JPH1022645A - Manufacturing method of printed wiring board with cavity - Google Patents

Abstract

(57) Abstract: In a method of manufacturing a printed wiring board having a cavity for accommodating a semiconductor element, the formation of the cavity is facilitated, the number of steps is reduced, and the productivity is improved. The method includes the following steps. a, a thermosetting and peelable organic material is applied to the inner layer substrate forming the bottom surface of the cavity by printing on the shape of the cavity, b, the organic material is cured by heating, and c, the shape of the cavity Laminating the prepreg cut out on the inner layer substrate; d, laminating another outer layer substrate on the cured organic material and the prepreg; e. Cutting out the shape portion of the cavity from the outer layer substrate of the laminate; f. The hardened organic material appearing in the cutout is peeled off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board having a cavity having an upwardly open cavity for mounting a semiconductor device.

[0002]

2. Description of the Related Art A cavity for accommodating a semiconductor element such as an IC or LSI is provided on one surface (hereinafter referred to as an upper surface), and the semiconductor element is fixed in the cavity, and the element is connected to a pad of a printed wiring board by a wire. Printed wiring boards that can be bonded are known.

FIG. 2 is a diagram showing a cross-sectional structure of such a printed wiring board. In this figure, reference numeral 10 denotes a printed wiring board, on the upper surface of which a rectangular recess or cavity 12, which is open upward, is formed. On the bottom surface of the cavity 12, a large number of electrodes, that is, pads 14, are formed adjacent to the four sides of the cavity 12 and arranged along each side. A large number of pads 16 are formed on the upper surface of the printed wiring board 10 and are adjacent to the four sides of the cavity 12 and are arranged along each side.

Reference numeral 18 denotes a semiconductor element, which is formed of a chip such as an IC or an LSI. The semiconductor element 18 is bonded and fixed to the bottom surface of the cavity 12, and then the semiconductor element 18
Are wire-bonded to pads 14,16. That is, the wire 20 connects the element 18 to the pads 14 and 16.

The reason why the pads 14 and 16 are provided in two steps on the bottom surface of the cavity 12 and the upper surface of the printed wiring board 10 is as follows. That is, as the number of external connection electrodes of the element 18 increases, the number of pads on the printed wiring board side increases, and it becomes necessary to reduce the pad pitch. However, equipment used for wire bonding (wire bonder)
There is a limit to the processing accuracy of Therefore, the pads 14 and 16 are divided into two stages so that the pad pitch can be expanded.

FIG. 3 is a view showing a conventional method of manufacturing the printed wiring board 10 having the cavity 12. As shown in FIG. This figure shows a circuit pattern formed in four layers. 30 in the figure
Is an inner layer substrate, and circuit patterns 2L and 3L of the second layer and the third layer are formed on the upper surface and the lower surface, respectively, by etching a copper foil stuck on both surfaces thereof.

On the upper surface of the inner substrate 30, a release film 32 with an adhesive is adhered in the shape of the cavity (corresponding to 12 in FIG. 2), and a prepreg obtained by cutting out a shape portion of the release film 32. 34 is placed. Here, the release film 32 is, for example, a Teflon film, and its thickness is substantially equal to that of the prepreg 34.

Then, the outer layer substrate 36 is stacked on the release film 32 and the prepreg 34, and the prepreg 38 and another outer layer substrate 40 are stacked on the lower surface of the inner layer substrate 30 (the state shown in FIG. 3A). Then, the whole is pressed and heated in the vertical direction to form the laminate 42 (FIG. 3B). In this state, a circuit pattern is formed on a copper foil previously adhered to the outer surfaces of the outer layer substrates 36 and 40, thereby forming first and fourth layer circuit patterns 1L and 4L, respectively.

Next, a cut is made in the laminated body 42 along the outer shape of the release film 32 from the surface side of the upper outer layer substrate 36 by a router 44 (counterbore processing). An opening having the same shape as the shape is formed (FIG. 3C). By removing the release film 32 appearing in the opening, a printed wiring board 48 in which the cavity 46 is formed is completed (FIG. 3D).

[00010]

Problems of the prior art In this conventional manufacturing method,
The positioning of the release film 32 was troublesome. That is, since the bonding position of the release film 32 is inside the inner layer substrate 30, it is very difficult to determine the position. Therefore, conventionally, a template having an opening at a position where the release film 32 is bonded is prepared, and the release film 32 is manually positioned and bonded using this template.

