JP2000177098A - Method and apparatus for printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide method and apparatus for printing capable of printing by drawing a printing substance from through holes without dragging the substance from a stencil mask in the holes even in the case that printing conditions such as a surface state of wall surfaces of the holes of the mask and type of a cream solder or the like are different. SOLUTION: The apparatus for printing having a filling means having a squeegee 8 or the like for filling cream solder 3 in through holes 2a in the state that a stencil mask 2 formed with the holes 2 is brought into contact with the surface to be printed of a base 1, and a driving means having a stepping motor 6 or the like for driving the base 1 t separate the mask 2 filled with the solder 3 from the base 1 comprises a controller 100 for controlling the driving means to start separating of the mask 2 from the base 1 when a preset waiting time is elapsed after filling of the solder 3 is finished. The setting of the waiting time is altered based on the printing conditions such as the type of the solder 3, a surface state of an inner periphery of the hole 2a and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing method and apparatus for printing a printing material on a printing surface of a printing object such as an electronic component, and more particularly, to a stencil mask having a through hole formed thereon. A printing method for printing the printing material on the printing surface by contacting the printing material with the printing material in the through holes of the stencil mask after contacting the printing material with the printing material. A method and an apparatus therefor. For the printing of the printing material, chip-shaped components such as a capacitor chip and a resistor chip, chip-shaped semiconductor elements such as ICs and LSIs, BGAs on which semiconductor elements are molded,
SMD (Surfac) for packages such as CSP, connectors, etc.
e Mount Device), when printing electrodes made of conductive paste on the electrode forming surface of electronic components such as substrates, and when printing spacers on liquid crystal panels, patch panels, etc.
This includes the case where Braille is printed on books such as picture books.

[0002]

2. Description of the Related Art Conventionally, as a method of printing a printing substance such as a conductive paste on a printing object such as the above-mentioned electronic component, a through-hole of a stencil mask (print mask) mounted on a printing surface of the printing object has been used. After a printing substance is filled using a squeegee as a filling member, a method of printing the printing substance by separating the printing object and the stencil mask has been proposed.

[0003]

However, in the printing method using the conventional stencil mask, when the stencil mask is separated from the printing object after the through-hole is filled with the printing material, the printing material is removed. Since the stencil mask is detached from the printing surface while the portion remains clogged in the through hole,
In some cases, good printing could not be performed.

The inventor of the present invention has examined in detail the releasability of a conductive paste as a printing substance when separating the electronic component as a printing object from a stencil mask. When using a stencil mask that has a small and smooth finish, after filling the paste into the through-holes of the stencil mask, the longer the waiting time until the start of separation of the plate, the more the paste removability is improved. It was found that the printing would be simple. This is because the tacking force (adhesive force) between the paste and the surface to be printed increases as the time passes, and the viscosity of the filled paste increases and hardens as the time passes. The unevenness of the wall surface is likely to be caught in the large through-hole, while the paste is integrated in the through-hole having a smooth inner wall surface, so that the increased tacking force improves the removability of the integrated paste. Conceivable. This improvement in removability is particularly remarkable when printing a paste having a large thixotropy such as a particle-containing paste (eg, cream solder). In addition, the optimal conditions for the waiting time until the release of the plate from which the good removability is obtained include the surface condition of the inner wall surface of the through hole and the type of the printing substance (particle diameter, initial viscosity, thixotropy). It is considered that it depends on the printing conditions such as the area ratio between the bottom surface (printing surface) of the hole and the inner wall surface, the degree of taper of the through hole, and the surface condition of the printing surface.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a method for printing even when the printing conditions such as the surface condition of the inner wall surface of the through-hole of the stencil mask and the type of printing substance are different.
Printing method and apparatus capable of performing good printing by allowing the printing substance to pass through the through-hole without causing the printing substance in the through-hole to be dragged by the stencil mask when separating the printing object and the stencil mask It is to provide.

