aligned along a line L perpendicular to the side a. １ The sides a of the hexagons in the alternate rows are aligned on the same straight line L ２ In this case, as shown in Fig. 3, the side X is set so as not to overlap with the gap 22 that is closest to the side X among the gaps of the hexagons adjacent in the direction perpendicular to the side X.

[0036] In step A, as shown in FIG. 3, a coating of metal paste may be provided in the bonding region 30 so as to further satisfy the following condition C: Side Y intersects with side a of the hexagon.

[0037] In this case, the area where the metal paste does not come into contact with the end of the second member can be further reduced, and the area of ​​the metal sintered body to which the end of the second member on the side Y is joined can be increased.

[0038] In step A, examples of a method for applying the metal paste include inkjet printing, super inkjet printing, screen printing, transfer printing, offset printing, jet printing, a dispenser, a jet dispenser, a needle dispenser, a comma coater, a slit coater, a die coater, a gravure coater, a slit coat, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, a bar coater, an applicator, a particle deposition method, a spray coater, a spin coater, a dip coater, and electrodeposition coating.

[0039] The thickness of the metal paste coating film may be 1 μm or more, 5 μm or more, 10 μm or more, or 20 μm or more from the viewpoint of ensuring good bonding properties and connection reliability, and may be 3000 μm or less, 1000 μm or less, 500 μm or less, 300 μm or less, 250 μm or less, 200 μm or less, or 150 μm or less from the viewpoint of suppressing cracking in the coating film and its dried film.

[0040] The coating film of the metal paste may be dried appropriately from the viewpoint of suppressing flow and the generation of voids during sintering. The gas atmosphere during drying may be air, an oxygen-free atmosphere such as nitrogen or a rare gas, or a reducing atmosphere such as hydrogen or formic acid. The drying method may be drying by leaving it at room temperature, drying by heating, or drying under reduced pressure.

[0041] For heat drying or reduced pressure drying, for example, a hot plate, a warm air dryer, a warm air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, a steam heating furnace, a hot plate press, etc. can be used. The drying temperature and time may be appropriately adjusted depending on the type and amount of the dispersion medium used. The drying temperature and time are preferably 50°C or higher and 150°C or lower in the air or an oxygen-free atmosphere.

[0042] By step A, as shown in FIG. 4, a coating film-formed region 10 made of a coating film of metal paste and a non-coating film-formed region 20 are provided in the bonding region 30 on the main surface of the first member 1.

[0043] In this embodiment, from the viewpoint of increasing the area of ​​the metal sintered body to which the end of the second member is joined, in step A, a coating of metal paste may be provided in the joining region 30 so as to further satisfy the following condition 2. Condition 2: For a hexagon through which side X passes in the pattern shown in Fig. 2, among the lines connecting the sides a of the hexagons in the alternate row that are closer to side X, the line connecting the sides a of the hexagons having a larger area within region 30 is designated as line La, and the other line is designated as line Lb (see Fig. 5), and the ratio [Da / Db] of the distance Da between side X and line La and the distance Db between side X and line Lb is 1 or less.

[0044] Furthermore, if the above condition (iii) is not satisfied, the total length of the side Y that overlaps with the hexagon may be set to be greater than the total length that does not overlap with the hexagon.

[0045] (Step B) In step B, a second member is placed on the first member provided with the coating film so as to align the bonding area, thereby obtaining a laminate.

[0046] The second member may be arranged using, for example, a chip mounter, a flip chip bonder, or a positioning jig made of carbon or ceramics.

[0047] (Step C) In step C, the laminate is heat-treated to sinter the coating film of the metal paste.

[0048] The heat treatment can be performed using a heating device having a pressure bonding mechanism, such as a hot plate, a warm air dryer, a warm air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, or a steam heating furnace.

[0049] The gas atmosphere during sintering may be an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the sintered body and the members to be joined. The gas atmosphere during sintering may be a reducing atmosphere from the viewpoint of removing surface oxides on the metal particles of the metal paste. Examples of the oxygen-free atmosphere include the introduction of an oxygen-free gas such as nitrogen or a rare gas, or a vacuum. Examples of the reducing atmosphere include pure hydrogen gas, a mixed gas of hydrogen and nitrogen such as forming gas, nitrogen containing formic acid gas, a mixed gas of hydrogen and a rare gas, and a rare gas containing formic acid gas.

