JP7325250B2 - Wiring circuit board and method for manufacturing wiring circuit board - Google Patents

Description

The present invention relates to a wired circuit board and a method for manufacturing the wired circuit board.

Conventionally, a wired circuit board on which electronic components such as an image sensor are mounted is known.

For example, an insulating base layer having an image pickup device opening, a conductive pattern having an image pickup device connection terminal, and an insulating cover layer are provided in this order, and the image pickup device connection terminal is exposed from the image pickup device opening. An imaging device mounting substrate has been proposed that is arranged so as to be flush with the surface opposite to the insulating layer (see, for example, Patent Document 1).

In such an image pickup device mounting substrate, the image pickup device is mounted by connecting terminals of the image pickup device and image pickup device connection terminals with solder bumps on the surface of the insulating base layer opposite to the cover insulating layer.

In order to manufacture such an imaging device mounting board, first, a photosensitive insulating material varnish is coated on a metal support and dried to form a base film, which is then exposed to a predetermined pattern and developed. , if necessary, is heat-cured to form a base insulating layer.

As a material for such a base insulating layer, for example, a polyimide precursor composition containing a polyimide precursor, an imide acrylate compound as a development accelerator, and a pyridine-based photosensitive agent has been proposed (see, for example, Patent Documents 2).

JP 2018-190787 A JP 2013-100441 A

However, in the image pickup device mounting board as described in Patent Document 1, from the viewpoint of improving the connection strength between the terminals of the image pickup device and the image pickup device connection terminals, there is a case where an underfill layer is provided between the mounting surface and the image pickup device. There is

However, when the base insulating layer is formed from the polyimide precursor composition described in Patent Document 2, under wet heat conditions, the adhesion of the underfill layer to the base insulating layer decreases, and the underfill layer becomes the base insulating layer. It may delaminate from the layer.

Further, the imaging device mounted on the imaging device mounting substrate may be removed and reworked for replacement or reuse. In this case, it is desired to peel off the underfill layer from the base insulating layer. At this time, if the adhesion between the insulating base layer and the underfill layer is excessively high, it becomes difficult to peel off the underfill layer from the insulating base layer, and as a result, there is a problem that the reworkability of the imaging device cannot be ensured.

INDUSTRIAL APPLICABILITY The present invention provides a wired circuit board capable of ensuring reworkability of electronic components while suppressing deterioration in adhesion of the second insulating layer to the first insulating layer under moist heat conditions, and manufacturing of the wired circuit board with good production efficiency. provide a way.

The present invention [1] comprises a first insulating layer containing polyimide, a development accelerator, and a photosensitive agent, and a terminal arranged on one surface in the thickness direction of the first insulating layer, The printed circuit board includes a printed circuit board in which the sum of the content of the development accelerator and the content of the photosensitive agent in one insulating layer is 5 ppm or more and 50 ppm or less.

According to such a configuration, since the sum of the content of the development accelerator and the content of the photosensitive agent in the first insulating layer is equal to or higher than the above lower limit, the electronic component is provided on one side in the thickness direction of the first insulating layer. Even if the wiring circuit board is placed under moist heat conditions after mounting and providing the second insulating layer between the first insulating layer and the electronic component, the adhesion of the second insulating layer to the first insulating layer decreases. can be suppressed.

Further, when the electronic component mounted on the printed circuit board is removed from the printed circuit board and reworked, the sum of the content of the development accelerator and the content of the photosensitive agent in the first insulating layer is equal to or less than the above upper limit. The adhesion of the second insulating layer to the first insulating layer can be adjusted so that the second insulating layer can be peeled off from the first insulating layer, and the reworkability of the electronic component can be ensured.

The present invention [2] includes the printed circuit board according to [1] above, wherein the development accelerator contains an imide acrylate compound and/or a polyethylene glycol compound.

According to such a configuration, since the development accelerator contains the imide acrylate compound and/or the polyethylene glycol compound, the sum of the content of the development accelerator and the content of the photosensitive agent in the first insulating layer is adjusted to the above range. While possible, the photosensitivity of the varnish containing the polyimide precursor, development accelerator, and photosensitizer can be ensured.

The present invention [3] comprises the steps of: preparing a metal support layer; forming a first insulating layer containing polyimide, a photosensitive agent, and a development accelerator on the metal support layer; forming a terminal on one side of the insulating layer in the thickness direction, and forming the first insulating layer comprises forming a polyimide precursor, a photosensitive agent, and a development accelerator on the metal support layer. , exposing and developing the varnish, and heating the developed varnish to 300° C. or higher and 400° C. or lower for 100 minutes or longer. including the manufacturing method of

According to such a method, the varnish after development is heated to 300° C. or more and 400° C. or less for 100 minutes or more, so that the total of the content of the photosensitive agent and the content of the development accelerator in the first insulating layer is 5 ppm. It can be adjusted to 50 ppm or less. As a result, the wiring circuit board described above can be efficiently manufactured by a simple method.

According to the wired circuit board of the present invention, the reworkability of the electronic component can be ensured while suppressing the deterioration of the adhesion of the second insulating layer to the first insulating layer under moist heat conditions.

