JP2007227712A - Multilayer printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer printed wiring board in which solder heat resistance can be enhanced by preventing a substrate from swelling owing to gas produced at the time of soldering. <P>SOLUTION: In at least one conductor layer, out-gas diffusion regions 14 from where conductors 13 on an insulating substrate 12 are removed regularly at a pitch of 11 mm or less are provided in a region other than a circuit forming portion. When a nonconductor 14 is square, for example, the conductors are arranged regularly at pitches P<SB>11</SB>and P<SB>12</SB>of 11 mm or less in both longitudinal and lateral directions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer printed wiring board, and relates to a technique for preventing a board from swelling by controlling an outgas generated in a soldering process performed during component mounting.

  A component is mounted on the multilayer printed wiring board, and is passed through a soldering process in order to electrically and mechanically join the component and the wiring pattern of the outer layer circuit. As one of the typical automatic soldering methods often used in mass production, a necessary amount of solder is applied to the substrate in advance by solder paste printing or the like, and the substrate is placed in a reflow furnace such as a far infrared ray or hot air circulation method. A method is known in which the solder on the substrate is heated and melted by passing it through. In this method, the multilayer printed wiring board is required to have solder heat resistance that can withstand a temperature higher than the solder melting point.

  However, some insulating base materials and adhesives used between conductor layers have poor solder heat resistance, and there is a tendency that abnormalities such as expansion of the interlayer are likely to occur due to outgassing during heating in the soldering process. In particular, for grounding, shielding, and other various reinforcements, in addition to the circuit forming portion, a region where a conductor layer is continuously formed in a large area (in the present invention, this may be referred to as a “circuit non-forming region”). ) Is likely to cause delamination due to swelling. This is because decomposition gas is generated due to heating of the substrate material during soldering, or gas adsorbed on the interface of the conductor layer in contact with the insulating base material or adhesive is released by heating. It is believed that. Since the diffusion of the gas generated in this way is blocked by the conductor layer, the insulating base material, the interlayer adhesive, the interface of the conductor layer and the inside of the interlayer adhesive will swell, causing abnormalities and destruction of the substrate. It becomes.

Conventionally, various measures have been taken to prevent such swelling and delamination. Examples of conventional techniques include the following.
In Patent Document 1, in a region of a conductor layer provided in a continuous state over a large area on an inner layer and an outer layer, dot-like, streaky, and lattice-like interlayer coupling portions are formed in a dense state with a pitch of 0.1 to 10 mm. By forming and integrally connecting the inner solid conductor layer provided in the inner layer and the outer solid conductor layer provided in the outer layer by these interlayer connection portions, the gas generated during the heating of soldering can be prevented. A method for maintaining a strong bonded state between layers and preventing delamination is shown.
Patent Document 2 discloses that in a laminated plate obtained by heating and press-molding a synthetic resin fiber nonwoven fabric layer impregnated with a thermosetting resin, the moisture diffusion coefficient of the laminated plate is reduced, specifically 1.3 × 10 ^−8. A method is shown in which delamination of the substrate does not occur due to heat in the reflow furnace by setting it to cm ² / sec or less.
JP-A-11-214845 Japanese Patent No. 3339357

However, according to the technique disclosed in Patent Document 1, the interlayer connection portion is formed by laminating an insulating resin of the outer layer on the inner solid conductor layer by coating or laminating, and processing the laminated insulating resin. A plurality of via holes or grooves penetrating the insulating resin, and forming a conductor layer together with an outer solid conductor layer on the inner wall surface of these via holes or grooves and connecting to the inner solid conductor layer. is required. For this reason, a significant increase in manufacturing cost cannot be denied, and since the conductor layer is formed as a solid conductor layer of the inner layer and the outer layer with respect to the insulating resin, the gas generated during soldering is reduced to the insulating base material, the interlayer It does not solve the fundamental problem of staying at the interface between the adhesive and the conductor layer or inside the interlayer adhesive.
Further, according to the technique disclosed in Patent Document 2, since usable insulating materials are remarkably limited, the application range is limited, and there is a concern about an increase in material cost.

