JP2010192792A - Method of selectively filling holes of printed circuit board with resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of selectively filling holes of a printed circuit board with resin. <P>SOLUTION: The method includes the following steps of: (a) boring first small holes in a first sheet-like member made of a magnetic material at the positions of holes to be filled with resin; (b) boring second small holes in a detachable second sheet-like member with adhesive properties at the positions of holes not to be filled with resin; (c) adhering the second sheet-like member obtained at step (b) onto the printed circuit board while adjusting the hole positions; (d) placing the printed circuit board obtained at step (c) on a placement table capable of changing a magnetic force while the surface on which the second sheet-like member is adhered is facing downward and sticking the first sheet-like member obtained at step (a) on the printed circuit board while adjusting the hole positions and applying the magnetic force, in a vacuum atmosphere; (e) applying the liquefied resin on the first sheet-like member; and (f) peeling off the first sheet-like member after releasing it from the vacuum state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for selectively filling a through hole formed in a printed wiring board with a resin.

  Conventionally, liquid viscous materials such as conductive paste and insulating resin paste are filled in through holes (for example, through holes or via holes) or non-through holes (for example, blind through holes or blind via holes) of a multilayer circuit board. Is known (for example, Patent Document 1). The filling described in this patent document is generally performed by stencil printing under a normal atmospheric pressure atmosphere (normal air atmosphere).

  However, as the number of stacked plates increases, the L / D (L is the depth of the hole and D is the diameter of the hole) of the through-holes and non-through-holes gradually increases. However, it has become difficult to quickly and uniformly fill the fine holes (for example, having a diameter of 50 μm). This is particularly noticeable in the case where the liquid viscous material is an insulating resin paste that is becoming more highly viscous.

A method for solving such a problem has also been proposed (for example, Patent Document 2).
FIG. 4 is a diagram illustrating an example of the case where this filling method is applied to resin filling into the through hole 11a of the substrate 11 in the order of steps. FIG. 4A schematically shows the situation at the start of resin filling by applying the stencil printing means. The through hole 11a is a through hole, and its lower end opening is sealed in advance by applying an easily peelable closing member, for example, an adhesive tape 61. As will be described later, the lower end opening is hermetically sealed in order to push and fill the resin using the differential pressure.

  In the state shown in FIG. 4A, in a vacuum atmosphere, for example, in a casing (not shown) kept under vacuum, the squeegee 7 is operated to allow the liquid resin 8 to pass through the through-hole portion 51 a of the stencil 51. The through holes 11a aligned with the holes 51a are respectively pushed and filled.

  FIG. 4B shows a state immediately after the liquid resin 8 has been pushed and filled, and an unfilled portion 91 is generated at the bottom of the through hole 11a. The occurrence of the unfilled portion 91 is presumed to be due to the fact that there is a limit to the filling pressure in the indentation filling by the squeegee 7 operation, and that the filling pressure is insufficient. If the unfilled portion 91 is left as it is, it may cause a decrease in product quality and performance, which is not preferable.

  In order to eliminate this unfilled portion 91, when the resin filling operation is completed in a vacuum atmosphere, for example, the vacuum atmosphere is opened to the atmosphere and returned to normal pressure.

  FIG. 4C shows the situation after returning to normal pressure. The unfilled portion 91 is a closed space sealed with the adhesive tape 61, and can be regarded as maintaining the degree of vacuum at the time of stencil printing, so there is a pressure difference with the external atmosphere (atmosphere). Arise. Due to this pressure difference, the liquid resin 8 is pushed toward the bottom of the through hole 11a, so that the resin is also filled in the unfilled portion 91, and the unfilled portion 91 is eliminated.

  After returning to normal pressure, the stencil 51 is released as shown in FIG. 4 (d), the liquid resin 8 is then heat-cured, and after curing, the adhesive tape 61 is peeled and removed to remove unfilled portions and A resin-filled layer 8a containing no bubbles is obtained.

Paragraph [0004] of Japanese Patent Laid-Open No. 10-27969 Paragraphs [0011] to [0017] of Japanese Patent Laid-Open No. 2000-183519

  On the other hand, not only does the L / D increase, but as the printed wiring board increases in density, the pitch between through holes is becoming narrower, and there are through holes filled with resin and through holes not filled with resin. Is starting to do. In addition, the printed wiring board has been increased in the number of layers, and the thickness of the board has naturally increased. In this case, there may be a case where the through holes filled with the resin and the through holes not filled with the resin must be provided at adjacent positions at a narrow pitch. Such a printed wiring board can be filled with resin in a through-hole filled with resin by using the above-described resin filling method as it is.