According to the method for manufacturing a wired circuit board of the present invention, the above-described wired circuit board can be efficiently manufactured.

FIG. 1 shows a plan view of an imaging element mounting board, which is one embodiment of the wired circuit board of the present invention. FIG. 2 shows a cross-sectional view of the imaging element mounting board shown in FIG. 1 taken along the line AA. 3A to 3D show manufacturing process diagrams of the imaging element mounting board shown in FIG. 2, FIG. 3A is a metal support preparation step and base insulating layer formation step, FIG. , the insulating cover layer forming step, and FIG. 3D shows the metal support removing step. 4E and 4F show process diagrams for mounting the imaging device on the imaging device mounting substrate subsequent to FIG. 3D, FIG. 4E showing the device connection step, and FIG. 4F showing the underfill forming step. FIG. 5 shows an imaging device provided with the imaging element mounting board shown in FIG.

1. Imaging Device Mounting Board An imaging device mounting board 1 (hereinafter referred to as mounting board 1) as an embodiment of the wired circuit board of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the mounting board 1 is a flexible printed circuit board (FPC) for mounting an imaging element 21 (see FIG. 4F, which will be described later) as an example of an electronic component, and is still equipped with the imaging element 21. not The mounting substrate 1 has a flat plate shape (sheet shape) that is substantially rectangular (rectangular shape) in plan view.

The mounting board 1 includes a housing placement portion 2 and an external component connection portion 3 .

The housing placement portion 2 is a portion where a housing 22 (described later, see FIG. 5) and an imaging device 21 are placed. Specifically, the housing placement portion 2 is a portion that overlaps with the housing 22 when projected in the thickness direction of the mounting board 1 when the housing 22 is placed on the mounting board 1 . A plurality of first terminals 10 (described later) as an example of terminals are arranged substantially in the center of the housing arrangement portion 2 .

The external component connection portion 3 is a region other than the housing arrangement portion 2 and is a portion for connecting with an external component. The external component connection portion 3 is arranged continuously with the housing arrangement portion 2 in the longitudinal direction of the mounting substrate 1 . A plurality of second terminals 11 (described later) are arranged in the external component connection portion 3 .

As shown in FIG. 2 , the mounting board 1 includes an insulating base layer 4 as an example of a first insulating layer, a conductive pattern 5 , and an insulating cover layer 6 arranged in this order in the thickness direction of the insulating base layer 4 . In addition, below, the thickness direction of the base insulating layer 4 is simply described as a thickness direction. In FIG. 2 , the upper side of the page is one side of the insulating base layer 4 in the thickness direction, and the lower side of the page is the other side of the insulating base layer 4 in the thickness direction.

As shown in FIG. 1, the insulating base layer 4 forms the outer shape of the mounting substrate 1 and has a substantially rectangular shape in plan view. The insulating base layer 4 is not supported by a metal support 19 (see FIGS. 3A to 3C), which will be described later, and the mounting substrate 1 does not include the metal support 19 (metal support layer).

The insulating base layer 4 has a plurality of first openings 7 and a plurality of second openings 8 .

The plurality of first openings 7 expose first terminals 10 (described later) from one side in the thickness direction. The plurality of first openings 7 are aligned and spaced from each other in the central portion of the housing arrangement portion 2 so as to form a rectangular frame shape. The first opening 7 penetrates the insulating base layer 4 in the thickness direction and has a substantially circular shape in plan view. The first opening 7 has a tapered shape in which the cross-sectional area of the opening decreases toward one side in the thickness direction (see FIG. 2).

The plurality of second openings 8 expose second terminals 11 (described later) from one side in the thickness direction. The plurality of second openings 8 are aligned and spaced apart from each other in the width direction of the mounting substrate 1 in the external component connection portion 3 . The second opening 8 penetrates the insulating base layer 4 in the thickness direction and has a substantially rectangular shape (rectangular shape) in plan view.

In addition, as shown in FIG. 2, the insulating base layer 4 has one surface 4A and the other surface 4B in the thickness direction.

One surface 4A of the insulating base layer is located on one side in the thickness direction. One surface 4A of the base insulating layer has a flat (smooth) shape and is entirely exposed. The other surface 4B of the insulating base layer is located on the other side in the thickness direction and located on the opposite side of the one surface 4A in the thickness direction. The other surface 4B of the insulating base layer is covered with an insulating cover layer 6. As shown in FIG.

Such a base insulating layer 4 contains polyimide, a development accelerator, and a photosensitive agent.

Polyimide is, for example, a polyimide described in JP-A-2018-190787, and includes a reaction product (cured product) of an acid dianhydride component and a diamine component. More specifically, polyimides are prepared by imidating a polyamic acid that is the reaction product of a dianhydride component and a diamine component.

As the acid dianhydride component, for example, an aromatic acid dianhydride (e.g., 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA)) described in JP-A-2018-190787, etc. biphenyltetracarboxylic acid dianhydrides, etc.), and aliphatic acid dianhydrides. An acid dianhydride component can be used individually or in combination of 2 or more types.

The dianhydride component preferably comprises an aromatic dianhydride, more preferably 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA). Also, the acid dianhydride component preferably comprises an aromatic acid dianhydride (3,3',4,4'-biphenyltetracarboxylic acid dianhydride).

