JP2004095675A - Method for printing thick film through hole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a through hole printing method capable of applying conductive paste of suitable thickness to all the inner wall surface of a through hole. <P>SOLUTION: In a printing process, paste 92 of a suitable quantity is applied to the inner wall surface 30 of the through hole and the peripheral edge of an aperture by sucking the paste 92 by relatively small suction Va capable of applying the paste 92 up to the intermediate position of the inwall surface 30. In a suction process, the paste 92 is spread to all the inner wall surface 30 by sucking the paste 92 with relatively large suction force Vb. Since a screen is separated from a substrate 12 in the suction process, excess inflow caused by the inflow of the paste 92 applied to a position separated from the through hole 28 can be suppressed, and the paste 92 of a suitable quantity applied to the peripheral edge of the aperture is spread to the inner wall surface 30. Consequently, the paste 92 of a suitable thickness can be applied to all the inner wall surface 30 of the through hole 28. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for printing a thick film conductive paste on a through hole of a circuit board.
[0002]
[Prior art]
For example, alumina (Al ₂ O ₃ ) Is applied to one surface of a ceramic substrate made of a thick film screen printing method or the like, and various thick film printing pastes such as conductors, resistors, and insulators are applied and fired to form a thick film. Known thick film circuit boards are known. In order to increase the mounting density in such a thick film circuit board, for example, a circuit pattern is provided on both sides of one side and the back side thereof, and a through conductor provided in a through hole penetrating the board in the thickness direction. Thus, the circuit patterns on both sides are connected at a plurality of locations.
[0003]
[Problems to be solved by the invention]
By the way, in forming the conductor pattern on one surface of the substrate, the above-mentioned through conductor is coated with the thick film conductor paste by applying the thick film conductor paste to the one surface while sucking from the other surface through the through hole. It is formed at the same time as the conductor pattern by flowing into the hole and then performing a baking treatment. The thick-film conductor paste having high fluidity immediately after application is caused to flow from the periphery of the opening toward the inside of the through hole by being sucked, and to flow down the inner wall surface while leaving a part. Therefore, the thick film conductor paste is applied to the inner wall surface so as to be continuous from one surface of the substrate, and the circuit patterns on both surfaces are connected by the through conductor generated from the thick film conductor paste.
[0004]
However, in the method of forming the through conductor as described above, if the suction force at the time of applying the thick film conductor paste is excessive, the amount of the paste flowing into the through hole becomes excessive, and the applied thickness on the inner wall surface is extended. Is excessive, so that the through conductor is easily peeled off from the inner wall surface after firing due to a difference in thermal expansion coefficient between the substrate and the thick film conductor. Conversely, if the suction force is too small, the amount of paste flowing in becomes too small and the coating thickness becomes too small, so the wire is broken at the ridge on the inner wall surface of the through hole or between the inner wall surface and the other surface of the substrate. Continuity failure easily occurs. Therefore, it is desired that the suction force is set to a size that can provide an appropriate inflow amount that is unlikely to cause these inconveniences and that a coating thickness is obtained. On the other hand, the thick film conductor paste is spread over the entire inner wall surface of the through hole. For this purpose, a relatively large suction force is required, which makes it difficult to set the suction force and control the coating thickness. In addition, as the suction force is increased, the thick-film printing screen is more strongly attracted to the substrate, and the separation of the printing plate becomes worse.
[0005]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a through-hole printing method capable of applying a conductive paste with an appropriate thickness to the entire inner wall surface of the through-hole.
[0006]
[Means for Solving the Problems]
In order to achieve such an object, the gist of the present invention is to provide a thick-film printing screen having a predetermined opening pattern using a thick-film printing screen. A method of printing a film through hole, comprising: (a) suctioning from the back surface of the substrate through the through hole with a predetermined first suction force into which the thick film conductor paste is drawn to an intermediate position on the inner wall surface of the through hole; A printing step of printing the thick-film conductor paste from the front side, and (b) after the printing step, the substrate is separated from the thick-film printing screen through the through-holes from the back surface of the substrate. By suctioning with a predetermined second suction force that is greater than the first suction force, the suction agent spreads the applied thick-film conductor paste over the entire inner wall surface of the through hole. And a step is to include.
