JP2915538B2 - Manufacturing method of multilayer printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a method for manufacturing a multilayer printed wiring board in which an inner layer board is arranged with high positional accuracy and operability is reduced at a low cost. .

(Prior Art) In recent years, as the speed and density of industrial electronic devices and the like have increased, multilayer wiring boards for mounting electronic components have been promoted. In particular, six or more conductive layers have been required. There is an increasing demand for multilayer wiring boards.

Conventionally, as shown in FIG. 4, such a multilayer wiring board includes a plurality of inner layer boards 14 having two wiring patterns 12, 13 for signal and power, for example, formed on both sides of an insulating board 11. A suitable number of prepregs 15a are sandwiched between the layers, the prepregs 15b and the outer copper foil 16 are laminated on both sides thereof, and then the whole is heated and pressed by a hot press or the like (not shown) to be integrally molded. Have been.
In such a manufacturing method, the alignment of the wiring patterns between the inner layer plates has been conventionally performed by the following various methods.

(A) Pin lamination method Guide holes (not shown) are formed at the same pitch at all predetermined positions to be laminated, such as the outer copper foil 16, the inner plate 14, the prepregs 15a and 15b, and a dedicated mold die. In this method, metal guide pins are erected at a predetermined pitch on a surface, and these pins are inserted into the guide holes to perform positioning.

(B) Multiple molding method (sequential method) First, a four-layer plate is formed and a circuit is completed, and then an inner layer plate is stacked one by one and molded, and this is repeated as necessary.

(C) Adhesive method A plurality of inner layer plates 14 and prepregs 15a are provided with holes for positioning, and the holes are stacked and set on a positioning jig. The gaps are bonded and fixed to each other.

(D) Eyelet method Eyelet is used instead of the adhesive in the adhesive method,
Fix in the aligned state. That is, as shown in FIG. 5, the eyelet 17 is driven into the inner layer plate 14 and the prepreg 15a which are sequentially stacked while being aligned, and
Is a method of mechanically fastening by caulking the tip portion 17a.

(Problems to be Solved by the Invention) However, these alignment and fixing methods have the following problems. That is, (a) the pin lamination method can perform high-accuracy alignment, but can use only a small press and has low productivity. In addition, there is a problem that it takes time to remove the pin after the heat and pressure molding and to remove the resin attached around the pin. (B) The multiple molding method has a drawback that it takes a long time to produce a final multilayer wiring board and cannot meet the market demand for a short delivery time. In addition, (c) the bonding method has a problem that not only the fixing strength is not sufficient, but also the bonding portion is deteriorated at the time of heating and pressurization, and the fixing portion is cracked or peeled off. (4) In the eyelet method, since the thickness of the eyelet 17 is small and the strength is not sufficient, as shown in FIG. 6, the heat generated by the prepreg 15a at the time of caulking or when the outer copper foil 16 is stacked and heated and pressed. The inner straight plate of the eyelet 17 is bent or distorted, and the inner layer plate is pulled in. As a result, there is a disadvantage that a positional shift occurs between the inner layer conductors.

The present invention has been made in view of the above circumstances, and accurately aligns a plurality of inner layers, and in particular, manufactures a multilayer printed wiring board having six or more conductor layers at high productivity and at low cost. Another object of the present invention is to provide a method for manufacturing a multilayer printed wiring board.

[Constitution of the Invention] (Means for Solving the Problems) The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a straight eyelet of the eyelet inserted into a positioning reference hole in the eyelet method is used. The inventors have found that the above object can be achieved by strengthening the eyelet wall with a washer-like object along the outer wall of the pipe portion, thereby completing the present invention.

That is, the present invention is a method for manufacturing a multilayer printed wiring board comprising a plurality of inner layer boards having inner layer wiring formed on both front and back surfaces, a prepreg cured layer, and an outer layer wiring. A bonding step of bonding a small flat plate at a reference position of at least one inner layer plate, and a positioning reference hole for penetrating the inner layer plate and the small plate at a reference position of the inner layer plate after the bonding step. A perforating step to be performed, a caulking tool is inserted into the positioning reference hole of the inner layer plate after the perforating step, and a caulking step of caulking together with the prepreg and other necessary inner layer plates. If necessary, a forming step of laminating an outer layer copper foil and integrally forming the same.