Examples of diamine components include aromatic diamines and aliphatic diamines described in JP-A-2018-190787. An acid dianhydride component can be used individually or in combination of 2 or more types.

The diamine component preferably comprises, more preferably consists of, an aromatic diamine.

Examples of aromatic diamines include phenylenediamines such as p-phenylenediamine (PPD).

Aromatic diamines also have two or more aromatic rings bonded by a single bond, and two or more amino groups each bonded directly or as part of a substituent on a separate aromatic ring. Also included are aromatic diamines. Such aromatic diamines are represented, for example, by general formula (1) below.

(In the general formula (1), a is a natural number of 0 or 1 or more, R ¹ is a hydrogen atom or a substituent. The amino group is attached to the bond between the benzene rings at the meta or para position. .)
As the substituent represented by R ¹ in the general formula (1), for example, an alkyl group having 3 or less carbon atoms such as a methyl group, such as a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, etc. 3 or less haloalkyl groups (preferably fluoroalkyl groups), such as halogen atoms such as chloro and fluoro.

In general formula (1) above, R ¹ preferably represents a substituent, more preferably a haloalkyl group, particularly preferably a fluoroalkyl group, particularly preferably a trifluoromethyl group.

Specific examples of the aromatic diamine represented by the general formula (1) include 2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl (also known as 2,2′-bis(trifluoromethyl)- 4,4'-diaminobiphenyl, TFMB) and the like.

Such an aromatic diamine preferably includes a combination of phenylenediamine and an aromatic diamine represented by general formula (1) above, more preferably phenylenediamine and R ¹ in general formula (1) above. is a fluoroalkyl group (trifluoromethyl group).

In such a diamine component, the content of the aromatic diamine represented by the general formula (1) is, for example, 15 mol% or more, preferably 20 mol% or more, for example 80 mol% or less, preferably 50 mol% or less. be.

Further, the acid dianhydride component contains 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), and the diamine component contains phenylenediamine (PPD) and 2,2′-ditrifluoromethyl When containing -4,4'-diaminobiphenyl (TFMB), the polyimide contains a structural unit A represented by the following general formula (2) and a structural unit B represented by the following general formula (3).

In such a polyimide, the molar ratio of the structural unit A represented by the general formula (1) to the structural unit B represented by the general formula (2) (structural unit A/structural unit B) is, for example, 15. /85 to 80/20, preferably 20/80 to 50/50.

Development accelerators include, for example, imidoacrylate compounds and/or polyethylene glycol compounds.

Imidoacrylate compounds include, for example, imidoacrylate compounds described in JP-A-2013-100441.

Specifically, the imide acrylate compound is represented by the following general formula (4).

(In general formula (4), R ² represents a hydrogen atom or a methyl group. R ³ represents a divalent hydrocarbon group having 2 or more carbon atoms.)
In general formula (4) above, R ² preferably represents a hydrogen atom.

In general formula (4) above, R ³ preferably represents an alkylene group having 2 or more carbon atoms, more preferably an ethylene group.

Specific examples of the imide acrylate compound represented by the general formula (4) include n-acryloyloxyethylhexahydrophthalimide.

Polyethylene glycol compounds include, for example, polyethylene glycol compounds described in JP-A-2013-100441.

Specifically, the polyethylene glycol compound is represented by the following general formula (5).

(In general formula (5), R ⁴ represents a hydroxyl group or a methoxy group. R ⁵ represents a hydrogen atom or a methyl group. b represents a natural number of 4 to 23.)
In the above general formula (5), the combination of R ⁴ and R ⁵ includes a hydroxyl group (R ⁴ ) and a hydrogen atom (R ⁵ ), a hydroxyl group (R ⁴ ) and a methyl group (R ⁵ ), a methoxy group (R ⁴ ) and methyl groups (R ⁵ ), preferably hydroxyl groups (R ⁴ ) and hydrogen atoms (R ⁵ ).

The number average molecular weight (Mn) of such a polyethylene glycol compound represented by the general formula (5) is, for example, 200 or more, for example, 1000 or less, preferably 400 or less. The number average molecular weight can be measured by gel permeation chromatography (GPC) and calculated in terms of polyethylene oxide.

Such a development accelerator preferably comprises an imide acrylate compound represented by the general formula (4).

Photosensitizers include, for example, pyridine-based photosensitizers described in JP-A-2013-100441.

Specifically, the pyridine-based photosensitizer is represented by the following general formula (6).

(In general formula (6), R ⁶ to R ¹⁰ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ⁶ to R ¹⁰ may be the same or different.)
In general formula (6) above, each of R ⁶ and R ⁷ preferably represents a hydrogen atom or a methyl group, and more preferably represents a hydrogen atom.

In general formula (6) above, R ⁸ preferably represents an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, most preferably an ethyl group.

In the general formula (6), each of R ⁹ and R ¹⁰ preferably represents an alkyl group having 1 to 4 carbon atoms, more preferably represents a methyl group or an ethyl group, and most preferably represents a methyl group. show.

Specific examples of the pyridine-based photosensitizer represented by the above general formula (6) include 1-ethyl-3,5-dimethoxycarbonyl-4-(2-nitrophenyl)-1,4-dihydropyridine and the like. mentioned.

