JP3240347B2 - Method of filling resin into hole of printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for filling a hole in a printed wiring board with a resin.

[0002]

2. Description of the Related Art When a resin is filled into a hole in a printed wiring board, for example, a through hole formed in a substrate of a double-sided printed wiring board or a via hole formed in a substrate of a laminated board in a multilayer printed wiring board, a stencil printing means is used. The method of filling with methane is excellent in mass productivity, efficiency, economy, etc., and thus tends to be widely used. However, in the filling method using the stencil printing means, when the hole is narrow and deep, such as a through hole or a via hole, it is difficult to completely fill the resin in every corner of the hole. Not only was there a possibility that an unfilled portion would remain at the bottom, but there was also a risk that bubbles would be trapped when the resin was filled. Insulating resin is filled in through holes or via holes with conductive plating, and conductive resin is filled in through holes or via holes with no conductive plating. If unfilled portions or bubbles remain inside, in the former case, cracks at the time of thermal shock tend to cause disconnection etc. in the conductive plating portion, and in the latter case, variation in resistance value occurs It is not preferable because it may cause

[0003] In addition, a resin filling method using stencil printing means applies an electronic component element such as a semiconductor element and a coil disposed in a bottomed hole of a substrate of a single-sided printed wiring board to the insulating resin for the same reason as described above. However, even in this case, bubbles remain or unfilled portions are generated between the bottom of the hole, the periphery and lower portion of the wire, the peripheral portion of the element, and the coil winding. This has led to lower quality and performance.

[0004]

In this case, if the filling of the resin by the stencil printing means is performed in a vacuum atmosphere, it is possible to prevent air entrapment at the time of filling and other residual air to some extent. However, generation of an unfilled portion of the resin still remains, and a solution to the problem has been desired.

An object of the present invention is to provide a resin filling method capable of preventing not only entrapment of air and remaining of air but also generation of an unfilled portion of the resin.

[0006]

According to the present invention, a liquid resin is filled into a hole in a printed wiring board by applying a stencil printing means in a vacuum atmosphere, and after filling the resin, the degree of vacuum in the vacuum atmosphere is reduced. A resin filling method for lowering at least 3.99 kPa toward normal pressure and then releasing the stencil, wherein a net is stretched at the lower end opening of the through hole of the stencil.
The resin on the tray is removed as excess resin together with the stencil when releasing the mold.
The present invention relates to a method for filling a hole in a printed wiring board with a resin.

[0007]

[0008]

[0009]

[0010]

[0011]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIGS. 1A to 1E show an example of a case in which the filling method of the present invention is applied to filling a resin into a through hole 2 of a substrate 1 in the order of steps. Fig. 1 (a)
The situation at the beginning of resin filling by stencil printing means is schematically shown. The through-hole 2 is a through-hole, and the lower end opening 2 a is sealed in advance by applying an easily peelable closing member, for example, an adhesive tape 3. The sealing of the lower end opening 2a is necessary for injecting and filling the resin using the differential pressure as described below.

In the state shown in FIG.
For example, in a casing (not shown) held in a vacuum, the squeegee 4 is operated to move the liquid resin 5 through the through-hole 7 of the stencil 6 into the through-hole 2 aligned with the through-hole 7. And press-fill.

FIG. 1B shows a state immediately after the completion of the press-filling of the liquid resin 5, and an unfilled portion 8 is formed at the bottom of the through hole 2. The occurrence of the unfilled portion 8 is presumed to be due to the fact that there is a limit to the filling pressure in the indentation filling by the operation of the squeegee 4, and the insufficient filling pressure has an effect. If the unfilled portion 8 remains, the quality of the product,
This is undesirable because it causes a decrease in performance.

According to the present invention, in order to erase the unfilled portion 8, the resin filling operation in a vacuum atmosphere is completed.
For example, a vacuum atmosphere is released to the atmosphere and returned to normal pressure.

FIG. 1C shows the situation after the pressure has been returned to normal pressure. The unfilled portion 8 is a closed space closed by the adhesive tape 3 and can be regarded as holding the degree of vacuum at the time of stencil printing. Therefore, the pressure difference between the unfilled portion 8 and the external atmosphere (atmosphere) is reduced. Occurs. Due to this pressure difference,
The liquid resin 5 is pushed toward the bottom of the through-hole 2, so that the unfilled portion 8 is also filled with the resin, and the unfilled portion 8 is erased.

After returning to normal pressure, the stencil 6 is released as shown in FIG. 1D, and then the liquid resin 5 is cured by heating.
After the curing, the pressure-sensitive adhesive tape 3 is peeled off to obtain a resin-filled layer 5A containing no unfilled portions and no air bubbles.

