JPH11154784A - Printing method of paste for thick film formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing deviation of the printing pattern and the target pattern and bridging between lands caused by paste seepage as well as reducing or preventing the occurrence of tomb stone phenomenon. SOLUTION: Immediately after printing given sides that constitute a target pattern, a paste for forming a thick film is printed in a given plane shape so that the paste is printed inside the desired region except at both ends of the sides. When the paste is printed on a square target pattern, the relationship between a pair of sides A with length AL and AG, the maximum distance between the side A and the furthest receded position (the maximum distance from the side A in almost perpendicular direction), (3/100)<(AG/AL)<(20/100). The relationship between a pair of sides B with length BL and BG, the maximum distance between the side B and the furthest receded position (the maximum distance from the side B in almost perpendicular direction), is (3/100)<(BG/BL)<(20/100).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing method for printing a paste for forming a thick film such as a cream solder or an electrode paste into a predetermined shape using a printing mask or screen.

[0002]

2. Description of the Related Art A thick film forming paste such as cream solder or electrode paste (hereinafter simply referred to as "paste") is printed in a predetermined pattern using a printing mask or screen. Conventionally, for example, a rectangular target pattern 5 as shown in FIG.
1, as shown in FIG.
In the case where the thick film forming paste 52 is printed so as to have the substantially same print pattern 54 as that of the thick film forming paste 54, as shown in FIG.
2 bleeds to form a print pattern 54a in which each side protrudes outwardly in a convex manner, and causes the following problem.

When forming lands for mounting small chip components on a circuit board wired at high density, it is necessary to print paste at a narrow pitch such that the pattern interval is 0.2 mm or less. In some cases, paste bleeding occurs after printing, (a) bridges occur between lands, (b) chip components rise, so-called tombstone phenomenon occurs, (c) solder balls frequently occur There is such a problem. Further, in order to make the paste less likely to bleed after printing, when the thickness of the mask or screen is reduced, (a) the amount of the paste is reduced, the fixing force is reduced, and (b) displacement occurs in the case of a large component. (c) At the time of mounting, there is a problem that reflow and heat treatment cannot be performed collectively with other components, which leads to a decrease in productivity and an increase in cost. Further, in order to prevent bleeding after printing, for example, it is necessary to increase the viscosity of the solder flux, or to increase the amount of solvent added, (a) the viscosity of the paste increases (B) the frequency of cleaning of the mask and screen increases,
(c) When performing squeegee printing, it is necessary to increase the squeegee pressure, which causes problems such as shortening of the life of the mask and the screen. There is a problem that it causes an increase. In addition, when printing conductor patterns for internal electrodes on ceramic green sheets, the bleeding of the paste causes variations in the electrode area, causing variations in capacitance and inductance, distortion in the electrodes, etc., and an increase in the rate of defective products. There is a problem of inviting.

The present invention solves the above-mentioned problems, and suppresses the occurrence of a difference in shape between a print pattern and a target pattern due to bleeding of a paste. It is an object of the present invention to provide a method for printing a thick film forming paste capable of reducing or preventing the occurrence of various problems such as the above.

[0005]

In order to achieve the above object, a method for printing a thick film forming paste according to claim 1 of the present application comprises:
In the case where the thick film forming paste is printed on a predetermined target pattern, for a predetermined side constituting the target pattern, immediately after printing, the thick film forming paste is applied to the side except for both ends of the side. It is characterized in that a thick film forming paste is printed in a predetermined planar shape so that printing is performed only up to a further retracted position.

According to a first aspect of the present invention, there is provided a method of printing a thick film forming paste on a predetermined side constituting a target pattern, immediately after printing, except for a portion excluding both ends of the side, up to a position retreated from the side. Since the forming paste is printed, even if the thick film forming paste bleeds after printing, the shape of the printed pattern does not significantly deviate from the target pattern. It is possible to efficiently reduce and prevent the above-mentioned various problems such as the bridge between lands and the tombstone phenomenon caused by the above.

According to a second aspect of the present invention, there is provided a method of printing a paste for forming a thick film, comprising the steps of:
In the case where a thick film forming paste is printed on a predetermined target pattern in the vicinity of the conductor so as not to be short-circuited with the conductor, of the sides constituting the target pattern, the side facing the conductor is printed. Immediately after that, the thick film forming paste is printed in a predetermined planar shape so that the thick film forming paste is printed only to a position recessed from the side in a portion excluding both ends of the side. Features.

