JPS6053308B2 - How to make a double-sided photomask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for creating a pair of front and back working masks for forming wiring patterns on both sides of a printed board by photo-etching. The purpose is to create one with the same conditions and obtain the same accuracy.

FIG. 1 is a cross-sectional view showing a method for manufacturing a double-sided printed board in order of steps. First, as shown in Figure A, a material such as glass cloth and epoxy resin is prepared in which copper foils 2 and 2' are adhered to both the front and back surfaces of an insulating substrate 1. Next, as shown in the diagram, copper foil 2
, 2' apply photoresist 3, 3' and dry.
A pattern-forming photomask 4, 4' is placed thereon and exposed. Then, when the masks 4 and 4' are removed and placed in a solvent, in the case of a positive type, only the parts that were exposed to light during the opening process will melt, leaving the parts that are not exposed to light.
It will look like the diagram below. When this is placed in a corrosive solution and the copper foil is etched, only the necessary parts of the copper foil remain, as is the case, and when the remaining photoresists 3 and 3' are subsequently removed,
The state shown in diagram E is reached. Finally, as shown in the figure, holes are drilled in the land portions of the through holes, through hole plating 5 is applied, and wiring patterns 2 and 2' on both sides are connected to complete the double-sided printed board. In the case of a multilayer printed board, prepare several sheets of patterned material as shown in Figure E, sandwich an insulating prepreg between them, press them together, and then perform hole drilling and through-hole plating. Create the wiring pattern 2 like this.
In printed boards with more than one layer, if the relative positions of the conductor patterns on each layer are not aligned accurately, the through-hole plating may not be formed in the center of the land and may be misaligned, or electrical characteristics may not be obtained as designed. Harmful effects will arise.

In order to prevent such problems, it is necessary to accurately align the front and back photomasks, ie, working masks, with respect to each other. In addition, the front mask and back mask are formed in the same way and are finished with the same precision.
What is needed is something that will evenly finish the pattern on the front side and the pattern on the back side of the printed board. The former mask alignment is normally performed as shown in FIG.

That is, a plurality of reference holes are made in the printed board material and the masks 4, 4'', and these reference pins 6, 6'' are inserted through them. At this time, the mask pattern A2 of the front side mask 4 is shown by a broken line, and the mask pattern B1 of the back side mask 4'' is shown by a solid line. , 2'' side to prevent light from going around during exposure. In Fig. 3, A is the front side mask, and the back side mask 4'' is a view seen from the printed side of the mask pattern.To pattern with this mask, the printed board is The materials are sandwiched and mounted so that the pattern-printed surfaces of each mask face each other, but at this time, it is necessary that the X-Y directions of both masks match exactly.In the past, the mask 4 for the front side and the mask 4 for the back side were used. Since the manufacturing conditions of the mask 4'' are different, both mask patterns are not uniformly finished, and as a result, the finishes of the wiring patterns on the front side and the back side of the printed board are also different.

FIG. 4 is a diagram showing a conventional working mask manufacturing method, in which the row of A diagrams shows the manufacturing process of the back mask, and the row of front diagrams shows the manufacturing process of the front mask. Reference numeral 7 denotes a suction drawing board of an automatic drawing device as shown in FIG. The drawing will be automatically drawn.

10 is an X-axis drive motor, and 11 is a Y-axis drive motor.

Positioning pins 12a and 12b are provided on two adjacent sides of the drawing board 7.
, 12c and 13a, 13b, 13c are planted,
Of these, for example, a front side drawing film 41 and a back side drawing film 4'' having positioning holes 12'' and 13'' at positions into which the pins 12a and 13a are inserted are prepared, and the pin 12a is inserted into each positioning hole 125. Set the drawing film on the drawing board 7 so that the pins 13a fit into the respective pins 13'. First, when creating the working mask 4'' for the back side, set the drawing film 4V for the back side on the drawing board 7 as described above. Then, an automatic drafting device draws a pattern BO for the back side based on the pattern data, and this is used as an original image.

Next, this original image is printed on another photosensitive film 4'' to obtain a working mask 4'', but at this time, the original image is turned upside down and illuminated from the back'', thereby inverting it as shown in pattern B1. That is, the original image is By baking and reversing it once, a working mask 4'' for the back side is obtained. To obtain the front surface working mask 4, the front surface drawing film 41 is set on the drawing board 7 as described above, a front surface pattern is drawn using an automatic drafting device, and this is used as the front surface original image.

At this time, the pattern is drawn with the completed printed board seen through from the back. Next, this original image is printed and reversed once on another photosensitive film 42 as in the case for the back surface, to obtain a reverse pattern A1. However, this pattern cannot be used as a working mask as it is, so pattern A1 is printed once again on another film 4 and reversed to obtain pattern A2, which is used as a printed board working mask. Therefore, the working mask 4 for the front surface is turned upside down as shown in FIG.
'', if you just stack the mask pattern B1 side on the back side of the printed board and expose it, the finished printed board will have the through-hole land of the front side pattern and the through-hole land of the back side pattern exactly. We will face each other.

By the way, as mentioned above, mask pattern 8 on the back side is obtained by printing and inverting the original once, but mask pattern A2 on the front side is obtained by printing and inverting twice. However, the printing reversal operation requires steps of immersing the film in a developer and drying it with hot air, which involves expansion and contraction of the film. Further, during the reversing operation, fine dust particles in the air may enter and adhere to the gaps between the films, causing so-called black spots or pinholes. For this reason, performing printing reversal twice means being subjected to such adverse conditions twice, and as a result, accuracy is naturally lower and defects are more likely to occur than when reversing once. Therefore, even in the finished printed board, the wiring pattern on the front surface and the wiring pattern on the back surface have different pattern finishes such as accuracy, and uniform quality cannot be obtained. The present invention solves these problems and provides a working mask that can provide uniform quality even between wiring patterns on the front and back sides.