FIG. 2 shows a conductive plating 9 in the through hole 2.
In this case, an insulating resin is used for forming the resin-filled layer 5A.

FIG. 3 shows a case where the conductive plating is not applied to the through-hole 2. In this case, a conductive resin is used for forming the resin filling layer 5A.

FIG. 4 shows a multilayer printed wiring board including the substrate 1 shown in FIG. 2 as an inner laminate, and FIG. 5 shows a multilayer printed wiring board including the substrate 1 shown in FIG. 3 as an inner laminate. In the drawing, reference numeral 10 denotes an insulating layer made of prepreg, and 11 denotes an outer laminate provided with a conductive film such as a copper foil.

When the resin-filled layer 5A of the through-hole 2 (in the case of a laminated board, usually called a via-hole) contains air bubbles and / or contains an unfilled portion 8, heat is generated during reflow. This may cause breakage of the conductive plating at the through hole 2 portion and cause swelling and peeling off from the through hole 2 portion. However, in the present invention, since no bubbles or unfilled portions are included, breakage, swelling, peeling, etc. Can be eliminated and the quality performance of the multilayer laminate can be improved.

FIGS. 6 and 7 show an example in which electronic components 13 such as semiconductor elements and coils are arranged in the bottomed hole 12 of the substrate 1. By filling with the liquid resin 5 (insulating property), a high-quality resin sealing layer (not shown) that does not include bubbles and unfilled portions can be formed.

The filling method of the present invention can also be applied to resin filling into the through-hole portion 14 of the substrate 1 at the time of forming a package as shown in FIG. In this case, the lower end opening 14 of the through hole 14
As in the case of the through hole 2 shown in FIG. 1, a is sealed by applying the easily peelable closing member 15. Closing member 1
The electronic component element 13 is arranged and fixed in advance on a surface facing the inside of the hole 14 of No. 5.

FIG. 9 shows the through hole 14 of the substrate 1 shown in FIG.
1A shows a state in which the liquid resin 5 is filled by applying vacuum printing means as in FIG. 1A. In this filled state, the bottom of the hole 14, especially around the electronic component element 13, etc. The unfilled portion 8 has occurred. This unfilled part 8 is shown in FIG.
Similarly to (c), erasing can be performed by releasing the vacuum atmosphere to the atmosphere and returning it to normal pressure, for example, and generating a pressure difference between the unfilled portion 8 and the external atmosphere.

FIG. 10 shows the situation when the stencil 6 is released after the unfilled portion is erased. In this case, the through holes 7 of the stencil 6
If the net 16 is stretched in the lower end opening 7a of the resin, the resin 5 'on the net 16 is removed as surplus resin, and the upper surface of the resin filling layer 5A can be substantially aligned with the surface of the substrate 1, so that the dimensional accuracy of the package can be improved. Can be increased. As shown in FIG. 11, the obtained package is inverted after being cured and released from the resin, and the conductor circuit 17 is formed by applying a printing means, for example.

The stencil with the net 16 is shown in FIGS.
(D) As shown in FIG.
Although not shown, the present invention is also applicable to filling the bottomed hole portion 12 with a resin as shown in FIGS.

In the present invention, the degree of vacuum at the time of stencil printing is:
From the viewpoint of not allowing air bubbles to remain, any of low, medium, and high vacuum levels may be used. Since there is a possibility that the efficiency may be reduced, a low vacuum degree, for example, 0.013 to 1.33 k
It is sufficient to maintain a low vacuum degree of Pa , preferably about 0.013 to 0.667 kPa , more preferably about 0.013 to 0.267 kPa . By the way, the degree of vacuum is 1.33 kPa
If the pressure is too low and the pressure is too close to normal pressure, air bubbles may be generated in the resin-filled layer, which is not preferable.

Reduction of the degree of vacuum in a vacuum atmosphere after vacuum stencil printing is usually performed by releasing the vacuum atmosphere to the atmosphere and lowering the pressure to the atmospheric pressure. However, the reduction to the atmospheric pressure is not always necessary. , At least about 3.99 kPa , for example, between 3.99 and 8.
The degree of vacuum may be reduced so that a pressure difference of about 00 kPa is generated. If the differential pressure does not reach 3.99 kPa , the effect of injecting and filling the resin toward the bottom of the hole and the effect of erasing the unfilled portion become insufficient, which is not preferable.