In addition, the sum (mass ratio) of the content ratio of the photosensitive agent and the content ratio of the development accelerator in the base insulating layer 4 is 5 ppm or more and 50 ppm or less. The sum of the content ratio of the photosensitive agent and the content ratio of the development accelerator can be measured by TOF-SIMS (the same applies hereinafter).

If the sum of the content of the photosensitive agent and the content of the development accelerator is equal to or greater than the above lower limit, the adhesion of the underfill layer 18 (described later) to the base insulating layer 4 is determined by the underfill layer 18 (described later). It can be adjusted so that it can be peeled off from the layer 4, and the reworkability of the imaging device 21 can be ensured. Further, when the sum of the content of the photosensitive agent and the content of the development accelerator is equal to or less than the above upper limit, it is possible to suppress deterioration in the adhesion of the underfill layer 18 (described later) to the insulating base layer 4 under moist heat conditions.

Moreover, the insulating base layer 4 can further contain known additives. Examples of known additives include sensitizers, polymerization terminators, chain transfer agents, leveling agents, plasticizers, surfactants, antifoaming agents and the like. The content of known additives in the insulating base layer 4 is, for example, 15% by mass or less, preferably 10% by mass or less.

The thickness of the insulating base layer 4 is, for example, 1 μm or more, preferably 3 μm or more, for example 30 μm or less, preferably 12 μm or less, more preferably 8 μm or less.

The conductor pattern 5 includes multiple first terminals 10 , multiple second terminals 11 (see FIG. 1 ), and multiple wirings 9 .

The plurality of first terminals 10 are aligned and spaced apart from each other so as to form a rectangular frame shape in the central portion of the housing arrangement portion 2 (see FIG. 1). The plurality of first terminals 10 are provided so as to correspond to the plurality of terminals 25 (see FIG. 4E) of the image sensor 21 to be mounted. Also, the plurality of first terminals 10 are provided corresponding to the plurality of first openings 7 . The first terminal 10 has a substantially circular shape in plan view. The first terminal 10 is filled in the first opening 7 and exposed from the insulating base layer 4 when viewed from one side in the thickness direction. One surface 10A of the first terminal 10 in the thickness direction has a flat (smooth) shape. One surface 10A of first terminal 10 in the thickness direction is substantially flush with one surface 4A of base insulating layer 4 . Thereby, the first terminal 10 is arranged on the one surface 4A of the insulating base layer 4 .

As shown in FIG. 1 , the plurality of second terminals 11 are aligned and spaced from each other in the external component connection portion 3 . The plurality of second terminals 11 are provided so as to correspond to the plurality of terminals (not shown) of the external component. Also, the plurality of second terminals 11 are provided corresponding to the plurality of second openings 8 . The second terminal 11 has a substantially rectangular shape (rectangular shape) in plan view. The second terminal 11 is filled in the second opening 8 and exposed from the insulating base layer 4 when viewed from one side in the thickness direction. One surface of the second terminal 11 in the thickness direction is substantially flush with one surface 4A of the insulating base layer 4 . Thereby, the second terminal 11 is arranged on the one surface 4A of the insulating base layer 4 .

As shown in FIG. 2 , the plurality of wirings 9 are arranged on the other side of the insulating base layer 4 in the thickness direction, specifically, on the other side 4B of the insulating base layer 4 .

A plurality of wirings 9 electrically connect a plurality of first terminals 10 and a plurality of second terminals 11 . Specifically, one end of each wiring 9 is recessed from the other surface 4</b>B into the first opening 7 and connected to each first terminal 10 . The other end of each wiring 9 drops into the second opening 8 from the other surface 4B and is continuous with each second terminal 11 .

Examples of the material of the conductor pattern 5 include metal materials such as copper, silver, gold, nickel, alloys containing them, and solder, and copper is preferred.

The thickness of the conductor pattern 5 is, for example, 1 μm or more, preferably 2 μm or more, and for example, 15 μm or less, preferably 10 μm or less.

The insulating cover layer 6 is arranged on the other side in the thickness direction with respect to the insulating base layer 4 so as to cover the conductor pattern 5 , specifically, on the other side 4B of the insulating base layer 4 . The outer shape of the insulating cover layer 6 is formed to be the same as the outer shape of the insulating base layer 4 .

Examples of materials for the insulating cover layer 6 include insulating materials. Examples of insulating materials include synthetic resins such as polyimide, polyamideimide, acrylic, polyethernitrile, polyethersulfone, polyethylene terephthalate, polyethylene naphthalate, and polyvinyl chloride. The insulating material preferably includes polyimide as in the base insulating layer 4 .

The thickness of the insulating cover layer 6 is, for example, 1 μm or more, preferably 2 μm or more, and for example, 30 μm or less, preferably 10 μm or less, more preferably 5 μm or less.

The thickness of the mounting substrate 1 (total thickness of the insulating base layer 4, the conductor pattern 5, and the insulating cover layer 6) is, for example, 3 μm or more, for example, 50 μm or less, preferably 30 μm or less.

