Solder material, layer structure, and method of forming layer structure

Abstract

A solder material is provided. The solder material may include metallic solder particles, a carboxylic acid, and an alcohol selected from the group consisting of methanol, ethanol, propan-1-ol, propan-2-ol, 2-methyl-1-propanol, butyl-1-ol, pent-1-ol, 1, 2-propanediol, 1, 3-propanediol, and glycerol.

Description

Technical Field

[0001] Various embodiments generally relate to solder materials, layer structures, methods of forming solder materials, and methods of forming layer structures. Background Art

[0002] Until now, solder pastes have contained a complex mixture of chemicals (commonly referred to as a "flux system") which provides a liquid component to make the metal particle mixture unnecessary and in addition contains several other components for various other purposes, such as thickeners, activators and surfactants. Summary of the invention

[0003] A solder material is provided. The solder material may include metal solder particles, carboxylic acid and an alcohol selected from the group consisting of methanol, ethanol, propan-1-ol, propan-2-ol, 2-methyl-1-propanol, butan-1-ol, pentan-1-ol, 1,2-propylene glycol, 1,3-propylene glycol and glycerol. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] In the accompanying drawings, the same reference numerals generally refer to the same parts in different views. The drawings are not necessarily drawn to scale, but emphasis is generally placed on illustrating the principles of the invention. In the following description, various embodiments of the invention are described with reference to the following drawings, in which:

[0005] Figure 1 shows a schematic diagram of solder material according to various embodiments and visualizes the reaction of the solder material to the soldering process;

[0006] Figure 2 shows a schematic diagram of solder material according to various embodiments and visualizes the reaction of the solder material to the soldering process;

[0007] Figure 3A shows a schematic diagram of a method of forming a layer structure according to various embodiments, Figure 3B Shown by application Figure 3A Schematic representation of the method shown or of the layer structure obtained by using the solder material according to various embodiments for forming the layer structure;

[0008] Figure 4 A flow chart showing a method of forming a layer structure according to various embodiments; and

[0009] Figure 5 A flow chart of a method of forming a layer structure according to various embodiments is shown. DETAILED DESCRIPTION

[0010] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced.

[0011] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

[0012] Various aspects of the present disclosure are provided for devices, and various aspects of the present disclosure are provided for methods. It should be understood that the basic properties of the device also apply to the method, and vice versa. Therefore, for the sake of brevity, repeated descriptions of these properties may have been omitted.

[0013] The basic method of various embodiments may be to use only metal particles as the solder material, and activate the surface of the metal particles with a reducing agent (eg, immediately before the low-melting-point component is melted).

[0014] This method can be achieved by providing only metal solder particles (or, alternatively, by mixing the metal solder particles with a volatile, non-reactive liquid to make the powder mixture easier to handle), applying the metal solder particles (or respectively applying the mixture) and soldering them using a reducing (e.g., formic acid) atmosphere.

[0015] To avoid the need for a furnace capable of providing a reducing (e.g., formic acid) atmosphere, another approach was pursued instead:

[0016] In various embodiments, a solder material is provided that may consist solely of a metal powder (e.g., a mixture of Ni particles and Sn particles) and a reducing binder (e.g., a combination of an alcohol and an acid for bonding and activating a preform solder, or even a single component such as an alcohol, ester, or aldehyde) to produce a solder paste having a reducing agent (e.g., an organic acid) inherently generated (e.g., when heated during the soldering process) to reduce oxides on the materials involved without the use of hazardous materials.

[0017] In various embodiments, the solder material may consist of only metal particles (or may consist essentially of metal particles), and a reducing agent may be provided via the atmosphere during the soldering process, or the solder material may be a mixture of metal powder (solder powder, e.g., metal solder particles) and a chemical or chemical mixture that may be used to generate a reducing agent (e.g., an organic acid, such as formic acid) during the process. The liquid material included in the solder material according to various embodiments may hold the solder material in place (a "bonding" function) in its initial state and during the soldering process, and may additionally reduce oxides on the outer surfaces of the metal particles and / or the metal surfaces to be joined before it evaporates, and may therefore also be referred to as a "reducing binder".

[0018] In various more specific embodiments, a bimodal size distribution of high melting point metal solder particles can be provided in combination with at least one type of low melting point metal solder particles and a mixture consisting of an alcohol selected from a specific group of alcohols (described below) and a carboxylic acid.

[0019] In various more specific embodiments, the solder material may include or consist of a powder mixture consisting of a bimodal Ni particle size distribution in combination with a Sn-based solder alloy and oxalic acid and glycerol.

[0020] At least during the soldering process, the reducing agent is capable of activating the passivated metal surfaces (e.g., metal surfaces to be joined and / or surfaces of metal solder particles included in the solder material). This generally means that the reducing agent is capable of reducing (and thereby possibly removing) oxide layers from the surfaces to be joined by solder (joining surfaces) and / or from the solder particles to allow a good connection.

[0021] In various embodiments, a solder material (e.g., solder paste) is provided that includes metal solder particles (sometimes simply referred to as metal particles or particles) and a reducing agent that is capable of chemically reacting with metal oxides during a soldering process, such as being capable of reducing metal oxides that may have formed on the metal solder particles.

[0022] The activation / reduction that occurs during the welding process may be due to the temperatures reached during the welding process.The maximum temperature during welding may be in the range of about 250°C to about 400°C.

[0023] In various embodiments, the solder material may be lead-free. The solder particles and the liquid in which the solder particles are dispersed may be lead-free.

[0024] The liquid that may consist of a certain type of alcohol or include or consist of a certain type of alcohol in combination with a carboxylic acid may be configured to evaporate completely or substantially completely during the soldering process. In other words, the solder material according to various embodiments is configured to form a solder layer without residue or a solder layer without residue substantially.

[0025] Figure 1 A schematic diagram of a solder material 100 according to various embodiments is shown and the reaction of the solder material to a soldering process is visualized.

[0026] The solder material 100 may include metallic solder particles 106 , also referred to simply as “solder particles”.