[0007]
【The invention's effect】
In this manner, in the printing step, the thick film conductor paste is applied to the middle position of the inner wall surface of the through-hole by the relatively small first suction force, so that the inner wall surface and the periphery of the opening have an appropriate thickness. The film conductor paste is applied, and in the suction step, the thick film conductor paste is spread over the entire inner wall surface of the through hole by suction with a relatively large second suction force. At this time, in the suction step, since the thick film printing screen is separated from the substrate, the flow of air in the direction along the surface of the substrate is significantly reduced as compared with during printing, so that the paste in that direction is used. Difficult to flow. Therefore, the thick film conductor paste applied to a position distant from the through-hole is suppressed from flowing in and an excessive amount of flow is suppressed, and an appropriate amount of the thick film conductor paste applied to the opening periphery and the inner wall surface in the printing process is reduced. It will be spread on the inner wall. Therefore, the thick film conductor paste can be applied to the entire inner wall surface of the through hole with an appropriate thickness.
[0008]
In other words, during printing, if the suction force is increased so that the thick film conductor paste can be spread over the entire inner wall surface of the through hole, the amount of paste flowing in becomes excessive, but the subsequent thick film printing screen and the substrate are separated. In this case, since there is little possibility that the amount of paste flowing in becomes excessive due to the magnitude of the suction force, it is possible to set a large suction force necessary to spread the entire inner wall surface. Therefore, by separating the printing process of applying an appropriate amount of the thick film conductor paste into the through hole and at a position where it can flow into the through hole, and the suction process of spreading this over the entire inner wall surface, the increase in the thickness of the through conductor is suppressed. While spreading over the entire inner wall surface, disconnection can be prevented. In addition, as a result, the setting of the first suction force and the second suction force, and hence the adjustment of the paste application amount, are facilitated, and the stability of the through-hole printing is enhanced, so that automation and continuity of printing can be easily performed. Become.
[0009]
Other aspects of the invention
Preferably, in the printing step, the first suction force is set to a size such that the thick film conductor paste does not remain in the opening pattern on the through hole. In this case, since the thick film conductor paste is prevented from remaining in the opening pattern of the thick film printing screen and clogging, the stability of through-hole printing is further enhanced.
[0010]
Preferably, in the suction step, the second suction force is set to a size that spreads the thick-film conductor paste up to an opening edge on the back surface side of the substrate. In this case, the thick-film conductor paste is applied beyond the ridge between the inner peripheral surface of the through hole and the back surface side opening edge, so that compared to the case where the thick film conductor paste remains on the inner peripheral surface, The reliability of conduction between the conductor patterns formed on both surfaces is improved. That is, in general, in forming a conductive pattern on both the front surface and the back surface of a substrate in through-hole printing, a thick-film conductive paste is simultaneously applied to the inside of the through-hole, so that the range expanded in the suction step is limited to the inner circumference. Even if it is fixed on the surface, conduction of the through conductor is ensured. However, as a result of suction from the opposite side of the coating surface, the coating thickness at the ridge between the coating surface and the inner peripheral edge of the through-hole is likely to be thin, so disconnection may occur unless the second suction force is adjusted with high precision. Can occur. According to the above, the application thickness at the ridge portion can be made sufficiently large, and the disconnection can be further suppressed.
[0011]
Preferably, the printing step is performed on a predetermined printing stage, and the moving step of moving the substrate on which the thick film conductor paste is applied to a suction stage provided separately from the printing stage. Wherein the suction step is performed in the suction stage. In this case, since the suction step is performed in the suction stage provided separately from the printing stage, there is a problem that the printing cycle is lengthened due to the time required for the suction and the processing efficiency is reduced. Be suppressed.