[0006]

In order to attain the above object, according to the first aspect of the present invention, a stencil mask having a through-hole is brought into contact with a printing surface of a printing object, and the stencil mask is provided with a through-hole. A printing method for printing the printing substance on the surface to be printed by separating the stencil mask and the object to be printed after filling the printing substance with the stencil mask. A waiting time until the separation between the stencil mask and the printing object is started is changed based on printing conditions. In the printing method according to the first aspect, by changing the waiting time based on the printing conditions, even when the printing conditions are different, the tacking force between the printing substance and the printing surface is strong and the through-hole of the stencil mask is formed. The stencil mask and the printing object can be separated from each other in a state in which the printing substance is hardly caught on the inner wall surface.

The invention according to claim 2 is a filling means for filling a through-hole of the stencil mask with a printing substance in a state where the stencil mask having the through-hole formed therein is in contact with the surface to be printed of the printing object;
A printing apparatus comprising: a driving unit for driving at least one of the stencil mask and the printing target so as to separate the stencil mask filled with the printing material and the printing target; and Control means for controlling the driving means is provided so as to start the separation between the stencil mask and the object to be printed at a point in time when a preset waiting time has elapsed after the filling is completed, and the waiting time is set to a printing condition. The setting can be changed on the basis of. In the printing apparatus according to the second aspect, the waiting time when controlling the driving unit is changed based on the printing condition, so that the tacking force between the printing material and the printing surface can be changed even when the printing condition is different. Is strong and the printing substance is hardly caught on the inner wall surface of the through hole of the stencil mask,
The stencil mask and the printing object can be separated.

According to a third aspect of the present invention, in the printing apparatus of the second aspect, a waiting time input means for inputting the setting data of the waiting time is provided.
In the printing apparatus according to the third aspect, when the user inputs the setting data of the waiting time using the waiting time input means, the setting of the waiting time is changed based on the setting data.

According to a fourth aspect of the present invention, in the printing apparatus according to the second aspect, a printing condition input means for inputting the printing condition data and a printing condition data input from the printing condition input means are provided. And a waiting time setting means for setting the waiting time. In the printing apparatus according to the fourth aspect, when the user inputs printing condition data using the printing condition input unit, the setting of the waiting time is changed by the waiting time setting unit based on the printing condition data. You.

According to a fifth aspect of the present invention, in the printing apparatus of the second, third or fourth aspect, a filling end detecting means for detecting completion of filling of the printing substance is provided, and based on a detection result of the filling end detecting means. To start counting the waiting time,
The above control means is constituted.
In the printing apparatus according to the fifth aspect, the control unit starts counting the waiting time based on the detection result of the filling end detecting unit that detects the end of the filling of the printing substance.

The printing conditions in the above-mentioned inventions include the surface condition of the inner wall surface of the through-hole of the stencil mask, the type of the printing substance (particle diameter, initial viscosity, thixotropy), and the bottom of the through-hole ( The area ratio between the (printing surface) and the inner wall surface, the degree of taper of the through hole, the surface condition of the printing surface, and the like can be given.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention relates to a method of forming an electrode made of a conductive paste as a printing substance on a printing surface (electrode forming surface) of a printed circuit board (hereinafter referred to as a “substrate”) as a printing object. An embodiment applied to a printing apparatus for printing will be described. FIG. 1 is a schematic configuration diagram of a printing apparatus according to the present embodiment. In this apparatus, a stencil mask 2 made of a plastic material mounted on a frame member 2b is fixed by a fixing member 4. The substrate 1 as an electronic component on which electrodes are to be printed is held on the stage 5 such that the electrode forming surface is on the upper surface. A drive means for driving the stage 5 in an X direction and a Y direction orthogonal to each other in a plane perpendicular to the paper surface of FIG. 1 is provided on a lower surface of the stage 5. This drive means
It is configured using a stepping motor 6 that can be rotated forward and backward, and a vertical movement mechanism 7 that includes a ball screw and a nut (not shown) that is driven to rotate by the motor 6.

The stencil mask used in the present embodiment has a through hole 2a formed by ablation using an ultraviolet laser beam from an excimer laser, and the inner wall surface of the through hole 2a is formed as described later. Even if the viscosity of the cream solder as a printing substance filled in the through hole is increased, the cream solder has a smooth surface that can be smoothly pulled out without being caught.

The stepping motor 6 is driven to rotate by a mask detachment mechanism driving device 101 controlled by a control device 100 including a CPU or the like as control means. By controlling the rotation of the stepping motor 6, the stage 5 can be driven up and down to move the substrate 1 to a printing position in contact with the stencil mask 2 or to separate the substrate 1 from the stencil mask 2.