[0027] In various embodiments, all solder particles 106 may have approximately the same size. In various embodiments, the solder particles 106 may have different sizes, such as a bimodal size distribution, or the solder particles may have three, four, or more size groups. The size of the solder particles 106 may generally be in the range of about 1 μm to about 80 μm. In the case of a bimodal size distribution, the first amount of particles may have a size in the range of about 1 μm to about 20 μm, and the second amount of particles may have a size in the range of about 30 μm to about 50 μm.

[0028] In various embodiments, the solder particles 106 may all include or consist of the same material. In various embodiments, the solder particles may include or consist of one material or a plurality of different materials. The material may be different depending on the size of the solder particles 106, and / or the material may be independent of the solder particle size. For example, the first group of solder particles 106 may include or consist of a first material, and the second group of solder particles 106 may include or consist of a second material. In various embodiments, the first group of solder particles 106 may have a first particle size, and the second group of solder particles 106 may have a second particle size. The first particle size and the second particle size may be the same or different (bimodal size distribution). In other embodiments, the first group of solder particles 106 may have two or more sizes, and / or the second group of solder particles 106 may have two or more sizes. The sizes of the first group of solder particles 106 and the second group of solder particles 106 may be the same and / or different. In a bimodal size distribution, the first amount of particles may optionally have a size in the range of about 1 μm to about 20 μm, while the second amount of particles may optionally have a size in the range of about 30 μm to about 50 μm. It should be noted that a "particle size" is actually a size distribution or size range, depending on the formation and / or selection process of the solder particles 106 that are assumed to have a specific predefined size.

[0029] The metal solder particles include low melting point metal solder particles 106 having a first melting temperature and high melting point metal solder particles 106 having a second melting temperature, wherein the first melting temperature is lower than the second melting temperature.

[0030] The low melting point metal solder particles 106 may optionally include or consist of at least one metal selected from the group consisting of Bi, Sn, Ga, Ge, Zn, and In (also referred to herein as low melting point materials). The metal solder particles 106 may, for example, include tin.

[0031] The high melting point metal solder particles 106 may include or consist of at least one metal selected from the group consisting of Ni, Cu, Ag, Au, Pt, and Pd (also referred to herein as high melting point materials).

[0032] As used herein, the terms “low melting point” and “high melting point” may be understood as relative terms relative to each other. In other words, the low melting point solder particles 106 may have a lower melting point than the high melting point particles 106 .

[0033] The metal solder particles 106 may, for example, include at least 30 wt % nickel based on the total weight of the metal solder particles or any other high melting point materials specified above.The low melting point metal solder particles 106 may, for example, include or consist of tin.

[0034] In various embodiments, the solder material may be configured for soldering temperatures between about 200°C and about 450°C.

[0035] The solder material 100 may include a carboxylic acid 102. Preferably, the carboxylic acid is a dicarboxylic acid.

[0036] The solder material 100 may further include an alcohol 104 selected from the group consisting of methanol, ethanol, propan-1-ol, propan-2-ol, ethylene glycol (ethane-1,2-diol), ethanolamine (2-aminoethanol), 2-methyl-1-propanol, butan-1-ol, pentan-1-ol, 1,2-propylene glycol, 1,3-propylene glycol, and glycerol.

[0037] When heated as part of the welding process, the carboxylic acid 102 may react with the alcohol 104 to form the reducing agent 114 .

[0038] In other words, when the solder material 100 is heated to a maximum temperature between about 200° C. and about 450° C., the carboxylic acid 102 may react with the alcohol 104 to form the reducing agent 114, which may not have been previously present in the solder material 100. The reaction may occur (e.g., well) before reaching a maximum soldering temperature (e.g., as described above), in particular before reaching a vaporization temperature of the carboxylic acid 102 or a vaporization temperature of the alcohol 104 that is lower than the maximum soldering temperature.

[0039] The carboxylic acid 102 may have the formula C n H 2n-2 O x , wherein n can be 2 to 10, and x can be 4 to 7.

[0040] The carboxylic acid 102 may be selected from linear or branched, substituted or unsubstituted C 2-10 Dicarboxylic acids or tricarboxylic acids, for example selected from linear or branched, substituted or unsubstituted C 2-6 Dicarboxylic acids or tricarboxylic acids, for example selected from linear or branched, substituted or unsubstituted C 2-6 A dicarboxylic acid or a tricarboxylic acid.

[0041] The carboxylic acid 102 may be selected from linear substituted or unsubstituted C2-10 Dicarboxylic acids or tricarboxylic acids, for example selected from linear substituted or unsubstituted C 2-6 Dicarboxylic acids or tricarboxylic acids, for example selected from linear substituted or unsubstituted C 2-6 A dicarboxylic acid or a tricarboxylic acid.

[0042] The carboxylic acid may be selected from linear, unsubstituted C 2-10 Dicarboxylic acids or tricarboxylic acids, preferably selected from linear, unsubstituted C 2-6 Dicarboxylic acids or tricarboxylic acids, most preferably selected from linear, substituted C 2-6 A dicarboxylic acid or a tricarboxylic acid.

[0043] The carboxylic acid may be selected from linear, unsubstituted C 2-10 dicarboxylic acids, preferably selected from linear, unsubstituted C 2-6 dicarboxylic acids, most preferably selected from linear, substituted C 2-6 Dicarboxylic acid.

[0044] The carboxylic acid 102 can be, for example, selected from the group consisting of caproic acid (hexanoic acid), enanthic acid (heptanoic acid), caprylic acid (octanoic acid), pelargonic acid (nonanoic acid), capric acid (decanoic acid), phenylacetic acid, benzoic acid, salicylic acid, aminobenzoic acid, 4-n-butylbenzoic acid, 4-tert-butylbenzoic acid, 3,4-dimethoxybenzoic acid, oxalic acid, succinic acid, glutaric acid, succinic acid, maleic acid, fumaric acid, malic acid, adipic acid, citric acid, ascorbic acid and malonic acid.

[0045] Alternatively, the carboxylic acid 102 may be, for example, selected from the group consisting of oxalic acid, succinic acid, glutaric acid, succinic acid, maleic acid, fumaric acid, malic acid, adipic acid, citric acid, ascorbic acid, and malonic acid.

[0046] Optionally, the carboxylic acid 102 may form 0.5 wt % to 1.0 wt % of the solder material 100 .