  The present invention has been made in view of the above circumstances, and provides a multilayer printed wiring board capable of preventing swelling of a substrate against gas generated during soldering and improving solder heat resistance. Let it be an issue.

In order to solve the above-mentioned problems, the present invention has an outgas diffusion portion in which conductors on an insulating substrate are regularly removed at a pitch of 11 mm or less in a region other than a circuit formation portion in at least one conductor layer. A multilayer printed wiring board is provided.
Examples of the outgas diffusion portion include a square non-conductor portion in which conductors are regularly removed at a pitch of 11 mm or less in both the vertical direction and the horizontal direction, and conductors are regularly removed at a pitch of 11 mm or less. And those composed of parallel, striped non-conductor portions.

  Since the multilayer printed wiring board of the present invention has an outgas diffusion portion in which the conductor on the insulating substrate is regularly removed at a pitch of 11 mm or less in a region other than the circuit formation portion in at least one conductor layer. The outgas can be released through this outgas diffusion part, and the gas generated during soldering stays in the insulating base material, interlayer adhesive, conductor layer interface and inside the interlayer adhesive and causes the swell. Therefore, it is possible to reliably prevent the substrate from swelling and to greatly improve the soldering heat resistance.

The present invention will be described below based on the best mode.
In the multilayer printed wiring board formed by laminating an insulating layer and a conductor layer, the present invention has a conductor layer formed continuously over a wide area in addition to a circuit forming portion for grounding, shielding, and other various reinforcements. In order to prevent the expansion of the substrate in the area where the circuit is present (in the present invention, this may be referred to as “circuit non-formation area”), the non-conductor in which the conductor on the insulating base material is not present in the circuit non-formation area The outgas diffusion part is configured by regularly forming the part with a pitch of 11 mm or less.

  In general, since a conductor layer such as a copper foil has low gas permeability, if a conductor layer exists continuously over a wide area, diffusion of outgas is prevented in that region. For this reason, the outgas stays in the interface of the insulating base material, the interlayer adhesive, and the conductor layer, and inside the interlayer adhesive, resulting in swelling and causing abnormalities and destruction of the substrate.

  Therefore, in the present invention, since the non-conductor portion is regularly formed as described above, the gas generated from the resin layer and the adhesive material such as the insulating base material permeates and diffuses through the resin layer and the adhesive material during soldering. When doing so, it can bypass the conductor layer, pass through the non-conductor portion, and finally reach the outside of the multilayer printed wiring board. In this way, the degassing of the outgas generated inside the resin layer or the adhesive is not blocked by the conductor layer, and the gas can be released naturally to the outside of the substrate, which may cause the substrate to swell. Absent. In this way, the fundamental problem that outgas stays in the insulating base material, interlayer adhesive, conductor layer interface and inside the interlayer adhesive and causes the swelling is solved, and the swelling of the substrate is ensured. And can greatly improve solder heat resistance.

There is no restriction | limiting in particular in the board | substrate material used by this invention. As the copper clad laminate (CCL), a two-layer CCL in which a copper foil is directly laminated on an insulating resin layer, and a three-layer CCL in which the insulating resin layer and the copper foil are bonded via an adhesive. Any of these can be used. Examples of the material for the insulating substrate include insulating resins such as polyimide, polyester, and liquid crystal polymer, but are not particularly limited thereto.
The method of forming the non-conductor portion is not particularly limited, but when the circuit is formed on the substrate, at the same time as the circuit is formed, the conductor in the region that becomes the circuit non-formation region is partially removed to expose the insulating layer. The method of making parts is preferred. According to this method, there is an advantage that there is no increase in processing steps and an increase in manufacturing cost is small.
In the multilayer printed wiring board of the present invention, the outgas diffusion part is provided in the circuit non-formation region, and the circuit formation part is not particularly limited. A multilayer printed wiring board has two or more conductor layers. In the present invention, it is sufficient that an outgas diffusion portion is formed in a circuit non-formation region in at least one of the conductor layers, and there is no circuit non-formation region or a conductor layer having a relatively small area. It is not necessary to provide an outgas diffusion part. In order to suppress the outgas stagnation as much as possible, it is preferable to provide an outgas diffusion portion in a circuit non-formation region in all the conductor layers.

