Porous resin film for metal layer laminated plate and metal layer laminated plate

Abstract

Provided are a porous resin film for a metal layer laminate and a metal layer laminate, each of which can suppress damage to a metal layer arranged on an inner circumferential surface of a through-hole in a high-temperature environment and has excellent electrical connection reliability. The porous resin film for a metal layer laminate (1) is used for lamination of a metal layer (4). The porous resin film for a metal layer laminate (1) has a minimum coefficient of thermal expansion X in a plane direction orthogonal to a thickness direction, and a coefficient of thermal expansion Z in the thickness direction. In the porous resin film for a metal layer laminate (1), the ratio (Z / X) of the coefficient of thermal expansion Z in the thickness direction to the minimum coefficient of thermal expansion X is 3.5 or less.

Description

Technical Field

[0001] This invention relates to porous resin films for metal laminates and metal laminates. Background Technology

[0002] It is known to use porous polyimide films in copper-clad laminates (see, for example, Patent Document 1 below). The copper-clad laminate comprises: a porous polyimide film having through holes; copper layers stacked on both sides of the film in its thickness direction; and copper-plated portions electrically connecting the films and disposed on the inner peripheral surfaces of the through holes. In the copper-clad laminate, the copper layers are patterned by etching and electrically connected to other substrates.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: WO2018 / 186486 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] When the pattern formed by the copper layer of Patent Document 1 is electrically connected to other substrates via reflow soldering, the copper-plated portion is easily damaged. In this case, there is a problem of reduced reliability of the electrical connection between the patterns disposed on both sides of the polyimide porous film.

[0008] This invention provides a porous resin film and a metal layer laminate that can suppress damage to the metal layer disposed on the inner peripheral surface of the through hole even under high temperature environment and have excellent electrical connection reliability.

[0009] Solution for solving the problem

[0010] The present invention (1) includes a porous resin film for metal layer laminate, which is used for laminating metal layers. The porous resin film for metal layer laminate has: a minimum coefficient of thermal expansion X in a plane direction orthogonal to the thickness direction and a coefficient of thermal expansion Z in the thickness direction, wherein the ratio (Z / X) of the coefficient of thermal expansion Z in the thickness direction to the minimum coefficient of thermal expansion X is 3.5 or less.

[0011] In this porous resin film used for the metal layer laminate, the ratio (Z / X) of the coefficient of thermal expansion Z in the thickness direction to the minimum coefficient of thermal expansion X is as low as 3.5 or less. Therefore, even at high temperatures, stress applied to the metal layer disposed on the inner peripheral surface of the through-hole can be suppressed. Consequently, damage to the aforementioned metal layer can be suppressed. As a result, a metal layer laminate with excellent electrical connection reliability can be manufactured.

[0012] The present invention (2) includes a metal layer laminate comprising: a porous resin film for metal layer laminate of (1) having a through hole extending through the aforementioned thickness direction; and a metal layer disposed on one side, the other side and the inner peripheral surface of the aforementioned porous resin film for metal layer laminate in the thickness direction and the aforementioned through hole.

[0013] In this metal layer laminate, damage to the metal layers is suppressed. Therefore, the electrical connection reliability of this metal layer laminate is excellent.

[0014] The effects of the invention

[0015] The porous resin film and metal layer laminate of the present invention can suppress damage to the metal layer disposed on the inner peripheral surface of the through hole even in high temperature environment, and the electrical connection reliability is excellent. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view of one embodiment of the porous resin film for metal layer laminates of the present invention.

[0017] Figure 2 To have Figure 1 The diagram shows a cross-sectional view of a metal laminate made of a porous resin film, where through holes have not yet been formed.

[0018] Figure 3 A cross-sectional view of a metal laminate with through holes. Detailed Implementation

[0019] Reference Figure 1 An embodiment of the porous resin film for the metal layer laminate of the present invention will be described. For example... Figure 1 As shown, the porous resin film 1 for the metal layer laminate has a thickness extending along a surface direction orthogonal to the thickness direction. The thickness of the porous resin film 1 for the metal layer laminate is not particularly limited. The thickness of the porous resin film 1 for the metal layer laminate is, for example, 2 μm or more, preferably 5 μm or more, and also, for example, 1000 μm or less, preferably 500 μm or less.