Inner layer plate, prepreg and outer layer copper foil used in the present invention,
For the present invention, the production method and raw materials are not particularly limited, and commonly used inner plates, prepregs and outer copper foils are used.

The small flat plate used in the present invention (it is also called a washer since it becomes a washer after perforation) can be used without any particular limitation in shape and material. Examples of the material of the washer include metals such as copper, brass, iron, and alloys thereof, or resins such as epoxy resin, polyimide resin, and polyester resin (both thermosetting resins and heat-resistant thermoplastic resins). Examples of these resins include impregnated cured products obtained by impregnating and curing resins such as glass cloth, nonwoven fabric, and paper, and those obtained by coating these resins with metal. Among them, it is preferable that dust, especially metal chips, is not generated and mixed when the positioning reference hole is formed. Since the thickness of the washer is used to prevent eyelet deformation during molding, it is preferable that the thickness of the washer be equal to the distance between the inner layers. The outer peripheral shape of the washer is not particularly limited, and may be any of a circle, a square, a rectangle, and a polygon.

As an adhesive for bonding the small flat plate to the inner layer plate in the present invention,
Although not particularly limited, it is necessary that the material be able to withstand the stress at the time of forming the reference hole, the chemical at the time of the blackening treatment, and the heat. Among these adhesives, a double-sided tape is effective from the viewpoint of workability. The surface to which the washer is bonded should be such that the washer is sandwiched between the inner plates and the eyelets are not distorted.

The outer layer copper foil is not always necessary, and the outer layer wiring may be formed by an additive method or the like.

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

FIG. 1 (a) is a schematic view of a small circular plate 1 made of metal or resin used in the present invention, FIG. 1 (b) is a longitudinal sectional view of the small small plate 1, and FIG. FIG. 1 is a longitudinal sectional view showing a state where 1 is bonded and fixed to an inner layer plate 3 having a circuit pattern formed on the front and back sides using an adhesive 2. Then, an alignment reference hole is formed from above the adhesively fixed small flat plate 1 with the dashed line in FIG. 1C as an axis. Next, as shown in FIG. 2, the inner plate 3 to which the washer 1 is bonded is
An inner layer plate 3b (a positioning reference hole is perforated only in the inner layer plate without the small flat plate being adhered) is overlapped via the prepreg 4, and the eyelets 5 are driven into the positioning reference holes, and The plates 3, 3b and the prepreg 4 are caulked. Next, the third
As shown in the figure, a prepreg 6 is superimposed on both sides of a caulked set of inner layers 3 and 3b (inner layer material), and an outer layer copper foil 7 is further superposed on both sides thereof. Can be manufactured.

In FIG. 3, one inner layer plate 3 with a washer and one inner layer plate 3b without a washer were caulked to combine an inner layer material having four inner wiring layers. By crimping one inner layer plate 3b without a washer via a prepreg, an inner layer material having six inner layer wirings can be formed.

(Operation) In the method for manufacturing a multilayer printed wiring board of the present invention, in order to secure the same positional accuracy as a multilayer printed wiring board having six or more layers with workability similar to that of a four-layer board, caulking is performed using a washer method using a washer. Is what you do. In other words, by using a washer in the eyelet method, it is possible to suppress the stress deformation of the eyelet hollow straight pipe portion during the heating and press-integral molding, eliminate the eyelet displacement and dent, and improve the positional accuracy. It is a thing.

(Examples) Next, the present invention will be described specifically with reference to examples.

Examples 1-2 Thickness in which a circuit pattern having a thickness of 70 μm was formed on both sides.
Two sets of two 0.2 mm inner layer plates were prepared, and a predetermined small metal or resin flat plate was bonded and fixed to each of the inner layer plates at a position where a reference hole was to be made. Next, after drilling a reference hole from the small flat plate, two prepregs having a thickness of 100 μm are overlapped, and then the inner layer plate having the other reference hole is overlapped and fastened and integrated by the eyelet method. Material. In this case, the thickness of the washer was adjusted so as to be the thickness after molding of two prepregs. Furthermore, a prepreg having a thickness of 100 μm is laminated on both sides of each inner layer material, and an outer copper foil having a thickness of 18 μm is laminated on the outer side thereof in order.
It was heated and pressed integrally at 5 ° C. and 4 to 40 kg / cm ² for 90 minutes to produce a multilayer printed wiring board having six layers.

