JP2000286552A - Multilayer circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure high connection reliability for both primary mounting and secondary mounting by laminating and integrating a plurality of both side copper clad substrates having different coefficient of thermal expansion containing a metal foil in an insulation layer through adhesive layers in the order of coefficient of thermal expansion. SOLUTION: First through third both side copper clad substrates 13 are laminated collectively in the order of coefficient of thermal expansion using adhesive layers 10 to produce a multilayer circuit board. In order to electrically connect the both side copper clad substrates 1-3 of the multilayer circuit board thus produced, through holes are drilled after collective lamination and subjected to through hole plating. A multilayer circuit board thus produced can be provided with a gradient in the coefficient of thermal expansion in the thickness direction thereof. Consequently, the coefficient of thermal expansion can be set low for the silicon chip mounting face having a low coefficient of thermal expansion and can be set high for the secondary mounting face to a glass epoxy substrate having a high coefficient of thermal expansion. According to the arrangement, highly reliable primary mounting and secondary mounting can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer circuit board suitable for mounting a semiconductor chip.

[0002]

2. Description of the Related Art With the recent miniaturization and high performance of electronic devices, semiconductor devices constituting electronic devices and multilayer printed wiring boards on which the electronic devices are mounted have been reduced in size and thickness and improved in performance.
High reliability is required. In response to these demands, the mounting method has shifted from a pin insertion type package to a surface mounting type package, and recently, a mounting method called flip chip mounting, in which a semiconductor chip is directly mounted on a substrate, has been studied.

However, the thermal expansion coefficient of the conventional glass epoxy substrate is as large as 15 to 18 ppm / ° C., and the thermal expansion coefficient is 3
When a silicon chip of ４4 ppm / ° C. is directly flip-chip mounted, stress is applied to the connection due to the difference in the coefficient of thermal expansion between the two. The stress generated due to the difference in the coefficient of thermal expansion between the chip and the substrate causes problems such as cracks in the solder or complete cutting in the case of solder bump connection.

In order to alleviate such stress, a method of injecting an adhesive called an underfill material between the chip and the substrate to prevent the stress from concentrating on the connection portion has been implemented. However, even with these methods, the reliability is not sufficient in consideration of the future increase in the size of the chip and the narrowing of the pitch of the pads. To ensure higher reliability, the thermal expansion coefficient of the substrate itself must be reduced. It is essential to lower. Against this background, the present applicant has already proposed a low thermal expansion substrate including a metal foil having a low thermal expansion coefficient in an insulating layer (Japanese Patent Application No. 9-260201).

[0005]

However, for example, the coefficient of thermal expansion of the substrate is determined by the coefficient of thermal expansion of the silicon chip (3.
When the temperature is lowered to 5 ppm / ° C.), the connection reliability between the chip and the substrate (primary mounting) is improved, but in applications requiring secondary mounting on another substrate (glass epoxy substrate), low heat is required. There is a problem that connection reliability is reduced due to a difference in thermal expansion coefficient between the expansion substrate and the glass epoxy substrate.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a multilayer circuit board that can ensure high connection reliability in both primary mounting and secondary mounting.

[0007]

In order to achieve the above object, in the multilayer circuit board of the present invention, a plurality of double-sided copper-clad substrates having different thermal expansion coefficients each containing a metal foil in an insulating layer have a large thermal expansion coefficient. The configuration is such that they are sequentially laminated via an adhesive layer and integrated.

That is, the present inventors have conducted intensive studies to obtain a multilayer circuit board capable of ensuring high connection reliability in both primary and secondary mountings. The present invention has found that when a plurality of different double-sided copper-clad substrates are laminated via an adhesive layer in order of increasing thermal expansion coefficient and integrated, high connection reliability can be ensured in both primary mounting and secondary mounting. Reached. That is, in the multilayer circuit board of the present invention, the coefficient of thermal expansion of the chip mounting surface is reduced, and the coefficient of thermal expansion of the surface connected to the glass epoxy substrate is increased, so that the primary mounting and the secondary mounting have high connection reliability. Nature can be secured.

Next, the present invention will be described in detail.