[0047] In various embodiments, alcohol 104 may be specifically selected from the group consisting of ethylene glycol (ethane-1,2-diol), ethanolamine (2-aminoethanol), 2-methyl-1-propanol, butan-1-ol, pentan-1-ol, 1,2-propylene glycol, 1,3-propylene glycol and glycerol.

[0048] The weight mixing ratio of alcohol:acid may be in the range of 5:1 to 100:1.

[0049] The carboxylic acid 102 and the alcohol 104 may together form 5 wt % to 50 wt % of the solder material 100 .

[0050] In various embodiments, the solder material 100 may be free or substantially free of solvents 108 other than the alcohol 104 .

[0051] In various embodiments, the solder material 100 may optionally further include a solvent 108. The solvent 108 may be configured to adjust the viscosity of the solder material 100 so as to make it suitable for an intended dispensing process, such as for forming a printable paste. On the other hand, in various embodiments, the combination of the carboxylic acid 102 and the alcohol 104 may also be referred to as a "binder" due to their combined adhesive properties that help hold the solder material 100 in place prior to the soldering process.

[0052] The solvent 108 may be a polar solvent or a non-polar solvent, for example selected from the group consisting of water, toluene, diethylene glycol, triethylene glycol, triethylene glycol dimethyl ether, ethylene glycol, dibutyl ether, Γ-butyrolactone, propylene carbonate, isopropyl alcohol, diethylene glycol monoethyl ether and diethylene glycol monobutyl ether acetate.

[0053] The alcohol 104 and the solvent 108 may have a weight mixing ratio (alcohol:solvent) in the range of 99:1 to 1:99, optionally between 80:1 and 1:80.

[0054] In one exemplary embodiment, the alcohol 104 may be glycerin, the solvent 108 may be propylene glycol, and optionally, the weight mixing ratio (alcohol:solvent) may be 20:80 wt %.

[0055] In one exemplary embodiment, the alcohol 104 may be glycerin, the solvent 108 may be water, and optionally, the weight mixing ratio (alcohol:solvent) may be 80:20 wt %.

[0056] The weight mixing ratio of the sum of alcohol 104 and optional solvent 108 to carboxylic acid 102 ((sum of alcohol and solvent):acid) may be in the range of 5:1 to 100:1, optionally between 10:1 and 30:1, further optionally about 20:1.

[0057] The solder material 100 may include or consist of any combination of the following:

[0058] Table 1:

[0059] List of potential alcohols List of potential dicarboxylic acids Corresponding reducing acid list List of potential solvents glycerin oxalic acid Formic acid <![CDATA[H2O]]> Ethylene glycol Malonic acid Acetic acid Isopropyl alcohol Ethanolamine Succinic acid 2-Propionic acid Diethylene glycol 1,2-Propanediol Glutaric acid Butyric acid Triethylene glycol 1,3-Propanediol Adipic acid Valeric acid Triethylene glycol dimethyl ether Citric acid Formic acid Ethylene glycol ascorbic acid, Dibutyl ether γ-Butyrolactone Propylene carbonate

[0060] The above Table 1 should be understood as follows:

[0061] Any alcohol 104 in the first column may be combined with a carboxylic acid 102 in the second column of the same row.

[0062] The alcohol 104 and the carboxylic acid 102 may form a reducing agent 114 (eg, an acid) when heated during the welding process, as listed in the third column of the same row.

[0063] Therefore, the solder material 100 may include or consist of oxalic acid and glycerol to form formic acid; or the solder material 100 may include or consist of malonic acid and ethylene glycol to form acetic acid; or the solder material 100 may include or consist of ethanolamine and succinic acid to form 2-propionic acid, or the solder material 100 may include or consist of 1,2-propylene glycol and glutaric acid to form butyric acid; or the solder material 100 may include or consist of 1,3-propylene glycol and adipic acid to form valeric acid; or the solder material 100 may include or consist of methanol and citric acid to form formic acid.

[0064] Any of these combinations may optionally be combined with any of the solvents 108 listed in the fourth column. One skilled in the art will be able to select an appropriate solvent 108 based on a given application. In other words, the fourth column listing the solvents 108 may not follow the row-by-row matching pattern of the first three columns. This is indicated by the double line separation of the fourth column.

[0065] For example, a combination of glycerol and oxalic acid may optionally be combined with any of the solvents 108 listed in the fourth column as appropriate for the intended application.

[0066] The solder material 100 may include or consist of oxalic acid and glycerol. As part of the soldering process, when heated, the oxalic acid may react with the glycerol to generate formic acid in situ.

[0067] Table 2:

[0068] List of potential alcohols List of potential dicarboxylic acids List of potential solvents glycerin oxalic acid <![CDATA[H2O]]> Ethylene glycol Malonic acid Isopropyl alcohol Ethanolamine (2-aminoethanol) Succinic acid Diethylene glycol 1,2-Propanediol Glutaric acid Triethylene glycol 1,3-Propanediol Adipic acid Triethylene glycol dimethyl ether Methanol Citric acid Ethylene glycol Ethanol ascorbic acid Dibutyl ether Propan-1-ol γ-Butyrolactone Propan-2-ol Propylene carbonate 2-Methyl-1-propanol Butan-1-ol Pentan-1-ol Diethylene glycol Diethylene glycol monoethyl ether Dipropylene glycol monoethyl ether 3-Amino-1,2-propanediol Isopropylidene Glycerin Ethanolamine

[0069] The above Table 2 should be understood as follows:

[0070] Any alcohol 104 of the first column may be combined with any carboxylic acid 102 of the second column, and optionally with any solvent 108 of the third column. The table entries should be understood as separate lists, rather than row by row, as indicated by the double lines between the columns.

[0071] In various embodiments, the weight ratio of the metal solder particles 106 is at least 80% based on the sum of the metal solder particles 106 , the carboxylic acid 102 , and the alcohol 104 (and optionally the solvent 108 ).

[0072] In various embodiments, the solder material 100 may consist of or consist essentially of the metallic solder particles 106 , the carboxylic acid 102 , and the alcohol 104 .

[0073] In various embodiments, the solder material 100 may be configured as a solder paste with or without a solvent 108 .

[0074] In various embodiments, the carboxylic acid 102 is a dicarboxylic acid.