The viscosity of the liquid resin to be applied to the filling to the substrate hole can be selected from a wide range, typically 20~200Pa
-It is appropriately selected and determined from the range of about s in consideration of the opening area and / or depth of the substrate hole. Generally speaking, relatively high-viscosity resin can be applied to filling holes having a relatively large opening area and low depth, for example, as applied to the production of a package, while a comparative example such as a through hole is used. A resin having a relatively low viscosity is applied to a hole having a small target opening area and a high depth.

The thickness of a stencil applied to vacuum stencil printing is as follows:
Although not particularly limited, a hole having a diameter of about 0.01 to 3.0 mm is usually used, and the through-holes are formed in the stencil in the same pattern as the holes to be filled.

The size of the mesh of the net 16 provided at the lower end opening of the stencil through-hole may be appropriately selected and determined depending on the viscosity of the resin to be used. When the mold is released, a mesh material that allows the surplus resin to remain substantially as it is on the net 16 and can be carried out together with the net 16 may be used. For example, for resin of about 50 Pa · s, 1
A mesh having a mesh size of about 100 to 200 is appropriate, and the mesh of the net 16 may be determined based on the viscosity of the resin based on the mesh. The material of the net is not particularly limited, but stainless steel is suitable in consideration of strength and durability.

It is desirable that the squeegee has as large an indentation filling pressure as possible. For example, a squeegee having a contact angle θ smaller than 90 ° as shown in FIGS.

In the present invention, a printed wiring board is
Applied to the manufacture of printed wiring boards (including single-sided, double-sided and multi-layer), semiconductor devices, chip parts, IC cards and memory cards, coil substrates, etc. All printed wiring boards.

[0033]

According to the present invention, when the resin is filled into the holes of the printed wiring board by applying the stencil printing, not only the entrainment of air and the residual air, but also the unfilled portions of the resin are performed. It is possible to provide a resin filling method that does not cause generation.

[Brief description of the drawings]

FIG. 1 is a process diagram schematically showing an example in which the filling method of the present invention is applied to resin filling of a through hole.

FIG. 2 is a longitudinal sectional view schematically showing a state of filling a resin into a through-hole provided with conductive plating.

FIG. 3 is a longitudinal sectional view schematically showing a resin filling state in a through-hole on which conductive plating is not applied.

4 is a longitudinal sectional view schematically showing a multilayer printed wiring board including the substrate shown in FIG. 2 as an inner laminate.

FIG. 5 is a longitudinal sectional view schematically showing a multilayer printed wiring board including the substrate shown in FIG. 3 as an inner laminate.

FIG. 6 is an explanatory view showing an example of a bottomed hole.

FIG. 7 is an explanatory view showing an example of another bottomed hole.

FIG. 8 is an explanatory view of a hole of a package substrate.

FIG. 9 is a view, corresponding to FIG. 1B, showing a state of filling the resin into the substrate hole of the package.

FIG. 10 is an explanatory diagram showing a state where the mold is released from the state of FIG. 9;

FIG. 11 is an explanatory diagram showing a situation where a conductor circuit is formed on the substrate surface of the package.

FIG. 12 is a process diagram showing a situation in which a stencil with a net is applied to resin filling of a through hole.

FIG. 13 is an explanatory diagram showing a preferred example of a squeegee.

FIG. 14 is an explanatory view showing another preferred example of the squeegee.

[Description of Signs] 1 substrate 2 through hole 3 adhesive tape 4 squeegee 5 liquid resin 6 stencil 7 through hole 8 unfilled portion 9 conductive plating 10 insulating layer 11 outer laminated plate 12 bottomed hole 13 electronic component element 14 penetrating Hole 15 Closing member 16 Net 17 Conductor circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-204545 (JP, A) JP-A-5-218617 (JP, A) JP-A-6-13751 (JP, A) JP-A-10-108 313015 (JP, A) JP-A-54-80559 (JP, A) JP-A-11-298138 (JP, A) JP-A-11-40590 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 1/11 H05K 3/28 H05K 3/40-3/42 H01L 21/56 H01L 23/28

Claims (2)

(57) [Claims] 1. A liquid resin is filled into a hole of a printed wiring board by applying a stencil printing means in a vacuum atmosphere, and after filling the resin, at least 3. A resin filling method for lowering the stencil by 99 kPa, and thereafter releasing the stencil, wherein a net is stretched at the lower end opening of the through hole of the stencil, and the resin on the net is removed as excess resin together with the stencil at the time of release. Filling a hole in a printed wiring board with a resin. 2. The degree of vacuum in a vacuum atmosphere during stencil printing is:
The filling method according to claim 1, wherein the pressure is 0.013 to 1.33 kPa.