Examples 3 to 4 The same procedures as in Examples 1 and 2 were carried out except for using four prepregs instead of the two prepregs used for the inner layer material and a washer having a thickness corresponding to the height after molding. The multilayer printed wiring boards of Examples 3 and 4 were manufactured in the same manner as Examples 1 and 2, respectively.

Comparative Example 1 A multilayer printed wiring board was manufactured in the same manner as in Examples 1 and 2, except that no washer was used in Examples 1 and 2.

Comparative Example 2 A multilayer printed wiring board was manufactured in the same manner as in Examples 3 and 4, except that the washer used in Examples 3 and 4 was not used.

The multilayer printed wiring boards manufactured in Examples 1 to 4 and Comparative Examples 1 and 2 were tested for misalignment, heat resistance, dimensional stability [dimensional change rate], and workability, and the results were obtained. The results are shown in Table 1. The multilayer printed wiring board of the present invention was excellent in various properties, and the effect of the present invention could be confirmed.

The tests for positional deviation, heat resistance, and dimensional stability shown in Table 1 were performed as follows.

Displacement of the inner layer plate: The displacement of the reference hole size between the wiring patterns of the inner layers was measured by a coordinate measuring instrument in both the vertical and horizontal directions.

Heat resistance: 260 after D-4 / 100 treatment of multilayer printed wiring board
After immersion in a 30 ° C. solder bath for 30 seconds, the state of the plate (measuring, etc.) was visually observed.

 Dimensional stability: The dimensional change was measured by the MIL method.

In Table 1, L1 and L2 represent the front and back wiring patterns of the first inner layer plate, and L3 and L4 represent the front and rear wiring patterns of the second inner layer plate, respectively. The back wiring patterns are respectively shown. In the table, the symbol ○ indicates good, the symbol で は is not good but not practically acceptable, and the mark 不良 indicates defective.

[Effects of the Invention] As is clear from the above description and Table 1, according to the method for manufacturing a multilayer printed wiring board of the present invention, a plurality of inner layer board patterns can be accurately aligned, and especially the inner layer This is effective when the distance between the boards is large. Then, a multilayer printed wiring board having six or more layers can be manufactured with good workability and at low cost.

[Brief description of the drawings]

FIG. 1 (a) is a sketch of a small flat plate used in the method for manufacturing a multilayer printed wiring board according to the present invention, and FIG. 1 (b) is FIG. 1 (a).
FIG. 1 (c) is a longitudinal sectional view showing a state in which the small flat plate of FIG. 1 (a) is bonded and fixed to an inner layer plate, and FIG.
FIG. 3 is a partial sectional view showing an inner layer material swaged by eyelets, FIG. 3 is a partial sectional view of a multilayer printed wiring board according to the manufacturing method of the present invention, and FIG. FIG. 5 is a partial sectional view for explaining a conventional eyelet method, and FIG. 6 is a partial sectional view for explaining distortion of a conventional multilayer printed wiring board after molding. 1 ... small flat plate (washer) 2 ... adhesive, 3, 3b, 14
…… Inner plate, 4,6,15a, 15b …… Pre-preg, 5,17 …… eyelet, 7,16 …… Outer layer copper foil.

Claims (1)

(57) [Claims] 1. A method of manufacturing a multilayer printed wiring board comprising a plurality of inner layer boards having inner layer wirings formed on both front and back surfaces, a prepreg hardened layer, and an outer layer wiring, wherein at least one of the plurality of inner layer boards is provided. A bonding step of bonding a small flat plate to a reference position of one inner layer plate, and a positioning reference hole for penetrating the inner layer plate and the small plate at a reference position of the inner layer plate after the bonding step. Drilling step, a caulking tool is inserted into the positioning reference hole of the inner layer plate after the perforation step, and a caulking step of caulking with the prepreg and other necessary inner layer plates,
A process of laminating a prepreg and, if necessary, an outer copper foil on the caulked inner layer board, and forming them integrally.