In the method of printing a paste for forming a thick film according to a second aspect of the present invention, of the sides constituting the target pattern, the side opposite to the conductor is immediately after printing except for both ends of the side. Since the thick film forming paste is printed only to the position recessed from the side, even if the thick film forming paste bleeds after printing, the printed pattern becomes larger than the target pattern, And short-circuit with the conductor. Note that the conductors disposed at predetermined positions include a print pattern formed by printing a thick film forming paste by the method of the present invention (that is, a plurality of print patterns are formed at predetermined intervals). Also in the case of disposing, by applying the present invention, a short circuit between adjacent conductors can be surely avoided).

According to a third aspect of the present invention, in the method of printing a thick film forming paste, the predetermined pattern of the target pattern is a straight line, and the printing pattern immediately after printing the thick film forming paste is:
In a portion corresponding to the side (straight line), a thick film forming paste is printed inside the side (straight line) so as to have a concavely curved shape.

When a predetermined side of the sides constituting the target pattern is a straight line, the print pattern immediately after printing the thick film forming paste is a side (straight line) at a portion corresponding to the side (straight line). ) By printing the thick film forming paste into a concavely curved shape inside, even if the thick film forming paste bleeds after printing, the shape of the print pattern will be different from the shape of the target pattern. It is possible to efficiently reduce and prevent the above-mentioned various problems such as bridges between lands and tombstone phenomenon, which have conventionally occurred due to the bleeding of the paste, without significant deviation.

According to a fourth aspect of the present invention, there is provided a printing method of a thick film forming paste, wherein when printing a thick film forming paste on a predetermined target pattern, a predetermined side of the target pattern and a printing pattern immediately after printing are printed. When the distance AG (the maximum distance from the side in the substantially vertical direction) between the side and the position most receded from the side is defined as AL, the length of the side is AL, (3/100) <(AG / AL) <(20/100).

The distance AG between the length AL of the side and the position most receded from the side is defined as (3/100) <(AG / AL) <
By setting it within the range of (20/100), it is possible to reliably prevent a predetermined side of the print pattern from greatly protruding from a predetermined side of the target pattern,
The present invention can be made more effective. In addition,
(3/100) <(AG / AL) <(20/100) The reason for setting the ratio AG / AL to 3/100 or less is to aim at a print pattern after the thick film forming paste oozes out. If it cannot be held inside the pattern, and if AG / AL is 20/100 or more, the area of the printed pattern becomes too small with respect to the target pattern, and the bonding strength of chip components to be mounted becomes insufficient, This is because desired electrical characteristics cannot be obtained during conduction.

According to a fifth aspect of the present invention, there is provided a method of printing a thick film forming paste, wherein when the thick film forming paste is printed on a rectangular target pattern, the length of a pair of sides A of the target pattern facing each other is set to be equal to each other. AL, the length of the other pair of sides B is B
L, the maximum distance AG (the maximum distance in a substantially vertical direction from the side) between the side A and the position of the print pattern most receded from the side A in the printing pattern immediately after printing is: ) <(AG / AL) <(20/100), the maximum distance between the side B and the position most receded from the side B of the print pattern immediately after printing (the maximum distance from the side in a substantially vertical direction) ) BG is in the range of (3/100) <(BG / BL) <(20/100).

When printing a thick film forming paste on a square target pattern, a pair of sides A opposed to each other are printed.
And the maximum distance AG between the position most retreated from the side A is (3/100) <(AG / AL) <(20/100), and the other pair of sides B and the most retreated from the side B are set. The maximum distance BG from the position is (3/100) <(BG / BL) <
By setting it to (20/100), it is possible to reliably prevent the print pattern from having a shape that greatly protrudes from the target pattern, so that the present invention can be made more effective. Note that the reason why the AG and BG are set to the above ranges is that if the range is below the above range, the area of the print pattern after the thick film forming paste oozes becomes larger than the area of the target pattern, and exceeds the above range. This is because the area of the printed pattern becomes too small with respect to the target pattern, the bonding force of the chip component to be mounted becomes insufficient, or it becomes impossible to obtain desired electrical characteristics during conduction.

According to a sixth aspect of the present invention, there is provided a printing method of a thick film forming paste, the printing mask or the printing mask having a shape corresponding to the printing pattern immediately after printing and having an opening through which the thick film forming paste passes. It is characterized in that a thick film forming paste is printed in a predetermined shape using a screen.

