JP2003204170A - Manufacturing method of multilayer printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a multilayer printed circuit board by which production is possible without molding failures with satisfactory reliability, on the condition that the thickness of a prepreg layer is less than three times of the thickness of an inner copper film, even when steps having a thickness of 105 μm or 175 μm of an inner copper foil are filled in the inner copper foil circuit, in the multilayer printed circuit board formed by combining prepregs having different performance, and to provide the multilayer printed circuit board. <P>SOLUTION: In the manufacturing method of the multilayer printed circuit board in which circuits are formed on one or more copper-clad plates and molded in one with a plurality of prepregs overlapped thereon, the prepregs are integrally molded into a multilayer by combining a prepreg including a resin impregnated thereto having the melt viscosity of 120 Pa.s or more at temperatures of 120-140°C with another prepreg including a resin having the melt viscosity of 80 Pa.s or less. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board. 2. Description of the Related Art A multilayer printed wiring board is obtained by forming at least one copper-clad laminate into a circuit as an inner layer, and alternately with a prepreg obtained by impregnating a resin such as a glass cloth with a resin and semi-curing. In general, they are superposed, heated and pressed to be integrally formed. Usually, the resin of the prepreg is made to have fluidity at the time of heating in order to fill the steps of the inner layer circuit. In order to secure the reliability as a printed wiring board, the thickness of the insulating layer is generally required to be at least twice as large as the thickness of the inner copper foil. Or adjust the resin performance. In recent years, a thick copper foil, such as 105 μm or 175 μm, which is equivalent to the thickness of one prepreg glass cloth, may be used as the inner copper foil for heat dissipation. In such a case, in order to ensure reliability, it is necessary to ensure that the thickness of the prepreg layer is at least three times the thickness of the inner copper foil, and this is actually performed. Recently, there has been a demand for thinner and lighter substrates having an inner copper foil having a thickness of 105 μm or 175 μm. May not be secured three times or more. As a countermeasure, it has been considered to use a plurality of prepregs having an extremely large resin flow in order to secure more resin for filling the steps of the inner layer circuit. However, when the resin flow is large, the timing of heat conduction is slightly different between the front and back of the board during multi-stage press molding, causing the fluidized resin to concentrate at specific locations, causing a local thickening phenomenon. Resulting in. Further, the resin rarely moves through the front and back of one glass cloth, and even if a plurality of prepregs having a large resin flow are overlapped, the flown resin is not used only for filling the steps. Therefore, in many cases, the heat resistance cannot be improved by the overlap. Furthermore, at the end of the substrate at the time of multilayer molding, the thickness of the board is reduced due to excessive flow of the resin. In an extreme case, the resin disappears and the whitening phenomenon occurs. In view of the above problems, the inventor of the present invention has studied and, as a result, has come to invent a measure for preventing the occurrence of defects at the time of multi-layer bonding due to a step in an inner layer circuit. Hereinafter, the contents will be described. SUMMARY OF THE INVENTION The present invention provides at least one
Forming a copper-clad circuit, forming a single layer by laminating these with a plurality of prepregs, in a method of manufacturing a multilayer printed wiring board, the resin impregnated in the prepreg,
It is characterized in that a prepreg having a melt viscosity at 120 to 140 ° C. of 120 Pa · s or more and a prepreg having a melt viscosity of 80 Pa · s or less are combined to form a multilayer integral molding. The arrangement of the prepreg is such that the melt viscosity at 120 to 140 ° C. is 8
A prepreg of 0 Pa · s or less is brought into contact with the inner layer circuit surface, and the melt viscosity at 120 to 140 ° C. is 120 Pa
・ Place s or more prepregs on the outside. In the case where two or more inner circuit boards are used, similarly, at a portion sandwiched between the inner circuit boards, the melt viscosity at 20 to 140 ° C. is 80
A prepreg of Pa · s or less is placed, and a
A prepreg having a melt viscosity at 140 ° C. of 120 Pa · s or more is arranged. In this case, if it is not necessary to arrange a prepreg of 80 Pa · s or less on both opposing surfaces due to the inner layer circuit shape of two or more inner layer circuit boards, it may be arranged only on one side. The melt viscosity is 80 Pa · s or less and 120 P
