WO2000030419A1

WO2000030419A1 - Method of manufacturing wiring boards

Info

Publication number: WO2000030419A1
Application number: PCT/JP1998/005193
Authority: WO
Inventors: Eiji Yoshimura
Original assignee: Daiwa Co., Ltd.
Priority date: 1998-11-18
Filing date: 1998-11-18
Publication date: 2000-05-25
Also published as: TW411748B; JP3325903B2; TW404149B

Abstract

A method of manufacturing a wiring board, characterized by comprising a step of disposing a peelable sheet, which has an opening corresponding to a through hole to be resin packed, on at least one surface of a substrate or substrate layer while aligning the openings with the through hole-carrying substrate or substrate layer; a step of forming a resin sheet, which is softened by heating, or solidified by cooling or curing, on the surface of the substrate which is provided with the peelable sheet; and a resin packing step including a step of burying a part of the resin sheet in the through hole while softening the resin sheet with heat and under pressure, and then solidifying the resin by cooling or curing, and a step of separating the peelable sheet from the substrate or substrate layer; this resin packing step enabling the packed resin to rarely encounter the occurrence of a defect, and the resin to be suitably packed in the through hole by using an inexpensive material and a simple step.

Description

Description Wiring board manufacturing method Technical field

The present invention relates to a method for manufacturing a wiring board having via holes or through holes formed for purposes other than conductive connection for conductive connection between wiring layers, and more particularly, to filling a resin into the through holes during a via hole forming process or the like. The present invention relates to a method of manufacturing a wiring board having a resin filling step for performing the above. Background art

In recent years, as electronic devices and the like have become smaller and lighter, the size of electronic components has been reduced, and the demand for higher density of wiring boards for mounting electronic components has increased. In order to increase the density of the wiring board, a method of increasing the wiring density of the wiring layer itself or a method of forming a multilayer structure by laminating a plurality of wiring layers have been adopted.

A method of manufacturing a multilayer wiring board includes a bonding method in which a wiring layer is formed on each of a plurality of base materials, and an insulating sheet is interposed between the base materials to perform bonding and the like, and a method in which a wiring pattern is formed. A build-up method in which an insulating layer is formed on the insulating layer and a wiring pattern is formed on the insulating layer, and then the insulating layer and the wiring pattern are sequentially formed to form a laminated structure. Exists.

According to the latter build-up method, it is not necessary to join a plurality of base materials and insulating sheets corresponding to each wiring layer as in the former, so that a thin multilayer wiring board can be formed with high density and relatively easily. be able to. For this reason, the latter can mount circuits and electronic components at a higher density than the former.

On the other hand, in a multilayer wiring board, it is necessary to make a conductive connection between the respective wiring layers according to the circuit design. For this reason, a so-called through hole in which a through hole is provided in a substrate or a base material layer to apply a plating or a conductive base, or a lower wiring layer exposed without forming an insulating layer in a build-up method. A structure in which a plating layer serving as an upper wiring layer was formed thereon was adopted. Of these interlayer connection structures, in particular, through holes Is used for a multilayer wiring board formed by a bonding method, an interlayer connection between both-sided wiring layers of a lowermost substrate in a build-up method, and the like.

Such through-holes are rarely finally made into products in a hollow state. In the case of the build-up method, in order to form the upper layer or to improve the high frequency characteristics, the through-hole of the lowermost base layer is usually used. The hole is filled with resin. Also in the joining method, resin is filled so as not to hinder the subsequent solder mask printing step and soldering step.

As a conventional resin filling method, for example, a method by screen printing, a method described in Japanese Patent Application Laid-Open No. 9-83140, and the like can be mentioned. In the latter filling method, a metal mask such as a stainless steel plate opened corresponding to the through hole is arranged, liquid resin is injected into the through hole, the metal mask is removed, and then the resin liquid is heated or the like. This is a method of curing.

However, since the ink and liquid resin used in the above method are liable to contain air bubbles during mixing and pouring of the preparation, defects are likely to occur in the cured resin, and control for injecting an appropriate amount of ink or the like is performed. There was a problem that was difficult. Further, since the metal mask and the like are expensive and must be reused, the process becomes complicated, and a series of steps such as a liquid resin injection step, a metal mask removal step, and a liquid resin heating step are performed. It was complicated and time-consuming, and was not a practical method.