[0020] <Coefficient of thermal expansion>

[0021] The porous resin film 1 for metal layer laminate has: the minimum coefficient of thermal expansion X in the surface direction and the coefficient of thermal expansion Z in the thickness direction.

[0022] The minimum coefficient of thermal expansion X is the lowest coefficient of thermal expansion in any direction along the surface. The minimum coefficient of thermal expansion X is not particularly limited as long as it satisfies the ratio (Z / X) described later. The minimum coefficient of thermal expansion X is, for example, 30.0 ppm / K or less, preferably 25.0 ppm / K or less. There is no particular limitation on the lower limit of the minimum coefficient of thermal expansion X. The lower limit of the minimum coefficient of thermal expansion X is, for example, 1 ppm / K, and also 10 ppm / K. The method for measuring the minimum coefficient of thermal expansion X is described in the examples described later.

[0023] The coefficient of thermal expansion Z in the thickness direction is not particularly limited as long as it meets the ratio (Z / X) described later. The coefficient of thermal expansion Z in the thickness direction is, for example, greater than the minimum coefficient of thermal expansion X mentioned above. Specifically, the coefficient of thermal expansion Z in the thickness direction is, for example, 100 ppm / K or less, preferably 90 ppm / K or less, more preferably 80 ppm / K or less, further preferably 70 ppm / K or less, and particularly preferably 60 ppm / K or less. If the coefficient of thermal expansion Z in the thickness direction is below the upper limit mentioned above, the ratio (Z / X) described later can be set to a desired range, i.e., a low ratio (Z / X). The lower limit of the coefficient of thermal expansion Z in the thickness direction is not particularly limited. The lower limit of the coefficient of thermal expansion Z in the thickness direction is, for example, 1 ppm / K, and also 10 ppm / K. The method for measuring the coefficient of thermal expansion Z in the thickness direction is described in the examples described later.

[0024] The ratio of the coefficient of thermal expansion Z in the thickness direction to the minimum coefficient of thermal expansion X (Z / X) is less than 3.5.

[0025] If the ratio of the coefficient of thermal expansion Z in the thickness direction to the minimum coefficient of thermal expansion X (Z / X) exceeds 3.5, the expansion in the thickness direction of the porous resin film 1 for metal laminates at high temperatures becomes excessive relative to the expansion in the surface direction of the porous resin film 1 for metal laminates. Therefore, when a conductive portion 5 is formed in the through-hole 9 of the porous resin film 10 for metal laminates having a through-hole 9, damage occurs in the conductive portion 5 when the metal laminate 10 is placed in a high-temperature environment. Consequently, the electrical connection reliability of the metal laminate 10 decreases. In other words, if the ratio of the coefficient of thermal expansion Z in the thickness direction to the minimum coefficient of thermal expansion X (Z / X) in the porous resin film 1 for metal laminates is less than 3.5, then the expansion in the thickness direction of the porous resin film 1 for metal laminates relative to the surface direction at high temperatures can be suppressed. Therefore, even when the aforementioned metal laminate 10 is placed in a high-temperature environment, damage to the conductive portion 5 can be suppressed. Thus, the reduction in the electrical connection reliability of the metal laminate 10 can be suppressed.

[0026] The ratio (Z / X) of the coefficient of thermal expansion in the thickness direction Z to the minimum coefficient of thermal expansion X is preferably 3.0 or less. Furthermore, there is no particular limitation on the lower limit of the ratio (Z / X) of the coefficient of thermal expansion in the thickness direction Z to the minimum coefficient of thermal expansion X. For example, the lower limit is 1, and further, for example, 1.5, or even 2.0.

[0027] The porous resin film 1 used in the metal laminate is porous. The porous resin film 1 used in the metal laminate has closed pores and / or continuous pores.

[0028] The porosity of the porous resin film 1 for the metal layer laminate is, for example, 50% or more, preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. It should be noted that the porosity of the porous resin film 1 for the metal layer laminate is, for example, less than 100%, and even more preferably less than 99%. A method for measuring the porosity of the porous resin film 1 for the metal layer laminate is described in the examples described later.

[0029] The porosity of the porous resin film 1 for metal laminates can be adjusted by the type and / or amount of the porosifying agent (described later).

