JPH10173345A - Multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent warping during heat treatment process by employing a laminate having basic material of woven fabric, where the filament composing a yarn has an elastic modulus of specified value or above, as an inner core material and then forming a conductor layer on the conductor layer of the inner core material through an insulation layer containing no reinforcing material. SOLUTION: A woven fabric in which the filament composing the yarn has an elastic modulus of 78.4GPa or above is employed as a basic material for composing an inner core material. Mean elastic modulus of the filaments composing the yarn is employed. The inner core material is formed by impregnating a woven fabric with an epoxy based resin for laminating and drying the woven fabric to produce a prepreg, laminating the required number of prepregs, applying a metal foil to one or both side thereof, hot-pressing the prepregs to produce a metal foil clad laminate and then forming a circuit. Finally, a conductor layer 15 formed on the conductors of the inner core through insulation layer containing no reinforcing fibers, thus forming a multilayer printed wiring board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multilayer printed wiring board.

[0002]

2. Description of the Related Art As a high-density multilayer printed wiring board corresponding to miniaturization and high integration of electronic components, an insulating resin layer containing no reinforcing fiber is interposed on a conductor layer of an inner core material made of a woven fabric as a base material. A multi-layer printed wiring board formed by forming a conductor layer by multi-layering has been used.

As such a multilayer printed wiring board, a metal-clad laminate based on a woven fabric is used as an inner core material, and an insulating resin layer and a conductor layer are sequentially formed on the conductor layer of the inner core material. There is a multi-layer printed wiring board by a build-up method of stacking and manufacturing. As a method of stacking the insulating resin layer and the conductor layer, a method in which a conductor layer is formed on a film of an epoxy resin or a polyimide resin and the like is stacked on the conductor layer of the inner core material, An insulating resin layer is formed using a photosensitive resin thereon, a conductor layer is formed thereon, and an insulating resin layer is formed thereon using a photosensitive resin, and the conductor layer is repeatedly formed to form a desired number of layers. A method for manufacturing a multilayer printed wiring board is known. As described above, when an insulating resin layer containing no reinforcing fibers other than the inner core material is formed, fine wiring having a wiring pitch of 200 μm or less and a via diameter of 200 μm or less can be easily formed.

[0004]

However, in addition to the inner core material, a multilayer printed wiring board in which an insulating resin layer containing no reinforcing fibers and a conductor layer are sequentially formed to form a multilayer is used in a reflow process and a component mounting process. In a process involving an equal heat treatment, there is a disadvantage that large warpage is likely to occur. In a multilayer printed wiring board in which the majority of component mounting is performed by surface mounting, the occurrence of large warpage hinders component mounting. An object of the present invention is to provide a multilayer printed wiring board in which warpage generated in a step involving heat treatment is small.

[0005]

According to the present invention, there is provided an inner core material comprising a laminate made of a woven fabric having a modulus of elasticity of a filament constituting a yarn of 78.4 GPa or more. This is a multilayer printed wiring board formed by forming a conductor layer via an insulating resin layer containing no reinforcing fibers.

Generally, the thermal expansion coefficient of the resin forming the insulating resin layer containing no reinforcing fibers is larger than 4 × 10 ⁻⁵ / ° C. However, the thermal expansion coefficient of the inner layer core material is 2 × 10 ^−5.
/ ° C. In a multilayer printed wiring board by a build-up method, warpage occurs due to a so-called bimetal phenomenon in a process involving heat treatment because an insulating resin layer containing no reinforcing fiber is biased on one surface of a core material. This warpage can be suppressed by increasing the modulus of elasticity of the inner layer core material, that is, by setting the modulus of elasticity of the filaments of the yarns of the woven fabric serving as the base material of the inner layer core material to 78.4 GPa or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As a woven fabric having a filament elastic modulus of 78.4 GPa or more constituting a yarn of the woven fabric,
For example, S-glass (filament elastic modulus is 84.3)
Woven fabric using GPa) yarns. Commercially available products of such a woven fabric include T glass cloth and the like manufactured by Nitto Boseki Co., Ltd. It is not necessary that all the filaments constituting the yarn of the woven fabric have an elastic modulus of 78.4 GPa or more, provided that the average value of the elastic modulus of the filaments constituting the yarn of the woven fabric is 78.4 GPa or more. Good.

The method for producing the inner layer core material is not particularly limited except that a woven fabric in which the filament constituting the yarn has an elastic modulus of 78.4 GPa or more is used. it can. For example, a woven fabric is impregnated with a resin for a laminate such as an epoxy resin or a polyimide resin and dried to form a prepreg. Press to form a metal-clad laminate on one or both sides. Then, the metal clad laminate is subjected to circuit processing by a known method to form an inner core material. Further, a multi-layered inner core material having undergone circuit processing via a prepreg or an insulating resin layer may be used as the inner core material.