By using a printing mask or a printing screen provided with an opening having a shape corresponding to the shape immediately after printing, a thick film forming paste can be easily and reliably printed in a predetermined shape of the present invention. Is possible, and the present invention can be made more effective.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1] In this embodiment,
An example in which a land for mounting a surface mount type electronic component (chip component) is printed on the surface of a substrate will be described. FIG. 1 is a plan view showing a mask used for carrying out the method for printing a thick film forming paste of the present invention, FIG. 2 is a diagram showing a target pattern of the thick film forming paste, and FIG. 3 is a printing pattern immediately after printing. FIG. 4 is a diagram showing a print pattern after a predetermined time has elapsed. In this embodiment, a thick film forming paste (this paste) is used for a square target pattern 1 as shown in FIG. 2 by using a mask 3 in which square openings 3a as shown in FIG. In the embodiment, cream solder) 2 (FIG. 3) was printed. The opening 3 of the mask 3
a, when the length of a pair of sides A facing each other of the target pattern 1 is AL and the length of the other pair of sides B is BL as shown in FIG. Is the maximum distance (the maximum distance from side A in the substantially vertical direction) AG to the most retreated position from (3/100) <(AG / AL) <(20)
/ 100), and the maximum distance BG between side B and the position most receded from side B (the maximum distance from side B in a substantially vertical direction) is (3/100) <(BG / BL)
It is formed so as to satisfy the requirement of being in the range of <(20/100). In the first embodiment, the AG and BG are both (5/100) to (20/10 /
More preferably, it is in the range of 0).

When the thick film forming paste 2 is printed using the mask 3, immediately after printing, as shown in FIG.
Each of the sides A, A and B, B recedes inward to obtain a concavely curved print pattern (print pattern immediately after printing) 4. Then, after a lapse of time (for example, one minute) after printing, the print pattern 4 expands due to the bleeding of the thick film forming paste 2, and as shown in FIG. A substantially rectangular pattern (a print pattern after a predetermined time has elapsed) 4a becomes a straight line.

By setting the AG and BG of the print pattern immediately after printing within the above range, the print pattern 4a after the thick-film-forming paste oozes should be held in a state close to the target pattern 1 and mounted. It is possible to secure a sufficient fixing force of the chip component and to obtain desired electric characteristics during conduction.

[Embodiment 2] Hereinafter, another embodiment of the present invention will be described. In this embodiment, an example will be described in which an elongated rectangular land for mounting an electronic component having a plurality of leads is densely printed on a substrate surface. FIG. 5 is a plan view showing a main part of a mask used for carrying out the method for printing a thick film forming paste of the present invention, FIG. 6 is a diagram showing a target pattern of the thick film forming paste, and FIG. FIG. 8 is a diagram showing a print pattern after a predetermined time has elapsed.

In this embodiment, as shown in FIG. 6, each target pattern 11 is an elongated rectangle, and the arrangement pitch P is 0.3 mm. In this embodiment, a thick film forming paste (a cream solder in this embodiment) is applied to a target pattern 11 as shown in FIG. 6 using a mask 13 having openings 13a as shown in FIG. 2) (FIG. 7) was printed. In addition, as shown in FIG. 5, the opening 13a of the mask 13
When the length of a pair of sides (long sides) A facing each other is AL and the length of the other pair of sides (short sides) B is BL, the side A
And the maximum distance between the most retracted position from side A (side A
Is the maximum distance in the vertical direction) AG is (3/100)
<(AG / AL) <(20/100), and the maximum distance (the maximum distance in the vertical direction from the side B) BG between the side B and the position most receded from the side B is BG , (3 /
100) <(BG / BL) <(20/100).

When the thick film forming paste 2 is printed using the mask 13, immediately after printing, each of the sides A, A and B, B recedes inward as shown in FIG. A printing pattern 14 (a printing pattern immediately after printing) having a curved shape is obtained. After a lapse of time (for example, one minute) after printing, the printing pattern 14 expands due to the bleeding of the paste 2 for forming a thick film, and as shown in FIG. A rectangular pattern that becomes a straight line (print pattern after a predetermined time has elapsed) 1
4a.

By setting the AG and BG of the print pattern in the above ranges, the print pattern after the thick film forming paste has oozed out is held close to the target pattern as in the case of the first embodiment. As a result, it is possible to secure a sufficient fixing force of the chip component to be mounted and to obtain desired electric characteristics at the time of conduction.

In each of the above embodiments, the case where lands are printed on the substrate has been described as an example. However, in the present invention, for example, an internal electrode pattern is printed on the surface of a ceramic green sheet in a manufacturing process of a multilayer ceramic capacitor. In such a case, a mask having an opening (paste passing portion for forming a thick film) having the above-mentioned shape or a mesh screen for squeegee printing may be used. And Ag-Pd, N
By printing a conductive paste using i, Cu, or the like as a conductive material, a good print pattern (internal electrode pattern) approximate to the target pattern can be formed. As a result, it is possible to improve the characteristics of electronic components such as multilayer ceramic capacitors.