[0075] The alcohol:(carboxylic acid) ratio may be in the range of about 5:1 to 100:1, such as in the range of 10:1 to 40:1, such as in the range of about 15:1 to 30:1, such as 20:1.

[0076] In various embodiments, the solder material 100 may include a solvent 108 to adjust the viscosity of the mixture to a desired application.

[0077] The solder material 100 may, for example, include a solvent 108 in an amount of up to, for example, 15 wt %, preferably up to 5 wt %.

[0078] The content of the alcohol and the carboxylic acid may be in the range of about 5 wt % to about 20 wt % of the solder material 100 , preferably in the range of about 11 wt % to about 16 wt %.

[0079] The ratio of (alcohol and solvent):acid may be in the range of about 5:1 to about 100:1, such as in the range of about 10:1 to about 40:1, such as in the range of about 15:1 to 30:1, such as 20:1.

[0080] As described above, in various embodiments, the solder material 100 may be configured for a soldering temperature between about 200° C. and about 450° C. At the soldering temperature, at least some of the solder particles 106 may melt, such as all solder particles 106 or, for example, between 20 wt % and 100 wt % of the solder particles 106 .

[0081] Upon heating, before and / or during melting of the solder particles 106 , the carboxylic acid 102 and the alcohol 104 may react to form the reducing agent 114 and reduce oxides that may be present on the solder particles 106 (and / or elsewhere in the solder material) and / or on surfaces to be joined by the soldering process.

[0082] In various embodiments, the evaporation temperature of the alcohol 104 and the carboxylic acid 102 (and optionally, the solvent 108) can be lower than the soldering temperature for which the lead-free solder material is configured. In other words, more than 95 wt%, preferably more than 98 wt%, more preferably about 99 wt%, and most preferably all of the alcohol 104 and the carboxylic acid 102 (and optionally the solvent 108) can evaporate during the soldering process. The same applies to the reducing agent formed in situ during the soldering process. Therefore, substantially only the material provided by the solder particles 106 can remain to form a connection between the joining surfaces, while the alcohol 104 and the carboxylic acid (and optionally, the solvent 108) can leave substantially no residue. In other words, the solder material 100 can be configured as a "no-clean" solder material 100, such as a solder paste.

[0083] As mentioned above, the solder material 100 may be used to join at least two (metal) surfaces.

[0084] Therefore, in various embodiments, the solder material 100 may be used to form the layer structure 301 . Figure 3B Various embodiments of such a layer structure 301 are shown.

[0085] The layer structure 301 may include a first metal layer 330, a second metal layer 332, and a solder layer 334, and the solder layer 334 is formed by soldering the first metal layer 330 to the second metal layer 332 using the solder material 100 as described above (or the solder material 200 to be described below). Since the solder layer 334 consists of only solder particles 106 or substantially consists of only solder particles 106, the reference numeral 106 is provided together with the reference numeral 334 for indicating the solder layer.

[0086] The soldering process may include heating at least the solder material 100 (using a heat source) to a predetermined soldering temperature. Typically, at least one of the first metal layer 330 and the second metal layer 332 may also be heated.

[0087] Figure 2 A schematic diagram of a solder material 200 according to various embodiments is shown and a reaction of the solder material to a soldering process is visualized.

[0088] As described above, in various embodiments, the solder material may be composed of metal particles and a reducing binder that may be formed from a single component to generate a solder paste that reduces oxides on the materials involved when heated during the soldering process.

[0089] The solder material 200 may be composed of metal solder particles 106 (eg, the metal particles 106 described above for the solder material 100 ) and a single component 202 , which may be any one of an alcohol, an ester, or an aldehyde.

[0090] In the case where a single component is formed by an alcohol, the alcohol may be a straight-chain or branched, substituted or unsubstituted alcohol of an alkane or alkene comprising 1 to 20 carbon atoms. In other words, the alcohol may be selected from the group consisting of a straight-chain alcohol of an alkane or alkene comprising 1 to 20 carbon atoms, a branched-chain alcohol of an alkane or alkene comprising 1 to 20 carbon atoms, a substituted alcohol of an alkane or alkene comprising 1 to 20 carbon atoms, and an unsubstituted alcohol of an alkane or alkene comprising 1 to 20 carbon atoms.

[0091] The alcohol may for example comprise 1 to 10 carbon atoms, such as 2 to 6 carbon atoms, such as 3 to 5 carbon atoms.

[0092] The alcohol may, for example, be at least one alcohol, for example at least one alcohol having a boiling point above 100° C., for example above 130° C., for example 150° C., and below the melting point of the solder particles 106 .

[0093] The alcohol may be selected from the group consisting of methanol, ethanol, propan-1-ol, propan-2-ol, 2-methyl-1-propanol, butan-1-ol, pentan-1-ol, 1-hexanol, 1-heptanol, 1-octanol.

[0094] In the case where the single component is formed by an ester, the ester may have the following general formula:

[0095]

[0096] Wherein, R1 and R2 are independently selected from a linear or branched, saturated or unsaturated, substituted or unsubstituted hydrocarbon group comprising 1 to 20 carbon atoms.

[0097] The single component may be, for example, octyl acetate.

[0098] In the case where the single component is formed by an aldehyde, the aldehyde may be selected from: linear or branched, substituted or unsubstituted aldehydes of alkanes or alkenes comprising up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N; substituted or unsubstituted aldehydes of cycloalkyl, cycloalkenyl or aryl groups comprising up to 20, preferably up to 12 carbon atoms; substituted or unsubstituted aldehydes of heterocycloalkyl, heterocycloalkenyl or heteroaryl groups comprising up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N; alkylcycloalkyl, alkenylcycloalkyl, alkylcycloalkenyl, alkenylcycloalkenyl, alkylcycloalkyl ... straight-chain or branched, substituted or unsubstituted aldehydes of heteroalkylcycloalkyl, heteroalkenylcycloalkyl, heteroalkylcycloalkenyl, heteroalkenylcycloalkenyl, heteroalkylaryl or heteroalkenylaryl having up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N; and straight-chain or branched, substituted or unsubstituted aldehydes of heteroalkylheterocycloalkyl, heteroalkenylheterocycloalkyl, heteroalkylheterocycloalkenyl, heteroalkenylheterocycloalkenyl, heteroalkylheteroaryl or heteroalkenylheteroaryl having up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N.