[0012]
Preferably, the printing step, the moving step, and the suction step are respectively performed on both surfaces of the substrate. In this way, the thick-film conductor paste flowing from both sides of the substrate is applied to the inner wall surface of the through-hole so as to overlap each other. Therefore, even if the paste thickness in the axial direction of the through hole becomes non-uniform due to the suction force, the suction time, the paste viscosity, etc., the non-uniformity is caused by the paste applied from both sides being overlapped with each other. Because of the relaxation or cancellation, the uniformity of the thickness is increased and the uniformity of the conductivity is enhanced. More preferably, the processing conditions for both sides of the substrate are substantially similar.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 is a perspective view showing an entire thick film circuit board 10 to which a through-hole printing method of the present invention is applied in a manufacturing process. The thick-film circuit board 10 includes, for example, a thick-film conductor, a thick-film resistor, a thick-film insulator, and the like on the front surface 14 and the rear surface 16 of a ceramic substrate 12 made of alumina or the like having a thickness of about 0.3 to 1 (mm). And electronic components such as semiconductors, resistors, capacitors, coils, and the like (not shown) are mounted on the front surface 14 and the rear surface 16 of the circuit pattern 18. The circuit pattern 18 is for connecting these mounted electronic components to each other to form an electronic circuit.
[0015]
In the circuit pattern 18 described above, for example, a width dimension formed by a thick film conductor having a thickness dimension of about 5 to several tens (μm), for example, about 20 (μm), is several tens (μm) to 1 (mm). And a plurality of wires 20 having a thickness of about several tens (μm) and a side of about 1 to 2 (mm). A plurality of thick film resistors 22 and the like are provided. The wiring 20 is formed by applying a thick-film copper paste by using a thick-film screen printing method or the like and baking it, as described later, and is a thick-film conductor containing copper as a conductor component. A terminal or the like of an electronic component is fixed to each end or intermediate part of the wiring 20, or a circular or rectangular land 24 for providing the thick film resistor 22, or provided on the front surface 14 and the rear surface 16. There are provided through-holes and lands 26 for connecting the interconnects 20 to each other. As shown in an enlarged view in FIG. 2, the through hole land 26 has a circular through hole 28 having an inner diameter of, for example, about 0.4 (mm) penetrating between the front surface 14 and the back surface 16. Are provided in an annular shape around the periphery of the lens.
[0016]
FIG. 3A is a diagram illustrating a cross-sectional structure near the through-hole land 26 in a cross-section taken along line III-III in FIG. On the inner wall surface 30 of the through hole 28, a through conductor 32 made of, for example, a thick film conductor similar to the wiring 20 is provided so as to penetrate from the front surface 14 to the back surface 16. As will be described later, the through conductor 32 is formed by applying a thick-film copper paste on the through-hole 28 using, for example, a thick-film screen printing method and firing the paste. The thickness dimension of the through conductor 32 on the inner wall surface 30 is, for example, about 20 to 40 (μm), and overlaps the through hole land 26 at both ends in the axial direction, that is, at each of the front surface 14 and the rear surface 16. As a result, the wirings 20 provided on both sides 14 and 16 of the substrate are connected to each other via the through conductor 32.
[0017]
Further, as shown in an enlarged manner in FIG. 3B, the through conductor 32 is fixed to the inner wall surface 30 in a range from the upper surface of the wiring 20 on the surface 14 to the opening edge of the through hole 28 on the rear surface 16 side. The first layer 32a includes a first layer 32a and a second layer 32b that is fixed on the first layer 32a in a range from the wiring 20 on the rear surface 16 to the opening edge of the through hole 28 on the front surface 14 side. In the axial direction of the through hole 28 (the vertical direction in FIG. 3), for example, one of the first layer 32a and the second layer 32b becomes thicker from the front surface 14 to the back surface 16 and the other is thinner. However, the through conductor 32 formed by stacking them has a substantially uniform thickness. For this reason, despite the fact that it is composed of a thick film copper which is easily peeled off with only a slight variation in the thickness dimension, disconnection between the front surface 14 and the back surface 16 is preferably suppressed.