Further, in the above embodiment, the case where the target pattern is a square and a slender rectangle has been described as an example. However, the present invention is applied to a case where the target pattern has a shape other than these (for example, the target pattern has a curved side). (In the case where the shape has such a shape).

In each of the above embodiments, the case where the shape of the portion receding from the predetermined side is a substantially arc-shaped curved shape has been described as an example. However, there are no special restrictions on the specific shape of the receded portion. Instead, for example, the shape of the receded side 24a can be an obtuse V-shape as in the print pattern 24 shown in FIG. 9A, and the print pattern shown in FIG. As shown in FIG. 34, the retreated side 34a can be formed in a saw-like shape.

Further, according to the present invention, the thick film forming paste is not printed on all the sides constituting the target pattern up to the receded position, but is printed on a predetermined side (for example, on the printing target). The side facing the conductor (for example,
It is also possible to configure so that only the side A) in the second embodiment is printed up to a position retracted by a predetermined distance from the side. In that case, let the length of the side be AL,
Assuming that the distance between the side and the position most receded from the side (the maximum distance from the side in the substantially vertical direction) is AG, (3/10
0) <(AL / AG) <(20/100). Note that the present invention is preferably applied when the coating thickness of the paste for forming a thick film is usually 150 μm or less, and the coating thickness is preferably 80 to 12 μm.
More preferably, it is in the range of 0 μm. This is because if the applied thickness of the thick film forming paste exceeds 150 μm, the bleeding of the paste after application tends to be severe, and
If the coating thickness is less than 80 μm, the bleeding of the paste after coating is not so problematic.

The present invention is not limited to the above embodiment in other respects, and various applications and modifications can be made within the scope of the invention.

[0030]

As described above, in the method for printing a thick film forming paste according to the first aspect of the present invention, a predetermined side constituting a target pattern is formed immediately after printing at a portion excluding both ends of the side. Since the thick film forming paste is printed only up to the position receded from the side, even if the thick film forming paste bleeds after printing, the shape of the print pattern greatly deviates from the shape of the target pattern. Without the problem, in the conventional printing method, the problems caused by the bleeding of the paste, namely, the occurrence of bridges between lands, the tombstone phenomenon, the occurrence of many solder balls, in order to prevent the bleeding of the paste after printing Decrease in adhesion due to insufficient amount of paste due to thinner mask and screen, misalignment of large parts, bleeding after printing Increasing the viscosity of the solder flux to prevent this, increasing the viscosity of the paste, increasing the frequency of cleaning of the mask and screen, shortening the life of the mask and screen, and causing static electricity due to variations in the electrode area due to bleeding of the paste Variations in characteristics such as capacitance, distortion of electrodes, and the like can be reduced or prevented, so that productivity and quality can be improved, costs can be reduced, and a defective rate can be reduced.

In the method of printing a paste for forming a thick film according to a second aspect of the present invention, of the sides constituting the target pattern, the side opposite to the conductor is obtained by removing the both ends of the side immediately after printing. Therefore, since the thick film forming paste is printed only to the position recessed from the side, even if the thick film forming paste bleeds after printing, the print pattern becomes larger than the target pattern, It is possible to reliably prevent a short circuit with the conductor by reaching the conductor.

Further, when the predetermined side of the side constituting the target pattern is a straight line as in the printing method of the thick film forming paste according to the third aspect, the printing immediately after the printing of the thick film forming paste is performed. In the case where the pattern is printed with the thick film forming paste such that the pattern corresponding to the side (straight line) has a concavely curved shape inside the side (straight line), the thick film forming paste is printed after printing. Even when the paste bleeds, the shape of the print pattern does not significantly deviate from the shape of the target pattern, and in the conventional method, bridges between lands and tombstone phenomena caused by the bleed of the paste in the conventional method. The above problems can be efficiently reduced and prevented.

Further, as in the method of printing a paste for forming a thick film according to claim 4, the distance AG between the length AL of the side and the position most receded from the side is set to (3/100) <(AG / A
L) <(20/100), it is possible to reliably prevent the predetermined side of the print pattern from greatly protruding from the predetermined side of the target pattern,
The present invention can be made more effective.

In a case where the thick film forming paste is printed on a rectangular target pattern as in the method for printing a thick film forming paste according to claim 5, a pair of sides A opposed to each other and the side A Maximum distance AG to the retracted position
To (3/100) <(AG / AL) <(20/100)
And the maximum distance BG between the other pair of sides B and the position most receded from the side B is (3/100) <(BG / BL)
By setting it to <(20/100), it is possible to reliably prevent the print pattern from having a shape that greatly protrudes from the target pattern, and the present invention can be made more effective.