2. Method for Manufacturing Imaging Device Mounting Board Next, a method for manufacturing the mounting board 1 will be described with reference to FIGS. 3A to 3D. The method for manufacturing the mounting substrate 1 includes, for example, a metal support preparation step, an insulating base layer forming step, a conductor pattern forming step, and an insulating cover layer forming step in this order.

As shown in FIG. 3A, in the metal support preparation step, a metal support 19 as an example of the metal support layer is prepared.

The metal support 19 has a flat plate shape that is substantially rectangular (rectangular) in plan view. The upper surface of the metal support 19 has a flat (smooth) shape.

Examples of the material of the metal support 19 include metal materials such as stainless steel, 42-alloy, and aluminum, preferably stainless steel.

The thickness of the metal support 19 is, for example, 5 μm or more, preferably 10 μm or more, and for example, 50 μm or less, preferably 30 μm or less.

Subsequently, in the insulating base layer forming step, the insulating base layer 4 containing the above-described polyimide, the above-described development accelerator, and the above-described photosensitive agent is formed on the upper surface of the metal support 19 . The thickness direction of the insulating base layer 4 shown in FIGS. 3A to 3D is opposite to the thickness direction of the insulating base layer 4 shown in FIG. on the side. That is, one surface 4A of the insulating base layer 4 is in contact with the metal support 19, and the other surface 4B of the insulating base layer 4 is located on the side opposite to the metal support 19 with respect to the one surface 4A.

Specifically, the insulating base layer forming step includes a step of applying varnish as a material of the insulating base layer 4 onto the metal support 19, a step of exposing and developing the applied varnish, and a step of heating the developed varnish. and

The varnish contains polyamic acid as an example of a polyimide precursor, the development accelerator described above, and the photosensitive agent described above.

A polyamic acid is the reaction product of the dianhydride component described above and the diamine component described above. For example, the above-described acid dianhydride component and the above-described diamine component are reacted in the presence of an organic solvent under conditions of, for example, 15° C. to 40° C. and 0.2 hours to 72 hours. Polyamic acid is thereby prepared.

The organic solvent is capable of dissolving the acid dianhydride component and the diamine component. Examples of organic solvents include polar aprotons such as N-methylpyrrolidone, dimethylformamide, dimethylsulfoxide, and acetonitrile. The organic solvents can be used singly or in combination of two or more.

Among the organic solvents, polar aprotons are preferred, and N-methylpyrrolidone is more preferred. In addition, the content rate of an organic solvent can be changed suitably.

Moreover, the content rate of the development accelerator in a varnish is 30 to 100 mass parts with respect to 100 mass parts of polyamic acids, for example.

Moreover, the content rate of the photosensitive agent in a varnish is 10 to 55 mass parts with respect to 100 mass parts of polyamic acids, for example.

Then, the varnish is applied to the entire upper surface of the metal support 19 and dried. This volatilizes the organic solvent and forms a base film.

The base film is then exposed through a photomask having a pattern corresponding to the openings (first opening 7 and second opening 8). After that, the base film is developed.

The developed base film is then heated to cure.

The heating temperature is 300° C. or higher, preferably 330° C. or higher and 400° C. or lower, preferably 380° C. or lower.

The heating time is 100 minutes or longer, preferably 110 minutes or longer, more preferably 120 minutes or longer, for example, 500 minutes or shorter, preferably 400 minutes or shorter, more preferably 350 minutes or shorter.

When the heating temperature is at least the above lower limit and the heating time is at least the above lower limit, polyamic acid is imidized to form polyimide, and most of the development accelerator and photosensitive agent are removed. Therefore, the sum of the content of the development accelerator and the content of the photosensitive agent in the insulating base layer 4 can be adjusted to the upper limit or less. Further, when the heating temperature is equal to or lower than the upper limit, the sum of the content of the development accelerator and the content of the photosensitive agent in the insulating base layer 4 can be ensured to be equal to or higher than the lower limit.

A base insulating layer 4 containing polyimide is thereby formed on the metal support 19 .

Subsequently, as shown in FIG. 3B, in the conductor pattern forming step, the conductor pattern 5 is formed in the above-described pattern on the upper surface (the other surface 4B) of the base insulating layer 4, the first opening 7 and the second opening 8. It is formed on the upper surface of the metal support 19 exposed from, for example, by an additive method or the like.

Thereby, the plurality of first terminals 10, the plurality of second terminals 11, and the plurality of wirings 9 are collectively formed. The first terminal 10 is arranged in the first opening 7 and contacts the upper surface of the metal support 19 . The second terminal 11 is arranged in the second opening 8 and comes into contact with the upper surface of the metal support 19 (not shown). As a result, the first terminal 10 and the second terminal 11 are arranged on the one surface 4A of the insulating base layer 4 . Also, the wiring 9 is arranged on the other surface 4B of the insulating base layer 4 .

Subsequently, as shown in FIG. 3C, in the insulating cover layer forming step, an insulating cover layer 6 is formed on the upper surface (the other surface 4B) of the insulating base layer 4 so as to cover the conductor pattern 5 . The insulating cover layer forming step can be performed in the same manner as the insulating base layer forming step.

Subsequently, as shown in FIG. 3D, in the metal support removing step, the metal support 19 is removed.

