JP2001217514A - Multi-layered wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the connection reliability of a solder joint part by suppressing curvature deformation accompanying heating and cooling as to a multi-layered wiring board having surface-mounted components soldered on its mount surface. SOLUTION: The multi-layered wiring board 11 has on both the top and reverse sides of a core base material 14 a built-up layer formed by stacking two insulating layers 15a and 15b, and a built-up layer 16 formed by stacking two insulating layers 16a and 16b. A conductor pattern 17 is provided between both the top and reverse sides of the multi-layered wiring board 11 and the insulating layers and lands 17a corresponding to solder bumps 13 of a surface- mounted component 12 are provided on the mount surface. The surface-mounted component 12 is mounted on the lands 17a coated with solder paste so that the solder bumps 13 are mounted, and then soldered by solder flow heating. At this time, the insulating layers 15a and 15b on the mount surface side are formed of resin materials which have a larger modulus of elasticity or a smaller coefficient of thermal expansion than the insulating layers 16a and 16b on the opposite surface side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a multilayer insulating layer mainly composed of a resin material, a conductor pattern between the surface and the insulating layer, and the surface is soldered to a surface mount component. The present invention relates to a multilayer wiring board having a mounting surface.

[0002]

For example, as shown in FIG. 5, in a mounting board incorporated in a small electronic device such as a mobile phone, a mounting surface (upper surface in the figure) of a multilayer wiring substrate (multilayer printed wiring board) 1 is used. In addition, for example, CSP (Chip Size Pack)
age) type or BGA (Ball Grid Array) type, a structure in which a small and high-density surface mount component 2 is surface mounted by reflow soldering.

The multilayer wiring board 1 has a build-up layer 4 composed of, for example, two insulating layers 4a on the front (upper) side of the core substrate 3 located at the center. Also, in this case, it is configured to include the build-up layer 5 including the two insulating layers 5a. At this time, each of the insulating layers 4
a and 5a are made of, for example, epoxy resin containing glass cloth, and all have the same material and thickness. The conductor pattern 6 is formed between the upper and lower surfaces of the multilayer wiring board 1 and between the insulating layers. Of these, the mounting surface (the upper surface in the figure) of the multilayer wiring board 1 is included.
Are formed with lands 6a corresponding to the solder bumps 7 provided on the electrodes 2a on the bottom surface of the surface mount component 2.

[0004] The surface mount component 2 is mounted on the multilayer wiring board 1.
Is mounted on the land 6a on the mounting surface of the multilayer wiring board 1 by, for example, screen-printing a solder paste (not shown), and then, as shown in FIG. The surface mount component 2 is mounted on the wiring board 1 such that the solder bumps 7 of the component 2 match the lands 6a. Then, by passing the multilayer wiring board 1 through a reflow furnace, the solder paste is melted and hardened, and solder bonding of the solder bumps 7 to the lands 6a is performed.

However, in the reflow soldering step, a preheating step in which the multilayer wiring board 1 is gradually heated from room temperature, a reflow step in which the multilayer wiring board 1 is heated to a peak temperature (for example, 230 ° C.), and a cooling step in which the multilayer wiring board 1 is gradually cooled to room temperature thereafter The multilayer wiring board 1 has different thermal expansion coefficients and elastic moduli between its constituent elements (insulating layers 4a, 5a and the conductor pattern 6), and the multilayer wiring board 1 has a difference between the mounting surface side and the opposite surface side. In the reflow process, the area, shape, and arrangement of the conductor pattern 6 are not uniform between
A deformation behavior such as a warp deformation occurs in the multilayer wiring board 1 due to the heating expansion and cooling contraction. For example, when the multilayer wiring board 1 is heated, a warp deformation that causes a downward convex shape is generated, and when the multilayer wiring board 1 is cooled, a warp deformation that causes an upwardly convex shape that is the opposite direction (return direction) occurs. I do.

