JPH04239193A - Filling method of via of through-hole - Google Patents

Abstract

PURPOSE:To prevent insufficient conduction and to lower costs by filling conductive paste using a squeegee in a through-hole of a green sheet which is prevented from deforming by lining with a porous sheet. CONSTITUTION:A porous sheet 3 is laminated on the rear side of a green sheet 2 with a through hole 1 to prevent deformation of the sheet 2. A porous sheet or a sheet formed by meshing fibers such as nylon is used as the sheet 3. The green sheet 2 is set to a print stage 5 and a screen 6 with a hole in a position corresponding to the through-hole 1 is laminated. A squeegee 7 is moved at a fixed speed on the screen 6 in arrow direction while carrying conductor paste 4 to charge the conductor paste 4 in the through hole 1. The sheet 3 removes excessive air inside the through hole 1 and prevents the conductor paste 4 from creeping and attaching. Thereby, it is possible to prevent insufficient conduction in vertical direction and to reduce costs.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for filling vias in through-holes, and in particular, in multilayer ceramic substrates for the electronic industry manufactured by the green sheet method, vias in through-holes are provided for electrical continuity between upper and lower layers. Regarding filling method.

0002

[Common Technology] In recent years, as computers have become faster and smaller, it has become necessary to increase the density and capacity of boards on which LSIs are mounted. However, in conventional printed wiring boards, the wiring connecting each element is in a planar direction.
Further, since there is a restriction on the through-hole pitch, there is a limit to realizing the above-mentioned high-density mounting board.

[0003] For this reason, multilayer ceramic substrates that have vertically expanded wiring to increase the density and have excellent thermal conductivity are attracting attention. Further, this multilayer ceramic substrate is generally manufactured using a green sheet method.

[0004] Here, some explanation will be given regarding the green sheet method.

FIG. 2 shows the manufacturing process of a multilayer ceramic substrate using the green sheet method. First, in the slurry process,
Ceramic powder, which is the base material for a multilayer ceramic substrate, is mixed with a solvent and a plasticizer to form a slurry. Next, this slurry is applied onto a carrier film to a uniform thickness using a doctor blade or the like, and dried using a dryer to produce a sheet-like ceramic tape. This ceramic tape is called a green sheet, and serves as a basic unit constituting layers in a multilayer ceramic substrate. Subsequently, a plurality of through holes are formed in the green sheet at appropriate positions using a punch or the like. Then, a circuit pattern is printed on the green sheet using conductive paste, and at this time, the previously formed through holes are filled with the conductive paste to form through holes that connect the upper and lower layers.

A plurality of green sheets printed with the above-mentioned conductive paste are laminated to form a circuit having desired performance. This green sheet laminate is fixedly joined by a heat press or the like, and then fired to form a multilayer ceramic substrate.

[0007]

2. Description of the Related Art Next, a conventional via filling method for through holes will be explained in detail with reference to the drawings.

FIG. 3 is a sectional view illustrating an example of a conventional via filling method for through holes. In FIG. 3, reference numeral 2 denotes a green sheet having through holes 1, and a sheet 8 is pasted to the back surface of this green sheet 2. As described in the section on common technology, the through hole 1 is a cylindrical hole formed in the green sheet 2 for wiring between upper and lower layers in a multilayer ceramic substrate. Then, conductive paste 4 is inserted into this through hole 1.
By filling the layers and stacking them, electrical connection between the upper and lower layers becomes possible. However, the green sheet 2 is easily deformed even at room temperature, and it is not preferable to leave it alone for a long time after forming the through holes 1. For this reason,
A sheet 8 is attached to the back surface of the green sheet 2 (the surface opposite to the circuit pattern printed surface) to prevent deformation.