FIG. 5 is a view showing a resin filling method of such a printed wiring board.
In the state shown in FIG. 5A, in a vacuum atmosphere, for example, in a casing (not shown) held in a vacuum, the squeegee 7 is operated to allow the liquid resin 8 to pass through the through hole 51a of the stencil 51. The through holes 11a aligned with the through-hole portions 51a are respectively pushed and filled. Here, 11b is a through hole that is not to be filled with the liquid resin 8, and the through hole 51 is not provided in the stencil 51 at a position corresponding to the through hole 11b.

FIG. 5B shows a state immediately after the liquid resin 8 has been pushed and filled, and an unfilled portion 91 is generated at the bottom of the through hole 11a.
In order to eliminate this unfilled portion 91, when the resin filling operation is completed in a vacuum atmosphere, for example, the vacuum atmosphere is opened to the atmosphere and returned to normal pressure.

  FIG.5 (c) has shown the condition after returning to a normal pressure. The unfilled portion 91 is a closed space sealed with the adhesive tape 61, and can be regarded as maintaining the degree of vacuum at the time of stencil printing, so there is a pressure difference with the external atmosphere (atmosphere). Arise. Due to this pressure difference, the liquid resin 8 is pushed toward the bottom of the through hole 11a, so that the resin is also filled in the unfilled portion 91, and the unfilled portion 91 is eliminated.

  However, it is the same as the unfilled portion 91 that the through hole 11b is also a closed space sealed by the adhesive tape 61, and naturally, a pressure difference from the external atmosphere (atmosphere) similarly occurs here. Due to this pressure difference, the liquid resin 8 above the printed wiring board 11 (in the region 95 in FIG. 5B) flows into the through hole 11b (8d in FIG. 5C). .

Further, since the printing frame is used because of stencil printing, there are the following disadvantages.
From the viewpoint of structure, first, the printing frame mechanism in the vacuum space is expensive, and secondly, since the vacuum space is widened, the time required for evacuation increases, and the means for evacuation requires a large amount of cost. Leading up. Thirdly, the printing frame is large and handling is troublesome because a large storage space is required.
On the other hand, since a clearance is required between the printing frame and the printed wiring board from the resin printing surface, the alignment accuracy decreases as the through-holes become narrower.

  The present invention has been made in order to solve the above-described problems. The resin-filled side of the printed wiring board is covered with a first sheet-like member having a hole at the position of the resin-filled through hole, and the resin-filled through-hole is not covered. The other surface of the printed wiring board was covered with a second sheet-like member having a hole at the position of the hole, and the first sheet member was released from the printed wiring board after releasing the vacuum state after filling with the resin. It is an object of the present invention to provide a method for selectively filling a hole of a printed wiring board, which enables resin filling only in the through hole to be filled with resin selectively in terms of quality.

According to the method of selectively filling a hole in a printed wiring board according to the present invention, a liquid resin is filled into the hole of the printed wiring board by applying a stencil printing means in a vacuum atmosphere, and after the resin is filled, a vacuum is applied. A method of filling a liquid resin into a hole of a printed wiring board that performs differential pressure filling by lowering the degree of vacuum in the atmosphere, and includes the following steps.
a) forming a first small hole in each position of the hole to be filled with resin in the printed wiring board in the first sheet-like member made of a magnetic material;
b) forming a second small hole at each position of the hole outside the resin filling target of the printed wiring board in the second sheet-like member that is adhesive and detachable;
c) A step of attaching the second sheet-like member obtained in step b) to the printed wiring board by aligning the hole positions;
d) In a vacuum atmosphere, the printed wiring board obtained in step c) is placed with the surface on which the second sheet member is attached facing down on a mounting table whose magnetic force can be varied. To the first sheet-like member obtained in the step a), the step of aligning the hole position and applying a magnetic force to closely contact the first sheet-like member;
e) a step of printing the liquid resin from above the first sheet-like member;
f) Step of peeling the first sheet-like member after releasing from the vacuum state

Further, another method of selectively filling a hole in a printed wiring board according to the present invention is to fill a liquid resin into the hole of the printed wiring board by applying a stencil printing means in a vacuum atmosphere, After filling the resin, a method of filling the liquid resin into the hole of the printed wiring board that performs differential pressure filling by lowering the degree of vacuum in the vacuum atmosphere, which includes the following steps: .
a) a step of covering both surfaces of the printed wiring board with a first sheet-like member and a second sheet-like member which are adhesive and detachable;
b) forming a first small hole in each of the first sheet-like members at the position of the hole to be filled with resin on the printed wiring board;
c) forming a second small hole in each of the second sheet-like members at positions of holes of the printed wiring board that are not to be filled with resin;
d) a step of printing the liquid resin from above the first sheet-like member in a vacuum atmosphere on the printed wiring board that has undergone the steps a) to c);
e) Step of peeling the first sheet-like member after releasing from the vacuum state

  The first sheet-like member is a magnetic body.