At this time, the solder paste is hardened at an early stage of the cooling process (for example, at 183 ° C. or lower).
FIG. 5 shows a state in which the solder bumps 7 are joined by the solder joints, that is, the positions of the solder bumps 7 with respect to the lands 6a are restricted.
As shown in (b) in an exaggerated manner, the multilayer wiring board 1 has a warp deformation behavior in a direction convex toward the mounting surface side. Therefore, there is a problem that a large tensile stress is applied to the outer solder joints in the cooling process.

When a large stress is applied to the solder joint, the solder joint itself is destroyed, the interface between the solder bump 7 and the electrode 2a of the surface mount component 2, or the solder and the land 6 are damaged.
There is a possibility that peeling may occur at the interface with a, and as a result, there is a problem that connection reliability is reduced. Note that such warpage deformation of the multilayer wiring board 1 is not limited to reflow soldering,
Even during actual use, it may occur depending on the use environment (environment in which the temperature change is large).

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a device in which a surface mount component is soldered to a mounting surface, and suppress warpage deformation caused by heating and cooling.
It is another object of the present invention to provide a multilayer wiring board capable of improving the connection reliability of a solder joint.

[0009]

SUMMARY OF THE INVENTION In a multilayer wiring board having a conductor pattern between a surface and a multilayer insulating layer, heating,
The warping deformation accompanying cooling is caused by the temperature exceeding the glass transition point of the resin material constituting the insulating layer at the time of heating, whereby the elastic modulus of the insulating layer is significantly reduced, and in that state, the area density of the conductor pattern is reduced. It is considered that the degree of thermal expansion and contraction is dominant. Further, at this time, the problem of the tensile stress on the solder joint portion is mainly the warpage deformation which becomes convex on the mounting surface side in the cooling process. The present inventors pay attention to the elastic modulus of such an insulating layer, and change the characteristics of the insulating layer, particularly the elastic modulus, between the mounting surface side and the opposite surface side by the following three means. As a result, it has been confirmed that warpage can be suppressed, and the present invention has been accomplished.

That is, the first means is that an insulating layer located on the mounting surface side and an insulating layer located on the opposite side thereof have
It is characterized in that resin materials having different characteristics are employed (the invention of claim 1). According to this, by changing the characteristics of the resin material between the insulating layer on the side where thermal expansion and contraction is large due to the area density of the conductor pattern and the insulating layer on the side where thermal expansion and contraction is small, thermal expansion is achieved. , The side with a small contraction follows the side with a large thermal expansion and contraction, thereby suppressing the occurrence of warpage. As a result, it is possible to suppress the warp deformation due to heating and cooling, and to improve the connection reliability of the solder joint.

In this case, the resin material constituting the insulating layer located on the mounting surface side can be one having a higher elastic modulus or a larger thermal expansion coefficient than the insulating layer located on the opposite side. (Invention of claim 2). This allows
Even if the thermal expansion and shrinkage is large on the side opposite to the mounting surface, the mounting surface can follow the thermal expansion and shrinkage, and the warping deformation becomes convex toward the mounting surface during cooling and shrinking. Can be suppressed. Incidentally, according to the study of the present inventors, by setting the elastic modulus of the insulating layer on the mounting surface side to 1.5 times or more, more preferably 3 times or more, the elastic modulus of the insulating layer on the opposite surface side, It is excellent in the effect of preventing warpage deformation.

In the case where the surface mounting component is reflow-soldered to the mounting surface, a resin material having a glass transition point higher than a reflow peak temperature can be adopted for the insulating layer located on the mounting surface side ( The invention of claim 3). Thereby, in the entire temperature range of the reflow soldering process,
The elastic modulus of the insulating layer on the mounting surface side does not decrease,
This is effective in suppressing warpage deformation.

[0013] The second means is that an insulating layer located on the mounting surface side and an insulating layer located on the opposite side are disposed between the insulating layer and the insulating layer.
It is characterized in that the thicknesses of these insulating layers are different (the invention of claim 4). According to this, by changing the thickness between the insulating layer on the side where thermal expansion and contraction is large and the insulating layer on the side where thermal expansion and contraction is small, the amount of warpage deformation can be reduced, As a result, it is possible to reduce the stress applied to the solder joint, and to improve the connection reliability of the solder joint.