[0030] The dielectric constant of the porous resin film 1 for the metal layer laminate at a frequency of 60 GHz is, for example, 2.5 or less, preferably 1.9 or less, more preferably 1.6 or less, and also, for example, more than 1.0. The dielectric constant of the porous resin film 1 for the metal layer laminate is measured by using a resonator method at a frequency of 60 GHz.

[0031] The dielectric loss tangent of the porous resin film 1 used in the metal layer laminate at a frequency of 60 GHz is, for example, less than 0.006, and also, for example, greater than 0. The dielectric loss tangent of the porous resin film 1 used in the metal layer laminate was measured by using a resonator method at a frequency of 60 GHz.

[0032] For example, thermosetting resins can be used as materials for porous resin films 1 used in metal laminates.

[0033] Examples of thermosetting resins include polycarbonate resins, polyimide resins, fluorinated polyimide resins, epoxy resins, phenolic resins, urea resins, melamine resins, diallyl phthalate resins, silicone resins, thermosetting polyurethane resins, fluoropolymers (polymers containing fluorinated olefins, specifically polytetrafluoroethylene (PTFE)), and liquid crystal polymers (LCPs). These can be used alone or in combination of two or more.

[0034] From the viewpoint of mechanical strength, polyimide resin is preferred among the aforementioned resins. It should be noted that details of the physical properties and manufacturing methods of polyimide resins are described, for example, in WO2018 / 186486.

[0035] The porous resin film 1 for the metal laminate can have a skin layer (not shown) formed on one side and the other side in its thickness direction.

[0036] Next, the manufacturing method of the porous resin film 1 for metal layer laminates will be described.

[0037] Specifically, first, a substrate film 2, as shown by the virtual lines, is prepared. The substrate film 2 extends along the surface direction. Materials for the substrate film 2 can include, for example, metal and resin. Since the substrate film 2 can be used as the first metal layer 11 in the metal layer laminate 10 (see reference...), Figure 2 Therefore, metals are preferred. Examples of metals include copper, iron, silver, gold, aluminum, nickel, and their alloys (stainless steel, bronze). Copper is a preferred metal. The thickness of the substrate film 2 is, for example, 0.1 μm or more, preferably 1 μm or more, and also, for example, 100 μm or less, preferably 50 μm or less.

[0038] Then, a varnish comprising the above-mentioned resin precursor, a pore-forming agent, a nucleating agent, and a solvent is prepared. The varnish is then applied to one side of the substrate film 2 in the thickness direction to form a coating film. The types and mixing ratios of the pore-forming agent, nucleating agent, and solvent in the varnish are, for example, described in WO2018 / 186486. In particular, the mass fraction (mixing ratio) of the pore-forming agent relative to 100 parts by mass of the precursor is preferably 20 parts by mass or more, more preferably 100 parts by mass or more, and preferably 300 parts by mass or less, more preferably 250 parts by mass or less.

[0039] The case where the resin is a polyimide resin will be described. The precursor of the polyimide resin is, for example, the reaction product of a diamine component and an acid dianhydride component. Examples of diamine components include aromatic diamines, aliphatic diamines, and alicyclic diamines. Aromatic diamines are preferred as diamine components.

[0040] Examples of aromatic diamines include the first diamine, the second diamine, and the third diamine.

[0041] The first diamine contains an aromatic ring. Examples of first diamines include phenylenediamine, dimethylphenylenediamine, and ethylmethylphenylenediamine. From the viewpoint of mechanical strength, phenylenediamine is preferred. Examples of phenylenediamines include o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine. p-phenylenediamine is preferred.

[0042] The second diamine contains a plurality of aromatic rings and ether bonds disposed therebetween. Examples of second diamines include oxodiphenylamine. Examples of oxodiphenylamines include 3,4'-oxodiphenylamine and 4,4'-oxodiphenylamine. From the viewpoint of mechanical strength, 4,4'-oxodiphenylamine is preferred.

[0043] The third diamine contains a plurality of aromatic rings and ester bonds disposed therebetween. The third diamine is a component used to reduce the aforementioned coefficient of thermal expansion (Z / X) of the porous resin film 1 for the metal laminate. Examples of the third diamine include aminobenzoic acid phenyl ester, and more preferably, 4-aminobenzoic acid (4-aminophenyl) ester.