  Further, the adhesion and detachability between the first sheet-like member and the printed wiring board is such that the printed wiring board is sandwiched between the first sheet-like member formed of a magnetic material and a magnet. It is characterized by a change in magnetic force.

  The second sheet-like member is an adhesive tape.

  Moreover, the hole diameter of the first small hole is the same as or slightly larger than the hole diameter of the corresponding resin filling target through hole.

  Further, the diameter of the second small hole is the same as or slightly smaller than the diameter of the corresponding through hole not to be filled with resin.

According to the present invention, the first sheet member provided with the first small hole in accordance with the position of the resin filling target through-hole is aligned with the resin filling target through-hole corresponding to the small hole on the printed wiring board. By adhering, it is possible to solve the disadvantages associated with the use of printing frames. In addition, the second sheet member provided with the second small hole in alignment with the through hole not to be filled with resin is aligned with the through hole not to be filled with resin corresponding to the small hole, and the first sheet-like member Covering the surface of the opposite side of the printed wiring board, and leaving the first sheet-like member in close contact with the printed wiring board immediately after being released from the vacuum state, the atmosphere is passed through this second small hole. Since the through holes are allowed to flow, the resin does not flow from the contact surface between the first sheet-like member and the printed wiring board. And even if the first sheet-like member is peeled from the printed wiring board after the air flows into the resin-filled through-hole, the pressure difference from the inside of the through-hole is eliminated, so the resin-filled through-hole is removed. Since the resin does not flow in, it is possible to solve the disadvantage of the resin flowing in due to the separation of the first sheet-like member from the printed wiring board.
Therefore, even when the resin filling target and the non-target through-hole are adjacent to each other at a narrow pitch, it is possible to selectively fill the through-hole of the printed wiring board with a stable quality selectively to the resin filling target through-hole. A selective resin filling method can be provided.

It is a figure which shows the process of the front | former stage of the selective resin filling method to the hole of the printed wiring board which becomes this invention. It is a figure which shows the process of the middle step of the selective resin filling method to the hole of the printed wiring board which becomes this invention. It is a figure which shows the process of the back | latter stage of the selective resin filling method to the hole of the printed wiring board which becomes this invention. It is a figure which shows the resin filling method to the through hole of the conventional printed wiring board in order of a process. It is a figure which shows a mode when it utilizes when the conventional filling method of FIG. 4 is selectively filled in process order.

Next, the present invention will be described in detail with reference to the drawings.
FIG. 1 to FIG. 3 are views showing a method of selectively filling a hole in a printed wiring board according to the present invention in the order of steps, FIG. 1 is a front portion thereof, FIG. 2 is a view showing an intermediate portion thereof, and FIG. 3 is a view showing the subsequent stage. 1 to 3, the same components as those in FIGS. 4 and 5 are denoted by the same reference numerals, and redundant descriptions are omitted when describing the contents of the invention.

  In FIG. 1 to FIG. 3, 1 is a printed wiring board to be selectively filled with resin, and a hole is formed in a copper-clad printed wiring board, and conductive plating is applied to the hole. (Hereinafter referred to as a printed wiring board), 2 is a conductive layer (including a copper-clad portion and a conductive plating portion) of this printed wiring board 1, 1a is a resin-filled through hole (hereinafter also referred to as a target through hole), 1b is a resin-filled non-target through-hole (hereinafter also referred to as non-target through-hole), 5 is a first sheet-like member that is aligned with the target through-hole 1a and a resin through-hole 5a is formed, and 6 is a target A second sheet-like member which is aligned with 1b in the outer through hole and formed with an air hole 6a when the vacuum state is opened, 7 is a squeegee, 8 is a liquid resin (hereinafter also referred to as resin), 9 is First and second Mounting table for mounting a printed circuit board 1 covered with over preparative shaped members 5, 21 is a schematic flow of air during the vacuum opening.

