JP2012069629A - Method for manufacturing printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a printed wiring board in which the distance between projections is reduced to increase wettability of underfill resin with a solder resist layer and to reduce the manufacturing cost.SOLUTION: A method for manufacturing a printed wiring board includes: providing a plurality of salient 22 with a spacing therebetween on one surface 21a of a mask film 21 in a direction parallel to the one surface; forming a mask pattern 23 on the mask film; carrying out mold release treatment on the one surface of the mask film; placing solder resist agent 3A on a substrate 2; placing the mask film on the solder resist agent with the one surface facing the solder resist agent; exposing the solder resist agent to form a solder resist layer 3 on which a plurality of salient conforming to a plurality of the salient on the mask film are formed; and removing the mask film from the solder resist layer.

Description

  The present invention relates to a method for manufacturing a printed wiring board.

  2. Description of the Related Art Conventionally, as a mobile phone, PHS (Personal Handyphone System), PDA (Personal Data Assistance, Personal Digital Assistants), etc. have become smaller and thinner, a multi-pin semiconductor element mounted on a printed wiring board. And narrowing of the pitch are progressing. On the other hand, an underfill resin layer is provided on the solder resist layer formed on the semiconductor element in order to reinforce the mechanical strength in the electrical connection portion between the printed wiring board and the semiconductor element. As a result, the filling property of the underfill resin to the lower part of the semiconductor element and the adhesion between the solder resist layer and the underfill resin layer are becoming difficult, and the underfill resin is filled. Further improvement in wettability and adhesion is required.

In order to improve the wettability and adhesion of the underfill resin applied to the surface of the solder resist layer, it has been studied to form a concavo-convex structure (plural protrusions) in the solder resist layer.
Examples of the method for forming a concavo-convex shape in the solder resist layer include the following documents.

Patent Document 1 and Patent Document 2 disclose a method of forming a solder resist layer having a level difference, that is, a concavo-convex structure by forming the solder resist layer so as to be overlapped in two stages.
In the method for producing a printed wiring board described in Patent Document 3, the surface of the pressure-sensitive adhesive layer of the tape is roughened, and then the pressure-sensitive adhesive layer is attached to an unexposed solder resist. After exposing to a photomask to form a predetermined shape, the pressure-sensitive adhesive layer is removed, and a circuit pattern is formed by copper plating on the outer surface of the solder resist layer in which the uneven structure is formed by the roughened pressure-sensitive adhesive layer. To do.
Patent Document 4 discloses a method of obtaining a solder resist layer having a concavo-convex structure by forming a solder resist layer on a support that has been subjected to a roughening treatment in advance, and removing the support after the formation of the wiring substrate. Is disclosed.

JP 2009-152317 A JP 2008-181931 A JP 2008-117929 A JP 2009-105393 A

However, since the method described in Patent Document 1 and Patent Document 2 cannot form a concavo-convex structure finer than the dimensional accuracy in the direction parallel to the surface of the solder resist layer, the solder resist layer and the underfill resin layer There is a problem that sufficient adhesion cannot be obtained.
Further, in the method described in Patent Document 3, since the uneven structure is formed on the solder resist agent by the adhesive, the solder resist layer is attached to the adhesive when the adhesive is removed after exposure, and the uneven structure is stabilized. There is a fear that it cannot be obtained.
And in the method of patent document 4, the support body which has an uneven structure is removed by etching after wiring board formation. For this reason, there is a problem that the support cannot be used repeatedly and the manufacturing process becomes expensive.

  The present invention has been made in view of such problems, and the printed wiring board has a reduced pitch as a result of improving the wettability of the underfill resin with respect to the solder resist layer and reducing the manufacturing cost. It aims at providing the manufacturing method of.