In addition, there is a case where the resin needs to be filled not only in the above-described through hole but also in a through hole that does not perform conductive connection.

Therefore, an object of the present invention is to provide a method of manufacturing a wiring board having a resin filling step in which a resin is less likely to cause a defect in a filled resin and a resin can be preferably filled in a through-hole by a simple process using an inexpensive material. Is to provide. Disclosure of the invention

The above object can be achieved by the present invention as described below. That is, the method for manufacturing a wiring board according to the present invention is characterized by including a resin filling step including the following steps.

(a) A release sheet having an opening corresponding to the through-hole on a substrate or an S # layer having a through-hole filled with resin, while aligning the opening, Step of arranging at least one side of the substrate or the base material layer,

(b) arranging a resin sheet which is softened by heating and solidified by cooling or hardening on a surface on which the release sheet is arranged,

(c) a step of embedding a part of the resin sheet in the through hole while softening the resin sheet by heating and pressing, and then solidifying by cooling or curing; and

(d) a step of peeling the peeling sheet from the substrate or the base material layer.

According to the present invention, since a resin sheet is used instead of a liquid resin, the amount of air bubbles is extremely small, and defects are hardly generated in the solidified resin. In addition, since the resin sheet is softened by heating, the steps corresponding to the conventional liquid resin supply / application step and injection step can be simplified, and the temperature, time, pressure and the like of heating and pressing (hot pressing) can be reduced. By adjusting, the amount of resin to be inserted can be easily controlled. Then, since the resin sheet can be solidified as it is after being embedded, there is no need to provide a step such as a metal mask removal step, and a step corresponding to the hardening step from the conventional injection step can be simplified. Furthermore, since the release sheet is used, the solidified resin sheet can be easily peeled, and at that time, the resin embedded and solidified in the through hole remains in the through hole and is filled with the resin. Will be. In the above, the release sheet is pressed by the resin sheet when heated and pressed, and adheres closely to the substrate. Therefore, it is not necessary to perform smooth processing with high precision as in a conventional metal mask. Etc. can be used. Therefore, there is no need for reuse, and the use of a transparent material facilitates alignment with the through-hole of the substrate.

As a result, it is possible to provide a method of manufacturing a wiring board having a resin filling step in which the filled resin is less likely to cause a defect and the resin can be suitably filled in the through-hole by a simple process using an inexpensive material. .

In the above, the through-hole may not be a conductive connection between wiring layers, but is preferably a through-hole for conductively connecting between a plurality of wiring layers. Such a through hole is frequently used in a multilayer wiring board as described above, and it is indispensable to fill the resin without defects in order to improve the high-frequency characteristics of the board and to form an upper layer of the build-up.

In addition, the resin filling step of the present invention may have an additional step as described below in addition to the above steps a to d, and in particular, after the step d, (e) It is preferable to have a step of flattening a protruding portion of the resin filled in the through hole of the substrate or the base material layer. By this step, a subsequent build-up upper layer forming step, that is, an insulating layer forming step, can be favorably performed.

As the resin sheet, a force ^s which can use any of various resin sheets containing a thermosetting resin or a thermoplastic resin as described below, the resin sheet is softened by heating. It is preferable that the resin sheet contains a resin material that cures at a high temperature. By using such a resin sheet, the resin can be cured by heating as it is after being embedded, so that a step such as cooling is not required, and the resin can be solidified in an extremely short time. Further, such a thermosetting resin has high heat resistance, so that it exhibits good performance and durability even in a high-temperature process such as a soldering process.

The a step may be any method as long as the release sheet is disposed on at least one side surface of the substrate or the base material layer. The a step includes disposing the release sheet on both surfaces of the substrate or the base material layer. It is preferable that This makes it possible to easily remove and remove the extra resin existing on both sides of the substrate or the like using the release sheet.

^ &.