Above the stage 5 moved to the printing position, a filling means for filling the cream solder 3 into the through holes 2a of the stencil mask 2 is provided. As shown in FIG. 2, the filling means includes a squeegee 8 for printing the cream solder 3 into the through-holes of the stencil mask 2, a holding member 8a for holding the squeegee 8, and a holding belt 8a for driving the holding member 8a. A squeegee drive mechanism (not shown) for driving in the middle and left and right directions is provided. The filling completion detecting means for detecting the completion of the filling of the cream solder 3 into the through-hole includes a projection 8b as a detected portion attached to one end of the holding member 8a, and a position at which the filling is completed. And an end sensor 103 composed of a light transmission type or light reflection type optical sensor arranged so as to block an optical path by the projection 8b. In addition,
As the end sensor 103, a magnetic sensor or the like that detects a magnet attached to the end of the holding member 8a may be used instead of the optical sensor.

The control device 100 includes a timer 100a for measuring a waiting time from the end of filling of the solder paste 3 into the through hole of the stencil mask 2, and data for storing setting data such as the waiting time. It has a storage unit and the like. The control device 100 includes the mask detachment mechanism driving device 101, the squeegee driving device 102 for driving the squeegee driving mechanism, and the end sensor 1
03 is connected. Further, the control device 100 is connected to a waiting time input device 104 including a numeric keypad, a dial, and the like as waiting time input means for the user to input the waiting time setting data.

In the printing apparatus having the above-described configuration, first, the stencil mask 2 is fixed by the fixing member 4, and then the motor 6 is driven to rotate, and the stage 5 holding the substrate 1 is lifted and brought into contact with the stencil mask 2. Then, the cream solder 3 is set on the upper surface of the stencil mask 2 and the squeegee 8 is moved in the direction of arrow A, so that the cream solder 3 is filled into the through holes 2a of the stencil mask 2 and printed (see FIG. 3A). ).

Next, when the end sensor 103 detects the projection 8b provided at the end of the holding member 8a holding the squeegee 8, the stencil mask 2 filled with the cream solder 3 and the substrate 1 are separated. In the state where the contact is maintained, the counting of the waiting time set in advance based on the printing condition is started. Then, after a predetermined waiting time has passed, the cream solder 3
In the state where the tacking force F is increased, the mask detachment mechanism driving device 101 is controlled to rotate the motor 6 to lower the stage 5 in the direction of arrow B in FIG.
The stencil mask 2 is separated from the stencil mask 2 (see FIG. 3B). By this separating operation, an electrode made of the cream solder 3 is formed on the electrode pad 1a of the substrate 1.

The setting of the waiting time before the separation operation is started depends on the type of the cream solder 3, the viscosity and thixotropy, the type of the stencil mask 2 and the state of the inner wall surface of the through hole, and the type of the electrode forming surface of the substrate 1. Settings are changed according to printing conditions such as printing and surface conditions. The setting data of the waiting time can be inputted from the waiting time input device 104 connected to the control device 100. Instead of directly inputting the waiting time, inputting the printing condition data from the input device such as the numeric keypad or dial as the printing condition inputting means, the control device 1 serving as the waiting time setting means.
The waiting time may be set within 00 in accordance with the printing condition data. The conversion data used when converting the data of the printing conditions into the data of the waiting time is obtained in advance by an experiment or the like.

As described above, according to the present embodiment, prior to the separation operation between the substrate 1 and the stencil mask 2, the smooth inner wall surface of the stencil mask 2 is waited for a waiting time set in advance based on printing conditions. The viscosity of the cream solder 3 filled in the through hole 2a is increased. By delaying the separating operation by a predetermined waiting time in this manner, the operation shown in FIG.
As shown in (b), the adhesive force (tacking force) of the cream solder 3 to the surface (electrode forming surface) of the electrode pad 1a.
Since F ′ can be increased, it is possible to improve the removability of the cream solder 3 and print a good electrode.
Moreover, even if the viscosity of the cream solder 3 increases due to the waiting time, the inner wall surface of the through hole 2a of the stencil mask 2 is smooth, so that the cream solder 3 in the through hole 2a does not catch on the inner wall surface. Stencil mask 2 and substrate 1
And can be satisfactorily separated. The through hole 2
In the case of printing conditions using a stencil mask 2 in which the inner wall surface a has irregularities as shown in FIG. 4, the viscosity of the cream solder 3 increases and the irregularities are more likely to be caught by the irregularities. Upon completion, the waiting time is set so that the separating operation between the substrate 1 and the stencil mask 2 is started immediately. By changing the setting of the waiting time based on the printing conditions in this manner, even when the printing conditions are different, the cream solder 3 in the through-hole 2a is removed by the stencil mask when separating the substrate 1 and the stencil mask 2. 2, the cream solder can be removed from the through-hole 2a without being dragged by the printing plate 2 and good printing can be performed.