As a method for removing the metal support 19, for example, a method of peeling the metal support 19 from the lower surface (one surface 4A) of the base insulating layer 4, for example, etching the metal support 19 (for example, dry etching, wet etching, etc.). and methods to do so.

Among the methods for removing the metal support 19, etching, more preferably wet etching, is preferred.

When wet-etching the metal support 19, an etchant such as a ferric chloride solution is used. Then, for example, the metal support 19 is removed by spraying an etchant from one side in the thickness direction of the metal support 19 .

Then, one surface 4A of base insulating layer 4, one surface 10A of first terminal 10, and one surface (not shown) of second terminal 11 are exposed.

As described above, the mounting substrate 1 including the insulating base layer 4, the conductive pattern 5, and the insulating cover layer 6 is manufactured.

3. Method of Mounting Imaging Device on Mounting Substrate For example, the mounting substrate 1 having the imaging device mounted thereon is provided in an imaging device such as a camera module.

Next, a method of mounting the imaging device 21 on the mounting substrate 1 will be described with reference to FIGS. 4E and 4F.

A method of mounting the imaging element 21 on the mounting substrate 1 includes an element connecting step and an underfill forming step.

As shown in FIG. 4E, in the device connecting step, first, the imaging device 21 is prepared.

The imaging element 21 is a semiconductor element that converts light into an electrical signal, and includes, for example, a solid-state imaging element such as a CMOS sensor and a CCD sensor. The imaging element 21 is formed in a substantially rectangular flat plate shape in plan view, and includes silicon such as a Si substrate, and photodiodes (photoelectric conversion elements) and color filters arranged thereon, although not shown. The imaging device 21 has a plurality of terminals 25 . The multiple terminals 25 correspond to the multiple first terminals 10 .

Then, a bonding material 26 such as a solder bump is placed on the first terminals 10 of the mounting board 1, and the first terminals 10 of the mounting board 1 and the terminals 25 of the imaging device 21 are electrically connected via the bonding material 26. Connecting.

As a result, the imaging element 21 is arranged in the central portion of the housing arrangement portion 2 of the mounting board 1 and flip-chip mounted on the mounting board 1 . At this time, the imaging element 21 is positioned on one side in the thickness direction with a gap from the one surface 4A of the insulating base layer 4 .

Next, as shown in FIG. 4F , in the underfill forming step, an underfill layer 18 as an example of a second insulating layer is formed between the imaging device 21 and the base insulating layer 4 .

Specifically, a liquid resin composition is injected between the imaging element 21 and the one surface 4A of the insulating base layer 4, and then cured by heating.

Examples of the material of the underfill layer 18 include resin materials such as epoxy resin, polyurethane resin, silicone resin, and polyester resin, preferably epoxy resin. Materials for the underfill layer 18 can be used alone or in combination of two or more.

The heating temperature is appropriately changed according to the material of the underfill layer 18, but is, for example, 100° C. or higher, preferably 120° C. or higher, for example, 150° C. or lower, preferably 130° C. or lower.

The heating time is appropriately changed according to the material of the underfill layer 18, but is, for example, 10 minutes or longer, preferably 30 minutes or longer, and for example, 120 minutes or shorter, preferably 60 minutes or shorter.

As a result, the underfill layer 18 is formed between the imaging element 21 and the one surface 4A of the insulating base layer 4. As shown in FIG. In other words, the underfill layer 18 is arranged on one side 4A of the insulating base layer 4 . In other words, the mounting board 1 on which the imaging element 21 is mounted has the underfill layer 18 .

By the above, the mounting of the imaging element 21 on the mounting substrate 1 is completed. Note that the mounting substrate 1 , the imaging element 21 and the underfill layer 18 constitute an imaging unit 27 .

Moreover, the mounting substrate 1 is not an imaging device to be described later, but a part of the imaging device, that is, a component for manufacturing the imaging device, and is an industrially applicable device. The mounting substrate 1 may be distributed as an independent component that does not include an image pickup device, or as an image pickup unit on which an image pickup device is mounted.

4. Imaging Device Next, the imaging device 20 including the imaging unit 27 will be described with reference to FIG.

The imaging device 20 includes an imaging unit 27 , a housing 22 , an optical lens 23 and a filter 24 .

The imaging unit 27 includes the mounting board 1 , the imaging element 21 and the underfill layer 18 .

The housing 22 is arranged on the housing arrangement portion 2 of the mounting substrate 1 so as to surround the imaging element 21 with a gap therebetween. The housing 22 has a substantially rectangular tubular shape in a plan view.

The optical lens 23 is arranged on the opposite side of the mounting board 1 from the imaging element 21 in the thickness direction with a gap therebetween. The optical lens 23 is formed in a substantially circular shape in a plan view, and is fixed to the housing 22 so that light from the outside reaches the imaging device 21 .

The filter 24 is arranged between the imaging element 21 and the optical lens 23 in the thickness direction with a gap therebetween and fixed to the housing 22 .

As shown in FIG. 4F, the present inventors found that when the imaging device 20 (imaging unit 27) is placed under moist heat conditions (for example, 100° C. or higher and relative humidity of 80% or higher), the underside of the base insulating layer 4 We have found that the adhesion of the fill layer 18 is reduced.