Further, since the release film 32 is adhered to the inner layer substrate 30 with an adhesive, a part of the adhesive is fixed and remains on the laminate 42 side by heating and pressing during lamination. Therefore, after the release film 32 has been peeled off, the remaining and adhered adhesive must be cleaned with a solvent. As described above, the conventional method requires a lot of man-hours for positioning the release film 32 and removing the adhesive, and thus has a problem that productivity is deteriorated.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a method of manufacturing a printed wiring board with a cavity in which a cavity can be easily formed, the number of steps can be reduced, and productivity can be improved. The purpose is to:

[0013]

According to the present invention, there is provided a method of manufacturing a printed wiring board having a cavity having an upwardly open cavity for mounting a semiconductor element, comprising the steps of: a) applying heat to an inner substrate forming a bottom surface of the cavity; Applying a curable and peelable organic material to the shape of the cavity by printing; b, heating and curing the organic material; c, laminating a prepreg cut into the shape of the cavity on the inner layer substrate; d, laminating another outer layer substrate on the cured organic material and the prepreg; e, cutting out the shape portion of the cavity from the outer layer substrate of the laminate; f, the cured organic material appearing in the cutout opening And a method for manufacturing a printed wiring board with a cavity, characterized in that:

[0014]

FIG. 1 is a view showing a manufacturing method of the present invention.
In this figure, the same parts as those in FIG. 2 are denoted by the same reference numerals. FIG.
Is a metal mask, and a mesh screen may be used instead. An opening 52 is formed in the metal mask 50 in a shape of a portion to be a cavity. The metal mask 50 is superimposed on the upper surface of the inner substrate 30 so as to be aligned, and an organic material 56 is printed by a known squeegee method using a squeegee (spatula) 54 (FIG. 1A).

Here, the organic material 56 is thermosetting and peelable, and is liquid or paste before heating. As the organic material 56, for example, a material containing vinyl chloride as a main component, a viscosity of 300 to 400 (PS), and a thixotropy of 1.2 to 1.8 is suitable. As such, there is a strip mask (trade name of an organic material sold by Taiyo Ink Co., Ltd.) used as a solder resist or the like.

The organic material 56 printed on the inner substrate 30 is cured by heating to form a film 56A (FIG. 1B). Thereafter, the same steps as those described with reference to FIG. 3 are performed. That is, on the upper surface of the inner layer substrate 30, the prepreg 34 obtained by cutting out the film 56A is stacked, and the outer layer substrate 36 is stacked thereon. Further, another outer layer substrate 40 is stacked on the lower surface of the inner layer substrate 30 via the prepreg 38 (FIG. 1C).

After the whole is pressurized and heated in the vertical direction, the film 5 is applied to the outer substrate 36 by the router 44.
A cut (spot facing) along the outer shape of 6A is cut out ((D) in FIG. 1). The printed wiring board 48 with the cavity 46 is obtained by removing the film 56A appearing in the cut-out opening (FIG. 1E).

The circuit pattern 2 of the second layer and the first layer
As shown in FIG. 2, a large number of pads 14 and 16 are formed on L and 1L. And this cavity 4
The semiconductor element 18 bonded in the pad 6
4 and 16 (see FIG. 2).
reference).

[0019]

According to the first aspect of the present invention, as described above, a thermosetting and releasable organic material is printed on the inner layer substrate in the shape of a cavity, which is heated and cured, and then formed into this cavity shape. The cut prepreg is laminated with an outer layer substrate, the shape of the cavity is cut out from the outer layer substrate, an opening is provided, and the cured organic material is peeled off.

Therefore, the cavity can be easily formed as compared with the conventional method of bonding the cavity-shaped release film. In addition, since a complicated process such as alignment of a release film is not required and a metal mask or the like can be simply positioned with respect to a substrate, work efficiency is increased, man-hours are reduced, and productivity is improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a process of one embodiment of the present invention.

FIG. 2 is an explanatory view of a printed wiring board with a cavity.

FIG. 3 is a diagram illustrating a conventional manufacturing method.

[Explanation of symbols]

 10, 48 Printed wiring board 12, 46 Cavity 14, 16 pad 18 Semiconductor element 20 Bonding wire 30 Inner substrate 32 Release film 34, 38 Prepreg 36, 40 Outer substrate 42 Laminated body 44 Router 50 Metal mask 52 Opening 54 Squeegee 56 Organic material 56A Film (cured organic material)

Claims (1)

[Claims] 1. A method of manufacturing a printed wiring board with a cavity having an upwardly open cavity for mounting a semiconductor element, the method comprising the steps of: a) a thermosetting and peelable organic material for an inner substrate forming a bottom surface of the cavity; Is applied to the shape of the cavity by printing; b, the organic material is cured by heating; c, a prepreg cut into the shape of the cavity is laminated on the inner layer substrate; d, the cured organic material and the prepreg E) cutting out the shape of the cavity from the outer layer substrate of the laminate, and f. Peeling off the cured organic material appearing in the cutout opening. Manufacturing method of printed wiring board with cavity.