[0044] It should be noted that, in addition to the first to third diamines, other examples of aromatic diamines include 4,4'-methylenediphenylamine, 4,4'-dimethylenediphenylamine, 4,4'-trimethylenediphenylamine, and bis(4-aminophenyl) sulfone.

[0045] The aforementioned diamine components can be used alone or in combination. Preferably, combinations of a first diamine, a second diamine, and a third diamine are preferred diamine components. More preferably, combinations of p-phenylenediamine, 4,4'-oxodiphenylamine, and 4-aminobenzoic acid (4-aminophenyl) ester are preferred diamine components.

[0046] It should be noted that p-phenylenediamine is sometimes abbreviated as PDA. 4,4'-Oxydiphenylamine (also known as 4,4'-diaminodiphenyl ether) is sometimes abbreviated as ODA. 4-Aminobenzoic acid (4-aminophenyl) ester is sometimes abbreviated as APAB.

[0047] The molar fraction of the first diamine in the diamine component is, for example, 10 mol% or more, preferably 20 mol% or more, and also, for example, 70 mol% or less, preferably 65 mol% or less. The molar fraction of the second diamine in the diamine component is, for example, 5 mol% or more, preferably 10 mol% or more, and also, for example, 40 mol% or less, preferably 30 mol% or less. The molar fraction of the third diamine in the diamine component is, for example, 5 mol% or more, preferably 10 mol% or more, and also, for example, 40 mol% or less, preferably 30 mol% or less.

[0048] <Acid dianhydride composition>

[0049] The dianhydride component may contain, for example, an acid dianhydride comprising an aromatic ring. Examples of acid dianhydrides comprising an aromatic ring include, for example, aromatic tetracarboxylic dianhydrides. Examples of aromatic tetracarboxylic dianhydrides include, for example, benzophenone tetracarboxylic dianhydride, biphenyl tetracarboxylic dianhydride, biphenyl sulfone tetracarboxylic dianhydride, and naphthalene tetracarboxylic dianhydride.

[0050] Examples of phenyl-1,2,4,5-tetracarboxylic acid dianhydrides include pyromellitic dianhydride (also known as pyromellitic dianhydride). Examples of benzophenone tetracarboxylic acid dianhydrides include 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride. Examples of biphenyl tetracarboxylic acid dianhydrides include 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride, 2,2',3,3'-biphenyl tetracarboxylic acid dianhydride, 2,3,3',4'-biphenyl tetracarboxylic acid dianhydride, and 3,3',4,4'-diphenyl ether tetracarboxylic acid dianhydride. Examples of biphenyl sulfone tetracarboxylic acid dianhydrides include 3,3',4,4'-biphenyl sulfone tetracarboxylic acid dianhydride. Examples of naphthalenetetracarboxylic dianhydrides include 2,3,6,7-naphthalenetetracarboxylic dianhydrides, 1,2,5,6-naphthalenetetracarboxylic dianhydrides, 1,2,4,5-naphthalenetetracarboxylic dianhydrides, and 1,4,5,8-naphthalenetetracarboxylic dianhydrides. They can be used alone or in combination. From the viewpoint of mechanical strength, biphenyltetracarboxylic dianhydrides are preferred as the acid dianhydride component, and 3,3',4,4'-biphenyltetracarboxylic dianhydrides are more preferred. It should be noted that 3,3',4,4'-biphenyltetracarboxylic dianhydrides are sometimes simply referred to as BPDA.

[0051] The ratio of diamine to dianhydride is adjusted such that, for example, the molar amount of the amino group (-NH2) in the diamine and the molar amount of the anhydride group (-CO-O-CO-) in the dianhydride are equal.

[0052] To prepare the precursor of the polyimide resin, the above-mentioned diamine component, the above-mentioned acid dianhydride component, and a solvent were mixed to prepare a varnish. The varnish was then heated to prepare a precursor solution. Next, a nucleating agent and a pore-forming agent were mixed into the precursor solution to prepare a porous precursor solution. Finally, the porous precursor solution was coated onto one side of the substrate film 2 in the thickness direction to form a coating film.

[0053] Subsequently, the coating is dried by heating to form a precursor film. Through the above heating, the solvent is removed while a precursor film with a phase-separated structure of polyimide resin precursor and porousing agent is prepared, in which the nucleating agent is formed into a nucleating agent.

