Printed circuit board manufacturing method

Abstract

The present invention provides a method for manufacturing printed circuit boards that allows for the even and nearly uniform application of a coating material to the entire surface of the printed circuit board. [Solution] A method for manufacturing a printed circuit board having a first surface having holes for inserting electronic components and for mounting electronic components, and a second surface which is the back side of the first surface and for soldering, comprising: a first step (step S01) of applying a coating material to the first surface; a second step (step S02) of mounting electronic components in the insertion holes; a third step (step S03) of soldering to the second surface; and a fourth step (step S04) of applying a coating material to the second surface.

Description

Technical Field

[0004] ,

[0006]

[0001] This disclosure relates to a method for manufacturing a printed circuit board.

Background Art

[0002] Conventionally, for printed circuit boards with electronic components mounted in a high-temperature and high-humidity environment, to prevent humidity, dew condensation, and insect intrusion, the printed circuit board is covered with an insulating resin to prevent malfunction and ignition of the electronic circuit.

[0003] In the technology described in Patent Document 1, a resin-coated mounting substrate having a protective structure is such that at least the printed circuit conductors and terminals of the printed circuit board and the relay block of the substrate unit formed by mounting a relay block as an electronic component on the printed circuit board are embedded in a sealing resin material cured within a bag-shaped body made of a thin-film resin film set within an injection mold, and the cured sealing resin material is formed by being demolded from the injection mold together with the bag-shaped body.

Prior Art Documents

Patent Documents

[0007] This allows for the protection of printed circuit boards without using large quantities of coating material, which is a sealing resin. [Brief explanation of the drawing]

[0008] [Figure 1] Flowchart illustrating the manufacturing method in this embodiment [Figure 2] Plan view of the circuit board in this embodiment [Figure 3] Diagram showing the component mounting structure in this embodiment [Figure 4] A diagram showing the component mounting structure in this embodiment. [Modes for carrying out the invention]

[0009] (Knowledge and other information that formed the basis of this disclosure) At the time the inventors conceived of this disclosure, applying a thin film of liquid to the entire component insertion surface of a printed circuit board on which electronic components are mounted was extremely unproductive.

[0010] In recent years, coatings have needed to be made as thin as possible to reduce costs and to minimize the amount of coating material used, thus demonstrating a growing need for recycling methods for printed circuit boards, which previously contained electronic components mounted on them and were coated with thick films, thus becoming industrial waste.

[0011] In conventional coating methods, printed circuit boards with electronic components mounted were placed in a dedicated resin case, and then a coating liquid resin was poured into the case, filling it with a large amount of liquid until the printed circuit board was completely submerged.

[0012] The inventors discovered that the coating material, which is a sealing resin, required large quantities of material, and that when the product was disposed of, it was classified as industrial waste, requiring environmental measures. To solve these problems, they arrived at the subject matter of this disclosure. This disclosure relates to a method for manufacturing a printed circuit board for which a coating material is applied to a printed circuit board on which large electronic components are mounted.

[0013] The embodiments will be described in detail below with reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art.

[0014] The attached drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0015] (Embodiment 1) Embodiment 1 will be described below. Figure 1 is a flowchart showing each step in the manufacturing method of the printed circuit board 1.

[0016] Figure 2 is a plan view showing an example of a printed circuit board 1. As shown in Figure 2, the printed circuit board 1 has holes 2 for inserting electronic components. For example, leads of electrolytic capacitors and resistors are inserted into these holes 2.

[0017] Embodiment 1 will be explained using the flowchart in Figure 1.

[0018] In step S01 of FIG. 1, first, mounting components such as chip resistors and chip capacitors are mounted on the component surface 3 (front side) of the printed circuit board 1 by reflow. More specifically, for example, cream solder is mounted on the printed circuit board 1, and the mounting components are mounted thereon, and then the cream solder is melted in a high-temperature furnace for soldering.

[0019] Subsequently, in step S02, only on the component surface (front side) 3 side of the printed circuit board 1, using the coating equipment 4, the thin film coating material 5 is spray-coated, for example, with a thickness of 30 micrometers to 200 micrometers. With this thin film coating material 5, the component surface 3 (front side) of the printed circuit board 1 and the electronic component 6 will be completely covered.