[0099] The aldehyde may alternatively be selected from the group consisting of glutaraldehyde, benzaldehyde, vanillin, furfural, hexanal, heptaldehyde, octanal, nonanal, malondialdehyde, glutaraldehyde, cinnamaldehyde and glycolaldehyde.

[0100] In various embodiments, an evaporation temperature of the alcohol, ester or aldehyde respectively included in the solder material may be lower than a soldering temperature for which the solder material is configured.

[0101] With regard to other aspects, for example with regard to the texture of the solder material 200 , evaporation without residue, etc., the soldering process, the solder material 200 and the method of forming the layer structure 301 may be similar or identical to the solder material 100 described above.

[0102] Figure 4 A flow chart 400 of a method of forming a layer structure according to various embodiments is shown.

[0103] The method may include arranging a layer of solder material 100 , 200 according to various embodiments between the first metal layer 330 and the second metal layer 332 (in 410 ), and heating at least the solder material 100 , 200 to a melting temperature of the solder material 100 , 200 (in 420 ).

[0104] In various embodiments, arranging the layer of solder material 100 , 200 may, for example, include printing, placing a paste using a mask and a squeegee, positioning a solid layer or sheet, etc., for example as known in the art.

[0105] In various embodiments, heating may be performed substantially as known in the art, for example at soldering temperatures as described above. Typically, at least one of the first metal layer 330 and the second metal layer 332 may also be heated to the melting temperature of the solder material 100 , 200 .

[0106] Figure 3A A method of forming a layer structure is visualized, wherein the layer structure 301 is formed in Figure 3B Shown in.

[0107] Figure 5 is a flow chart 500 of a method of forming a layer structure, for example Figure 3A as visualized in .

[0108] The method may include arranging a layer of solder material 300 composed of metallic solder particles 106 between the first metal layer 330 and the second metal layer 332 .

[0109] The method may further include placing the solder material 300 in an atmosphere including the reducing agent 302 , and heating at least the solder material 300 to a melting temperature of the metallic solder particles 106 .

[0110] In other words, during the soldering process, the solder material 300 may be provided with only the reducing agent 302 , and it is sufficient that the solder material 300 is composed of only the metal particles themselves.

[0111] The reducing agent 302 may be or include, for example, formic acid, acetic acid, 2-propionic acid, butyric acid, or valeric acid.

[0112] Alternatively, the metal solder particles 106 may have the properties of the metal solder particles 106 as described above.

[0113] Various examples are described below:

[0114] Example 1 is a solder material. The solder material may include metal solder particles, carboxylic acid and alcohol, wherein the alcohol is selected from the group consisting of methanol, ethanol, propan-1-ol, propan-2-ol, ethylene glycol (ethane-1,2-diol), ethanolamine (2-aminoethanol), 2-methyl-1-propanol, butan-1-ol, pentan-1-ol, 1,2-propylene glycol, 1,3-propylene glycol and glycerol.

[0115] In Example 2, the subject matter of Example 1 can optionally include the carboxylic acid being configured to generate a reducing agent when combined with an alcohol when heated as part of a welding process.

[0116] In Example 3, the subject matter of Example 2 may optionally include: the carboxylic acid has the formula C n H 2n-2 O x , where n=2 to 10 and x=4 to 7.

[0117] In Example 4, the subject matter of Example 2 or 3 may optionally include: the carboxylic acid is selected from the group consisting of caproic acid (caproic acid, hexanoic acid), enanthic acid (enanthic acid, heptanoic acid), caprylic acid (caprylic acid, octanoic acid), pelargonic acid (pelargonic acid, nonanoic acid), capric acid (capric acid, decanoic acid), phenylacetic acid, benzoic acid, salicylic acid, aminobenzoic acid, 4-n-butylbenzoic acid, 4-tert-butylbenzoic acid, 3,4-dimethoxybenzoic acid, oxalic acid, succinic acid, glutaric acid, succinic acid, maleic acid, fumaric acid, malic acid, adipic acid, citric acid, ascorbic acid and malonic acid.

[0118] In Example 5, the subject matter of any of Examples 2-4 can optionally include: the carboxylic acid forms 0.5 wt % to 1.0 wt % of the solder material.

[0119] In Example 6, the subject matter of any one of Examples 1-5 may optionally include: the alcohol is selected from the group consisting of ethylene glycol (ethane-1,2-diol), ethanolamine (2-aminoethanol), 2-methyl-1-propanol, butan-1-ol, pentan-1-ol, 1,2-propylene glycol, 1,3-propylene glycol and glycerol.

[0120] In Example 7, the subject matter of any one of Examples 1-6 can optionally include a weight mixing ratio of alcohol:acid in a range of 5:1 to 100:1.

[0121] In Example 8, the subject matter of any of Examples 1-7 can optionally include the carboxylic acid and the alcohol together forming 5 wt % to 50 wt % of the solder material.

[0122] In Example 9, the subject matter of any of Examples 1-8 can optionally further include a solvent.

[0123] In Example 10, the subject matter of Example 9 can optionally include: the solvent is a polar solvent or a non-polar solvent.

[0124] In Example 11, the subject matter of Example 9 or 10 may optionally include: the solvent is selected from the group consisting of water, toluene, diethylene glycol, triethylene glycol, triethylene glycol dimethyl ether, ethylene glycol, dibutyl ether, Γ-butyrolactone, propylene carbonate, isopropyl alcohol, diethylene glycol monoethyl ether and diethylene glycol monobutyl ether acetate.

[0125] In Example 12, the subject matter of any of Examples 9-11 can optionally include: the alcohol and the solvent having a weight mixing ratio (alcohol:solvent) in the range of 99:1 to 1:99, optionally between 80:1 and 1:80.

[0126] In Example 12a, the subject matter of any one of Examples 9-12 can optionally include: the alcohol is glycerol, the solvent is propylene glycol, and optionally, the weight mixing ratio (alcohol:solvent) is 20:80 wt %.

[0127] In Example 12b, the subject matter of any of Examples 9-12 can optionally include: the alcohol is glycerol, the solvent is water, and optionally, the weight mixing ratio (alcohol:solvent) is 80:20 wt %.