As shown in FIG. 1, the multilayer circuit board of the present invention comprises a plurality of double-sided copper-clad boards having different coefficients of thermal expansion. A metal foil is provided in the layer (in FIG. 1, the multilayer circuit board is composed of first to third double-sided copper-clad boards).

The above-mentioned metal foil controls the coefficient of thermal expansion of the entire double-sided copper-clad board, and changes the coefficient of thermal expansion of the entire double-sided copper-clad board by changing the type of metal and the thickness of the metal foil. be able to. That is, when controlling the entire coefficient of thermal expansion of the double-sided copper-clad board according to the type of metal, the first metal foil used for the first double-sided copper-clad board is selected to have a small coefficient of thermal expansion, The second metal foil used for the double-sided copper-clad substrate is selected to have a higher coefficient of thermal expansion than the first metal foil. The third metal foil used for the third double-sided copper-clad substrate is selected to have a higher coefficient of thermal expansion than the second metal foil. On the other hand, when controlling the entire thermal expansion coefficient of the double-sided copper-clad board by the thickness of the metal foil, a metal foil made of the same metal type is used, and the relationship of the thickness is as follows: the first metal foil> the second metal foil. Metal foil> third metal foil is set. Of course, both the method of changing the metal type and the method of changing the thickness of the metal foil may be used in combination.

As the type of the metal foil, any type can be used.
S, copper, nickel, aluminum, an iron-nickel alloy, and an iron-nickel-cobalt alloy are recommended. In particular, an iron-nickel (-cobalt) -based alloy is preferably used because different alloys having different coefficients of thermal expansion are obtained depending on the content ratio of iron and nickel. Such a metal foil having a thickness of 10 to 300 μm is suitably used.
Below this range, the coefficient of thermal expansion of the entire double-sided copper-clad board will not be stable, and above this range, the connection reliability of the double-sided circuit will decrease.

The Young's modulus at room temperature of the adhesive used for laminating and integrating each of the above double-sided copper-clad substrates is 1.0.
It is better to set it to GPa or less. This is because, when a double-sided copper-clad substrate having a different coefficient of thermal expansion is integrated, the multilayered substrate may warp with the side with the lower coefficient of thermal expansion (first double-sided copper-clad substrate). This warpage is more likely to occur as the difference between the coefficients of thermal expansion of the double-sided copper-clad substrates increases. For this reason, if the Young's modulus at room temperature of the adhesive is set low, it is possible to absorb the distortion caused by the difference in the coefficient of thermal expansion,
The warpage of the substrate can be minimized.

The adhesive is not particularly limited,
For example, epoxy type, polyimide type, polyimide-epoxy mixed type, polyetherimide, etc. are used.

An example of a method for manufacturing a multilayer circuit board according to the present invention will be described. That is, first, the through-hole connecting holes 11 are formed.
The laminated body 21 in which the conductor layer (copper foil) is formed on one side of the insulating layer is bonded to both sides of the first metal foil 11 having the opening a with an adhesive 22 (see FIG. 3), and the conductors are formed on both sides. A substrate 23 having the layer 7a is produced (see FIG. 4). Then, a hole 24 smaller than the through hole connection hole 11a is formed.
Is opened, copper plating is performed, and both conductor layers 7a are connected by through-hole plating portions 14 (see FIG. 5). Next, a circuit is formed on both conductor layers 7a by a normal etching method,
(See FIG. 6).

Next, in the same manner as in the above method, the second,
Third double-sided copper-clad substrates 2 and 3 (see FIG. 7) are manufactured. Here, the coefficient of thermal expansion of the second double-sided copper-clad board 2 is larger than the coefficient of thermal expansion of the first double-sided copper-clad board 1, and the coefficient of thermal expansion of the third double-sided copper-clad board 3 is the second. It is set to be larger than the coefficient of thermal expansion of the double-sided copper-clad board 2.