In order to solve the above problems, the present invention proposes the following means.
In the method for manufacturing a printed wiring board of the present invention, a plurality of convex portions are provided on one surface of a mask film at intervals in a direction parallel to the one surface, and a mask pattern is formed on the mask film. The one side of the mask film is subjected to a mold release treatment, a solder resist agent is disposed on the substrate, the mask film is placed on the solder resist agent, and the one surface is on the solder resist agent side. Arranging and exposing the solder resist agent to form a solder resist layer formed with a plurality of protrusions corresponding to the plurality of convex portions of the mask film, and removing the mask film from the solder resist layer It is characterized by that.

According to the method for producing a printed wiring board of the present invention, the shape of a plurality of convex portions formed on the mask film is transferred to a liquid solder resist agent, and the solder resist agent is exposed to form a solder resist layer. A plurality of protrusions corresponding to the plurality of protrusions are formed on the solder resist layer. In general, the dimensional accuracy in the width direction of the protrusions that can be formed on the mask film can be made smaller than the dimensional accuracy in the direction parallel to the surface of the solder resist layer.
For this reason, the pitch of the protrusions formed on the solder resist layer becomes narrower than before, and when the underfill resin layer is provided on the protrusions of the solder resist layer, for example, the underfill resin wets with respect to the solder resist layer. Thus, the underfill resin layer can be reliably connected to the solder resist layer.

  In addition, since the mold release treatment is performed on one side of the mask film, the mask film can be easily removed from the solder resist layer, and the manufacturing cost of the printed wiring board can be reduced by repeatedly using the mask film. Can do.

It is a top view of the printed wiring board manufactured with the manufacturing method of the printed wiring board of embodiment of this invention. It is sectional drawing of the cutting line BB in FIG. It is front sectional drawing of the mask film used with the manufacturing method of the printed wiring board of embodiment of this invention. It is a figure which shows the state by which the soldering resist agent was apply | coated to one side of a board | substrate in the manufacturing method of the same printed wiring board. It is a figure which shows the state by which the mask film was arrange | positioned on the soldering resist agent in the manufacturing method of the same printed wiring board. It is a top view of the printed wiring board of the modification of embodiment of this invention. It is a top view of the printed wiring board of the modification of embodiment of this invention. It is a top view of the printed wiring board of the modification of embodiment of this invention.

Hereinafter, a printed wiring board manufactured by a method for manufacturing a printed wiring board according to an embodiment of the present invention (hereinafter referred to as “manufacturing method”) will be described with reference to FIGS. 1 to 8.
As shown in FIGS. 1 and 2, the printed wiring board 1 includes a substrate 2, a solder resist layer 3 disposed on one surface 2a of the substrate 2, a wiring pattern (not shown) formed of copper or the like. It has.

The substrate 2 is formed in a rectangular shape when viewed in the thickness direction using an insulating resin or the like. In the following description, for convenience of explanation, the X axis and the Y axis are set parallel to two adjacent sides when viewed in the thickness direction of the substrate 2. Each of these X axis and Y axis is parallel to one surface 2 a of the substrate 2. Furthermore, if the Z axis orthogonal to the X axis and the Y axis is defined, the Z axis direction is the thickness direction of the substrate 2.
On one surface 2 a of the substrate 2, a plurality of conductor lands 8 are arranged at intervals in the X-axis direction and the Y-axis direction. The conductor land 8 is electrically connected to the aforementioned wiring pattern.

The solder resist layer 3 is disposed on a portion of the one surface 2a of the substrate 2 where the conductor land 8 is not provided. That is, the solder resist layer 3 is formed with a plurality of through holes 3 a that penetrate in the Z-axis direction and whose inner diameter is set slightly larger than the outer diameter of the conductor land 8 at positions corresponding to the conductor lands 8. .
The solder resist layer 3 is disposed away from the conductor land 8 by forming the through hole 3a.