[0128] In Example 13, the subject matter of any one of Examples 9-12 may optionally include: a weight mixing ratio of the sum of the alcohol and the solvent to the carboxylic acid ((sum of the alcohol and the solvent): acid) in the range of 5:1 to 100:1, optionally between 10:1 and 30:1, and further optionally about 20:1.

[0129] In Example 14, the subject matter of any one of Examples 1-13 may optionally include or consist of one of a group of combinations consisting of oxalic acid and glycerol, malonic acid and ethylene glycol, ethanolamine and succinic acid, 1,2-propylene glycol and glutaric acid, 1,3-propylene glycol and adipic acid, and methanol and citric acid.

[0130] In Example 15, the subject matter of any of Examples 1-14 can optionally include or consist of oxalic acid and glycerol.

[0131] In Example 16, the subject matter of Example 15 can optionally include the oxalic acid being configured to generate formic acid when combined with glycerol when heated as part of a welding process.

[0132] In Example 17, the subject matter of any one of Examples 1-16 can optionally include: a weight ratio of the metal solder particles is at least 80% based on the sum of the metal solder particles, the carboxylic acid, and the alcohol.

[0133] In Example 18, the subject matter of any of Examples 1-17 can optionally include that the solder material is configured as a solder paste.

[0134] In Example 19, the subject matter of any of Examples 1-18 can optionally include: the carboxylic acid and the alcohol having an evaporation temperature lower than a soldering temperature for which the solder material is configured.

[0135] In Example 20, the subject matter of any of Examples 1-19 can optionally include the solder material consisting of or consisting essentially of the metal solder particles 106 , the carboxylic acid, and the alcohol.

[0136] In Example 21, the subject matter of any of Examples 1-20 can optionally include: the carboxylic acid is a dicarboxylic acid.

[0137] Example 22 is a solder material. The solder material may be composed of metal solder particles and a single component, and the single component is any one of alcohol, ester or aldehyde.

[0138] In Example 23, the subject matter of Example 22 may optionally include: the alcohol is a linear or branched, substituted or unsubstituted alcohol of an alkane or alkene including 1 to 20 carbon atoms.

[0139] In Example 24, the subject matter of Example 22 or 23 may optionally include: the alcohol is selected from the group consisting of methanol, ethanol, propan-1-ol, propan-2-ol, 2-methyl-1-propanol, butan-1-ol, pentan-1-ol, 1-hexanol, 1-heptanol, and 1-octanol.

[0140] In Example 25, the subject matter of Example 24 can optionally include: the ester has the following general formula:

[0141]

[0142] Wherein, R1 and R2 are independently selected from a linear or branched, saturated or unsaturated, substituted or unsubstituted hydrocarbon group comprising 1 to 20 carbon atoms.

[0143] In Example 26, the subject matter of Examples 22 or 25 can optionally include: the single component is octyl acetate.

[0144] In Example 27, the subject matter of Example 22 may optionally include: the aldehyde is selected from: a linear or branched, substituted or unsubstituted aldehyde of an alkane or alkene having up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N; a substituted or unsubstituted aldehyde of a cycloalkyl, cycloalkenyl or aryl group having up to 20, preferably up to 12 carbon atoms; a substituted or unsubstituted aldehyde of a heterocycloalkyl, heterocycloalkenyl or heteroaryl group having up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N; an alkylcycloalkyl, alkenylcycloalkyl, alkylcycloalkenyl, alkenylcycloalkenyl group having up to 20 carbon atoms; straight-chain or branched, substituted or unsubstituted aldehydes of heteroalkylcycloalkyl, heteroalkenylcycloalkyl, heteroalkylcycloalkenyl, heteroalkenylcycloalkenyl, heteroalkylaryl or heteroalkenylaryl having up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N; and straight-chain or branched, substituted or unsubstituted aldehydes of heteroalkylheterocycloalkyl, heteroalkenylheterocycloalkyl, heteroalkylheterocycloalkenyl, heteroalkenylheterocycloalkenyl, heteroalkylheteroaryl or heteroalkenylheteroaryl having up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N.

[0145] In Example 28, the subject matter of Example 22 or 27 can optionally include: the aldehyde is selected from the group consisting of glutaraldehyde, benzaldehyde, vanillin, furfural, hexanal, heptaldehyde, octanal, nonanal, malondialdehyde, glutaraldehyde, cinnamaldehyde and glycolaldehyde.

[0146] In Example 29, the subject matter of any of Examples 22-28 can optionally include that an evaporation temperature of the alcohol, ester, or aldehyde respectively included in the solder material is lower than a soldering temperature for which the solder material is configured.

[0147] In Example 30, the subject matter of any of Examples 1-29 can optionally include: the metal solder particles have a bimodal size distribution, such as a first amount of particles having a size in a range of about 1 μm to about 20 μm, and a second amount of particles having a size in a range of about 30 μm to about 50 μm.

[0148] In Example 31, the subject matter of any one of Examples 1-30 may optionally include: the metal solder particles include low melting point metal solder particles having a first melting temperature and high melting point metal solder particles having a second melting temperature, wherein the first melting temperature is lower than the second melting temperature.

[0149] In Example 32, the subject matter of Example 31 may optionally include: the low melting point metal solder particles include or consist of at least one metal selected from the group consisting of Bi, Sn, Ga, Ge, Zn and In.

[0150] In Example 33, the subject matter of Example 31 or 32 may optionally include: the high melting point metal solder particles include at least one metal selected from the group consisting of Ni, Cu, Ag, Au, Pt and Pd or are composed of at least one metal selected from the group consisting of Ni, Cu, Ag, Au, Pt and Pd.

[0151] In Example 34, the subject matter of any of Examples 1-33 can optionally include the metal solder particles comprising at least 30 wt % nickel based on a total weight of the metal solder particles.

[0152] In Example 35, the subject matter of any of Examples 1-33 can optionally include that the metal solder particles include tin.

[0153] In Example 36, the subject matter of any of Examples 1-35 can optionally include that the solder material is configured for a soldering temperature between about 200°C and about 450°C.

[0154] Example 37 is a layer structure. The layer structure may include a first metal layer, a second metal layer, and a solder layer formed by soldering the first metal layer to the second metal layer using the solder material according to any one of Examples 1-36.