Further, according to the present embodiment, since the control is performed so as to wait for the predetermined waiting time based on the detection result of the end sensor 103, the filling time of the cream solder 3 varies or the setting of the filling time is changed. Even if the charging is completed, after the filling is completed, the measurement of the waiting time after the filling can be started reliably and promptly.

In the above embodiment, the waiting time after filling the cream solder 3 is the time required for the processing in the next step (for example, the chip mounting step) and the time required for the filling processing by the squeegee 8 and the separation processing. May be set to be substantially the same as the time difference between. For example, when 60 seconds are required for the next process and 30 seconds are required for the filling process and the separation process, the waiting time is set to 30 seconds. When the waiting time is set in this manner, the viscosity of the cream solder 3 can be increased during the waiting time until the next step after the substrate 1 and the stencil mask 2 are separated from each other. It is not necessary to secure a waiting time for increasing the viscosity of the paste. Therefore, it is necessary to improve the removability of the cream solder 3 to print a good electrode, and to improve the efficiency of the manufacturing process in the electrode printing step on the substrate 1 and the subsequent steps. Can be.

Further, in the printing apparatus of the above embodiment,
As shown in FIG. 5, a preliminary sensor 105 for detecting the protrusion 8b of the squeegee 8 may be provided prior to the end sensor 103. In this configuration, the movement speed of the squeegee 8 during the interval is controlled to be sufficiently slow so that the waiting time elapses from the time when the protrusion 8b is detected by the preliminary sensor 105 to the time when the protrusion 8b is detected by the end sensor 103. You. When the protrusion 8b is detected by the end sensor 103, the separating operation between the substrate 1 and the stencil mask 2 is started immediately. FIG. 6 is a block diagram showing a schematic configuration of the squeegee driving device 102 in this device. In this squeegee driving device 102, a motor 102a for driving the squeegee driving mechanism and a motor driving power supply circuit 10
A switch 102c that is ON / OFF controlled by the control device 100, a variable resistor R1 for setting a moving speed at the time of filling the cream solder, and an ON / OFF control by the control device 100 are connected to a power supply line between the control device 100 and the power supply line 2b. Switch 102
d, and a resistor R2 for speed setting during the waiting time are connected. The resistance value of the variable resistor R1 can be changed by a squeegee speed dial on an operation panel (not shown). In the squeegee driving device 102, when the protrusion 8b is detected by the spare sensor 105, the contact of the switch 102d in FIG. 6 is switched from the terminal C to the terminal D, and the current flowing through the motor 102a decreases. The moving speed of the squeegee 8 becomes slow. When the predetermined waiting time has elapsed, the end sensor 1
03, the protruding portion 8b is detected, the switch 102c is turned off, the movement of the squeegee 8 is stopped, and the lowering operation of the stage 5 is started.
And the stencil mask 2 begin to separate.

In the above embodiment, the case where the substrate 1 is moved has been described.
Can be applied to the case where the stencil mask 2 is moved while the stencil mask 2 is fixed, or the case where both are moved.

In each of the above embodiments, the case where cream solder is filled as the conductive paste has been described. However, the present invention can be applied to the case where another conductive paste other than the cream solder is filled. It is.