The control of the coefficient of thermal expansion of each of the double-sided copper-clad substrates 1 to 3 can be performed by selecting the type and thickness of the metal foils 11 to 13 (see FIG. 7) used for this. For example, the first metal foil 11 used for the first double-sided copper-clad substrate 1 is made of iron (64% by weight) -Ni (36 wt.
%) Alloy (thermal expansion coefficient = 1.5 ppm / ° C.), a 50 μm thick iron (58% by weight) -Ni (42% by weight) alloy having a second metal foil 12 used for the second double-sided copper-clad substrate 2 (Coefficient of thermal expansion = 4.5 ppm / ° C.) The third metal foil 13 used for the third double-sided copper-clad substrate 3 is made of SUS430 having a thickness of 50 μm.
(Coefficient of thermal expansion = 10.4 ppm / ° C.).

The first to third double-sided copper-clad substrates 1 to 3 are collectively laminated in ascending order of thermal expansion coefficient using an adhesive layer 10 (see FIG. 7) to produce a multilayer circuit board. Each double-sided copper-clad board 1 to 3 of the multilayer circuit board thus manufactured
In order to electrically connect the through holes, a through hole is opened using a drill or the like after batch lamination, and then through hole plating is performed. Also, holes are formed in an adhesive layer such as an adhesive film for bonding the first and second double-sided copper-clad substrates 1 and 2 and the second and third double-sided copper-clad substrates 2 and 3 with a drill, a punch, a laser, or the like. After the holes are filled with a conductive material, the holes may be laminated at once.

The multilayer circuit board of the present invention thus obtained can have a gradient of the coefficient of thermal expansion in the thickness direction of the board, and the coefficient of thermal expansion of the silicon chip mounting surface having a small coefficient of thermal expansion can be reduced. In addition, it is possible to set a high coefficient of thermal expansion of the secondary mounting surface on a glass epoxy substrate or the like having a large coefficient of thermal expansion. Therefore, an MCM (multi-chip module) substrate on which a bare chip is flip-chip mounted or a CPS
(Chip size package) It is suitably used as a daughter port of an interposer or the like, and can perform highly reliable mounting in both primary mounting and secondary mounting.

[0020]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows an embodiment of the multilayer circuit board of the present invention. In the figure, reference numerals 1 to 3 denote first to third double-sided copper-clad substrates, which are laminated and integrated by an adhesive layer 10 made of a polyimide-based adhesive. Each of the double-sided copper-clad substrates 1 to 3 is configured by forming circuits 7 to 9 made of copper foil on both front and back surfaces of insulating layers 4 to 6 made of a polyimide resin. Are provided with first to third metal foils 11 to 13. Reference numerals 14 to 16 denote through-hole plated portions, which electrically connect the circuits 7 to 9 on both the front and back surfaces. Reference numerals 17 and 18 denote circuits (circuits 7 and 8) of two double-sided copper-clad substrates (first and second double-sided copper-clad substrates 1 and 2 and second and third double-sided copper-clad substrates 2 and 3) vertically adjacent to each other. And solder (conductive material) for electrically connecting the circuits 8 and 9).

In this embodiment, the coefficient of thermal expansion of the second metal foil 12 is greater than the coefficient of thermal expansion of the first metal foil 11, and the coefficient of thermal expansion of the third metal foil 13 is Is larger than the coefficient of thermal expansion of the second double-sided copper-clad board 2, the coefficient of thermal expansion of the second double-sided copper-clad board 1 is larger than that of the first double-sided copper-clad board 1. Has a coefficient of thermal expansion of 2
Is set to be larger than the coefficient of thermal expansion of the double-sided copper-clad substrate 2.

The above-mentioned multilayer circuit board can be manufactured as follows. That is, first, two single-sided copper-clad polyimide laminates 21 are attached to both surfaces of the first metal foil 11 in which the through-hole connection holes 11a are opened using two adhesive sheets 22 made of a polyimide-based adhesive. Match (see FIG. 3). In this way, a base material 23 in which the conductor layer 7a made of copper foil is formed on both front and back surfaces of the insulating layer 4 made of polyimide resin is produced (see FIG. 4). Then, FIG.
As shown in (1), a small hole 24 is formed at the position of the through-hole connecting hole 11a, copper plating is performed on the small hole 24, and the conductor layers 7a on both surfaces are connected by a through-hole plated portion 14. Next, a circuit is formed on both the conductor layers 7a by a normal etching method, and the first double-sided copper-clad substrate 1 is manufactured (FIG. 6).
reference).