  First, a copper-clad laminate is prepared, holes are formed at predetermined positions using known means, conductive plating is performed, printed wiring board 1 provided with through-holes 1a and 1b, and first through the positions of target through-holes 1a. The first sheet-like member 5 provided with a through-hole portion 5a that is one small hole, and the second sheet-like member provided with a through-hole portion 6a that is a second small hole at the position of the non-target through hole 1b 6 is prepared (FIG. 1A).

  The first sheet-like member 1 is formed of a magnetic material, and the thickness and the diameter of the through-hole portion 5a provided here are determined according to the diameter of the target through-hole 1a and the resin filling amount. It is preferable that the diameter is equal to or slightly larger than the diameter of the target through hole 1a. The reason why it is formed of a magnetic material is to keep the first sheet-like member 1 in close contact with the printed wiring board 1 with a necessary magnetic force as will be described later.

  Further, the second sheet-like member is formed of an adhesive tape, and the thickness and the diameter of the through-hole portion 6a provided therein are the diameter of the non-target through-hole 1b and the inflow of air when the vacuum is released. Although it is determined according to time, it is preferable that the diameter is the same as or slightly smaller than the diameter of the non-target through hole 1b.

  Next, the second sheet-like member 6 is attached to one surface of the printed wiring board 1 (the lower surface in FIG. 1B) by aligning the non-target through-hole 1b and the through-hole portion 6a. (FIG. 1 (b)). Up to this point, it is not necessary to carry out in a vacuum atmosphere.

Next, magnetic force generation that exerts a magnetic force on the magnetic material placed on the resin filling mechanism (not shown) and the mounting table 9 on the printed wiring board 1 on which the first sheet-like member 5 and the second sheet-like member 6 are attached. Place in vacuum-tight casing with mechanism.
The printed wiring board 1 is placed on the mounting table 9 with the second sheet-like member 6 side down, and the first surface of the printed wiring board 1 (the upper surface in FIG. 1B) is the first. The sheet-like member 5 is placed with the target through-hole 1a and the through-hole 5a aligned.

  This casing is provided with the above-described magnetic force generation mechanism (not shown) so that the magnetic force can be generated or stopped, so that the alignment between the first sheet-like member 5 and the printed wiring board 1 is completed. Thus, the first sheet-like member 5 and the printed wiring board 1 are fixed in close contact with each other by generating a magnetic force so as not to cause positional fluctuation (FIG. 1C). Instead of this magnetic force generation mechanism, a permanent magnet moving mechanism is provided, and by moving this permanent magnet, the effect of the magnetic force is changed to produce the same effect as the generation and stop of the magnetic force. Also good.

Next, the resin is filled into the target through hole 1a using the resin filling mechanism.
Specifically, the resin 8 is supplied to the end of the first sheet-like member 5 (on the left side in FIG. 2D), and the squeegee 7 is supplied with a predetermined pressing force according to L and D of the target through-hole 1a. The resin 8 supplied by moving the printed wiring board 1 to the mounting table 9 through the sheet-like member 5 and moving it to the right side in the figure through the through-hole 5a of the first sheet-like member 5 Each hole 1a is pushed and filled (FIGS. 2D and 2E). Since this filling operation is the same as that of the prior art, it is not particularly shown here, but the target through hole 1a is not completely filled with the resin 8 but has an unfilled portion.

  Next, the vacuum state of the casing is released and returned to atmospheric pressure (FIG. 3 (f)). At this time, the resin 8 is further pushed into the through hole portion 5a of the first sheet-like member 5 due to the air flow indicated by 21 so that the unfilled portion is eliminated. As described in the prior art. On the other hand, since the through-hole portion 6a of the second sheet-like member 6 is maintained in a vacuum, air flows as indicated by 21 so as to eliminate the differential pressure from the atmospheric pressure, and after a certain period of time, the target through-hole 1b is filled with air (21a in FIG. 3 (g)). Further, since the first sheet-like member 5 and the printed wiring board 1 are in close contact with each other as described above, there is almost no air flow (FIG. 3G).

Next, after the magnetic force generation mechanism is operated to stop the generation of the magnetic force to eliminate the close contact state between the first sheet-like member 5 and the printed wiring board 1, the first sheet-like member 5 is moved to the printed wiring board 1. Peel from.
The air flow 21 is generated between the first sheet-like member 5 and the printed wiring board 1 as shown in the figure. At this time, the atmospheric pressure is applied to the exposed portion of the resin 8 and the upper portion of the non-target through hole 1b, but the resin is not pushed into the target through hole 1a more than before, and the non-target through hole 1b Since the air 21a has already flown and there is no pressure difference, air does not flow here (FIG. 3 (h)).