A plurality of projecting portions 9 projecting at intervals in the X-axis direction are formed on a surface 3b located on the opposite side of the solder resist layer 3 from the substrate 2. In the present embodiment, the projecting portion 9 is formed to extend in the Y-axis direction, and is formed in a rectangular shape in which the cross sections by planes parallel to the Y-axis are equal. Furthermore, the interval between the adjacent protrusions 9 is set to be equal.
An uneven structure is formed in the solder resist layer 3 by the surface 3 b and the plurality of protrusions 9.

As shown in FIG. 2, the printed wiring board 1 of the present embodiment includes an underfill resin layer 4 disposed on the solder resist layer 3 and a BGA (Ball Grid Array) connected on the underfill resin layer 4. ) And LGA (Land Grid Array) and other grid array type semiconductor elements (semiconductor elements) 5 can constitute the semiconductor device 10.
As the material for the underfill resin layer 4, a material having a contact angle of less than 90 ° when coated on the solder resist layer 3 having a flat surface is used. When the material of the solder resist layer 3 is an epoxy material, examples of the underfill resin that satisfies this condition include an epoxy material and a urethane material.
The grid array type semiconductor element 5 has a plurality of contacts (not shown) on the surface connected to the underfill resin layer 4.
When viewed in parallel to the Z-axis direction, the solder resist layer 3 and the protruding portion 9 are arranged in ranges that respectively surround a plurality of contacts of the grid array type semiconductor element 5.
The contacts of the grid array type semiconductor element 5 and the conductor lands 8 are electrically connected by a solder ball (not shown) or the like.

Here, the general description about the wettability of liquids, such as underfill resin, arrange | positioned on solid surfaces, such as the soldering resist layer 3, is given.
Regarding the influence of the solid surface shape on the wettability of the liquid on the solid surface, Formula (1), which is the Wenzel formula, is known.
cos θ ′ = r × cos θ (1)
Here, θ ′ is the apparent contact angle of the liquid on the solid surface having the concavo-convex structure, θ is the contact angle of the liquid on the smooth solid surface, and r is the surface of the solid surface having the concavo-convex structure with respect to the surface area of the smooth solid surface. Surface area ratio (r ≧ 1).
That is, when the contact angle of the underfill resin on the smooth surface of the solder resist layer is smaller than 90 °, the formula (1) increases the contact area between the surface of the solder resist layer and the underfill resin, that is, It shows that the contact angle of the underfill resin decreases as the surface of the solder resist layer becomes rougher. Thereby, the wettability of the underfill resin is improved.

Further, the wettability of the liquid disposed over two different types of solid surfaces can be obtained by the equation (2) which is the Cassie equation.
cos θ ′ = A ₁ × cos θ ₁ + A ₂ × cos θ ₂ (2)
In equation (2), θ ′ is the apparent contact angle of the liquid on the solid surface having a concavo-convex structure, θ ₁ and θ ₂ are the respective contact angles on different smooth solid surfaces, and A ₁ and A ₂ are It is an area ratio of solid surfaces different from each other (where A ₁ + A ₂ = 1).
When Expression (2) is applied to the configuration of the printed wiring board 1 of the present embodiment, the contact angle of the liquid underfill resin when the surface of the solder resist layer 3 is smooth is θ ₁ , and between the adjacent protrusions 9. the contact angle of the underfill resin in the recess formed in the theta _2. When the underfill resin is filled in the recess without a gap, the surface of the recess can be approximated as an underfill resin, and θ ₂ can be regarded as 0 °.
In other words, the formula (2) shows that the contact angle of the underfill resin is reduced and the wettability is improved by forming a fine uneven structure on the surface of the solder resist layer and filling the recess with the underfill resin. Is shown.