  The configuration of the outgas diffusion portion provided in the circuit non-formation region will be described with reference to FIGS. FIG. 1 and FIG. 2 are drawings in which only a circuit non-formation region in a conductor layer in which an outgas diffusion portion is provided in a circuit non-formation region is partially enlarged in a multilayer printed wiring board. FIG. 1A and FIG. 2A are cross-sectional views showing single-sided CCLs 11 and 21 having conductor layers 13 and 23 on insulating base materials 12 and 22 as substrate materials before forming an outgas diffusion portion. FIG.

As an example of the configuration of the outgas diffusion part formed in the circuit non-formation region, as shown in FIGS. 1B and 1C, the circuit non-formation region of each substrate 11 constituting the multilayer printed wiring board 10 In FIG. 1, the conductive layer 13 on the insulating base 12 is removed, and the non-conductor portions 14 and 14 that are square in two directions perpendicular to each other along the substrate surface (two directions in the vertical direction and the horizontal direction in FIG. 1B). ,... Are arranged in a large number. In this case, to avoid accumulation of gas by the conductor layer 13, the non-conductor portion 14, 14, it is desirable to ... both longitudinal pitch _{P 11} and lateral pitch _{P 12} and 11mm below. Thereby, it becomes the structure excellent in the effect which prevents the floating of a conductor and the swelling (delamination) of a board | substrate.
In FIG. 1B, the vertical pitch P ₁₁ is the distance between the centers of the two adjacent non-conductor portions 14, 14, and the horizontal pitch P ₁₂ is the two adjacent pitches P ₁₂ . The distance between the centers of the non-conductor portions 14 and 14 in the horizontal direction.

As another example of the configuration of the outgas diffusion portion formed in the circuit non-formation region, as shown in FIGS. 2B and 2C, the circuit of each substrate 21 constituting the multilayer printed wiring board 20 is not formed. The structure which formed the stripe-like nonconductor parts 24, 24, ... parallel to the conductor layer 23 on the insulating base material 22 in the formation area is mentioned. In this case, to avoid accumulation of gas by the conductor layer 23, it is desirable to non-conductive area 24, 24, ... of the pitch _{P 2} of 11mm or less. Thereby, it becomes the structure excellent in the effect which prevents the floating of a conductor and the swelling (delamination) of a board | substrate.
Here, parallel streaks of the non-conductor portion 24, 24, ... and the pitch _{P 2} of a distance between the centers of two adjacent non-conductive area 24, 24.

  In addition, the shape of the non-conductor portion in the present invention is not limited to a square shape or a parallel stripe shape, and a shape obtained by deforming a square shape, a shape obtained by deforming a parallel stripe shape, or the like can also be adopted. is there.

  The method of laminating the single-sided substrates 11 and 21 in which non-conductor portions are regularly provided in the circuit non-formation region is not particularly limited. For example, as shown in FIGS. 1 (d) and 2 (d), the adhesives 15 and 25 The multilayer printed wiring boards 10 and 20 shown in FIG. 1 (e) and FIG. 2 (e) can be manufactured by stacking and integrating them with heat and pressure. In the multilayer printed wiring boards 10 and 20 of the present invention, the number of stacked substrates 11 and 21 and the number of circuit layers are not particularly limited.

  In this embodiment, as shown in FIG. 5, a first substrate 1 having a circuit formation portion 1a and a circuit non-formation region 1b and a second substrate 2 having a circuit formation portion 2a and a circuit non-formation region 2b are produced. (See the upper part of FIG. 5), these substrates 1 and 2 are aligned and laminated, and in the circuit forming portion 2a, a two-layered multilayer printed wiring board 3 in which the circuit is interlayer-conductive (not shown) is produced. (See the lower part of FIG. 5). In each of the substrates 1 and 2, between the circuit forming portions 1a and 2a and the circuit non-forming regions 1b and 2b, a predetermined or larger conductor gap is secured by the copper foil removing portions 1c and 2c to prevent a short circuit.