[0018]
The thick film resistor 22 is made of, for example, RuO ₂ , SnO ₂ , LaB ₆ A thick film resistor paste mainly composed of, for example, is formed on a land 24 provided at an end portion of the wiring 20 by using a thick film screen printing method or the like in the same manner as the wiring 20 and is baked. However, since the details are not necessary for understanding the present embodiment, description thereof will be omitted.
[0019]
Meanwhile, the thick film circuit board 10 configured as described above is one in which the circuit pattern 18 is formed using, for example, a printing device 34 shown in FIG. In FIG. 4, the printing device 34 includes three stages: a supply stage 36, a printing stage 38, and a suction stage 40. The printing stage 38 is for applying a thick-film conductor paste or a thick-film insulator paste to the substrate 12. The supply stage 36 is configured to sequentially supply the substrates 12 arranged at predetermined printing positions on the printing stage 38. The suction stage 40 is for applying the conductive paste into the through holes 28 of the substrate 12 to which the thick-film conductive paste has been applied. The substrate 12 is moved between these three stages 36, 38, 40 by a transfer device 41 such as a conveyor.
[0020]
The printing stage 38 includes a printing mechanism 46 in which a squeegee 42 and a scoop 44 are supported so as to be able to move up and down, and a screw shaft 48 and a motor 50 for moving the printing mechanism 46 in the left-right direction in the drawing. A moving device 52 and a screen plate 54 are provided. The printing device 34 is provided with, for example, two mounting tables 56 and 57 that are configured to be movable in the left-right direction in the figure and that have suction jigs 58 (see FIG. 5 described later) on the upper surface, respectively. When the sheet is sent to the printing stage 38 by the transfer device 41, it is placed on the mounting table 56, is positioned at a predetermined position, and is sucked on the suction surface 60 of the suction jig 58. Further, when sent from the printing stage 38 to the suction stage 40, it is sucked by the suction jig 58 provided on the mounting table 57.
[0021]
The suction jigs 58 provided on the mounting tables 56 and 57 are configured in the same manner as each other, for example, and FIG. 5 is a perspective view showing the whole thereof. The suction jig 58 includes an upper suction plate 62 having the suction surface 60 and a lower support plate 64 fixed on a mounting table 56 of the printing press. The suction plate 62 has a side of, for example, several tens (mm) to one hundred and several tens (mm), for example, about 160 (mm), and a thickness of about several (mm) to several tens (mm), for example, about 10 (mm). The inner peripheral side part except the outer peripheral part of about ten and several (mm) from the outer peripheral edge is formed in the shape of a rectangular plate of the same size as the thickness of the substrate 12 as compared with the outer peripheral part. It is concave. The suction surface 60 is provided on the inner peripheral portion, and the substrate 12 is placed on the concave portion.
[0022]
Further, of the inner circumferential side portion, a range on the inner circumferential side further about 10 (mm) than the inner circumferential edge 66 of the outer circumferential side portion is a rectangular shape of about several tens (mm) per side penetrating the suction plate 62 in the thickness direction. Six openings 68 are provided in a grid pattern. The support plate 64 is provided with a common exhaust passage 70 that is open at the end face thereof, and the six openings 68 communicate with the exhaust passage 70. The hole 72 opened in the suction surface 60 between the opening 68 and the inner peripheral edge 66 of the outer peripheral portion is a suction hole for adsorbing the substrate 12 on the outer peripheral side of the area where the through hole 28 is provided. There is, for example, formed in a size of about 5 (mm) in diameter.