For this reason, according to the present invention, by improving the drawing process of the original image, a method is adopted in which both the front side mask and the back side mask can be obtained by one printing reversal. Fifth
The drawings are diagrams showing the first embodiment of the present invention in the order of steps, with the (a) diagram showing the process of obtaining a mask for the back surface, and the diagram at the front (b) showing the process of obtaining a mask for the front surface.

The method for creating the working mask for the back side is the same as before.
The original film 4'' is set on the drawing board 7, a pattern B for the back side is drawn using an automatic drafting device, and this original image is printed once and reversed to obtain a working mask 4''. To obtain a surface working mask, first of all, the drawing board 7 on which the original film is placed is rotated 90 degrees from the normal state shown in Fig. A to bring it into the state of 7'' in the opening drawing. Position the reference pins 12a, 13a at the lower right.In this state, position the original film 41a with the reference pins 13a, 12a and set it.Next, in the control device 8 of FIG. Original pattern A can be created automatically by changing the value to + and reverse polarity.
. In other words, the original pattern A at the beginning of Figure 4 was obtained.
In contrast to the Y-direction data that is stored in ten directions as shown in FIG. 18CS. The same pattern as the reversed pattern A1 is obtained as the original pattern AJ. Therefore, by simply printing and reversing the original image 41a of the present invention once, a mask 4a having the same pattern as the conventional working mask 4, such as A1'', can be obtained.In the end, the working mask 4'' for the back side is also the working mask for the front side. Both masks 4a can be obtained by simply printing and reversing the original image once, so both masks go through the exact same process.
A working mask with the same quality on the front and back sides can be obtained. FIG. 6 shows another embodiment, in which the (a) diagram shows the process of obtaining a mask for the back side, and the front diagram shows the process of obtaining a mask for the front side.

In this embodiment as well, the process of obtaining the working mask 4'' for the back side is the same as the conventional one. Set the original film 41b in the same position as in the case of film 4. Then, when drawing, in the automatic drawing machine shown in FIG. Replace and connect the input cables.In other words, input Y-direction data to the x-axis drive motor 10, and input data to the Y-axis drive motor 1.
1 will be input with data in the X direction. Then, the original pattern A is drawn based on this input. '' is the conventional original pattern AO of the opening in Figure 4, and the positioning hole 12''-
The pattern is obtained by inverting the page 180 degrees around the diagonal line in the 13'' direction.If this original pattern 8' is rotated 90 degrees in the direction of the arrow within the plane, the original pattern in the embodiment shown in FIG. A.'' will be exactly the same. Therefore, this original pattern A. When I is baked and reversed once, a surface mask 4b having the same pattern ^i as the front surface mask 4 at the opening in FIG. 4 and the front surface mask 4a in FIG.
is obtained. In this case as well, the original image only needs to be printed and reversed once. As described above, according to the present invention, in the original drawing process, it is possible to draw the same pattern as the original pattern after completing the conventional one-time reversal, compared to the conventional method that required printing and reversal twice. Therefore, a working mask for both the front and back sides can be created by reversing the printing once.

For this reason, the working mask for the front side and the working mask for the back side are created under exactly the same conditions, and printed boards exposed and photo-etched using these masks have a uniform finish on both the front and back wiring patterns. The quality and characteristics as designed can be obtained. Since the surface mask also requires only one printing and reversal, defects such as sunspots and pinholes can be avoided, and the complicated work process is halved, greatly improving work efficiency. A multilayer printed board can be obtained by stacking two or more double-sided printed boards made using the working mask of the present invention with prepreg sandwiched between them.

In the above explanation, the upper side of the printed board has been described as the front side and the lower side as the back side, but it is completely free to define which side is the front side or the back side.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the method for manufacturing a double-sided printed board in order of process, Fig. 2 is a perspective view showing the mask alignment method when manufacturing a double-sided printed board, and Fig. 3 A shows the working mask on the front side.
The opening is a view of the back side working mask, respectively, viewed from the mask pattern side. FIG. 4 is a diagram showing a conventional method for manufacturing a working mask for a double-sided printed board, in which the diagram A shows the manufacturing process for a mask for the back side, and the diagram at the front shows the manufacturing process for a mask for the front side. FIGS. 5 and 6 are diagrams showing a method of manufacturing a working mask for a double-sided printed board according to the present invention, respectively, in which FIG. FIG. 7 is a perspective view of the automatic drafting device. In the figure, 4, 4a, 4b are working masks for the front side, 4'' is a working mask for the back side,
41 is an original image, 41a, 41b are original images, ``, AO'' are original image patterns, A1', Al2 are mask patterns, 7 is a drawing board, 10 is an x-axis drive motor Ill is a Y-axis drive motor, 1
2a to 12c and 13a to 13c are positioning pins.

Claims (1)

[Claims] 1. In a method for creating a pair of front and back working masks for forming a conductor pattern on both the front and back sides of a printed board by photo-etching, the working mask for the back side comprises:
The mask pattern is automatically drawn on the mask installation drawing board of an automatic drafting device, and the original image is created by printing and reversing it once. The original drawing is created by rotating it 90 degrees and reversing the polarity of one of the X and Y input data of the automatic drawing device, and then printing this original drawing once and inverting it. A method for making a double-sided photomask. 2. In a method for creating a pair of front and back working masks for forming conductor patterns on both the front and back sides of a printed board by photo-etching, the working mask for the back side is:
The mask pattern is automatically drawn on the mask-attached drawing board of the automatic drafting device, and the original image is created by printing and reversing it once. A method for producing a double-sided photomask, characterized in that the original picture is drawn by replacing and inputting direction data, and the original picture is produced by printing and reversing it once.