[0050] From the viewpoint of reducing thermal damage to the members to be joined and improving yield, the maximum temperature reached during the heat treatment may be 200°C or higher and 450°C or lower, 250°C or higher and 400°C or lower, 250°C or higher and 350°C or lower, or 250°C or higher and 300°C or lower.

[0051] The holding time for the maximum temperature may be 1 minute or more and 60 minutes or less, or 1 minute or more and less than 40 minutes, or 1 minute or more and less than 30 minutes, from the viewpoint of volatilizing all of the dispersion medium and improving the yield. In particular, when the maximum temperature is 250°C or more, sintering tends to proceed sufficiently with a holding time of 60 minutes or less.

[0052] <Jointed Body> The joined body of the present embodiment includes a first member, a second member, and a joining portion that joins the first member and the second member and includes a metal sintered body.

[0053] In the joined body of this embodiment, the surface shape of the joined side of the second member is a rectangle having two sets of parallel sides X and Y and all right angles, and the first member has a main surface wider than this rectangle. The joint is provided in a region on the main surface of the first member corresponding to the rectangle, and includes a hexagonal metal sintered body having three sets of parallel sides a, b, and c arranged in a honeycomb pattern at predetermined intervals. Furthermore, in the joined body, side X of the second member and side a of the hexagonal metal sintered body are parallel, and the length of side X that is not continuously in contact with the metal sintered body does not exceed the length of side a.

[0054] The bonded body of this embodiment can be obtained by the above-described method for manufacturing a bonded body of this embodiment.

[0055] In the bonded structure of this embodiment, the second member may be a semiconductor element. Examples of the semiconductor element include those described above. In such a case, the bonded structure becomes a semiconductor device. The resulting semiconductor device can have sufficient die shear strength and connection reliability.

[0056] Examples of semiconductor devices include power modules including diodes, rectifiers, thyristors, MOS gate drivers, power switches, power MOSFETs, IGBTs, Schottky diodes, and fast recovery diodes, as well as transmitters, amplifiers, high-brightness LED modules, semiconductor laser modules, logic, and sensors.

[0057] 1...first member, 2...second member, 3...joint, 10...coated region, 20...non-coated region, 100...joint

Claims

1. A method for producing a joined body comprising a first member, a second member, and a joint comprising a sintered body of a metal paste containing metal particles that joins the first member and the second member, wherein the surface shape of the joining side of the second member is a rectangle having two sets of parallel sides X and Y and all right angles, and the first member has a main surface that is wider than the rectangle, the method comprising: step A of applying a coating of the metal paste in a predetermined pattern on the main surface of the first member in an area corresponding to the rectangle; step B of arranging the second member on the first member with the coating provided in accordance with the area to obtain a laminate; and step C of sintering the coating of the laminate to form the joint, wherein in step A, the pattern is a honeycomb arrangement of hexagons having three sets of parallel sides a, b, and c at predetermined intervals, and the coating is applied to the area so as to satisfy the following conditions A and B. Condition A: Side X and side a of the hexagon are parallel. Condition B: Side X does not overlap the gap between adjacent hexagons in the direction perpendicular to side X.

2. The method for manufacturing a bonded body according to claim 1, wherein the pattern is such that the centers of the hexagons are aligned on the same straight line perpendicular to side a, and the sides a of the hexagons in alternate rows overlap on the same straight line.

3. The method for producing a bonded body according to claim 2, wherein in step A, the coating film is provided on the region so as to further satisfy the following condition C: Side Y intersects with side a of the hexagon.

4. A joined body comprising a first member, a second member, and a joint including a metal sintered body that joins the first member and the second member, wherein the surface shape of the joined side of the second member is a rectangle having two sets of parallel sides X and Y and all corners are right angles, the first member has a main surface that is wider than the rectangle, the joint is provided in an area on the main surface of the first member that corresponds to the rectangle, the joint includes a hexagonal metal sintered body having three sets of parallel sides a, b, and c arranged in a honeycomb pattern at predetermined intervals, the side X and the side a of the hexagonal metal sintered body are parallel, and the length of the side X that is not in continuous contact with the metal sintered body does not exceed the length of the side a.

5. The assembly according to claim 4, wherein the second member is a semiconductor element.

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