On the other hand, the wiring board of the present invention is a wiring board manufactured by any one of the above manufacturing methods. In such a wiring board, since the filled resin has few defects, the reliability of the board in terms of conductive connectivity, high-frequency characteristics, and the like is enhanced. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a process chart (1) to (5) showing an example of a method for manufacturing a wiring board of the present invention. FIG. 2 is a process chart (6) to (9) showing an example of a method for manufacturing a wiring board according to the present invention. FIG. 3 is a process chart (10) to (13) showing an example of a method for manufacturing a wiring board of the present invention. FIG. 4 is a partial cross section showing an example of a multilayer wiring board that can be formed according to the present invention.

In each of the figures, 1 denotes a release sheet, la denotes an opening, 2 denotes a resin sheet, 14 denotes a filled resin, 14a denotes a protruding portion, BL denotes a base material layer, and TH denotes a through hole. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail based on its best embodiment. In the present embodiment, an example is shown in which release sheets are arranged on both surfaces of a base material layer.

First, as shown in FIG. 1 (1), a through hole 10a is formed in a base material 10. Next, as shown in FIG. 1 (2), copper plating is applied to the front and back surfaces of 0 and the through hole 10a. At this time, the plating layers 11 and 12 are formed on the front and back of the substrate 10, respectively, and these plating layers 11 and 12 are formed on the inner surface of the through hole 10a. Layer 13 is conductively connected. In this way, a base material layer BL on which a through hole TH for filling the resin is formed is prepared.

In step a, as shown in FIG. 1 (3), the release sheet 1 having the opening 1a opened corresponding to the through hole TH is aligned with the opening la in the base material layer BL. In addition, they are arranged on both sides of the base material layer BL. The release sheet 1 may have a certain degree of heat resistance and strength. For example, various release papers used in the production of a double-sided wiring board by hot pressing, and various types of resin such as sapphire resin. A release film made of a heat-resistant resin can be used. As a method of forming the opening la in the release sheet 1 at an accurate position, a method of forming the opening la in the release sheet 1 at the same time as forming the through hole 10 a in 10, There is a method of forming the through hole 10a in the material 10 using the same perforation pattern as forming the through hole 10a. The step b, in which the alignment is easy by using the highly transparent release sheet 1, is as follows: As shown in Fig. 1 (4), the surface on which the release sheet 1 is placed is softened by heating and cooled or cooled. A resin sheet 2 that is solidified by curing is provided. The resin sheet 2 in the present embodiment is a resin sheet containing a resin material that softens when heated and hardens at a high temperature. Specifically, a prepreg in which an epoxy resin is impregnated into glass fiber or the like, and a prepreg in which a copper foil layer is formed on one surface of the prepreg are commercially available and can be used in the present invention. The invention is not limited thereto, and any of various resin sheets containing various thermosetting resins, thermoplastic resins having a certain degree of heat resistance, and the like can be used. In particular, when a thermosetting resin containing an epoxy resin as a main component is used, good filling can be performed since the heat shrinkage is small. In step c, as shown in FIG. 1 (5), the resin sheet 2 is softened by heating and pressing, a part of the resin sheet 2 is embedded in the through-hole TH, and then solidified by curing. In the present embodiment, the softening of the resin sheet 2 is performed at 80 to 250 ° C., and is controlled by adjusting the temperature of the press surface of the heat press device. In addition, the amount of resin to be embedded can be controlled by the degree of softening, time, pressure and the like.However, since the excess resin 2 & flows out to the back side of the lower layer BL and can be removed in a later step, it is particularly strict. No control is required. When the above prepreg is used, since the content ratio of the resin impregnated in the glass fiber is determined, the amount of the resin to be embedded is also determined to some extent. In the above hot press, the base material layer BL is placed on a press table (not shown). It is preferable that the press table does not prevent the excess resin 2a from flowing out to the lower side of the base material layer BL.However, even if a press table having a smooth surface is used, The resin can be embedded by flowing the resin into the gap between the release sheet 1 and the sheet. Examples of a material that does not prevent the excessive resin 2a from flowing out include a perforated plate having a larger diameter opening, a jig having a concave portion, and an inorganic porous material corresponding to the through hole TH.

The embedded resin is usually cured at a higher temperature (for example, 130 to 250 ° C.) than at the time of softening, but in the present embodiment, the softening and the curing are performed in a single heating process. The resin can be embedded and solidified in a very short time at a time. After these steps, the layer BL is removed from the hot press.