[0023]
Further, the opening 68 is connected to an exhaust pump 76 via the exhaust passage 70 and the switching valve 74, and the suction hole 72 is connected to another exhaust pump 78. The switching valve 74 has a suction position shown in the drawing for connecting the exhaust passage 70 to the exhaust pump 76 and sucking it from the opening 68, and a release position for disconnecting those connections and releasing the opening 68 to atmospheric pressure. It is electrically switched between the two positions, for example, in accordance with a command from the control device 80. The control device 80 is provided commonly to the suction jigs 58 provided on the mounting tables 56 and 57 or individually provided for each, and includes an input / output circuit and a central processing unit (CPU). ), A storage device (RAM, ROM), etc., and also controls the operation of the exhaust pumps 76, 78 while utilizing the temporary storage function of the RAM in accordance with a program stored in the ROM in advance. For example, when the exhaust pump 76 is operated and the switching valve 74 is located at the suction position, the suction is controlled through the opening 68 by the suction force controlled by the control device 80, and the suction hole 72 is operated when the exhaust pump 78 is operated. It is designed to be sucked.
[0024]
In FIG. 5, reference numeral 82 denotes a fixed or movable positioning pin for positioning the substrate 12 at a predetermined position, and reference numeral 84 denotes a position when the substrate 12 coated with the thick film printing paste is replaced with another substrate. A push-up pin for pushing up the printed substrate 12 from the suction surface 60. Further, in FIG. 5, the support plate 64 is drawn in the same size as the suction plate 62. However, the size of the support plate 64 is arbitrary within a range sufficiently larger than the substrate area. The support plate may also serve as 56 or the like.
[0025]
7 (a) to 7 (a) to 7 (d) showing the state of the pattern forming method on the thick film circuit board 10 using the above-described printing apparatus 34 in the main steps of the process according to the process chart shown in FIG. This will be described with reference to c). In the conductor forming step performed after manufacturing the substrate 12 provided with the through holes 28, first, in the mounting step 86, the substrate 12 is placed on the transfer device 41 of the supply stage 36, for example, with the front surface 14 positioned above. It is placed in the direction. Next, in a printing step 88, after the substrate 12 is sent to the printing stage 38, is positioned on the mounting table 56, and is sucked by the suction jig 58, the thick film conductor paste (thick film screen printing method) is applied to the surface 14 thereof. For example, a thick film copper paste) is printed.
[0026]
FIG. 7A is a diagram for explaining an implementation state of the printing process 88 described above. The substrate 12 is placed on the suction surface (upper surface) 60 of the suction jig 58, and is fixed to the suction surface 60 by operating the exhaust pump 78, and the switching valve 74 is moved to the position shown in FIG. And the exhaust pump 76 is operated to exhaust air from the exhaust passage 70. Since the suction jig 58 closes the opening 68 and the suction hole 72 of the substrate 12, the substrate 12 is in a state of sucking from the back surface 16 side through the through hole 28 positioned on the opening 68. . In this state, the thick-film copper paste 92 is supplied onto the screen 90 of the screen plate 54, and the squeegee 42 is slid in one direction, for example, in the direction of arrow S in FIG. The film copper paste 92 is extruded from the opening 94 of the screen 90 and is applied to the substrate surface 14. The application position is set at the position where the wiring 20 is formed and on the through hole 28, etc., but as shown in the figure, the thick copper paste 92 applied on the through hole 28 stays near the opening edge thereof. I have. As described above, in the present embodiment, the thick-film copper paste 92 is applied to the substrate surface 14 while being sucked from the back surface 16 side of the substrate 12 through the through holes 28.