In each of the above embodiments, the substrate 1
Although the case of printing the electrodes has been described, the present invention,
When bump electrodes are collectively formed on a wafer on which a plurality of semiconductor elements are mounted on a substrate, electrodes are mounted on a BGA or CSP type package in which a semiconductor chip is molded, or on connectors or the like mounted on the substrate. Can be applied to the case of forming the same, and a similar effect can be obtained. In addition, the present invention is not limited to printing an electrode made of a conductive paste on an electrode forming surface of an electronic component such as the substrate, printing a spacer on a liquid crystal panel, a patch panel, or the like, and applying Braille to a book such as a picture book. It can be applied to printing.

[0027]

According to the first to fifth aspects of the present invention, even when the printing condition such as the surface condition of the inner wall surface of the through-hole of the stencil mask and the type of the printing substance is different, the tacking force between the printing substance and the surface to be printed is different. The stencil mask and the object to be printed can be separated from each other in a state where the printing material is strong and the printing substance is hardly caught on the inner wall surface of the through-hole of the stencil mask. Therefore,
Even when the printing conditions are different, when the printing object and the stencil mask are separated from each other, the printing material in the through-hole is not dragged by the stencil mask, and the printing material passes through the through-hole to perform good printing. There is an effect that can be.

In particular, according to the third aspect of the present invention, the user can change the setting of the optimum waiting time according to the surface condition of the inner wall surface of the through-hole of the stencil mask and the printing conditions such as the type of the printing substance. This has the effect.

In particular, according to the invention of claim 4, printing conditions such as the surface condition of the inner wall surface of the through-hole of the stencil mask and the type of printing substance are simply input by the user. There is an effect that an optimum waiting time can be set according to the setting.

In particular, according to the invention of claim 5, even when the filling time of the printing substance varies or the setting of the filling time is changed, after the completion of the filling, the timing of the waiting time is surely measured. And can be started quickly.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a printing apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of the stencil mask and the squeegee of the printing apparatus as viewed from above.

FIG. 3A is an explanatory view showing a state of cream solder filled in a through hole of a stencil mask by the printing apparatus. (B)
FIG. 4 is an explanatory diagram showing a state of cream solder in a through hole during a separating operation in the printing apparatus.

FIG. 4 is an explanatory view showing a state of cream solder in the through-hole during the separating operation when a stencil mask having large irregularities on the inner wall surface of the through-hole is used.

FIG. 5 is a plan view of a stencil mask and a squeegee in a printing apparatus according to another embodiment as viewed from above.

FIG. 6 is a block diagram illustrating a schematic configuration of a squeegee driving device in the printing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 1a Electrode pad 2 Stencil mask 2a Through hole 3 Cream solder 4 Fixing member 5 Stage 6 Stepping motor 7 Ball screw 8 Squeegee 8a Holding member 8b Projection 100 Control device 101 Mask detachment mechanism drive device 102 Squeegee drive device 103 End sensor 104 Waiting time input device 105 Spare sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/34 505 H05K 3/34 505C

Claims (5)

[Claims] 1. A stencil mask having a through-hole formed therein is brought into contact with a printing surface of an object to be printed, and after filling a through-hole of the stencil mask with a printing substance, the stencil mask is separated from the object to be printed. A printing method for printing the printing substance on the surface to be printed, wherein a waiting time from the end of the filling of the printing substance to the start of separation between the stencil mask and the printing target is reduced. A printing method wherein the printing method is changed based on printing conditions. 2. A filling means for filling a through-hole of a stencil mask with a printing substance in a state where the stencil mask having a through-hole formed thereon is in contact with a printing surface of a printing object; A printing apparatus comprising: a stencil mask and a driving unit that drives at least one of the stencil mask and the printing target so as to separate the stencil mask and the printing target. Control means for controlling the driving means is provided so as to start the separation between the stencil mask and the printing target when the set waiting time has elapsed, and the setting of the waiting time can be changed based on printing conditions. A printing device, comprising: 3. The printing apparatus according to claim 2, further comprising a waiting time input unit for inputting the setting data of the waiting time. 4. The printing apparatus according to claim 2, wherein the printing condition input means for inputting the printing condition data, and the waiting time is set based on the printing condition data input from the printing condition input means. And a waiting time setting unit. 5. The printing apparatus according to claim 2, further comprising a filling completion detecting means for detecting completion of filling of the printing substance, and measuring the waiting time based on a detection result of the filling completion detecting means. A printing apparatus, wherein the control means is configured to start the printing.