As the insulating resin layer containing no reinforcing fibers, a film formed of a conventional epoxy resin, polyimide resin, or the like can be used. In this case, after the resin film is pasted on the copper foil and a hole is formed in an IVH (interstitial via hole) forming layer, the hole and the inner layer circuit are aligned and laminated and integrated. Thereafter, the wiring layer is formed by plating including the inner wall of the hole. Further, an insulating resin layer is formed using a photosensitive resin. In this case, when an IVH is used as a build-up, exposure and development are performed through a photomask in order to form a hole serving as a via hole. Thereafter, a surface roughening treatment or the like is performed, and the conductors are made conductive by plating. Then, the plating layer formed on the photosensitive resin layer is etched to form a circuit.

[0010]

【Example】

Example 1 1,000 g of bisphenol A, 37% formalin 22
0 g and 10 g of oxalic acid were charged into a four-necked flask equipped with a cooling tube and a stirrer, refluxed for 2 hours to react, and then dehydrated and concentrated to obtain a bisphenol A novolak resin. 60 parts by weight of the obtained bisphenol A novolak resin, bisphenol A novolak type epoxy resin (Epiclon N-865 (trade name) manufactured by Dainippon Ink and Chemicals, Inc.)
100 parts by weight, 1-cyanoethyl-2-ethyl-4-methylimidazole 0.5 part by weight and bisphenol-based antioxidant (Yoshinox BB (trade name) manufactured by Yoshitomi Pharmaceutical Co., Ltd.) 5 parts by weight were dissolved in 100 parts by weight of methyl ethyl ketone to obtain an epoxy resin varnish.

A T-glass cloth having a modulus of elasticity of 84.3 GPa (WTX116F (trade name), manufactured by Nitto Boseki Co., Ltd., weight: 10)
(8 g / cm ² was used), and the resin was impregnated and dried so that the resin content after the impregnation and drying was 51% by weight and the thickness was 0.1 mm to obtain a prepreg. Four prepregs are laminated, copper foil of 18 μm thickness is laminated on both surfaces thereof, inserted by a head plate, and heated and pressed at a temperature of 175 ° C. and a pressure of 3 MPa for 60 minutes under a reduced pressure of 13 to 80 hPa, and a double-sided copper-clad laminate. I got a board. Next, the obtained double-sided copper-clad laminate was etched to form a circuit, and an inner core material was obtained. On one side of the inner layer core material, a copper foil of 18 μm thickness is laminated via an epoxy-based adhesive film and inserted with a head plate.
Under the reduced pressure of a, heating and pressing were performed at a temperature of 175 ° C. and a pressure of 3 MPa for 60 minutes to obtain a three-layer printed wiring board. As the epoxy-based adhesive film, a high-molecular-weight epoxy resin-based adhesive film (AS-3000, manufactured by Hitachi Chemical Co., Ltd.)
(Product name)).

The obtained three-layer printed wiring board is 3 × 200
mm into a test piece.
After passing through a reflow process under the conditions of 2 ° C., 2 minutes, main heating at 230 ° C. and 30 seconds, the maximum amount of warpage was measured. as a result,
The maximum amount of warpage was 0.5 mm. The maximum amount of warpage was determined in accordance with JIS C 6481 by applying a straightedge to the long side of the concave side of the test piece and measuring the maximum distance between the straightedge and the surface of the test piece.

Comparative Example The elastic modulus of the glass filament constituting the yarn of the cloth is 7
2.5 GPa E-glass cloth (manufactured by Nitto Boseki Co., Ltd., WEX116F (trade name), weight 108 g / cm)
^A three-layer printed wiring board was obtained in the same manner as in Example 1 except that ² ) was used.

The maximum warpage of the obtained three-layer printed wiring board was measured in the same manner as in Example 1. as a result,
The maximum amount of warpage was 2.1 mm.

[0015]

According to the present invention, in a multi-layer printed wiring board in which a conductor layer is formed on a conductor layer of an inner core material via an insulating resin layer containing no reinforcing fiber, this occurs in a process involving heat treatment. Warpage can be reduced.

Claims (1)

[Claims] An elastic modulus of a filament constituting a yarn is 7
A multilayer printed wiring board in which a laminate having a woven fabric of 8.4 GPa or more as a base material is used as an inner core material, and a conductor layer is formed on a conductor layer of the inner core material via an insulating resin layer containing no reinforcing fiber. .