Therefore, the present inventors have made various studies on the findings, and found that the decrease in adhesion of the underfill layer 18 under wet heat conditions is the sum of the content of the development accelerator and the content of the photosensitive agent in the base insulating layer 4. and completed the present invention.

As shown in FIG. 4F, in the mounting board 1, the sum of the content of the development accelerator and the content of the photosensitive agent in the insulating base layer 4 is equal to or higher than the above lower limit. Therefore, even when the imaging device 20 (imaging unit 27 ) is placed under moist heat conditions, it is possible to suppress deterioration in adhesion of the underfill layer 18 to the insulating base layer 4 .

In addition, the sum of the content of the development accelerator and the content of the photosensitive agent in the base insulating layer 4 is equal to or less than the above upper limit. Therefore, when the imaging device 21 mounted on the mounting board 1 is removed from the mounting board 1 and reworked, the underfill layer 18 can be peeled off from the insulating base layer 4 . As a result, reworkability of the imaging device 21 can be ensured.

Development accelerators also include imidoacrylate compounds and/or polyethylene glycol compounds. Therefore, while the sum of the content of the development accelerator and the content of the photosensitive agent in the base insulating layer 4 can be adjusted within the above range, the photosensitivity of the varnish containing the polyimide precursor, the development accelerator, and the photosensitive agent can be ensured.

Further, in the method for manufacturing the mounting substrate 1, as shown in FIGS. 3A to 3D, a varnish containing a polyimide precursor, a development accelerator, and a photosensitive agent is applied onto the metal support 19, and then the varnish is applied. The (base film) is exposed and developed, and then the varnish (base film) is heated at the above heating temperature and for the above heating time to form the insulating base layer 4 .

Therefore, the sum of the content of the development accelerator and the content of the photosensitive agent in the insulating base layer 4 can be adjusted within the above range. As a result, it is possible to efficiently manufacture the above-described mounting substrate 1 using a simple method.

<Modification>
In the above-described embodiment, the imaging element mounting board 1 (mounting board 1) for mounting the imaging element 21 is described as the wired circuit board of the present invention, but the application of the wired circuit board is not limited to this. . For example, it is suitably used for FPCs used in smartphones, personal computers, game machines, and the like.

Further, in the mounting board 1, the layers adjacent to each other in the thickness direction are adhesive-less FPCs that are bonded without an adhesive, but the present invention is not limited to this. Adhesive layers can also be provided between layers that are adjacent to each other in the thickness direction. On the other hand, from the viewpoint of thinning, it is preferable that the mounting board 1 be an adhesive-less FPC as in the above embodiment.

Moreover, as shown in FIG. 2, the mounting board 1 includes an insulating base layer 4, a conductor pattern 5, and an insulating cover layer 6, but the configuration of the mounting board 1 is not limited to this. For example, the mounting substrate 1 may further include a shield layer arranged on one side in the thickness direction of the insulating cover layer 6 to block electromagnetic waves from the outside, and a second insulating cover layer covering the shield layer.

Further, in the imaging device 20, as shown in FIG. 5, the imaging device 21 is flip-chip mounted on the mounting board 1, but it can also be mounted on the mounting board 1 by wire bonding.

Even in such a modified example, the same effects as those of the above-described embodiment can be obtained. Moreover, the above-described embodiment and modifications can be appropriately combined.

EXAMPLES The present invention will be explained more specifically below by showing Reference Examples and Reference Comparative Examples. The present invention is not limited to Reference Examples and Reference Comparative Examples. In addition, specific numerical values such as the mixing ratio (content ratio), physical property values, and parameters used in the following description are the corresponding mixing ratios ( content ratio), physical properties, parameters, etc. can.

Production example 1
4.0 g (20 mmol) of 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFMB, aromatic diamine having a haloalkyl group as a substituent) and p-phenylenediamine (PPD, aromatic Diamine) (8.65 g (80 mmol)) was put into a 500 ml separable flask, dissolved in 200 g of dehydrated N-methyl-2-pyrrolidone (NMP), and the liquid temperature was brought to 50° C. in an oil bath under a nitrogen stream. The mixture was monitored with a thermocouple and stirred while heating. After confirming that they were completely dissolved, 29.4 g of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA, aromatic dianhydride) was added thereto over 30 minutes. 100 mmol) was mixed in a separable flask, stirred at 50° C. for 5 hours, and then cooled to room temperature to obtain a polyimide precursor solution.

Next, in the polyimide precursor solution, 74 parts by weight of n-acryloyloxyethylhexahydrophthalimide (development accelerator), 1-ethyl-3, 14 parts by mass of 5-dimethoxycarbonyl-4-(2-nitrophenyl)-1,4-dihydropyridine (photosensitizer) was added to prepare a varnish.

Reference Examples 1 and 2 and Reference Comparative Example 1
A metal support made of stainless steel is prepared, the varnish prepared in Production Example 1 is applied to the upper surface of the metal support, and then dried at 80 ° C. for 10 minutes to form a base film (polyimide precursor film). formed.