In step d, as shown in FIG. 2 (6), the release sheet 1 is peeled from the base material layer BL. Peeling of the peeling sheet 1 can be carried out manually or by mechanical operation by simply peeling both off from the ends. At this time, both the upper release sheet 1 and the resin sheet 2 are separated from the base material layer BL, and at the same time, the resin sheet 2 and the embedded and solidified filling resin 14 are cut off. Further, the lower release sheet 1 is peeled off from the layer BL together with the excess resin 2a, and at the same time, the filling resin 14 and the excess resin 2a are cut off. As a result, the filling resin 14 having a shape as shown in FIG. 2 (7) is filled in the through hole TH.

The step e is for flattening the protruding portion 14a of the filling resin 14 filled in the through hole TH which is a through hole. For flattening, for example, belt the surface of S layer BL It can be performed by lightly polishing with sanding, puff polishing or the like. By this polishing, the surface of the filling resin 14 is formed almost flush with the plating layers 11 and 12 and flattened. Further, by forming a predetermined mask on the printing layers 11 and 12 using photolithography technology and performing an etching process, the wiring layers 15 and 16 having a predetermined pattern can be formed. (See Figure 2 (8)).

Next, as shown in FIG. 2 (9), after an insulating resist 17 is applied on the surface, only the region connected to the upper layer is opened using photolithography. On the insulating resist, an insulating resist 18 is further applied in the same manner, and similarly, only the above-mentioned region is opened using the photolithography technique. This opening region is the filling resin 14 and the wiring portion around the filling resin 14 in the figure.

Further, as shown in FIG. 3 (10), a coating material 19 containing a large number of fillers in a predetermined reactive resin is screen-printed on the insulating resist 18 of the second layer. Is applied so as to avoid the filled resin 14 and its surrounding wiring. As the reactive resin of the coating material 19, various thermosetting resins or photocurable resins can be used. As the filler contained therein, elutable fine particles such as calcium carbonate, for example, particles having a particle size of about several meters are used.

After the coating material 19 is applied and cured by heating or light irradiation, its surface is lightly polished with a puff (dashed arrow A in the figure) as shown in Fig. 3 (11), and then several tens of By performing sand blasting using abrasive grains having a particle size of about m, a uniform rough surface is formed and the filler embedded near the surface is exposed. By performing soft etching using an acid solution for cleaning in this state, the filler is eluted to form fine irregularities on the surface.

After this, a step of forming a through hole 10b in the substrate is provided as necessary. This through hole 10b is formed by drilling or the like, like the through hole 10a shown in FIG. 1 (1). The through-hole 10b is provided at a portion where conductive connection between the wiring layer 16 and the upper wiring layer is required.

As shown in FIG. 3 (12), an electroless plating is performed on the surface of the coating material 19 roughened in this way to form a first plating layer 20 over the entire surface. The second plating layer 21 is formed by plating. In this way, the plating layer is formed into two layers The reason for this is to maintain the smoothness of the surface of the plating layer while increasing the adhesion strength of the plating layer. The conductive connection portion C is formed by these plating layers.

Next, as shown in FIG. 3 (13), the printing layers 20 and 21 are etched by the same photolithography technique as described above to form a wiring layer 22 in a predetermined pattern. When a wiring layer is further formed above this wiring layer, the filling resin 23 is filled into the through holes 1 Ob by the resin filling step of the present invention in the same manner as the filling resin 14 described above. be able to. Also, the resin 24 is filled into the concave portion formed above the conductive connection portion C by screen printing or the like.

According to the above process, since the opening surface of the filling resin 14 is mechanically polished and flattened, the upper surface of the wiring layer can be flattened to form an upper layer structure. Therefore, it is possible to prevent the topographical effect on the upper layer (such as the unevenness of the lower layer affecting the formation of the upper layer and causing the wiring to be lost or disconnected). Then, by forming a wiring layer further thereon, a multilayer wiring board 30 as shown in FIG. 4, for example, can be manufactured.