[0020] At this time, since the coating thickness of the thin film coating material 5 is thin, for the holes 2 for inserting electronic components for component insertion in the next process, it is necessary to confirm and select a material that will not be blocked by the thin film coating material 5 due to the surface tension of the thin film coating material 5. After the coating material application is completed, the coating material is cured, and the overall coating on the printed circuit board on the component surface 3 (front side) is completed.

[0021] FIG. 3 shows a view when the thin film coating material 5 is applied only on the component surface (front side) 3 side of the printed circuit board 1 using the coating equipment 4. By moving the printed circuit board 1 while discharging the thin film coating material 5 from the coating equipment 4, the thin film coating material 5 can be applied to the entire component surface (front side) 3 side of the printed circuit board 1.

[0022] Incidentally, by fixing the printed circuit board 1 and moving the coating equipment 4, the thin film coating material 5 may also be applied to the entire component surface (front side) 3 side of the printed circuit board 1.

[0023] In FIG. 3, it seems that the thin film coating material 5 is not applied on the electronic component 6, but actually, the thin film coating material 5 is applied on the electronic component 6.

[0024] Next, in step S03, electronic components are mounted into the holes 2 for inserting electronic components on the component side 3 (surface) of the printed circuit board 1.

[0025] The components inserted in step S03 include, for example, components with leads such as electrolytic capacitors, transistors, and regulators. Subsequently, the electronic components are soldered from the solder side (back side) 7.

[0026] Next, in step S04, the thin film coating material 5 is spray-coated to a thickness of, for example, 30 to 200 micrometers using the coating equipment 4, only on the solder side (back side) 7 of the printed circuit board 1. This thin film coating material 5 completely covers the solder side (back side) 7 of the printed circuit board 1.

[0027] By moving the printed circuit board 1 while releasing the thin film coating material 5 from the coating equipment 4, the thin film coating material 5 can be applied to the entire solder side (back side) 7 of the printed circuit board 1.

[0028] Alternatively, the printed circuit board 1 may be fixed in place, and the coating equipment 4 may be moved to apply the thin film coating material 5 to the entire solder side (back side) 7 of the printed circuit board 1.

[0029] Figure 4 shows the process of applying the thin film coating material 5 to the solder side (back side) 7 of the printed circuit board 1 using the coating equipment 4. As shown in Figure 4, the thin film coating material 5 completely covers the solder side (back side) 7 of the printed circuit board 1.

[0030] Step 04 is a process in which the soldering lead portion and the soldering surface (back side) 7 side of the SMT (Surface Mount Technology) component, which is almost flat despite having some irregularities, are coated with a coating material to a thickness of 30 to 200 micrometers using a coating equipment, and the coating material is allowed to cure to complete the process.

[0031] In this disclosure, after mounting electronic components to be placed on the component side 3 (front side) of the printed circuit board 1, a thin film coating material is spray-coated to a thickness of 30 to 200 micrometers using a coating equipment 4 to completely cover the printed circuit board and the electronic components. Furthermore, after inserting and soldering the electronic components, the solder side (back side) 7 is similarly spray-coated to completely cover the printed circuit board and the electronic components.

[0032] Alternatively, the electronic components to be placed on the component side 3 (front surface) of the printed circuit board 1 may be mounted, the electronic components inserted and soldered, and then a thin film coating material to a thickness of 30 to 200 micrometers may be spray-coated onto the component side 3 (front surface) using a coating device 4. Subsequently, the solder side (back surface) 7 may also be spray-coated in the same manner to completely cover the printed circuit board and the electronic components.

[0033] Figure 2 also shows a plan view of the component surface 3 (surface) of the printed circuit board 1 as seen from above after the application of the thin film coating material 5 in this embodiment. Although a portion of the thin film coating material 5 is spray-coated over the entire printed circuit board 1, the holes 2 for inserting components such as electronic components into the printed circuit board 1 in the next process are not filled due to the surface tension of the material. The size of the holes 2 in this case is defined as φ0.7 or larger. Similarly, the large holes 8 on the printed circuit board 1 are not filled with the thin film coating material 5.