[0155] Example 38 is a method of forming a layer structure. The method may include arranging a layer of solder material according to any of Examples 1-36 between a first metal layer and a second metal layer, and heating at least the solder material to a melting temperature of at least a portion of metal solder particles of the solder material.

[0156] Example 39 is a method of forming a layer structure. The method may include arranging a layer of solder material composed of metal solder particles between a first metal layer and a second metal layer, arranging the solder material in an atmosphere including a reducing agent, and heating at least the solder material to a melting temperature of at least a portion of the metal solder particles.

[0157] In Example 40, the subject matter of Example 39 can optionally include: the metal solder particles have a bimodal size distribution, such as a first amount of particles having a size in a range of about 1 μm to about 20 μm, and a second amount of particles having a size in a range of about 30 μm to about 50 μm.

[0158] In Example 41, the subject matter of Example 39 or 40 may optionally include: the metal solder particles include low melting point metal solder particles having a first melting temperature and high melting point metal solder particles having a second melting temperature, wherein the first melting temperature is lower than the second melting temperature.

[0159] In Example 42, the subject matter of Example 41 may optionally include: the low melting point metal solder particles include or consist of at least one metal selected from the group consisting of Bi, Sn, Ga, Ge, Zn and In.

[0160] In Example 43, the subject matter of Example 41 or 42 may optionally include: the high melting point metal solder particles include or consist of at least one metal selected from the group consisting of Ni, Cu, Ag, Au, Pt and Pd.

[0161] In Example 44, the subject matter of Examples 39-43 can optionally include the metal solder particles comprising at least 30 wt % nickel.

[0162] In Example 45, the subject matter of Examples 39-44 can optionally include the metal solder particles comprising tin.

[0163] Although the present invention has been particularly shown and described with reference to specific embodiments, it will be appreciated by those skilled in the art that various changes may be made to the present invention in form and detail without departing from the spirit and scope of the present invention as defined by the appended claims. Therefore, the scope of the present invention is indicated by the appended claims, and therefore it is intended to cover all changes within the meaning and scope of the equivalents of the claims.

Claims

1. A lead-free solder material, comprising: Metal solder particles; carboxylic acid; and Alcohol, the alcohol selected from the group consisting of: Methanol; Ethanol; Propan-1-ol; Propan-2-ol; Ethylene glycol (ethane-1,2-diol); Ethanolamine (2-aminoethanol); 2-Methyl-1-propanol; Butan-1-ol; Pentan-1-ol; 1,2-Propanediol; 1,3-propylene glycol; and glycerin.

2. The lead-free solder material according to claim 1, in, The carboxylic acid is configured to combine with the alcohol to generate a reducing agent when heated as part of a welding process.

3. The lead-free solder material according to claim 2, in, The carboxylic acid has the formula: C n H 2n-2 O x in: n=2 to 10 x=4 to 7.

4. The lead-free solder material according to claim 2 or 3, wherein The carboxylic acid is selected from the group consisting of: Hexanoic acid, Heptanoic acid, bitter, Nonanoic acid, Decanoic acid, Phenylacetic acid, benzoic acid, Salicylic acid, Aminobenzoic acid, 4-n-Butylbenzoic acid, 4-tert-Butylbenzoic acid, 3,4-Dimethoxybenzoic acid, oxalic acid, Succinic acid, Glutaric acid, Succinic acid, Maleic acid, Fumaric acid, Malic acid, Adipic acid, ascorbic acid, Citric acid, and Malonic acid.

5. The lead-free solder material according to any one of claims 2 to 4, in, The carboxylic acid forms 0.5 wt % to 1.0 wt % of the lead-free solder material.

6. The lead-free solder material according to any one of claims 1 to 5, in, The alcohol is selected from the group consisting of: Ethylene glycol (ethane-1,2-diol); Ethanolamine (2-aminoethanol); 2-Methyl-1-propanol; Butan-1-ol; Pentan-1-ol; 1,2-Propanediol; 1,3-propylene glycol; and glycerin.

7. The lead-free solder material according to any one of claims 1 to 6, in, The weight mixing ratio of alcohol:acid is in the range of 5:1 to 100:

1.

8. The lead-free solder material according to any one of claims 1 to 7, in, The carboxylic acid and the alcohol together form 5 wt % to 50 wt % of the lead-free solder material.

9. The lead-free solder material according to any one of claims 1 to 8, wherein The lead-free solder material further includes a solvent.

10. The lead-free solder material according to claim 9, wherein The solvent is a polar solvent or a non-polar solvent.

11. The lead-free solder material according to claim 9 or 10, wherein The solvent is selected from the group consisting of: water; Toluene; Diethylene glycol; triethylene glycol; Triethylene glycol dimethyl ether; Ethylene glycol; Dibutyl ether; γ-Butyrolactone; Propylene carbonate; Isopropyl alcohol; Diethylene glycol monoethyl ether; and Diethylene glycol monobutyl ether acetate.

12. The lead-free solder material according to any one of claims 9 to 11, wherein The alcohol and the solvent have a weight mixing ratio (alcohol:solvent) in the range of 99:1 to 1:99, optionally between 80:1 and 1:

80.

13. The lead-free solder material according to any one of claims 9 to 12, wherein: The weight mixing ratio of the sum of the alcohol and the solvent to the carboxylic acid ((sum of alcohol and solvent):acid) is in the range of 5:1 to 100:1, optionally between 10:1 and 30:1, further optionally about 20:

1.

14. The lead-free solder material according to any one of claims 1 to 13, wherein The lead-free solder material comprises one of a group of combinations or consists of one of a group of combinations, the group of combinations consisting of the following: oxalic acid and glycerol; Malonic acid and ethylene glycol; ethanolamine and succinic acid; 1,2-Propanediol and glutaric acid; 1,3-propanediol and adipic acid; and Methanol and citric acid.

15. The lead-free solder material according to any one of claims 1 to 14, wherein The lead-free solder material includes or consists of oxalic acid and glycerin.

16. The lead-free solder material according to claim 15, in, The oxalic acid is configured to generate formic acid when combined with the glycerol when heated as part of a welding process.

17. The lead-free solder material according to any one of claims 1 to 16, in, The weight ratio of the metal solder particles is at least 80% based on the sum of the metal solder particles, the carboxylic acid and the alcohol.