That is, according to the configuration of the printed wiring board 1 of the present invention, when the underfill resin is applied to both ends in the X-axis direction of the protruding portion 9 in the solder resist layer 3, the semiconductor that is the central portion of the solder resist layer 3. The underfill resin penetrates to the center of the mounting portion of the element 5 without a gap, and the contact area with the underfill resin is increased due to the fine uneven structure of the solder resist layer 3, so that the adhesion of the underfill resin is good. can get.
Since the uneven structure of the solder resist layer 3 increases the surface area and improves the wettability, the narrower the width of the protrusion 9 (in the X-axis direction) is, for example, preferably 30 μm or less, and 10 μm or less. Is more preferable. Further, as described above, since the protrusion height (Z-axis direction) of the protrusion 9 needs to be filled with the underfill resin in the recess, it is equal to or less than the width of the protrusion 9, that is, (height / width). It is preferable that the value obtained from the formula is 1.0 or less.

Next, the manufacturing method of this embodiment for manufacturing the printed wiring board 1 configured as described above will be described.
First, as shown in FIG. 3, on one surface 21a of the sheet-like mask film 21, a plurality of convex portions 22 are provided at intervals in the X-axis direction that is parallel to the one surface 21a. A mask pattern 23 having a predetermined shape is formed on the mask film 21. Each of the plurality of convex portions 22 is formed in a shape extending in the Y-axis direction.
As a material of the mask film 21, a polyester material such as polyethylene terephthalate and polyethylene naphthalate having a thickness of 50 μm or less, more preferably 25 μm or less is used. The plurality of convex portions 22 can be formed using, for example, a thermal imprint method in which a fine pattern is transferred from a mold while the mask film 21 is heated and pressurized.

And after forming the some convex part 22, a mold release process is performed to the one surface 21a of the mask film 21. FIG.
As the mold release process, for example, a process of applying a fluorine-based water repellent to one surface 21a of the mask film 21 and forming a thin film having a water repellent effect on the one surface 21a is used. The thickness of the thin film is not particularly limited, but if it is too thick, the shape of the convex portion 22 of the mask film 21 may be affected. Therefore, the thickness of the thin film is preferably 100 nm or less.

Next, as shown in FIG. 4, a plurality of conductor lands 8 are arranged on one surface 2 a of the substrate 2 at intervals in the X-axis direction and the Y-axis direction. Then, a solder resist agent 3 </ b> A that is liquid and has photosensitivity is applied onto one surface 2 a of the substrate 2 and the conductor land 8.
The method of applying the solder resist agent 3A is not particularly limited, and for example, a screen printing method, a spray coating method, a curtain coating method, a roll coating method, or the like can be used as appropriate.

As shown in FIG. 5, the mask film 21 is arranged on the solder resist agent 3A so that one surface 21a is on the solder resist agent 3A side. At this time, the mask film 21 is disposed so that the convex portion 22 does not contact the one surface 2 a of the substrate 2.
Subsequently, the solder resist agent 3 </ b> A is exposed to form the solder resist layer 3 corresponding to the mask pattern 23 of the mask film 21. At this time, the protrusion 9 of the solder resist layer 3 is formed between the adjacent protrusions 22 of the mask film 21.
Next, development processing is performed, and the mask film 21 is removed from the solder resist layer 3.

The printed wiring board 1 is manufactured by the procedure described so far.
Furthermore, the semiconductor device 10 is manufactured by connecting the grid array type semiconductor element 5 to the solder resist layer 3 of the printed wiring board 1 by the underfill resin layer 4.

As described above, according to the manufacturing method of the present embodiment, the shape of the plurality of convex portions 22 formed on the mask film 21 is transferred to the solder resist agent 3A, and the solder resist agent 3A is exposed to expose the solder resist layer. By forming 3, a plurality of protrusions 9 corresponding to the plurality of protrusions 22 are formed in the solder resist layer 3.
In general, the dimensional accuracy in the X-axis direction of the protrusions 22 that can be formed on the mask film 21 by a thermal imprint method or the like can be made smaller than the dimensional accuracy in the X-axis direction of the solder resist layer 3. For this reason, the pitch of the protrusions 9 formed in the solder resist layer 3 is narrower than in the prior art, and when the underfill resin is provided on the protrusions 9, for example, the wettability of the underfill resin with respect to the solder resist layer 3. The underfill resin layer 4 can be reliably connected to the solder resist layer 3.