At this time, the insulating layer located on the mounting surface side is
The thickness can be made larger than that of the insulating layer located on the opposite side (the invention of claim 5). As a result, even if the thermal expansion and contraction are large on the side opposite to the mounting surface, the mounting surface can follow the thermal expansion and contraction. Warp deformation can be suppressed.

Further, in the third means, the amount of glass cloth contained in the resin material differs between the insulating layer located on the mounting surface side and the insulating layer located on the opposite side. However, it is characterized (the invention of claim 6). According to this, the elastic modulus of the insulating layer can be changed by the amount of glass cloth contained in the resin material,
The side where the thermal expansion and contraction is small follows the side where the thermal expansion and contraction becomes large, so that the occurrence of warpage can be suppressed.
As a result, it is possible to suppress the warp deformation caused by heating and cooling, and to improve the connection reliability of the solder joint.

In this case, the insulating layer located on the mounting surface side is
It can be configured so that the content of the glass cloth is larger than that of the insulating layer located on the opposite side (the invention of claim 7). As a result, even if the thermal expansion and contraction are large on the side opposite to the mounting surface, the mounting surface can follow the thermal expansion and contraction. Warp deformation can be suppressed. In addition, the same control of the warpage deformation is performed in the resin of the insulating layer.
It is also possible to dispose an inorganic filler having a high elastic modulus or a low coefficient of thermal expansion, such as silica (SiO2) powder, on the mounting surface side.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment (corresponding to claims 1, 2 and 3) embodying the present invention will be described with reference to FIGS. FIG. 1 schematically shows a state in which, for example, a CSP (Chip Size Package) type surface mounting component 12 is mounted on a mounting surface (upper surface in the figure) of a surface of a multilayer wiring board 11 according to the present embodiment. As is well known, the surface mount component 12 is a rectangular package 12.
The electrode 12b on the lower surface of FIG. Many solder bumps 13 (electrodes 12b) are provided in an array.

On the other hand, the multilayer wiring board 11 has a build-up layer 1 composed of, for example, two insulating layers 15a and 15b on the front side (upper side) of a core base 14 composed of a resin material.
5 and also on the lower side of the core base material 14, in this case, the build-up layer 1 composed of two insulating layers 16a and 16b.
6. Among them, build-up layer 15
The surface side (the upper side in the figure) of the (insulating layer 15b) is a mounting surface. Each of the insulating layers 15a, 15b and 16a, 1
6b is mainly composed of a resin material,
The material will be described later.

A conductive pattern 17 formed by plating copper foil, for example, is formed between the upper and lower surfaces of the multilayer wiring board 11 and between the insulating layers. A land 17 a corresponding to the solder bump 13 provided on the bottom surface of the surface mount component 12 is formed on the mounting surface of the multilayer wiring board 11. The surface of the multilayer wiring board 11 is covered with a solder resist (not shown) except for a necessary part (the land 17a). The conductor pattern 17 is formed to have a small area density on the mounting surface side (the build-up layer 15 side) and a larger area density on the opposite surface side (the build-up layer 16 side).

As will be described later, the mounting of the surface mount component 12 on the multilayer wiring board 11 is performed by applying a solder paste (not shown) to the lands 17a on the mounting surface of the multilayer wiring board 11, 17a so that each solder bump 13 is placed on the surface mount component 12a.
Is mounted (temporary joining) in a positioning state, and then reflow heating is performed through a reflow furnace.
In this embodiment, a commonly used eutectic solder having a Sn / Pb weight ratio of 63/37 is adopted as the solder paste, and the reflow peak temperature is 230 to 24.
It is set to 0 ° C. and solidifies at 183 ° C. or less.

In this embodiment, the multilayer wiring board 1
In the insulating layer that constitutes No. 1, resin materials having different characteristics are employed between the insulating layers 15a and 15b located on the mounting surface side and the insulating layers 16a and 16b located on the opposite side. In this case, the insulating layer 15a on the mounting surface side,
15b is formed of the insulating layer 16 on the opposite side.
The elastic material has a higher elastic modulus than the resin material constituting the a and 16b.