[0027]
The suction force Vc from the suction hole 72 is a relatively large value that is sufficient for fixing the substrate 12 and that there is almost no air flow through the gap between the substrate 12 and the suction surface 60. On the other hand, the suction force Va from the opening 68 via the exhaust passage 70 is caused, for example, by the thick-film copper paste 92 applied to the peripheral portion of the through hole 28 slightly flowing toward the through hole 28 and the through-hole A relatively small value such that the thick copper paste 92 pressed into the opening 94 located on the hole 28 does not remain in the opening 94, for example, about 35 (Hz) when sucked by a blower with an inverter. Is set to a value. Since the suction force is set to a relatively small value during printing as described above, the thick-film copper paste 92 applied on and in the vicinity of the through hole 28 is caused to flow toward the inside of the through hole 28. However, the expanding range is limited to a position on the peripheral edge and an intermediate position of the inner wall surface 30. Further, when the squeegee 92 passes, the screen 90 is quickly separated from the substrate 12 according to its own restoring force. As shown in the timing chart of FIG. 8, the suction force (negative pressure) in the opening 68 is maintained at Va from before the squeegee 92 is lowered until the squeegee 92 is completely raised. FIG. 7 schematically shows a cross-sectional structure of the suction jig 58, and does not exactly match FIG. In the present embodiment, the above-mentioned suction force Va corresponds to the first suction force.
[0028]
After the paste 92 is applied to the front surface 14 as described above, in the moving step 96, the suction state on the printing stage 38 is released, and the transport device 41 sends the substrate 12 to the suction stage 40.
[0029]
In the suction step 98, while the fluidity of the applied paste 92 is kept sufficiently high, the substrate 12 is sucked by the suction jig 58 of the mounting table 57 by sucking the suction paste 72 with the suction force Vc. After that, by operating the exhaust pump 76, suction is performed from the exhaust passage 70 by the suction force Vb for a predetermined time, for example, about 3 to 7 seconds, for example, 5 seconds. That is, as shown in FIG. 8, the suction force is increased from Va to Vb. The suction force Vb is a value sufficiently larger than the suction force Va, and is set to a value of about 50 (Hz) (ie, about 1.5 times) when suction is performed by a blower with an inverter, for example. . The predetermined time is determined such that the paste 92 is sufficiently spread according to the size of the substrate 12, the number of through holes 28, the viscosity of the paste, and the like. Therefore, the paste 92 remaining in the range from the peripheral portion of the through hole 28 to the upper portion (middle position) of the inner wall surface 30 is drawn into the through hole 28 while the portion remaining on the peripheral portion is drawn into the through hole 28 and the inner wall surface thereof. Spread over the entire 30. That is, the paste 92 is applied to a range from the upper surface 14 to the upper edge of the through hole 28 on the rear surface 16 side.
[0030]
FIGS. 9A to 9C are diagrams illustrating changes in the application state of the paste 92 in the printing step 88 and the suction step 98. At the stage immediately after printing shown in FIG. 9A, since the suction force Va during printing is relatively small, the paste 92 applied on the through-holes 28 is the upper portion of the surface 14 and the inner wall surface 30 on the surface 14 side. Is applied relatively thickly only in the range. On the other hand, in the stage during suction shown in FIG. 9B, the paste 92 continuously applied from the surface 14 to the inner wall surface 30 is sucked through the through hole 28 with a relatively large suction force Vb. Therefore, it flows (flows down) on the inner wall surface 30 toward the back surface 16 side. FIGS. 9C and 7B show the application state after the end of the suction. Only the paste 92 applied on the peripheral portion of the through hole 28 and the inner wall surface 30 is spread, so that the inner wall surface 30 has a thin and uniform thickness. The film thickness after completion of the suction is, for example, about 30 (μm). Note that, in (b), an alternate long and short dash line indicates a coating state before the start of flow.
[0031]
Further, as shown in FIG. 9C, after the suction is completed, the paste 92 is spread to the peripheral portion of the through hole 28 on the back surface 16. That is, the suction force Vb, the suction time, and the like are such that the paste thickness on the inner wall surface 30 is substantially uniform, and the through hole 28 is formed as in the first layer 32a of the through conductor 32 shown in FIG. The paste 92 is set so as to flow until it spreads over the opening edge on the back surface 16 side. In the present embodiment, the above-mentioned suction force Vb corresponds to the second suction force. The suction forces Va and Vb are appropriately determined according to the paste viscosity, room temperature, pressure loss in the exhaust passage 70 and the like.