Next, second and third double-sided copper-clad substrates 2 and 3 are manufactured in the same manner as described above (see FIG. 7). Thereafter, an adhesive layer 10 made of a polyimide-based adhesive is provided on the upper surfaces of the second and third double-sided copper-clad substrates 2 and 3, holes 26 are formed in the adhesive layer 10, and solder holes 27 are formed in the holes 26. After filling, the first, second and third double-sided copper-clad substrates 1, 2, 3
Are collectively laminated in this order to produce the multilayer circuit board shown in FIG.

As described above, in the above-described embodiment, a gradient of the coefficient of thermal expansion can be provided in the thickness direction of the multilayer circuit board, and highly reliable mounting can be performed for both the primary mounting and the secondary mounting.
Therefore, the coefficient of thermal expansion of the silicon chip mounting surface can be set low, and the coefficient of thermal expansion of the secondary mounting surface on the glass epoxy substrate or the like can be set high.

[0026]

Embodiment 1 A metal foil made of an alloy of 36% by weight of nickel and 64% by weight of iron (thickness of thermal expansion: 1.5 ppm) having a thickness of 100 μm
/ ° C) on both sides of a two-layer base material made of 18 μm thick copper foil and 13 μm thick polyimide (manufactured by Mitsui Chemicals: NEOF)
LEX NEX-131R) is a polyimide-based adhesive sheet (manufactured by Nippon Steel Chemical Co., Ltd .: SPB-035A, Young's modulus 1.7).
GPa) and heat and pressure bonding (40 Kg / cm ² ,
(200 ° C., 1 hour) to produce a first double-sided copper-clad substrate.

Next, a second double-sided copper-clad substrate was produced in the same manner as described above, except that a titanium foil having a thickness of 100 μm (coefficient of thermal expansion: 8.6 ppm / ° C.) was used. Furthermore, thickness 1
SUS-631 having a thermal expansion coefficient of 11.8 ppm /
C)), except that a third double-sided copper-clad substrate was produced in the same manner as described above. When the thermal expansion coefficients of these first to third double-sided copper-clad substrates were measured, each was 3.5 ppm /
° C, 9.5 ppm / ° C, and 12.5 ppm / ° C.

The first to third double-sided copper-clad substrates having different coefficients of thermal expansion are bonded to a polyimide-based adhesive (UPE Kosan: UP
A-83, Young's modulus 0.6 GPa), heat and pressure bonding (40 kg / cm ² , 150 ° C., 1
Then, a multilayer circuit board having six conductor layers was manufactured.

[0029]

Embodiment 2 A metal foil made of an alloy of 42% by weight of nickel and 58% by weight of iron having a thickness of 100 μm (coefficient of thermal expansion: 4.5 ppm)
/ ° C) on both sides of a two-layer base material made of 18 μm thick copper foil and 13 μm thick polyimide (manufactured by Mitsui Chemicals: NEOF)
LEX NEX-131R) is a polyimide-based adhesive sheet (manufactured by Nippon Steel Chemical Co., Ltd .: SPB-035A, Young's modulus 1.7).
GPa) and heat and pressure bonding (40 Kg / cm ² ,
(200 ° C., 1 hour) to produce a first double-sided copper-clad substrate.

Next, a metal foil made of an alloy having a thickness of 40 μm and comprising 42% by weight of nickel and 58% by weight of iron (coefficient of thermal expansion: 4.5)
ppm / ° C.) in the same manner as described above, except that
Was produced. Further, a third double-sided copper-clad substrate is produced in the same manner as described above, except that a metal foil (coefficient of thermal expansion: 4.5 ppm / ° C.) made of an alloy of 42% by weight of nickel and 58% by weight of iron having a thickness of 20 μm is used. did. When the thermal expansion coefficients of these first to third double-sided copper-clad substrates were measured,
6.3 ppm / ° C, 9.5 ppm / ° C, and 12.
It was 0 ppm / ° C.