In the conventional manufacturing method, a photomask is used in addition to the tape. However, in this embodiment, it is only necessary to use the mask film 21 on which the mask pattern 23 is formed, so that the printed wiring board 1 can be easily manufactured. .
Moreover, since the mold release process is performed on one surface 21a of the mask film 21, the mask film 21 can be easily removed from the solder resist layer 3, and the printed wiring board 1 can be used by repeatedly using the mask film 21. The manufacturing cost can be reduced.

Since the method of applying a fluorine-based water repellent to one surface 21a of the mask film 21 to form a thin film is used as the mold release treatment, the mask film 21 can be reliably removed from the solder resist layer 3.
In the manufacturing method of this embodiment, after providing the some convex part 22 in the one surface 21a of the mask film 21, a mold release process is performed to one surface 21a. Therefore, when the solder resist agent 3A is exposed, the solder resist layer 3 can be prevented from adhering to the one surface 21a of the mask film 21, and the shape of the plurality of convex portions 22 of the mask film 21 can be reduced to the solder. The resist layer 3 can be stably transferred.

  Furthermore, according to the manufacturing method of the present invention, the concavo-convex structure can be formed over the entire range of the surface 3b of the solder resist layer 3 including the portion on which the grid array type semiconductor element 5 is mounted. The uneven structure can be formed only in the region. That is, for example, in a portion where it is desired to prevent the underfill resin from flowing, such as an LED (Light Emitting Diode) mounting portion or an ACF (Anisotropic Conductive Film) pressure bonding portion, the solder resist layer in the vicinity thereof is not formed with an uneven structure. The wettability of the underfill resin can be partially suppressed.

In addition, the material of the mask film 21 is not limited to a polyester-type material, but is excellent in the transmittance | permeability of the light used at the time of exposure, and the polyethylene-type material, polystyrene-type material, etc. which can form an uneven | corrugated structure with a thermal imprint method A thermoplastic material or the like can be used. As an alternative to the mask film 21, for example, a quartz plate having a thickness of 3 mm or less, more preferably 1 mm or less may be used. In this case, the concavo-convex structure is formed by electron beam drawing and dry etching.
Further, the mold release treatment may be performed by forming a monomolecular film having a water repellent effect by using a silane coupling agent having a Teflon (registered trademark) -based molecular structure.

  Further, when viewed in parallel with the Z-axis direction, the solder resist layer 3 and the protruding portion 9 are arranged in ranges that respectively surround a plurality of contacts of the grid array type semiconductor element 5. Therefore, the wettability of the underfill resin layer 4 with respect to the solder resist layer 3 is improved over a wider range than the range where the contacts on the surface of the grid array type semiconductor element 5 connected to the underfill resin layer 4 are disposed. Thus, the grid array type semiconductor element 5 can be stably connected to the solder resist layer 3 by the underfill resin layer 4.

As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The change of the structure of the range which does not deviate from the summary of this invention, etc. are included.
For example, in the said embodiment, the uneven structure formed in the soldering resist layer 3 of the printed wiring board 1 can be formed in various shapes as shown below.
For example, in the embodiment, the protrusions 9 are formed on the surface 3b of the solder resist layer 3 so as to be spaced apart from each other in the X-axis direction and extend in the Y-axis direction. However, as in the printed wiring board 31 shown in FIG. 6, a plurality of protrusions 32 are formed on the surface 3b of the solder resist layer 3 so as to be spaced apart from each other in the X-axis direction and the Y-axis direction. May be configured.
In this modification, the intervals between the protrusions 32 adjacent to each other in the X-axis direction and the Y-axis direction are set to be equal.
By forming the printed wiring board 31 in this way, the shape of the concavo-convex structure is complicated and the formation of the concavo-convex structure is somewhat difficult as compared with the printed wiring board 1 of the above embodiment, but the underlayer in the solder resist layer 3 Since the contact area with the fill resin can be further increased, the wettability and adhesion of the solder resist layer 3 can be further improved, and the underfill resin layer 4 can be more reliably connected to the solder resist layer 3.