[0054] Subsequently, for example, the porosizing agent is extracted (extracted or removed) from the precursor membrane using supercritical extraction with supercritical carbon dioxide as a solvent.

[0055] Subsequently, the precursor film is cured by heating to form a porous resin film 1 for metal layer laminates made of polyimide resin. The other side of the porous resin film 1 for metal layer laminates is in contact with the substrate film 2 in the thickness direction.

[0056] Then, as needed, such as Figure 1As shown by the solid line, the substrate film 2 is removed. For example, if the material of the substrate film 2 is metal, it is dissolved using a stripping solution. FeCl3 can be used as an example of a stripping solution. Thus, a porous resin film 1 for a metal layer laminate is obtained.

[0057] Next, as Figure 3 As shown, a metal layer laminate 10 having a porous resin film 1 for metal layer laminates will be described. This metal layer laminate 10 has a porous resin film 1 for metal layer laminates and a metal layer 4.

[0058] The porous resin film 1 for the metal layer laminate includes through holes 9. The through holes 9 penetrate the thickness direction of the porous resin film 1 for the metal layer laminate. The shape and size of the through holes 9 in top view are not particularly limited.

[0059] The metal layer 4 integrally comprises: a first metal layer 11, a second metal layer 12, and a conductive portion 5.

[0060] The first metal layer 11 is disposed on the other side of the porous resin film 1 for the metal layer laminate in the thickness direction. Examples of metals used in the substrate film 2 can be used as the material for the first metal layer 11. Copper is a preferred material for the first metal layer 11. The thickness of the first metal layer 11 is, for example, 0.1 μm or more, preferably 1 μm or more, and also, for example, 100 μm or less, preferably 50 μm or less.

[0061] The second metal layer 12 is disposed on the thickness direction side of the porous resin film 1 for the metal layer laminate. It should be noted that the second metal layer 12 can be disposed on the thickness direction side of the porous resin film 1 for the metal layer laminate using an adhesive layer (not shown). As the material of the first metal layer 11, metals exemplified in the substrate film 2 can be used. Copper is preferred. The thickness of the second metal layer 12 is, for example, 0.1 μm or more, preferably 1 μm or more, and also, for example, 100 μm or less, preferably 50 μm or less.

[0062] A conductive portion 5 is disposed in the porous resin film 1 for metal layer lamination, facing the through hole 9 on the inner peripheral surface 7. Specifically, the conductive portion 5 is in contact with the inner peripheral surface 7. The conductive portion 5 connects the first metal layer 11 and the second metal layer 12 facing the through hole 9. Thus, the conductive portion 5 electrically connects the first metal layer 11 and the second metal layer 12. The material of the conductive portion 5 is the same as the material of the first metal layer 11. The thickness of the conductive portion 5 is, for example, 1 μm or more, preferably 10 μm or more, and also, for example, 500 μm or less, preferably 250 μm or less. The thickness of the conductive portion 5 is the length from the inner peripheral surface 7 to the inside of the through hole 9.

[0063] The manufacturing method of the metal laminate 10 will be described. First, prepare... Figure 2The metal layer laminate shown is a laminate 8 consisting of a porous resin film 1, a first metal layer 11, and a second metal layer 12. If the substrate film 2 is made of metal, it can be directly supplied as the first metal layer 11 without removal. On the other hand, the second metal layer 12 is disposed on one side of the porous resin film 1 in the thickness direction. Thus, as... Figure 2 As shown, a porous resin film 1 for metal layer laminates sandwiched between a first metal layer 11 and a second metal layer 12 along the thickness direction is obtained.

[0064] After that, as Figure 3 As shown, a through hole 9 is formed that penetrates the laminate 8 along the thickness direction. Examples of methods for forming the through hole 9 include drilling and laser processing.

[0065] Subsequently, for example by plating, a conductive portion 5 is formed on the inner circumferential surface 7. The conductive portion 5 has a cylindrical or columnar shape.

[0066] Thus, a metal laminate 10 is manufactured.

[0067] Then, the first metal layer 11 and the second metal layer 12 are patterned by etching or the like. Then, the first metal layer 11 is electrically connected to another substrate (not shown) by reflow soldering, for example. The temperature during reflow soldering is, for example, 100°C or higher, and also 150°C or lower.