[0034] On the solder side 6 (back side), after the coating of the component side 3 (front side) is completed, surface-mount electronic components and leaded electronic components on the solder side 6 (back side) are inserted into the component holes and soldered. Then, using the coating equipment 4, a thin film coating material 5 is spray-coated to a thickness of 30 to 200 micrometers, completely covering the printed circuit board and electronic components.

[0035] In this embodiment, the distance (t1) between the inner sides of the two lands is set to 0.23 mm to 0.25 mm. However, if t1 is smaller than 0.23 mm, problems may arise such as printing errors due to misalignment during bond printing or bridging during soldering.

[0036] Furthermore, if t1 is greater than 0.25mm, there is a higher possibility of soldering errors due to misalignment during component mounting. By setting the distance t1 to 0.23mm to 0.25mm, the above problems can be resolved.

[0037] Furthermore, while the longitudinal dimension (t4) of each of the two pads is set to 0.65 mm or more, in the case of small SMD (Surface Mount Device) components with a size of 0.6 mm x 0.3 mm, the pads to be soldered are very small. If t4 is smaller than 0.65 mm, there is a risk that moisture gas may be generated between the board and the solder during flow soldering, hindering the soldering process. By setting the longitudinal dimension t4 to 0.65 mm or more, the above problem can be resolved.

[0038] Additionally, copper foil is connected to each of the other three directions of each pad to allow circuit patterns, such as the GND pattern and power supply pattern circuits, to be drawn in.

[0039] A solder resist is formed around the lands and circuit patterns. This solder resist prevents the soldering area of ​​the land from becoming abnormally large when the pattern is drawn in by the insulating print (resist ink).

[0040] By performing bond printing between the inner surfaces of two pads and then placing the small SMD component on top of it, the small SMD component is temporarily fixed in place.

[0041] Afterward, the printed circuit board is flipped over again, and if there are any irregularly shaped electronic components, they are mounted by hand or using a robotic mounting machine. Flow soldering is then performed to solder the printed circuit board and the mounted small SMD components, enabling electrical conductivity.

[0042] In mounting structures for small SMD components with a size of 0.6mm x 0.3mm, patterns drawn into each of the two lands, or in the case of ground plane routing, the ground plane can be connected to the circuit pattern's entry pattern to form a thermal pattern (a cross-shaped pattern).

[0043] This configuration allows for a design where the land sizes of the two lands do not differ drastically, and also suppresses the amount of heat applied to the lands, meaning that the temperature of the two lands can be kept the same. This prevents component misalignment, component cracking, and other problems.

[0044] In this embodiment, the component side 3 is referred to as the front surface and the solder side 7 as the back surface; however, the component side 3 may be referred to as the first surface and the solder side 7 as the second surface.

[0045] Furthermore, in this embodiment, the term "printed circuit board" is used to refer to both a circuit board in which only conductive wiring is provided on or inside an insulating substrate and no electronic components are mounted, and a circuit board in which electronic components are soldered to it. Depending on the part of the description in this embodiment, the circuit board may be described as having electronic components mounted or not, but those skilled in the art will easily understand what state the printed circuit board is described in each part of this embodiment.

[0046] [1-2. Effects, etc.] According to the printed circuit board manufacturing method described in this disclosure, even in areas where the printed circuit board has tall, large electronic components and short, small electronic components, and where, when viewed from directly above the mounting surface of the large electronic components, the small electronic components may be hidden by the shadow of the large electronic components, or the underside of the electronic components or the leads of the electronic components to be coated may not be visible, the coating material can be applied uniformly and evenly to the entire surface of the printed circuit board.

[0047] This method eliminates the need for specialized jigs for coating printed circuit boards, and since it uses a spray coating method that does not require complex operations such as using equipment when applying the coating material, the coating cycle time can be shortened. Furthermore, although there are some irregularities, the coating material can be applied to the reflow soldering surface on the back side using the same method as the surface for mounting large electronic components.