The first to third double-sided copper-clad substrates having different coefficients of thermal expansion are bonded to a polyimide adhesive (UPE Kosan: UP
A-83, Young's modulus 0.6 GPa), heat and pressure bonding (40 kg / cm ² , 150 ° C., 1
Then, a multilayer circuit board having six conductor layers was manufactured.

[0032]

Example 3 The polyimide adhesive used in Example 1 (UPA-83, manufactured by Ube Industries, Ltd., Young's modulus 0.6 GP)
Instead of a), the first to third double-sided copper-clad substrates having different coefficients of thermal expansion are thermally expanded using a polyimide adhesive (SPB-035A, manufactured by Nippon Steel Chemical Co., Ltd., Young's modulus: 1.7 GPa). Heat and pressure bonding (40 kg / cm ² , 150
C., 1 hour) in the same manner as in Example 1 above.
A multilayer circuit board having six conductor layers was manufactured.

The thermal expansion coefficients of the front and back surfaces of the multilayer circuit boards of Examples 1 to 3 and the warpage of the boards were measured, and the following results were obtained. The results are shown in Table 1 below. As is clear from Table 1, all of the products of Examples 1 to 3 have different thermal expansion coefficients on the front and back of the substrate. Moreover, there is almost no warpage of the substrate. However, the product of Example 3
The warpage of the substrate is slightly larger than the products of the first and second embodiments. By using substrates having different coefficients of thermal expansion on the front and back in this way, it is possible to improve the reliability of bare chip mounting (primary mounting) and the reliability of secondary mounting on a motherboard. , MCM substrate, etc.

[0034]

[Table 1]

[0035]

As described above, according to the multilayer circuit board of the present invention, the coefficient of thermal expansion of the chip mounting surface is reduced and the coefficient of thermal expansion of the surface connected to the glass epoxy substrate is increased. High connection reliability can be ensured in both the secondary mounting and the secondary mounting.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the configuration of a multilayer circuit board according to the present invention.

FIG. 2 is a sectional view showing an embodiment of the multilayer circuit board of the present invention.

FIG. 3 is a cross-sectional view showing a manufacturing process of the multilayer circuit board.

FIG. 4 is a sectional view showing a manufacturing process of the multilayer circuit board.

FIG. 5 is a cross-sectional view showing a manufacturing process of the multilayer circuit board.

FIG. 6 is a cross-sectional view illustrating a step of manufacturing the multilayer circuit board.

FIG. 7 is a cross-sectional view showing a step of manufacturing the multilayer circuit board.

[Explanation of symbols]

 1-3 double-sided copper-clad board 4-6 insulating layer 10 adhesive layer 11-13 metal foil

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Masakazu Sugimoto 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Kei Nakamura 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Takuji Okei 1-1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation F Term (Reference) 5E346 AA06 AA12 AA15 AA16 AA22 AA25 BB01 BB15 CC10 CC31 CC32 CC34 CC37 CC41 EE01 EE05 EE12 GG28 HH07 HH11

Claims (5)

[Claims] 1. A multilayer structure in which a plurality of double-sided copper-clad substrates each having a different coefficient of thermal expansion containing a metal foil in an insulating layer are laminated via an adhesive layer in the order of increasing coefficient of thermal expansion and integrated. Circuit board. 2. The multilayer circuit board according to claim 1, wherein the coefficient of thermal expansion of the double-sided copper-clad board is controlled by changing the coefficient of thermal expansion of a metal foil contained in an insulating layer. 3. The multilayer circuit board according to claim 1, wherein a coefficient of thermal expansion of the double-sided copper-clad board is controlled by changing a thickness of a metal foil included in an insulating layer. 4. The multilayer circuit board according to claim 1, wherein a Young's modulus at room temperature of an adhesive used for lamination integration is 1.0 GPa or less. 5. The metal foil is made of one or more metals selected from titanium, SUS, copper, nickel, aluminum, iron-nickel alloy, and iron-nickel-cobalt alloy. The multilayer circuit board according to claim 1.