[0068] The metal laminate 10 is used for wireless communication, such as fifth-generation (5G) standards, and high-speed flexible printed circuit boards (FPCs).

[0069] (Effects of one implementation method)

[0070] In the porous resin film 1 used for this metal layer laminate, the ratio (Z / X) of the coefficient of thermal expansion Z in the thickness direction to the minimum coefficient of thermal expansion X is as low as 3.5 or less. Therefore, stress applied to the conductive portion 5 (the metal layer 4 disposed on the inner peripheral surface 7 of the through hole 9) under high-temperature conditions can be suppressed. Thus, damage to the conductive portion 5 can be suppressed. Damage includes cracks and broken wires. As a result, a metal layer laminate 10 with excellent electrical connection reliability can be manufactured.

[0071] Figure 3 In the metal laminate 10 shown, damage to the conductive portion 5 is suppressed. Therefore, the electrical connection reliability of the metal laminate 10 is excellent.

[0072] (Modified Example)

[0073] In the following variations, the same reference numerals are used to mark the same components and processes as in the first embodiment described above, and detailed descriptions are omitted. Furthermore, unless otherwise specified, the variations can achieve the same effects as the first embodiment. Moreover, the first embodiment and its variations can be appropriately combined.

[0074] Example

[0075] The present invention will be further described in detail below with examples and comparative examples. It should be noted that the present invention is not limited by the examples and comparative examples. In addition, the specific values ​​of mixing ratios (including ratios), physical property values, parameters, etc. used in the following description can be replaced with the upper limit (defined as "below" or "less than") or lower limit (defined as "above" or "more than") of the mixing ratios (including ratios), physical property values, parameters, etc., corresponding to those described in the above "Specific Embodiments".

[0076] (Example 1)

[0077] In a reaction apparatus equipped with a stirrer and a thermometer, 71.37 g (0.66 mol) of PDA, 44.05 g (0.22 mol) of ODA, and 50.22 g (0.22 mol) of APAB were added, along with 2300 g of N-methyl-2-pyrrolidone (NMP) as a solvent, and the mixture was stirred to prepare an NMP solution of PDA, ODA, and APAB. It should be noted that the NMP solution contains 1.10 mol of diamine.

[0078] Then, 323.64 g (1.10 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (3,3',4,4'-BPDA) was slowly added to the NMP solution of PDA, ODA and APAB, followed by 331 g of N-methyl-2-pyrrolidone (NMP). The mixture was heated to 80 °C and stirred for 10 hours to obtain a polyimide precursor solution.

[0079] To obtain a porous precursor solution, 100 parts by weight of the solids component of the polyimide precursor solution were mixed with 3 parts by weight of PTFE powder with a median particle size of less than 1 μm as a nucleating agent, 200 parts by weight of polyoxyethylene dimethyl ether (manufactured by Nippon Oil Co., Ltd., grade: MM400) with a weight average molecular weight of 400 as a porosifying agent, and 4 parts by weight of 2-methylimidazole (manufactured by Shikoku Chemical Co., Ltd., 2Mz-H) to form a porous precursor solution. This porous precursor solution was coated onto a copper substrate film 2 (first metal layer 11) using a comma-coating method to form a coating film. The coating film was then dried at 120–160°C for approximately 7 minutes to produce a precursor film with a thickness of 50 μm.

[0080] The precursor film was immersed in carbon dioxide pressurized to 30 MPa at 60°C for 8 hours to promote the extraction and removal of the porosizing agent, phase separation of residual NMP, and the formation of pores. Afterwards, the carbon dioxide pressure was reduced.

[0081] Subsequently, the precursor film is heat-treated under vacuum at a temperature of 300°C to 400°C for about 5 hours to promote the removal of residual components and imidization, thereby obtaining a porous resin film 1 for metal layer laminates disposed on one side of the substrate film 2 in the thickness direction.

[0082] Subsequently, the substrate film 2 and the porous resin film 1 for the metal layer laminate are immersed in a FeCl3 solution, causing the substrate film 2 to dissolve and be removed. Thus, the porous resin film 1 for the metal layer laminate is manufactured. The dielectric constant and dielectric loss tangent of the porous resin film 1 for the metal layer laminate at a frequency of 60 GHz are 1.51 and 0.002, respectively.