Further, like the printed wiring board 41 shown in FIG. 7, in the printed wiring board 31 of the modified example, it protrudes between the conductor lands 8 adjacent to each other in the X-axis direction and the Y-axis direction on the surface 3 b of the solder resist layer 3. Instead of the part 32, a protruding part 42 and a protruding part 43 may be provided.
The protrusions 42 are formed between the conductor lands 8 adjacent in the X-axis direction so as to be spaced apart from each other in the Y-axis direction and extend in the X-axis direction. Similarly, the protrusions 43 are formed between the conductor lands 8 adjacent in the Y-axis direction so as to be spaced apart from each other in the X-axis direction and extend in the Y-axis direction.
By forming the printed wiring board 41 in this manner, the wettability of the underfill resin between the conductor lands 8 adjacent to each other in the X-axis direction and the Y-axis direction on the solder resist layer 3 is further improved. Underfill resin can be filled between the solder resist layer 3 and the grid array type semiconductor element 5 without generating a gap between the conductor lands 8 that affect the above.

Further, as in the printed wiring board 51 shown in FIG. 8, instead of the protruding portion 9 of the printed wiring board 1 of the above embodiment, the surface 3b of the solder resist layer 3 is spaced apart from each other in the X-axis direction and the Y-axis. You may form the some protrusion part 52 extended and formed in the direction. The protrusion 52 is configured such that the width of the protrusion 52 and the interval between the protrusions 52 adjacent to each other in the X-axis direction become narrower toward the center in the X-axis direction in the solder resist layer 3.
By forming the printed wiring board 51 in this way, when the grid array type semiconductor element 5 is arranged at the center of the solder resist layer 3 when viewed in parallel with the Z-axis direction, the X of the grid array type semiconductor element 5 is displayed. The wettability of the underfill resin in the central portion in the axial direction can be improved.

In the embodiment and the modification thereof, the inner diameter of the through hole 3 a of the solder resist layer 3 is set to be slightly larger than the outer diameter of the conductor land 8. However, the inner diameter of the through hole 3 a may be set equal to the outer diameter of the conductor land 8.
In the embodiment, the semiconductor element is the grid array type semiconductor element 5 such as BGA or LGA. However, the semiconductor element is not limited to the grid array type semiconductor element, and other surface-mount type semiconductor elements such as SOP (Small Outline Package) and QFP (Quad Flat Package) may be used.

  In the embodiment and the modification thereof, the mold release process is a process of forming a thin film by applying a fluorine-based water repellent to one surface 21 a of the mask film 21. However, the release treatment may be, for example, a process of forming a thin film on one surface 21a by spraying or vapor-depositing a fluorine-based water repellent on one surface 21a of the mask film 21. it can.

DESCRIPTION OF SYMBOLS 3 Solder resist layer 3A Solder resist agent 21 Mask film 21a One surface 22 Convex part 23 Mask pattern

Claims (2)

On one surface of the mask film, while providing a plurality of convex portions spaced apart from each other in a direction parallel to the one surface, forming a mask pattern on the mask film,
A mold release treatment is performed on the one surface of the mask film,
Place solder resist agent on the substrate,
The mask film is placed on the solder resist agent so that the one surface is on the solder resist agent side,
By exposing the solder resist agent, a solder resist layer is formed in which a plurality of protrusions corresponding to the plurality of protrusions of the mask film are formed,
A method for producing a printed wiring board, comprising: removing the mask film from the solder resist layer.   The method for manufacturing a printed wiring board according to claim 1, wherein the release treatment is a treatment for forming a thin film by applying a fluorine-based water repellent to the one surface of the mask film.

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