Example 1
In the following, an example is shown in which square non-conductor portions are provided at equal pitches so that the circuit non-formation region has a lattice shape (see FIG. 1 for the circuit non-formation region).

・ Substrate configuration (single-sided substrate / adhesive sheet / single-sided substrate)
Single-sided CCL11: polyimide 12 thickness 25 μm, single-sided copper foil 13 thickness 25 μm
Adhesive sheet 15: acrylic adhesive sheet, sheet thickness 25 μm (manufactured by DuPont, trade name: Piralux LF)
Pitch of non-conductor portion 14: longitudinal direction P ₁₁ and transverse direction P ₁₂ ; 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm, 11.5 mm, 12 mm, 12.5 mm, 13 mm, 13 .5mm, 14mm, 14.5mm, 15mm

-Board | substrate preparation procedure (1) As shown to Fig.1 (a), single-sided CCL11 comprised from the polyimide 12 and the single-sided copper foil 13 is prepared.
(2) The single-sided CCL 11 is patterned to form a circuit in the circuit-forming portion, and at the same time, the out-gas diffusion portion and the single-sided copper foil 13 on the polyimide 12 are arranged at an equal pitch so that the circuit-unformed region has a lattice shape. Are formed regularly (P ₁₁ = P ₁₂ ). FIG. 1B is a partially enlarged plan view of a circuit non-formed region, and FIG. 1C is a cross-sectional view of the substrate shown in FIG. 1B cut along the line AA.
(3) Another single-sided substrate 11 having a circuit and an outgas diffusion portion formed thereon is prepared in the same manner as (1) and (2) above, and the polyimide 12 side of one single-sided substrate 11 and the other single-sided substrate 11 are prepared. The multi-layer printed wiring board 10 according to the first embodiment is obtained (see FIGS. 1D and 1E).

(Example 2)
In the following, an example is shown in which a line-shaped non-conductor portion parallel to one direction is provided in a circuit non-formation region (see FIG. 2 for the circuit non-formation region).

・ Substrate configuration (single-sided substrate / adhesive sheet / single-sided substrate)
Single-sided CCL21: polyimide 22 thickness 25 μm, single-sided copper foil 23 thickness 25 μm
Adhesive sheet 25: acrylic adhesive sheet, sheet thickness 25 μm (manufactured by DuPont, trade name: Piralux LF)
Pitch P ₂ of non-conductor portion 24: 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6 .5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, 10.5mm, 11mm, 11.5mm, 12mm, 12.5mm, 13mm, 13.5mm, 14mm, 14.5mm , 15mm

-Board | substrate preparation procedure (1) As shown to Fig.2 (a), the single-sided CCL21 comprised from the polyimide 22 and the single-sided copper foil 23 is prepared.
(2) A pattern is formed on the one-sided CCL 21 to form a circuit in the circuit forming portion, and at the same time, in the non-circuit forming region, non-conductor portions 14 and 14 that become parallel streaky outgas diffusion portions along one direction. ... are regularly formed. 2B is a partially enlarged plan view of a circuit non-formation region, and FIG. 2C is a cross-sectional view of the substrate shown in FIG. 2B cut along the line BB.
(3) Another single-sided substrate 21 in which a circuit and an outgas diffusion portion are formed in the same manner as in (1) and (2) above is prepared, and the polyimide 22 surface of one single-sided substrate 21 and the other single-sided substrate 21 The multilayer printed wiring board 20 according to the second embodiment is obtained (see FIGS. 2D and 2E).

(Test example)
A moisture absorption reflow test was performed on the multilayer printed wiring boards 10 and 20 produced in Examples 1 and 2 in order to examine the solder heat resistance characteristics. The test conditions were based on JEDEC's moisture absorption reflow standard LEVEL3.
The substrates of Examples 1 and 2 were left in a wet heat bath at a temperature of 30 ° C./relative humidity of 60% for 192 hours, then taken out from the wet heat bath, and after 15 minutes, far infrared rays were applied at a peak of 260 ° C./20 seconds. The substrate was put into a reflow furnace, and the number of swelled portions of the substrate was counted. The results are shown in FIGS. 3 and 4, respectively.