[0032]
In the drying step 100 and the baking step 102, the substrate 12 on which the thick-film copper paste 92 has been applied as described above is sequentially subjected to drying and baking processing at a predetermined temperature according to the type of the paste 92. As a result, the thick film wiring 20 is generated from the paste 92 applied to the substrate surface 14, and at the same time, the first layer 32 a of the through conductor 32 is generated from the paste 92 applied to the through hole 28.
[0033]
The mounting step 86 to the baking step 102 are performed on the substrate back surface 16 side under substantially the same conditions as the front surface 14 side. That is, also on the back surface 16 side, in the printing step 88, the paste 92 is applied while being suctioned by the weak suction force Va, and is strong in the suction step 98 after being moved to the suction stage 40 provided separately from the printing stage 38. By performing suction for a predetermined time with the suction force Vb, and further performing drying and baking treatment, a conductor film such as the wiring 20 is formed on the back surface 16, and the second layer 32 b of the through conductor 32 is formed in the through hole 28 by the first layer 32 b. It is formed over the layer 32a. Each of the suction forces Va and Vb is a value slightly smaller than that at the time of printing on the front surface side, and is a value of about 30 (Hz) and 45 (Hz) when suction is performed by a blower with an inverter, respectively. That is, for example, the suction force in the suction step 98 is set to about 1.5 times that in the printing step 88. Further, the suction time in the suction step is set to, for example, the same time as that on the front side. FIG. 7C shows a state after the application and suction from both sides are completed in this way. Also at this time, the above-mentioned suction force Vb, suction time, and the like are set so that the paste 92 flows until it spreads to the opening edge of the through hole 28 on the surface 14 side, so that as shown in FIG. The second layer 32b of the through conductor 32 is formed in a range extending between both surfaces of the substrate 12. As a result, a conductor pattern such as the wiring 20 is formed on both surfaces of the substrate 12 and the through conductor 32 is formed in the through hole 28 with an appropriate thickness, and thereafter, a conductor, a resistor, an insulator, and the like are laminated. By doing so, the above-described thick film circuit board 10 is obtained.
[0034]
As described above, in the present embodiment, in the printing step 88, the inner wall surface 30 and the inner wall surface 30 of the through hole are sucked by the relatively small suction force Va to which the paste 92 is applied up to the intermediate position of the inner wall surface 30 of the through hole. An appropriate amount of paste 92 is applied to the periphery of the opening, and in the suction step 98, the paste 92 is spread over the entire inner wall surface 30 by suction with a relatively large suction force Vb. At this time, since the screen 90 is separated from the substrate 12 in the suction step 98 performed in a stage different from printing, the paste 92 applied to a position distant from the through hole 28 flows in, and the amount of inflow is reduced. Since the excess is suppressed, an appropriate amount of paste 92 applied to the periphery of the opening and the inner wall surface 30 in the printing step 88 is spread on the inner wall surface 30. Therefore, the paste 92 can be applied to the entire inner wall surface 30 of the through hole 28 with an appropriate thickness.
[0035]
Moreover, in the present embodiment, the suction force Va in the printing step 88 is set to a size that does not leave the paste 92 in the opening 94 on the through-hole 28, so that the clogging of the screen 90 is suitably suppressed. There are advantages.
[0036]
Further, in the present embodiment, the suction force Vb in the suction step 98 is set to a size that spreads the paste 92 up to the opening edge on the back surface 16 side, so that the interconnections 20 formed on both surfaces 14 and 16 of the substrate 12 There is also an advantage that the reliability of conduction between them is improved.
[0037]
Further, in the present embodiment, the suction step 98 is performed by the suction stage 40 prepared separately from the printing stage 38 in which the printing step 88 is performed. In comparison, there is an advantage that the processing efficiency is enhanced. That is, the next printing can be started earlier for each sheet of the substrate 12 for about 7 seconds required for the suction step 98, so that, for example, the machine cycle and the processing capacity are improved to about 1.4 times.