In the case where a printing mask or a printing screen having an opening having a shape corresponding to the shape immediately after printing is used as in the printing method of the paste for forming a thick film according to claim 6, The paste for film formation can be easily and reliably printed in the predetermined shape of the present invention, and the present invention can be made more effective.

[Brief description of the drawings]

FIG. 1 is a plan view showing a mask used for printing a thick film forming paste in one embodiment of the present invention.

FIG. 2 is a view showing a target pattern to be formed by printing a thick film forming paste in one embodiment of the present invention.

FIG. 3 is a view showing a print pattern immediately after printing a thick film forming paste in one embodiment of the present invention.

FIG. 4 is a view showing a printing pattern after printing a thick film forming paste and passing a predetermined time in one embodiment of the present invention.

FIG. 5 is a plan view showing a mask used for printing a thick film forming paste in another embodiment of the present invention.

FIG. 6 is a view showing a target pattern to be formed by printing a thick film forming paste in another embodiment of the present invention.

FIG. 7 is a view showing a printing pattern immediately after printing a thick film forming paste in another embodiment of the present invention.

FIG. 8 is a view showing a printing pattern after printing a thick film forming paste and passing a predetermined time in another embodiment of the present invention.

FIGS. 9A and 9B are diagrams showing another example of a print pattern of a thick film forming paste.

FIG. 10 is a view showing a target pattern when printing a thick film forming paste by a conventional method.

11A is a diagram showing a print pattern immediately after printing by a conventional method for printing a thick film forming paste, and FIG. 11B is a diagram showing a print pattern after a predetermined time has elapsed after printing. .

[Explanation of symbols]

1,11 Target pattern 2 Thick film forming paste 3,13 Mask 3a, 13a Mask opening 4,14,24,34 Print pattern immediately after printing 4a, 14a Print pattern 24a, 34a after elapse of predetermined time Sides receded A pair of sides facing each other B other pair of sides AL Length of a pair of sides facing each other BL Length of another pair of sides AG Maximum distance between the most retreated position from side A BG From side B Maximum distance between most retracted position

Claims (6)

[Claims] When printing a thick film forming paste on a predetermined target pattern, a predetermined side constituting the target pattern is printed immediately after printing on a portion excluding both ends of the side. A method for printing a thick film forming paste, wherein the thick film forming paste is printed in a predetermined planar shape so that the paste is printed only to a position recessed from the side. 2. A printed object having a conductor disposed at a predetermined position, in the vicinity of the conductor, so as not to be short-circuited with the conductor.
In the case where the thick film forming paste is printed on a predetermined target pattern, of the sides constituting the target pattern, a predetermined side of the side facing the conductor, immediately after printing, excluding both ends of the side. And printing the thick-film forming paste in a predetermined planar shape so that the thick-film forming paste is printed only to a position receded from the side. 3. The printing method according to claim 1, wherein the predetermined side of the target pattern is a straight line, and the printing pattern immediately after printing the thick film forming paste is:
3. A thick film forming paste is printed on a portion corresponding to the side (straight line) so as to have a concavely curved shape inside the side (straight line).
The printing method of the paste for forming a thick film according to the above. 4. When printing a thick film forming paste on a predetermined target pattern, a distance between a predetermined side of the target pattern and a position most receded from the side of the print pattern immediately after printing (the AG is in the range of (3/100) <(AG / AL) <(20/100), where AL is the length of the side. The printing method of the paste for forming a thick film according to claim 1. 5. When printing a thick film forming paste on a rectangular target pattern, the length of a pair of sides A of the target pattern facing each other is defined as A.
L, when the length of the other pair of sides B is BL, the maximum distance between the side A and the position most receded from the side A of the print pattern immediately after printing (in a direction substantially perpendicular to the side (3/100) <(AG / AL) <(20/100), the maximum distance between the side B and the position most receded from the side B of the print pattern immediately after printing. The distance (the maximum distance from the side in the substantially vertical direction) BG is in the range of (3/100) <(BG / BL) <(20/100). The method for printing a paste for forming a thick film according to any one of the above-mentioned items. 6. A thick film forming paste having a predetermined shape is formed by using a printing mask or a printing screen having an opening through which the thick film forming paste passes, the shape corresponding to the printing pattern immediately after printing. The method for printing a paste for forming a thick film according to any one of claims 1 to 5, wherein the paste is printed on the paste.