More specifically, a resin material having a glass transition point higher than the reflow peak temperature (230 to 240 ° C.), for example, a polyamideimide resin is employed for the insulating layers 15 a and 15 b located on the mounting surface side. I have. Alternatively, a wholly aromatic polyester resin or the like can be employed.
On the other hand, a resin material having a glass transition point below the reflow peak temperature, for example, a commonly used amine-based curing agent or a curing agent such as phenol novolak or cresol novolac is added to the insulating layers 16a and 16b on the opposite surface side. Bisphenol A type epoxy resin is used. Alternatively, a polyethylene resin, a polybutylene terephthalate resin, or the like can be employed. At this time, according to the study by the present inventors, the insulating layer 15 on the mounting surface side is used.
The elastic moduli of the insulating layers 16a, 16b on the opposite side
It is desirable that the elastic modulus of b is 1.5 times or more, more preferably 3 times or more.

Next, the operation of the above configuration will be described with reference to FIG. When mounting the surface mount component 12 on the mounting surface of the multilayer wiring board 11, first, as described above,
A solder paste application step of applying a solder paste on the multilayer wiring board 11 (land 17a) is performed by a known method (screen printing or the like). Next, the surface mount component 12 is placed on the multilayer wiring board 11 to which the solder paste has been applied.
Is mounted so that the solder bumps 13 are arranged on the lands 17a. In this case, this mounting step is performed using, for example, a high-speed chip mounter, and is performed in a highly accurate positioning state by, for example, control using a visual recognition device.

Then, a reflow step of reflow heating the multilayer wiring board 11 on which the surface mount components 12 are mounted is executed. This reflow process is performed in the multilayer wiring board 11
Is carried out at a predetermined speed through a not-shown reflow furnace. At this time, the inside of the reflow furnace is
A preheat zone, a reflow zone, a cooling zone, and the like are provided according to the temperature distribution, and the solder paste on the multilayer wiring board 11 is melted and hardened by passing through each of the temperature zones in turn, so that the surface mount component is formed. 1
The two solder bumps 13 correspond to the lands 1 on the multilayer wiring board 11.
7a, and electrical and mechanical connections are made.

In the reflow process, for example, the type and thickness of the multilayer wiring board 11, the type of the surface mount component 12,
For example, an appropriate temperature profile as shown in FIG. 2 is adopted according to the type (solidification point) of the solder paste.
In this case, the multilayer wiring board 11 on which the surface mount components 12 are mounted is heated from a normal temperature (time A) with a predetermined curve in the preheating zone, and reaches a peak temperature (time B; for example, 230 ° C.) in the reflow zone. The solder paste is melted by being heated, and is cooled with a predetermined curve in a subsequent cooling zone, so that the solder paste is hardened.

Thus, in the reflow process,
The multilayer wiring board 11 has its components (insulating layer 15
a, 15b, 16a, 16b and the conductor pattern 17) have different coefficients of thermal expansion, and the multilayer circuit board 11 and the surface mount component 12 have different coefficients of thermal expansion. Due to factors such as unevenness in the area, shape, and arrangement (area density) of the conductor pattern 17 between the conductor pattern 17 and the opposite side, mounting is performed on the side where the area density of the conductor pattern 17 is large (the build-up layer 16 side). Surface side (Build-up layer 15
Side), the thermal expansion and contraction are greater than that of the multilayer wiring board 1
In FIG. 1, deformation behavior such as warpage deformation and deformation in the recovery direction occurs.

At this time, the solder paste is hardened at the beginning of the cooling process (for example, at a time point C when the temperature is 183 ° C. or less), so that the position of each solder bump 13 with respect to each land 17a is restricted by the solder joint. The multilayer wiring board 11 is warped in a direction in which the inside becomes convex upward, and therefore, there is a problem that a large tensile stress is applied to the solder joint portion located on the outside. When a large stress is applied to the solder joint as described above, there is a possibility that the solder joint itself is destroyed, or separation occurs at the interface between the solder and the solder bump 13 or at the interface between the solder and the land 17a.