In the case of Example 1, as shown in FIG. 3, when the pitch of the non-conductor portions was 12.5 mm or more, the substrate was swollen after reflow. When the pitch of the non-conductor portion is in the range of 0.1 to 12 mm, the substrate does not swell after reflow.
In the case of Example 2, as shown in FIG. 4, when the pitch of the non-conductor portions was 11.5 mm or more, the substrate was swollen after reflow. When the pitch of the non-conductor portion is in the range of 0.1 to 11 mm, the substrate does not swell after reflow.
From the above results, it is necessary to set the pitch of the outgas diffusion portion by the non-conductor portion to 11 mm or less in order to obtain a substrate that does not swell after reflow and has excellent solder heat resistance.

  The multilayer printed wiring board of the present invention can be used for various electric devices, electronic devices and the like.

It is a figure which shows the manufacturing method of the multilayer printed wiring board which concerns on Example 1 of this invention in order of a process, (a) is sectional drawing which shows the copper clad laminated board used as a board | substrate material, (b) is a square nonconductor part. The partial enlarged plan view of the circuit non-formation area | region of the board | substrate which shows the formed area | region, (c) is sectional drawing which follows the AA line of the board | substrate shown in (b), (d) is a board | substrate with which the nonconductor part was formed Sectional drawing in the circuit non-formation area | region which shows the state which pinches | interposes an adhesive material in between, (e) is sectional drawing in the circuit non-formation area | region which shows a multilayer printed wiring board. It is a figure which shows the manufacturing method of the multilayer printed wiring board which concerns on Example 2 of this invention in order of a process, (a) is sectional drawing which shows the copper clad laminated board used as a board | substrate material, (b) is parallel stripe-like non- The partial enlarged plan view of the circuit non-formation area | region of the board | substrate which shows the area | region in which the conductor part was formed, (c) is sectional drawing in alignment with the BB line of the board | substrate shown in (b), (d) is a non-conductor part formed Sectional drawing in the circuit non-formation area | region which shows the state which pinches | interposes an adhesive material between the produced | generated boards, (e) is sectional drawing in the circuit non-formation area | region which shows a multilayer printed wiring board. It is a test result of Example 1, Comprising: It is a graph showing the relationship between a nonconductor part pitch and the number of swelling locations. It is a test result of Example 2, Comprising: It is a graph showing the relationship between a non-conductor part pitch and the number of swelling locations. It is a schematic plan view which shows the multilayer printed wiring board produced in the Example, and the two board | substrates which comprise this.

Explanation of symbols

P ₁₁ ... Vertical pitch of the non-conductor portion in the substrate of Example 1, P ₁₂ ... Horizontal pitch of the non-conductor portion in the substrate of Example 1, P ₂ ... Pitch of the non-conductor portion in the substrate of Example 2 , 1, 2... Each substrate constituting the multilayer printed wiring board, 1a, 2a... Circuit forming portion, 1b, 2b... Circuit non-formation region, 3 ... multilayer printed wiring board, 10, 20 ... multilayer printed wiring board, DESCRIPTION OF SYMBOLS 21 ... Board | substrate (single-sided CCL), 12, 22 ... Insulating base material (polyimide), 13, 23 ... Conductor layer (copper foil), 14, 24 ... Outgas diffusion part (non-conductor part), 15, 25 ... Adhesive (Adhesive sheet).

Claims (3)

  A multilayer printed wiring board having an outgas diffusion portion in which a conductor on an insulating substrate is regularly removed at a pitch of 11 mm or less in a region other than the circuit formation portion in at least one conductor layer.   The said outgas diffusion part consists of a square non-conductor part by which the conductor was regularly removed by the pitch of 11 mm or less about two mutually perpendicular directions along a substrate surface. Multilayer printed wiring board.   2. The multilayer printed wiring board according to claim 1, wherein the outgas diffusion portion is composed of parallel streaky non-conductor portions from which conductors are regularly removed at a pitch of 11 mm or less.

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