[0048] In this embodiment, the mounting structure for chip components is a mounting structure for chip components in which both terminal electrodes of a small SMD component are soldered to two lands on a printed circuit board 1, and the shape is such that there is enough distance between the two lands formed on the printed circuit board 1 to facilitate bond printing.

[0049] This makes it possible to stably bond small SMD components, which are chip components, onto the printed circuit board 1, which was previously impossible, and enables the mounting and placement of components. Furthermore, by defining the dimensions between two lands, it is possible to eliminate bond printing defects and prevent small SMD components from falling off during flow soldering.

[0050] Furthermore, the chip components are small SMD components measuring 0.6mm x 0.3mm, with a shape where the distance between the two lands is 0.23mm to 0.25mm.

[0051] This allows for stable bond printing of small SMD components, which are 0603 size chip components, onto the printed circuit board 1, enabling component mounting and placement. Furthermore, by specifying the distance between two lands to 0.23mm to 0.25mm, bond printing defects and the detachment of small SMD components during flow soldering can be eliminated.

[0052] Furthermore, the mounting structure for chip components is a chip component mounting structure in which the terminal electrodes of both ends of a small SMD component are soldered to two lands on the printed circuit board 1, and the two lands are shaped so that each land is longer on the outside and the longitudinal dimension of one land is 0.65 mm or more.

[0053] This allows for improved solder contact and solder wettability during flow soldering by defining the outer dimensions of the two lands.

[0054] Furthermore, the mounting structure for the chip component is such that both ends of the chip component are placed on two lands on the printed circuit board 1. In the mounting structure of a chip component to which terminal electrodes are soldered, the shape is such that the pattern can be drawn into the land, or the shape becomes a thermal land when a solid pattern is applied.

[0055] This allows for pattern routing along the shape of the pattern pull-in to the protrusions on the two lands, thereby mitigating stress on the mounted small SMD components due to the expansion and contraction of the printed circuit board 1 and eliminating component failure. Furthermore, when performing solid pattern pull-in, routing the pattern along the shape of the protrusions creates a thermal land, which stabilizes the amount of solder during flow soldering, thus improving soldering quality.

[0056] (Other embodiments) As described above, Embodiment 1 has been explained as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this and can be applied to embodiments that have been modified, replaced, added, or omitted. Furthermore, it is possible to create new embodiments by combining the components described in the above embodiment.

[0057] Therefore, other embodiments are illustrated below.

[0058] The present invention is not limited to the examples described above, and the shape and size of the chip components may be any. Furthermore, the shape of the lands, patterns, and resists may also be, for example, a shape with a radius (R) or a pattern arrangement that is only present in the areas where the pattern is actually drawn. A key feature is that the same amount of solder can be applied to two lands during flow soldering, making it possible to equalize the stress on the terminals at both ends of the chip component due to the expansion and contraction of the printed circuit board.

[0059] Since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the claims or their equivalents. [Industrial applicability]

[0060] The printed circuit board manufacturing method disclosed herein can be widely applied to the manufacturing methods of printed circuit boards used in household electrical appliances, commercial electrical appliances, and the like. [Explanation of Symbols]

[0061] 1 Printed circuit board 2 holes 3. Component side 4. Coating equipment 5 Thin-film coating materials 6 Electronic Components 7 Solder side 8 holes

Claims

1. A method for manufacturing a printed circuit board having a first surface with holes for inserting electronic components and on which electronic components are mounted, and a second surface which is the back side of the first surface and on which soldering is performed, The first step is to apply a coating material to the first surface, A second step involves inserting the electronic component into the insertion hole, A third step involves soldering to the second surface, A method for manufacturing a printed circuit board, comprising a fourth step of applying the coating material to the second surface.

2. The method for manufacturing a printed circuit board according to claim 1, wherein the thickness of the applied coating material is 30 μm to 200 μm, and the diameter of the insertion hole is 0.7 mm or more.

3. A method for manufacturing a printed circuit board according to claim 1 or 2, wherein, before the first step, a low-profile small electronic component is mounted on the first surface and welded into place.

4. A method for manufacturing a printed circuit board according to claim 1 or 2, wherein a low-profile small electronic component can be mounted on the second surface.

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