This multilayer wiring board 30 is a six-layer board having a circuit configuration of six layers of wiring layers 31 to 36 in the board. Blind via hole structures 37, 38a to 38c are formed in the interior, and the blind via hole structures 38a to 38c are filled with resin by the resin filling step of the present invention. It was done. The blind via hole structure 38a connects the first wiring layer and the second wiring layer, and can be formed by the above-described resin filling step. The blind via hole structure 38 b connects the first wiring layer to the third wiring layer. When forming the third wiring layer, a through hole is formed, and the resin filling step of the present invention is performed there. It can be formed by filling in. The same applies to the blind via hole structure 38c.

The multi-layer wiring board 30 is a surface-mount type having a brand 39, and the through-holes 40 are provided for wiring connection. On the other hand, resin filling can be performed according to the present invention. [Another embodiment]

(1) In the above-described embodiment, an example is shown in which the release sheets 1 are arranged on both sides of the base material layer BL. However, the release sheet 1 may be arranged on only one side surface (the hot press side) of the layer. Good. In that case, removal of excess resin flowing out to the back side of the hot press poses a problem, but can be suitably removed by the following method.

That is, the resin is controlled by the above-described method so that the amount of excess resin flowing out is reduced as much as possible. After solidification is performed as it is, the excess resin can be removed by the flattening step. In addition, a mesh sheet or the like is interposed between the press table and the base material layer, and excess resin flowing out to the back side of the base layer is fixed to the mesh sheet or the like, and a mesh sheet or the like is formed. Exfoliation can remove excess resin. When a mesh sheet or the like is used, it is not necessary to position the openings as in the case of the peeling sheet, and the operation becomes simpler.

(2) In the above embodiment, an example was described in which a prepreg containing a thermosetting resin was used as the resin sheet 2, but a resin sheet made of a thermoplastic resin may be used. In that case, considering the soldering process, it is necessary to use a resin sheet with a high melting point, and it is necessary to heat and press at a high temperature. In addition, the resin can be solidified by leaving the hot pressed surface away from the resin sheet and cooling it by standing or air cooling o

(3) In the above-described embodiment, an example has been described in which the base material layer having a through hole that electrically conductively connects the wiring layers as the through hole is to be filled with the resin. It is also possible to fill a wiring board having holes with a resin.

(4) In the above-described embodiment, an example is shown in which the through-hole for conductively connecting the first wiring layer and the second wiring layer is filled with resin, and then the upper layer is further formed. The subsequent step can be performed without filling the resin. In such a case, the resin filling step of the present invention may be performed using an opening for the peeling sheet that is not provided for some of the through holes. Thus, a resin in which some of the through holes are not filled with the resin can be formed. Industrial applicability

INDUSTRIAL APPLICABILITY The present invention is useful for a method for manufacturing a wiring board having via holes for conductive connection between wiring layers or through holes formed for purposes other than conductive connection. More specifically, when filling the through-hole with a resin in a via-hole forming process or the like, the filled resin The resin can be suitably filled by a simple process using an inexpensive material with few defects. Therefore, the present invention has high industrial applicability.

Claims

The scope of the claims

1. (a) A release sheet having an opening corresponding to the through-hole is placed on a substrate or a base material layer having a through-hole filled with resin, while aligning the opening, the substrate or Arranging at least one side surface of the base material layer,

(b) arranging a resin sheet which is softened by heating and solidified by cooling or curing on the surface on which the release sheet is arranged,

(c) a step of embedding a part of the resin sheet in the through hole while softening the resin sheet by applying heat and pressure, and then solidifying by cooling or curing; and

(d) removing the release sheet from the substrate or base material layer

A method for manufacturing a wiring board having a resin filling step including:

2. The manufacturing method according to claim 1, wherein the through hole is a through hole for conductively connecting a plurality of wiring layers.

3. After step d,

3. The manufacturing method according to claim 1, further comprising: (e) flattening a protruding portion of the resin filled in the through hole of the substrate or the base material layer.

4. The method according to any one of claims 1 to 3, wherein the resin sheet is a resin sheet containing a resin material which is softened by heating and hardened at a high temperature.

5. The production method according to any one of claims 1 to 4, wherein, in the step (a), the release sheet is disposed on both surfaces of the substrate or the base material layer.

6. A wiring board manufactured by the manufacturing method according to any one of claims 1 to 5.