Subsequently, after exposure and development, the base film was cured at the heating temperature and heating time shown in Table 1 under a nitrogen atmosphere. Thus, a base insulating layer containing polyimide was formed.

Then, the metal support was removed by spraying an aqueous solution of ferric chloride (etchant) onto the metal support. This exposed one surface of the base insulating layer.

Thus, an insulating base layer was obtained.

In each insulating base layer, the sum of the content of the development accelerator and the content of the photosensitive agent was measured. Table 1 shows the results.

Further, it was confirmed by FT-IR that curing of all base insulating layers was completed.

Reference Comparative Example 2
Kapton 100H (manufactured by DuPont) was provided as the base insulating layer. Kapton 100H contained no development accelerators or photosensitizers.

<Initial Adhesion of Underfill Layer>
An underfill layer was formed on one side of the insulating base layer of each reference example and each reference comparative example, and the initial adhesive strength of the underfill layer to the base insulating layer was measured.

Specifically, a liquid epoxy resin composition was applied to one surface of the insulating base layer after the PCT test, and then dried at 125° C. for 10 minutes to form an underfill layer. The thickness of the underfill layer was about 40 μm.

Next, a double-sided tape (No. 5000ns, manufactured by Nitto Denko) was attached to the surface of the underfill layer opposite to the insulating base layer to prepare a laminate. The laminate includes a base insulating layer, an underfill layer, and a double-sided tape in order in the thickness direction.

Next, the laminate was cut into flat strips having a width of 5 mm, and the laminate was fixed to a sample table provided in the following apparatus with a double-sided tape. The sample stage had a cylindrical shape that was rotatably supported, and had an outer diameter of 20 cm. Also, the laminate was adhered to the peripheral surface of the sample table.

Then, the base insulating layer was peeled off from the underfill layer under the following conditions. Table 1 shows the results.

Apparatus; SVZ-50NB (manufactured by IMADA)
Pulling angle; 90° (that is, the pulling direction is the radial direction of the sample table)
Tensile speed; 10 mm/min <Adhesion decrease rate of underfill layer after wet heat>
Prior to the measurement of adhesion, a pressure cooker test (PCT test) was performed on the base insulating layer of each reference example and each reference comparative example. Specifically, each base insulating layer was placed under conditions of 120° C., 100% relative humidity, and 1.9 atm pressure for 100 hours.

Thereafter, in the same manner as described above, an underfill layer was formed on one side of the insulating base layer after the PCT test, and the adhesion of the underfill layer to the insulating base layer after the PCT test was measured. Then, the rate of decrease in adhesion of the underfill layer after the PCT test (adhesion after PCT test/initial adhesion) was calculated. Table 1 shows the results.

<Discussion>
As shown in Table 1, in Reference Example 1, in which the sum of the content of the development accelerator and the content of the photosensitive agent in the base insulating layer is 50 ppm or less, the content of the development accelerator in the base insulating layer and the photosensitivity Compared to Reference Comparative Example 1 in which the total content of the agent exceeds 50 ppm, the adhesion of the underfill layer to the base insulating layer after the PCT test (that is, after being placed under moist heat conditions) is reduced. significantly suppressed.

In Reference Example 1, the sum of the content of the development accelerator and the content of the photosensitive agent in the insulating base layer was 5 ppm or more, and the initial adhesion of the underfill layer to the insulating base layer was 200 gf/cm or less. adjusted. When the adhesive strength exceeds 200 gf/cm as in Reference Comparative Example 2, it is difficult to peel off the underfill layer from the base insulating layer when reworking the electronic component. In this regard, in Reference Example 1, the adhesion force is 100 gf/cm or less, and the reworkability of electronic parts can be ensured.

REFERENCE SIGNS LIST 1 mounting substrate 4 base insulating layer 4A one side 10 first terminal 18 underfill layer

Claims (3)

A first insulating layer containing polyimide, a development accelerator, and a photosensitive agent, the first insulating layer having one surface and the other surface in the thickness direction, and an opening penetrating the first insulating layer in the thickness direction a first insulating layer having a portion ;
A terminal filled in the opening , the one surface in the thickness direction being exposed to one side, and a wiring arranged on the other surface of the first insulating layer, the wiring continuing to the terminal. a conductor pattern having wiring ,
The printed circuit board, wherein the sum of the content of the development accelerator and the content of the photosensitive agent in the first insulating layer is 5 ppm or more and 50 ppm or less. 2. The printed circuit board according to claim 1, wherein the development accelerator contains an imide acrylate compound and/or a polyethylene glycol compound. providing a metal support layer;
A first insulating layer containing polyimide, a development accelerator, and a photosensitive agent on the metal support layer , the first insulating layer having one side and the other side in the thickness direction, forming a first insulating layer having an opening extending through the thickness direction ;
A terminal filled in the opening , the one surface in the thickness direction being exposed to one side, and a wiring arranged on the other surface of the first insulating layer, the wiring continuing to the terminal. and forming a conductor pattern having
The step of forming the first insulating layer includes:
applying a varnish containing a polyimide precursor, a development accelerator, and a photosensitive agent onto the metal support layer;
exposing and developing the varnish;
and heating the developed varnish to 300° C. or higher and 400° C. or lower for 100 minutes or longer.

Images