JPS62281400A - Multilayer bonding of printed board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for bonding printed circuit boards, and particularly to a method for manufacturing a multilayer printed circuit board with little change in thickness dimension after bonding. The present invention relates to a multilayer adhesion method for printed circuit boards suitable for.

[Conventional technology]

In general, a multilayer printed circuit board consists of a board with a circuit pattern formed on one or both sides, and an adhesive sheet (made by impregnating a glass cloth base material with resin and then heat-treating the resin to make it semi-cured).
It is manufactured by stacking sheets (prepreg) alternately and heating and pressurizing them. In manufacturing such a multilayer printed circuit board,
Conventionally, pressure was applied when bonding multiple layers of printed circuit boards using a two-step pressurization method of low pressure and high pressure, or a single-step pressurization method in which high pressure was applied from the beginning.

Regarding the two-stage pressure method and the one-stage pressure method mentioned above, please refer to "Printed Circuit Handbook" (Kinda Kagakusha) P.

23-12 to 23-17.

[Problem that the invention seeks to solve]

The above-mentioned conventional techniques cannot simultaneously solve all of the problems that occur with the recent increase in the density of circuit patterns and the increase in the number of layers of paperboard, such as changes in the height of the resin, generation of voids, and warpage. The object of the present invention is to simultaneously solve problems such as changes in resin thickness dimensions, generation of voids, and warping that occur when bonding multiple layers of printed circuit boards, which have been difficult.

[Means for solving problems]

The above purpose is to reduce the pressure force when adhering multiple layers of printed circuit boards.
When the prepreg resin, which is the adhesive for printed circuit boards, starts melting, the primary contact pressure is extremely low, then when the resin stops flowing after melting, the pressure is switched to the secondary high pressure, and finally when the resin hardens, the tertiary low pressure is applied. This is achieved by depressurizing.

[For production]

The low pressure of the primary contact allows the prepreg resin to melt uniformly,
Maintain time to viscosity with proper fluidity. This-
At the timing of transition from the holding time of the next pressure to the second high pressure, the amount of resin flow between the adhesive layers changes, and the thickness between the adhesive layers changes.

The tertiary high pressure maintains the prepreg resin while it has fluidity, from melting to beginning hardening, and functions to eliminate air bubbles (adhesion voids) generated in the prepreg layer by flushing them away.

The resin hardens by heating and shrinks by cooling. At this time, when hardening and molding is performed under high pressure, distorted expansion and contraction occurs. During this curing, by releasing the pressure to a low tertiary pressure, uniform expansion and contraction occurs, making it possible to suppress variations in dimensional changes.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows how printed circuit boards are bonded in multiple layers, and this embodiment shows the case where three printed circuit boards 1 are bonded. That is, after forming the inner layer circuit pattern, an adhesive prepreg 2 is sandwiched between each substrate 1 whose surface has been treated with chemicals etc. as a pre-adhesion treatment, and guide pins 4 are used to prevent each substrate 1 from shifting. Align and laminate.

Fix with mirror plate 3. Thereafter, this laminated board is heated and pressed with a hot plate 5 of an adhesive hot press to form a multilayer printed board.

The present invention divides the pressurizing force during multilayer adhesion of the printed circuit board into three stages according to the process from melting of the prepreg resin to curing, and the contact pressure is extremely low at the start of melting (-next contact pressure).
The point at which the resin stops flowing after melting is at high pressure (secondary high pressure), and during curing, the pressure is released at low pressure (secondary low pressure).

FIG. 1 is a flowchart, and FIG. 2 is a temperature/pressure profile.

Initially, the temperature of the hot plate 5 is set to Ti (120-140°C) and maintained for t2 hours (15-30 minutes). Thereafter, the temperature is increased to T2 (160-175°C) and held for 1 hour (60,120 minutes), after which it is cooled to room temperature.

Immediately after the temperature T is applied, the resin of the prepreg starts to melt from a semi-hardened state, and as the temperature changes to T2, it changes to a uniformly molten state and a fluid state. It becomes a state where there is no.

Pressure is applied to the laminated substrate when the prepreg resin starts to melt from semi-hardened as mentioned above, and the primary contact force P is extremely low.
(1 kg/a+f), and hold for a period of time (5 to 10 minutes) (step 101). after that.

After the prepreg resin is uniformly melted, the secondary pressure P,
Increase the pressure to (30-40 kg/cn?). Then, the fluidity of the resin disappears and it is held for 1 hour (30 to 50 minutes) (
Step 102). Due to the secondary pressure, air bubbles between the adhesive layers are extruded or crushed to disappear. After that, the tertiary pressure P2 (5 to 15 kg/c
J) Depressurize and leave for more than 4 hours (60-120 minutes)
This is held until the end of the 5-hour press (step 103).

The resin has the property of expanding when heated and shrinking when cooled. When hardened and molded under high pressure, distorted expansion and contraction occurs. By releasing the pressure to a lower pressure as the tertiary pressure during curing, uniform expansion and contraction occurs and variations in dimensional changes can be suppressed to a small level.

According to this example, in the case of three layers, the variation in the thickness dimension change of the multilayer bonded substrate is 3σ = 0.1 with the conventional bonding method.
5% (however, σ indicates the thickness dimensional change in one J& board), it can be reduced to 3σ = 0°05 to 0.08%, and it is also possible to prevent the occurrence of adhesive voids. can. Furthermore, the amount of warp deformation after multi-layer bonding has been reduced from 0.6% with conventional high-pressure curing molding to 0.3%, less than half, which is equivalent to that of simply low-pressure curing molding. Obtainable.

〔Effect of the invention〕

According to the present invention, +8 of the prepreg resin during multilayer adhesion
This has the effect of eliminating adhesive voids due to extrusion, crushing, etc. due to the high pressure during melting, and the effect of eliminating variations in substrate deformation by removing pressure during curing and molding after the resin has lost its fluidity.

[Brief explanation of drawings]

Figure 1 is a flowchart of the pressurizing process during multilayer bonding according to the present invention, Figure 2 is a profile diagram of temperature and pressure, and Figure 3
The figure is a cross-sectional view of a multilayer structure such as a printed circuit board or prepreg. 1... Printed circuit board, 2... Prepreg, 3...
Mirror plate, 4... Guide pin, 5... Hot plate. 6... Pressure profile, 7... Temperature profile, 101, 102, 103... Pressurizing step. ′”′・Go(j'-:,)・′ E1i:2 z3 Jtt5
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Claims (2)

[Claims] (1) In a method of laminating a printed circuit board on which a circuit pattern is formed and a resin that is an adhesive for the printed circuit board, and applying heat and pressure to bond the printed circuit board in multiple layers, first, when the resin starts to melt due to heating, a low pressure is applied. A printed circuit board characterized by applying pressure at (primary pressure), then switching to high pressure (secondary pressure) when the resin loses its fluidity, and then releasing to low pressure (tertiary pressure) when the resin begins to harden. Multilayer adhesive method. (2) The method for adhering multiple layers of printed circuit boards according to claim 1, wherein the heating temperature is increased after the pressure is switched to a high pressure, and is decreased after the pressure is low.