[0083] (Example 2)

[0084] Similar to Example 1, a porous resin film 1 for metal layer laminates was manufactured. The mass fraction of polyoxyethylene dimethyl ether was changed from 200 parts by mass to 150 parts by mass. The dielectric constant and dielectric loss tangent of the porous resin film 1 for metal layer laminates at a frequency of 60 GHz were 1.70 and 0.002, respectively.

[0085] (Example 3)

[0086] Similar to Example 1, a porous resin film 1 for manufacturing a metal layer laminate was produced. However, the mass fraction of polyoxyethylene dimethyl ether was changed from 200 parts by mass to 50 parts by mass.

[0087] The dielectric constant and dielectric loss tangent of the porous resin film 1 used in the metal layer laminate are 2.00 and 0.002, respectively, at a frequency of 60 GHz.

[0088] (Comparative Example 1)

[0089] In a reaction apparatus equipped with a stirrer and a thermometer, 1444 g (13.36 mol) of PDA and 669 g (3.34 mol) of ODA were added, followed by 28534 g of NMP and stirring to prepare an NMP solution of PDA and ODA. It should be noted that the NMP solution contains 16.70 mol of diamine.

[0090] Then, 4913 g (16.70 mol) of BPDA was slowly added to the solution. Further, 3 parts by mass of PTFE powder with a median particle size of less than 1 μm as a nucleating agent and 6658 g of N-methyl-2-pyrrolidone (NMP) were added and stirred. The mixture was stirred at 25 °C for 3 hours, and then heated to 80 °C and stirred for 20 hours to obtain a polyimide precursor solution.

[0091] To a solid content of 100 parts by weight of the polyimide precursor solution, 200 parts by weight of polyoxyethylene dimethyl ether (Nippon Oil Co., Ltd., grade: MM400) with a weight average molecular weight of 400, 4 parts by weight of 2-methylimidazolium (Shikoku Chemical Co., Ltd., 2Mz-H), and 5091 parts by weight of N-methyl-2-pyrrolidone (NMP) were added as a pore-forming agent and stirred to obtain a homogeneous solution. This solution was then coated onto a copper foil using a die-coating method and dried at 120°C for 7 minutes to prepare a precursor film with a phase-separated structure and a thickness of approximately 60 μm.

[0092] The precursor film was immersed in carbon dioxide pressurized to 30 MPa at 60°C for 8 hours to promote the extraction and removal of polyoxyethylene dimethyl ether, phase separation of residual NMP, and pore formation. Afterwards, the carbon dioxide pressure was reduced.

[0093] Then, the precursor film is heat-treated under vacuum at a temperature of 300°C to 400°C for about 5 hours to promote the removal of residual components and imidization, thereby obtaining a porous resin film 1 for metal layer laminate disposed on one side of the thickness direction of the first metal layer 11.

[0094] Subsequently, the first metal layer 11 and the metal layer laminate are immersed in a FeCl3 solution, thereby dissolving and removing the first metal layer 11. Thus, the porous resin film 1 for the metal layer laminate is manufactured. The dielectric constant and dielectric loss tangent of the porous resin film 1 for the metal layer laminate at a frequency of 60 GHz are 1.51 and 0.006, respectively.

[0095] The molar fraction of the third diamine (APAB) and the mass fraction of the pore-forming agent in each example and comparative example are recorded in Table 1.

[0096] <Evaluation>

[0097] For the porous resin film 1 used in the metal layer laminates of each embodiment and comparative example, the following items were evaluated. The results are recorded in Table 1.

[0098] (Porosity of porous resin film 1 for metal laminate)

[0099] The porosity of the porous resin film 1 for the metal layer laminate is determined by calculation based on the following formula.

[0100] The dielectric constant of the porous resin film 1 used in the metal laminate is equal to the dielectric constant of air × porosity + the dielectric constant of polyimide × (1 - porosity).

[0101] Here, the dielectric constant of air is 1, and the dielectric constant of polyimide is 3.5, therefore,

[0102] The dielectric constant of the porous resin film 1 used in the metal layer laminate is equal to the porosity plus 3.5(1-porosity).