[0038]
As mentioned above, although one Example of this invention was described in detail, this invention can be implemented also in another aspect.
[0039]
For example, in the embodiment, the case where the present invention is applied to the thick film printing method for manufacturing the thick film circuit board 10 having the circuit patterns 18 on both surfaces 12 and 14 has been described. Even if the substrate is provided with the circuit pattern 18 only on the substrate 14, as long as the substrate is provided with a plurality of through holes 28 and through conductors 32 for the purpose of drawing out the terminal from the circuit pattern 18 to the back surface 16 side and providing the terminal. And can be similarly applied.
[0040]
In the embodiment, the case where the thick film conductor paste is the copper paste 92 has been described. However, the present invention is also applicable to a case where various conductor pastes such as a silver paste selected according to the use of the circuit board 10 are used. Is applied.
[0041]
Further, the suction force Va in the printing step 88 and the suction force Vb in the suction step 98 are not limited to the values shown in the embodiment. The latter is appropriately determined according to the opening diameter of the through hole 28, the thickness dimension of the substrate 12, the fluidity and viscosity of the paste 92, so that the paste 92 spreads over the entire surface of the through hole 28.
[0042]
In the embodiment, the suction step 98 is performed by the suction stage 40 provided separately from the printing stage 38. However, when there is no particular problem in terms of processing efficiency, the suction stage 40 is not provided. After the printing step 88, the suction step 98 may be performed on the printing stage 38 as it is. That is, after the lifting of the squeegee 92 is completed, the suction force from the opening 68 may be increased from Va to Vb.
[0043]
Although not specifically exemplified, the present invention can be variously modified without departing from the gist thereof.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a circuit board manufactured by applying a through-hole printing method of the present invention.
FIG. 2 is an enlarged plan view showing a through hole provided in the circuit board of FIG. 1;
3A is a diagram showing a cross section taken along line III-III in FIG. 2, and FIG. 3B is a diagram showing a right half thereof in an enlarged manner.
FIG. 4 is a diagram illustrating a configuration of a printing apparatus for manufacturing the circuit board of FIG.
FIG. 5 is a perspective view illustrating a configuration of a suction jig provided in the printing apparatus of FIG. 4;
FIG. 6 is a process diagram illustrating a process of performing conductor printing on a circuit board using the printing apparatus of FIG. 4;
FIGS. 7A to 7C are views for explaining an implementation state at a main part stage of the process of FIG. 6;
FIG. 8 is an example of a timing chart showing the operation of a squeegee and a change in suction force in the manufacturing process shown in FIG. 6;
FIGS. 9 (a) to 9 (c) are views for explaining paste application states in a printing step and a suction step.
[Explanation of symbols]
28: Through hole
30: Inner wall
38: Printing stage
40: Suction stage
92: Thick copper paste
98: suction step

Claims (3)

A method of printing a thick-film through-hole by printing a thick-film conductor in the through-hole of a substrate having a through-hole using a thick-film printing screen having a predetermined opening pattern,
A printing step of printing the thick-film conductor paste from the front side while suctioning from the back surface of the substrate through the through-hole with a predetermined first suction force in which the thick-film conductor paste is drawn to an intermediate position on the inner wall surface of the through-hole; When,
After the printing step, the substrate is suctioned from the back surface of the substrate through the through hole with a predetermined second suction force larger than the first suction force while being separated from the thick film printing screen. And a suction step of spreading the applied thick-film conductor paste over the entire inner wall surface of the through-hole. 2. The method of printing a thick film through hole according to claim 1, wherein in the printing step, the first suction force is set to such a size that the thick film conductor paste does not remain in the opening pattern on the through hole. 3. The printing of the thick film through hole according to claim 1 or 2, wherein in the suction step, the second suction force is set to a size that spreads the thick film conductor paste up to an opening edge on the back surface side of the substrate. Method.

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