Next, the screen printing method, which is a means for filling the paste 4, is composed of a printing stage 5, a screen 6, and a squeegee 7. The printing stage 5 is provided so that a green sheet 2 having through holes 1 formed therein, which is a printing medium, is fixed thereon, and the positional relationship with the screen 6 is determined at this time. Further, holes are formed in the screen 6 at positions corresponding to the through holes 1 provided in the green sheet 2 so that the conductive paste 4 can pass therethrough. The squeegee 7 moves at a constant speed in the direction of the arrow while carrying the conductive paste 4 over the screen 6. When the squeegee 7 passes over the holes in the screen 6, the carried conductor paste 4 is pushed downward by the ridgeline of the squeegee 7 and is filled into the through hole 1. Further, at this time, the sheet 8 prevents the conductive paste 4 from adhering to the printing stage 5 and prevents the conductive paste 4 from going around to the back surface of the green sheet 2 during via filling.

0010

[Problems to be Solved by the Invention] The conventional via filling method for through-holes described above has no air permeability because the sheet is pasted on the back of the green sheet, and when filling the through-holes with conductive paste, air escapes. There was a drawback that it did not come out and the vias were insufficiently filled. For this reason, when manufacturing a multilayer ceramic substrate, electrical conduction defects tend to occur, resulting in a disadvantage that the final substrate becomes expensive.

[0011]

[Means for Solving the Problems] The method for filling vias in through holes of the present invention involves pasting a green sheet having through holes and a breathable sheet to prevent deformation on the back side of the green sheet, and then using a screen printing method to The method is characterized in that the through holes of the green sheet are filled with a conductive paste.

0012

Embodiments Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view illustrating an embodiment of the present invention. In FIG. 1, reference numeral 2 denotes a green sheet having through holes 1, and a conventional sheet for preventing deformation is pasted on the back side of the green sheet 2 instead of the sheet 3 having air permeability. For this sheet 3,
For example, a porous sheet having holes communicating with the interior of the sheet or a sheet made of a mesh of fibers such as nylon can be used. In addition, the screen printing method, which is a means of filling the conductor paste 4, uses the printing stage 5,
It is composed of a screen 6 and a squeegee 7. The printing stage 5 is provided so that a green sheet 2 having through holes 1 formed therein, which is a printing medium, is fixed thereon, and the positional relationship with the screen 6 is determined at this time. In addition, a conductive paste 4 is placed on the screen 6 at a position corresponding to the through hole 1 provided in the green sheet 2.
A hole is formed to allow it to pass through. The squeegee 7 moves at a constant speed in the direction of the arrow while carrying the conductive paste 4 over the screen 6. When the squeegee 7 passes over the holes of the screen 6 described above, the carried conductive paste 4 is pushed downward by the ridgeline portion of the squeegee 7 and is filled into the through hole 1. Further, at this time, the breathable sheet 3 discharges excess air in the through hole 1 when filling the via, and prevents the conductive paste 4 from adhering to the printing stage 5.
This prevents the conductive paste 4 from going around to the back surface of the.

[0014]

[Effects of the Invention] The method for filling vias in through-holes of the present invention uses a breathable sheet as the sheet pasted on the back side of the green sheet, so that when filling conductive paste into the through-holes, the through-holes are filled with conductive paste. This has the effect of making it easier for some air to escape, and allowing the through holes to be appropriately filled with conductive paste. Therefore, when manufacturing a multilayer ceramic substrate, there is no via filling defect in the through hole, and no electrical conduction defect occurs due to this, resulting in an effect that the final substrate is inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating an embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of a multilayer ceramic substrate using a green sheet method.

FIG. 3 is a cross-sectional view illustrating an example of a conventional via filling method for a through hole.

[Explanation of symbols]

1 Through hole 2 Green sheet 3. Breathable sheet 4 Conductor paste 5 Printing stage 6 Screen 7 Squeegee 8 Sheet

Claims (1)

[Claims] 1. A green sheet having through holes and a breathable sheet for preventing deformation are attached to the back side of the green sheet, and then the through holes of the green sheet are filled with a conductive paste by a screen printing method. A method for filling vias in through-holes.