That is, the exposed portion of the resin 8 is deformed according to the viscosity and slightly spreads in all directions, and does not enter the non-target through hole 1b.
Thus, the selective resin filling into the hole of the printed wiring board is completed separately for the target through hole 1a and the non-target through hole 1b.

In the resin filling method described above, the first sheet-like member 5 provided with the through-hole portion 5a and the second sheet-like member 6 provided with the through-hole portion 6a are prepared in advance, and the printed wiring board 1 is covered with these. Is the method.
Instead of this method, each surface of the printed wiring board is covered with a first sheet-like member and a second sheet-like member not previously provided with a through hole, and the first sheet-like member, the printed wiring board, After the second sheet-like member and the printed wiring board are prevented from changing in position, the through hole portion may be provided.

DESCRIPTION OF SYMBOLS 1 Printed wiring board 1a Through hole for resin filling 1b Through hole not for resin filling 2 Conductive layer 5 First sheet member 5a Through hole 6 Second sheet member 6a Through hole 7 Squeegee 8 Liquid resin 8a Resin filling Layer 9 Mounting table 11 Substrate 11a Through hole 51 Stencil 51a, 61a Through hole 61 Adhesive tape 91 Unfilled part

Claims (7)

The printed circuit board is filled with the liquid resin in the hole of the printed wiring board by applying stencil printing means in a vacuum atmosphere, and after filling the resin, the vacuum pressure in the vacuum atmosphere is reduced to fill the differential pressure. A method for selectively filling a hole of a printed wiring board with a liquid resin in a hole, comprising the following steps.
a) forming a first small hole in each position of the hole to be filled with resin in the printed wiring board in the first sheet-like member made of a magnetic material;
b) forming a second small hole at each position of the hole outside the resin filling target of the printed wiring board in the second sheet-like member that is adhesive and detachable;
c) A step of attaching the second sheet-like member obtained in step b) to the printed wiring board by aligning the hole positions;
d) In a vacuum atmosphere, the printed wiring board obtained in step c) is placed with the surface on which the second sheet member is attached facing down on a mounting table whose magnetic force can be varied. To the first sheet-like member obtained in the step a), the step of aligning the hole position and applying a magnetic force to closely contact the first sheet-like member;
e) a step of printing the liquid resin from above the first sheet-like member;
f) Step of peeling the first sheet-like member after releasing from the vacuum state The printed circuit board is filled with the liquid resin in the hole of the printed wiring board by applying stencil printing means in a vacuum atmosphere, and after filling the resin, the vacuum pressure in the vacuum atmosphere is reduced to fill the differential pressure. A method for selectively filling a hole of a printed wiring board with a liquid resin in a hole, comprising the following steps.
a) a step of covering both surfaces of the printed wiring board with a first sheet-like member and a second sheet-like member which are adhesive and detachable;
b) forming a first small hole in each of the first sheet-like members at the position of the hole to be filled with resin on the printed wiring board;
c) forming a second small hole in each of the second sheet-like members at positions of holes of the printed wiring board that are not to be filled with resin;
d) a step of printing the liquid resin from above the first sheet-like member in a vacuum atmosphere on the printed wiring board that has undergone the steps a) to c);
e) Step of peeling the first sheet-like member after releasing from the vacuum state   The method for selectively filling a hole in a printed wiring board according to claim 1, wherein the first sheet-like member is a magnetic body.   The adhesion and detachability between the first sheet-like member and the printed wiring board are such that the printed wiring board is sandwiched between the first sheet-like member and the magnet according to claim 3, and the magnetic force of the magnet varies. The method for selectively filling a hole in a printed wiring board according to claim 1 or 2, wherein   The method for selectively filling a hole in a printed wiring board according to claim 1, wherein the second sheet-like member is an adhesive tape.   3. The selective resin filling into the hole portion of the printed wiring board according to claim 1, wherein a hole diameter of the first small hole is the same as or slightly larger than a hole diameter of a corresponding through hole to be filled with resin. 4. Method.   3. The selective resin to the hole of the printed wiring board according to claim 1, wherein a hole diameter of the second small hole is the same as or slightly smaller than a hole diameter of a corresponding through hole not to be filled with resin. Filling method.

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