18. The lead-free solder material according to any one of claims 1 to 17, wherein The lead-free solder material is configured as a solder paste.

19. The lead-free solder material according to any one of claims 1 to 18, in, The carboxylic acid and the alcohol have evaporation temperatures lower than a soldering temperature for which the lead-free solder material is configured.

20. The lead-free solder material according to any one of claims 1 to 19, wherein The lead-free solder material consists of or essentially consists of metal solder particles, carboxylic acid and alcohol.

21. The lead-free solder material according to any one of claims 1 to 20, in, The carboxylic acid is a dicarboxylic acid.

22. A lead-free solder material, consisting of: Metal solder particles; and A single component of any of alcohols, esters or aldehydes.

23. The lead-free solder material according to claim 22, in, The alcohol is a linear or branched, substituted or unsubstituted alcohol comprising an alkane or alkene having 1 to 20 carbon atoms.

24. The lead-free solder material according to claim 22 or 23, in, The alcohol is selected from the group consisting of: Methanol; Ethanol; Propan-1-ol; Propan-2-ol; 2-Methyl-1-propanol; Butan-1-ol; Pentan-1-ol; 1-Hexanol; 1-Heptanol; 1-Octanol.

25. The lead-free solder material according to claim 24, in, The esters have the following general formula: in, R1 and R2 are independently selected from linear or branched, saturated or unsaturated, substituted or unsubstituted hydrocarbon groups comprising 1 to 20 carbon atoms.

26. The lead-free solder material according to claim 22 or 25, in, The single component is octyl acetate.

27. The lead-free solder material according to claim 22, in, The aldehyde is selected from: linear or branched, substituted or unsubstituted aldehydes comprising alkanes or alkenes having up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N; Substituted or unsubstituted aldehydes comprising a cycloalkyl, cycloalkenyl or aryl group having up to 20, preferably up to 12, carbon atoms; substituted or unsubstituted aldehydes comprising a heterocycloalkyl, heterocycloalkenyl or heteroaryl group having up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N; A straight or branched, substituted or unsubstituted aldehyde comprising an alkylcycloalkyl, alkenylcycloalkyl, alkylcycloalkenyl, alkenylcycloalkenyl, alkylaryl or alkenylaryl group having up to 20 carbon atoms; a straight or branched, substituted or unsubstituted aldehyde comprising a heteroalkylcycloalkyl, heteroalkenylcycloalkyl, heteroalkylcycloalkenyl, heteroalkenylcycloalkenyl, heteroalkylaryl or heteroalkenylaryl group having up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N; and A straight or branched, substituted or unsubstituted aldehyde comprising a heteroalkylheterocycloalkyl, heteroalkenylheterocycloalkyl, heteroalkylheterocycloalkenyl, heteroalkenylheterocycloalkenyl, heteroalkylheteroaryl or heteroalkenylheteroaryl group of up to 20 carbon atoms and 1 to 6 heteroatoms selected from O, S and N.

28. The lead-free solder material according to claim 22 or 27, in, The aldehyde is selected from the group consisting of: Glutaraldehyde; Benzaldehyde; Vanillin; Furfural; Hexanal; Heptanal; Octanal; Nonanal; Malondialdehyde; Glutaraldehyde; Cinnamaldehyde; and Glycolaldehyde.

29. The lead-free solder material according to any one of claims 22 to 28, in, The evaporation temperature of the alcohol, the ester or the aldehyde included in the lead-free solder material accordingly is lower than a soldering temperature for which the lead-free solder material is configured.

30. The lead-free solder material according to any one of claims 1 to 29, in, The metal solder particles have a bimodal size distribution.

31. The lead-free solder material according to any one of claims 1 to 30, in, The metal solder particles include low melting point metal solder particles having a first melting temperature and high melting point metal solder particles having a second melting temperature, the first melting temperature being lower than the second melting temperature.

32. The lead-free solder material according to claim 31, in, The low melting point metal solder particles include or consist of at least one metal selected from the group consisting of: Bi; Sn; Ga; Ge; Zn; and In.

33. The lead-free solder material according to claim 31 or 32, in, The high melting point metal solder particles include or consist of at least one metal selected from the group consisting of: You; Cu; Ag; Au; Pt; and Pd.

34. The lead-free solder material according to any one of claims 1 to 33, wherein The metal solder particles include at least 30 wt % nickel based on the total weight of the metal solder particles.

35. The lead-free solder material according to any one of claims 1 to 34, wherein The metal solder particles include tin.

36. The lead-free solder material according to any one of claims 1 to 35, wherein The lead-free solder material is configured for soldering temperatures between about 200°C and about 450°C.

37. A layer structure comprising: A first metal layer; A second metal layer; and A solder layer formed by soldering the first metal layer to the second metal layer using the lead-free solder material according to any one of claims 1 to 36.

38. A method of forming a layer structure, the method comprising: Between the first metal layer and the second metal layer Layout A layer of lead-free solder material according to any one of claims 1 to 36; and At least the lead-free solder material is heated to a melting temperature of at least a portion of metallic solder particles of the lead-free solder material.

39. A method of forming a layer structure, the method comprising: disposing a layer of solder material composed of metal solder particles between the first metal layer and the second metal layer; placing the solder material in an atmosphere including a reducing agent; as well as At least the solder material is heated to a melting temperature of at least a portion of the metallic solder particles.

40. The method according to claim 39, in, The metal solder particles have a bimodal size distribution.

41. The method according to claim 39 or 40, in, The metal solder particles include low melting point metal solder particles having a first melting temperature and high melting point metal solder particles having a second melting temperature, the first melting temperature being lower than the second melting temperature.

42. The method according to claim 41, in, The low melting point metal solder particles include or consist of at least one metal selected from the group consisting of: Bi; Sn; Ga; Ge; Zn; and In.

43. The method according to claim 41 or 42, in, The high melting point metal solder particles include or consist of at least one metal selected from the group consisting of: You; Cu; Ag; Au; Pt; and Pd.

44. The method according to any one of claims 39 to 43, wherein: The metal solder particles include at least 30 wt % nickel.

45. The method according to any one of claims 39 to 44, wherein: The metal solder particles include tin.

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