However, in the present embodiment, the insulating layers 15a, 15b on the side of the build-up layer 15 on the side where the thermal expansion and contraction are small.
Since 15b is made of a resin material having a large elastic modulus,
Build-up layer 16 on the side where thermal expansion and contraction increase
It is possible to follow the thermal expansion and contraction of the side, thereby suppressing the occurrence of warpage. At this time, a resin material having a glass transition point higher than the reflow peak temperature is used for the insulating layers 15a and 15b. In the entire temperature range of the reflow process, the insulating layers 15a, 15
The elastic modulus of 5b does not decrease, and the effect of suppressing the warpage is extremely excellent.

Therefore, according to this embodiment, the surface mounting component 12 is mounted on the mounting surface by reflow soldering.
The resin material constituting the insulating layers 15a and 15b located on the mounting surface side is replaced with the insulating layers 16a and 1 located on the opposite side.
By setting the elastic modulus to be larger than 6b, it is possible to suppress the warp deformation that becomes convex on the mounting surface side during the cooling shrinkage in the reflow step. As a result, an excellent effect of effectively preventing stress from being applied to the solder joint and improving the connection reliability of the solder joint can be obtained. Further, even when the product after mounting is used, it is possible to improve the durability against the thermal stress applied in the usage environment of the product.

FIG. 3 shows a second embodiment (corresponding to claims 4 and 5) of the present invention. The difference between the multilayer wiring board 21 according to the second embodiment and the multilayer wiring board 11 according to the first embodiment is that the multilayer wiring board 21 is located between the insulating layer located on the mounting surface side and the insulating layer located on the opposite side. Therefore, instead of using different resin materials, the thicknesses of the insulating layers are different.

That is, the multilayer wiring board 21 has, for example, two insulating layers 22a, 22a on the front side (upper side) of the core base material 14.
2b, and also in this case, two insulating layers 23a, 23
3b.
Among them, the thickness of the insulating layers 22a and 22b forming the build-up layer 22 on the mounting surface side is larger than the thickness of the insulating layers 23a and 23b forming the build-up layer 23 on the opposite surface side.

According to this, the insulating layers 22a and 22b located on the mounting surface side are replaced with the insulating layers 2a located on the opposite side.
By making the thickness larger than 3a and 23b, the amount of warping deformation due to thermal expansion and contraction during the reflow step or actual use can be reduced, as in the first embodiment. Reduce the stress applied to the joint,
As a result, the connection reliability of the solder joint can be improved.

FIG. 4 shows a third embodiment (corresponding to claims 6 and 7) of the present invention. The difference between the multilayer wiring board 31 according to the third embodiment and the multilayer wiring board 11 of the first embodiment is that the multilayer wiring board 31 is located between the insulating layer located on the mounting surface side and the insulating layer located on the opposite side. Thus, instead of using different resin materials, the amount of glass cloth contained in the resin material is changed.

That is, the multilayer wiring board 31 is provided on the front side (upper side) of the core base material 14, for example, with two insulating layers 32a, 32
2b, and also in this case, two insulating layers 33a, 3
It has a build-up layer 33 made of 3b.
The insulating layers 32a and 32b constituting the build-up layer 32 on the mounting surface side have, for example, a resin content of 49.3.
% Of an epoxy resin containing glass cloth, and the insulating layers 33a and 33b constituting the build-up layer 33 on the opposite side have a resin content of, for example, 6%.
An epoxy resin prepreg sheet containing 1.5% glass cloth is employed.

According to this, the insulating layers 32a and 32b located on the mounting surface side are replaced with the insulating layer 3 located on the opposite side.
3a and 33b, the elastic modulus can be made larger than that of the first embodiment. Therefore, similarly to the first embodiment, it is possible to suppress the warping during the reflow process and the thermal expansion and contraction during actual use. . As a result, it is possible to effectively prevent stress from being applied to the solder joint and improve the connection reliability of the solder joint.