[0103] Porosity = (3.5 - dielectric constant of porous resin film 1 for metal laminate) / 2.5

[0104] Porosity (%) = [(3.5 - dielectric constant of porous resin film 1 for metal laminate) / 2.5] × 100

[0105] (Minimum coefficient of thermal expansion X of porous resin film 1 for metal laminate)

[0106] A metal laminate was cut into 4mm × 40mm pieces using a porous resin film 1 to prepare a sample. The sample was mounted on a thermomechanical analysis apparatus (TA Instruments TMA Q400). A load of 0.01N was applied along the edge of the sample, and the temperature was increased from 0℃ to 200℃ at a heating rate of 2.0℃ / min, and then cooled from 200℃ to 0℃ at a cooling rate of 5.0℃ / min. Subsequently, the temperature was increased from 0℃ to 200℃ at a heating rate of 2.0℃ / min, and the average coefficient of thermal expansion from 0℃ to 200℃ was calculated. For multiple surface directions, the average coefficient of thermal expansion was calculated, and the minimum value among them was taken as the minimum coefficient of thermal expansion X.

[0107] (The coefficient of thermal expansion Z in the thickness direction of the porous resin film 1 used for metal laminate)

[0108] The metal laminate was cut into 5mm × 5mm pieces using porous resin film 1 to prepare samples. The samples were mounted on a laser dilatometer (ULVAC Riko Co., Ltd., LIX-1 type laser dilatometer), and measurements were performed after a preheating treatment at 200℃. Measurements were conducted under a constant heating rate of 2℃ / min in helium atmosphere, within a temperature range of -65℃ to 200℃, while applying a load of approximately 17g along the thickness direction.

[0109] The formulas for calculating the minimum thermal expansion coefficient X and the thermal expansion coefficient Z are as follows.

[0110] T: Temperature (25℃)

[0111] L0: Sample length at 25℃

[0112] L: Expansion from the reference temperature

[0113] L / L0: Linear expansion ratio from the reference temperature to each temperature.

[0114] Coefficient of thermal expansion = {(ΔL / L0)T1 - (ΔL / L0)T2} / (T1 - T2)

[0115] <Damage to the conductive part>

[0116] Through-holes are formed in the porous resin film 1 of the metal laminate by drilling. The through-holes are circular in plan view and have a diameter of 300 μm. Subsequently, a conductive part 5 made of copper is formed on the inner circumferential surface of the through-holes by electroless copper plating and electrolytic copper plating to prepare the sample.

[0117] The thickness of the conductive part 5 is 10 μm.

[0118] The resistance value of the sample was measured during a temperature cycling test (a thermal cycling test between -65°C and 150°C) to detect cracks in the conductive part 5. The damage to the conductive part 5 was evaluated according to the following criteria.

[0119] <Benchmark>

[0120] ○: No cracks are generated in the conductive part 5 until 2000 cycles.

[0121] △: Cracks appear in the conductive part 5 after more than 1000 cycles but less than 2000 cycles.

[0122] ×: Cracks will appear in the conductor 5 after 1000 cycles.

[0123] [Table 1]

[0124] Table 1

[0125]

[0126] It should be noted that the above-described invention is provided as an example of the implementation of this invention, but these are merely examples and are not intended to be limiting. Modifications of this invention that will be obvious to those skilled in the art are included in the foregoing claims.

Claims

1. A porous resin film for use in metal layer lamination, wherein the film is used for laminating metal layers. The porous resin film used in the metal layer laminate comprises polyimide resin. The precursor of the polyimide resin is the reaction product of a diamine component and an acid dianhydride component. The diamine component comprises a diamine containing multiple aromatic rings and ester bonds disposed between them. The porous resin film used in the metal layer laminate has: a minimum coefficient of thermal expansion X in the plane direction orthogonal to the thickness direction, and a coefficient of thermal expansion Z in the thickness direction. The ratio of the coefficient of thermal expansion Z in the thickness direction to the minimum coefficient of thermal expansion X, i.e., Z / X, is less than 3.

5.

2. A metal laminate, comprising: A porous resin film for a metal layer laminate of claim 1 having a through hole extending through the thickness direction; and, A metal layer is disposed on one side, the other side, and the inner peripheral surface of the through hole in the thickness direction of the porous resin film of the metal layer laminate.

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