Combine more than a · s. If the combination is outside this range, the effect may not be obtained. Preferably, the combination is 70 Pa · s or less and 150 Pa · s or more. The prepreg has different melt viscosity values as shown in the claims. However, it is preferable that the other characteristics, that is, the curing time, the resin flow, etc., be as close as possible. The numerical range must be adjusted according to the pressing conditions. Otherwise, the intended effect may not be obtained depending on the heating conditions at the time of the multilayer press, and in some cases, molding defects may occur. In the above prepreg manufacturing method, when only the melt viscosity is changed without greatly changing the resin flow or the curing time, it is often difficult to achieve the prepreg only by the prepreg coating conditions. It is necessary to study from the composition of. In the case of an epoxy resin, three types of resins are generally used: a component of the epoxy resin body, a curing agent, and a curing accelerator. An amine-based curing agent and an amine-based catalyst are often used as a curing accelerator.
In the prepreg of the present invention, the components of the resin main body are not changed,
This was achieved by increasing the amounts of the curing agent and the curing accelerator and balancing the amounts of the two components with reference to the moldability during multilayer adhesion. Regarding the multilayer molding press conditions, it is necessary to grasp the optimum conditions in order to simultaneously press two types of prepregs having different melt viscosities. The melt viscosity at 120-140 ° C. is 80 Pa
・ The prepreg of s or less should be in contact with the inner layer circuit surface,
By disposing a prepreg having a melt viscosity of 120 Pa · s or more at 120 to 140 ° C. outside thereof, at the time of press molding, a resin of a low prepreg having a low melt viscosity in contact with an inner circuit board flows out to fill a step on a circuit surface. . The resin of the prepreg with high melt viscosity on the side not in contact with the inner circuit board also flows out, but the viscosity is higher than that of the prepreg on the circuit surface side,
The outflow is slow. In this way, the low-viscosity prepreg resin fills the steps of the inner circuit board first, and then the high-viscosity prepreg resin works to flow and flatten. In this way, even if there is no prepreg layer having a thickness of at least twice the thickness of the inner layer copper foil, it is possible to perform multi-layer molding without causing molding defects. Examples and Comparative Examples 1 and 2 As an inner circuit board, a glass epoxy double-sided copper-clad laminate MCL-E having a base material layer having a nominal thickness of 0.4 mm and a double-sided copper foil of 105 μm was used.
-67S (trade name of Hitachi Chemical Co., Ltd.) was prepared, and a copper foil on both sides was formed in a circuit. The following two types of prepregs were prepared, and the materials were composed in the combinations shown in Table 1. The temperature was raised at 3 ° C./min and the maximum temperature was 1 in a multi-stage press.
The molded body was integrally molded at 70 ° C., a heating time of 120 minutes and a pressure of 25 kg / cm 2. Prepreg used 1: GE-67N glass epoxy prepreg (trade name of Hitachi Chemical Co., Ltd.) Glass cloth type # 2117 Resin content 52% Resin flow 17% Melt viscosity 70 Pa · s Prepreg used 2: GE-67N glass epoxy prepreg (Hitachi Chemical (Industrial Co., Ltd.) Glass cloth type # 2117 Resin content 52% Resin flow 19% Melt viscosity 160 Pa · s As can be seen from Table 1, Examples, Comparative Example 1,
In each of Comparative Examples 2, the ratio of the thickness of the prepreg layer to the inner copper foil was 3 or less. As shown in Table 1, the evaluation results of the moldability show that, in Comparative Examples 1 and 2, a moldability defect occurred, but in Examples of the present invention, no defect occurred in all items. . [Table 1] The multilayer printed wiring board manufactured by combining prepregs having different performances according to the present invention has an inner copper foil of 1
Even in the case of filling a step in a circuit of a thick inner copper foil of, for example, 05 μm or 175 μm, it is possible to manufacture the prepreg layer without forming defects without securing the prepreg layer not less than three times the thickness of the inner copper foil, and the reliability is also required. Filling multilayer printed wiring boards can be manufactured.

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 4F100 AB17B AB17D AB17E AG00                       AK53 BA02 BA03 BA04 BA05                       BA06 BA07 BA08 BA13 DG11                       DH01A DH01C DH01E EJ17                       EJ42 EJ82 GB43 JA06A                       JA06C JA06E JL02 YY00A                       YY00C YY00E                 5E346 AA05 AA06 AA12 AA15 AA32                       AA38 BB01 CC02 CC09 CC32                       DD02 EE02 EE06 EE09 EE13                       EE20 GG28 HH08 HH11

Claims (1)

Claims: 1. A method for manufacturing a multilayer printed wiring board, comprising forming at least one copper-clad board as a circuit, superimposing these on a plurality of prepregs, and integrally molding the prepregs. A resin impregnated with a prepreg having a melt viscosity at 120 to 140 ° C. of 120 Pa · s or more and 80 Pa
A method for manufacturing a multilayer printed wiring board and a product thereof, wherein a prepreg of s or less is combined to form a multilayer integrated circuit.