In the first to third embodiments, the means for suppressing the warp deformation accompanying the thermal expansion and contraction is as follows.
There are three ways to change the characteristics (elastic modulus) of the resin material that forms the insulating layer, change the thickness of the insulating layer, and change the glass cloth content of the insulating layer between the mounting surface side and the opposite surface side. Although the means are independently adopted, two of them may be combined or all three may be combined.
Further, the number and thickness of the insulating layers may be varied, and the elastic modulus may be sequentially changed (inclined) for each insulating layer.

In addition, the present invention is not limited to the above-described embodiment.
Not limited to P type, for example, QFP type, BGA
The present invention can be applied to all surface mount components of various types of packages such as type and MCM type, and the material of the solder paste may be lead-free solder.
Further, the material and the like of the insulating layer and the conductor pattern constituting the wiring board may be appropriately changed and changed without departing from the gist, for example, various materials may be adopted.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention, and is a longitudinal sectional view schematically showing a state in which surface mount components are mounted on a multilayer wiring board.

FIG. 2 is a diagram schematically showing a state of a temperature-time curve and a deformation behavior of a substrate in reflow heating.

FIG. 3 is a view corresponding to FIG. 1, showing a second embodiment of the present invention;

FIG. 4 is a view corresponding to FIG. 1, showing a third embodiment of the present invention;

FIG. 5 is a longitudinal sectional view showing a conventional example, showing a state in which surface-mounted components are mounted on a multilayer wiring board (a) and a state in which warpage occurs (b).

[Explanation of symbols]

In the drawings, 11, 21 and 31 are multilayer wiring boards, 12 is a surface mount component, 13 is a solder bump, 14 is a core base material,
16, 22, 23, 32 and 33 are build-up layers, 15
a, 15b, 16a, 16b, 22a, 22b, 23
a, 23b, 32a, 32b, 33a, 33b are insulating layers, 17 is a conductor pattern, and 17a is a land.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/46 H01L 23/12 N (72) Inventor Yasuaki Matsunaga 1-1-1 Showa-cho, Kariya-shi, Aichi Stock F term in DENSO (reference) 5E319 AA03 AA07 AB05 AC02 BB04 BB05 BB07 CC33 GG11 GG20 5E343 AA16 AA17 AA18 BB54 ER54 GG20 5E346 AA12 AA38 CC04 CC08 CC09 CC10 CC12 CC13 CC40 FF45 HH11

Claims (7)

[Claims] 1. A multilayer wiring comprising a multilayer insulating layer mainly composed of a resin material, a conductor pattern between the surface and the insulating layer, and the surface having a mounting surface to which a surface mount component is soldered. A multilayer wiring board, wherein a resin material having different characteristics is adopted between an insulating layer located on the mounting surface side and an insulating layer located on the opposite side. 2. A resin material constituting the insulating layer located on the mounting surface side has a higher elastic modulus or a larger coefficient of thermal expansion than the insulating layer located on the opposite side. The multilayer wiring board according to claim 1, wherein: 3. A method for reflow soldering a surface mount component to the mounting surface, wherein a resin material having a glass transition point higher than a reflow peak temperature is used for an insulating layer located on the mounting surface side. 3. The multilayer wiring board according to claim 2, wherein: 4. A multilayer wiring comprising a multilayer insulating layer mainly composed of a resin material, a conductor pattern between the surface and the insulating layer, and the surface having a mounting surface to which a surface mount component is soldered. A multilayer wiring board, wherein the thickness of the insulating layer is different between the insulating layer located on the mounting surface side and the insulating layer located on the opposite side. 5. The multilayer wiring board according to claim 4, wherein the insulating layer located on the mounting surface side is thicker than the insulating layer located on the opposite side. 6. A multilayer wiring comprising a multilayer insulating layer mainly composed of a resin material, a conductor pattern between the surface and the insulating layer, and the surface having a mounting surface to which a surface mount component is soldered. A substrate, wherein the amount of glass cloth contained in the resin material is different between the insulating layer located on the mounting surface side and the insulating layer located on the opposite side. Multilayer wiring board. 7. The multilayer wiring according to claim 6, wherein the insulating layer located on the mounting surface side has a larger glass cloth content than the insulating layer located on the opposite side. substrate.