Patent Publication Number: US-6909065-B2

Title: Altering method of circuit pattern of printed-circuit board, cutting method of circuit pattern of printed-circuit board and printed-circuit board having altered circuit pattern

Description:
This is a Division of application Ser. No. 08/711,656 filed Sep. 9, 1996 now U.S. Pat. No. 6,415,504. The disclosure of the prior application(s) is hereby incorporated by reference herein in its entirety. 

   BACKGROUND OF THE INVENTION 
   (1) Field of the Invention 
   The present invention generally relates to methods for altering and cutting circuit patterns of a printed-circuit board and a printed-circuit board, and more particularly to an altering method for altering a circuit pattern on an inner layer of a multi-layer printed-circuit board (an organic printed-circuit board, such as a glass-epoxy board and a polyimide board, and an inorganic printed-circuit board, such as a ceramic board), a cutting method for cutting a circuit pattern of a printed-circuit board, applicable to the altering method, and a printed-circuit board having an altered circuit pattern. 
   (2) Description of the Related Art 
   Conventionally, in a printed-circuit board in which a circuit pattern corresponding to electronic circuits for electronic equipment is formed, spare circuit lines, spare connecting pads, spare via-holes used to electrically connecting circuit patterns on stacked layers and the like are often additionally formed for alteration of the circuit pattern based on design changes of the electronic circuits. When the design changes of the electronic circuits have been made, a new circuit pattern can be formed using the spare circuit lines, the spare connecting pads and the spare via-holes. In addition, the circuit pattern corresponding to the original electronic circuits is cut so as to be altered into a circuit pattern corresponding to the design changed electronic circuits. 
   Due to the use of such printed-circuit boards, even if the design changes of the electronic circuits are made, it is not necessary to make a new printed-circuit board corresponding to the design changed electronic circuits. Thus, the printed-circuit board having the circuit pattern corresponding to the design changed circuits can be rapidly prepared. 
   On the other hand, in recent years, printed-circuit boards have been miniaturized by increasing the density of the circuit pattern. Thus, since forming of the spare circuit lines, the spare connecting pads and the spare via-holes prevents the density of the circuit pattern from being increased, there is a tendency to abandon formation of these spare elements. 
   However, in a case where a printed-circuit board from which the spare elements, such as the spare circuit lines, the spare connecting pads and the spare via-holes are omitted is used, it is difficult to alter a circuit pattern on an inner layer of the printed-circuit board when the design changes of the electronic circuits have been made. 
   In addition, in a case where the circuit pattern on the inner layer of the printed-circuit board is altered, the circuit pattern is generally cut. In this case, the circuit pattern on the inner layer of the printed-circuit board has to be accurately cut with consideration to a position of an adjacent circuit pattern. In particular, in a case where the circuit is cut, in a non-contacting manner, using a high energy beam, such as an electron beam or a laser beam, metal powder generated by the abrasion of material of the circuit pattern causes insulation defects. The insulation defects must be prevented. 
   SUMMARY OF THE INVENTION 
   Accordingly, a general object of the present invention is to provide methods for altering and cutting a circuit pattern of a printed-circuit board and a printed-circuit board having an altered circuit pattern, in which the disadvantages of the aforementioned prior art are eliminated. 
   A first specific object of the present invention is to provide an altering method which can easily alter a circuit pattern on an inner layer of a printed-circuit board. 
   The above objects of the present invention are achieved by a method for altering a circuit pattern of a printed-circuit board, comprising the steps of: (a) removing a portion of the printed-circuit board so that the circuit pattern inside the printed-circuit board is exposed; and (b) connecting an exposed portion of the circuit pattern obtained in step (a) to another portion of the printed-circuit board by a conductive body so that a circuit path is formed between the exposed portion of the circuit pattern and the another portion of the printed-circuit board. 
   According to the altering method of the present invention, a new circuit path which connects the circuit pattern to another portion of the printed-circuit board can be formed without spare circuit lines, spare lands and the like. 
   A second specific object of the present invention is to provide a cutting method by which a circuit pattern can be accurately cut in consideration of a position of another circuit pattern. 
   The above object of the present invention is achieved by the following methods: 
   A method for cutting a circuit pattern located under a sheet-shaped circuit pattern inside a printed-circuit board comprising the steps of (a) forming a first cutting hole which passes through the sheet-shaped circuit pattern, the first cutting hole having a first aperture area, and (b) forming a second cutting hole which expands from a bottom surface of the first cutting hole and passes through the circuit pattern so that the circuit pattern is cut, the second cutting hole having a second aperture area narrower than the first aperture area; 
   A method for cutting a circuit pattern inside a printed-circuit board comprising the steps of (a) removing a portion with a predetermined depth of the printed-circuit board, and (b) expanding the portion which is removed in a direction parallel to the surface of the printed-circuit board, so that the circuit pattern is cut while the portion which is removed is being expanded; 
   A method for cutting a circuit pattern inside a printed-circuit board comprising the steps of (a) adjusting a mask of a beam so that a projection area of the beam projected onto a surface of the printed-circuit board has a predetermined length in a direction parallel to a width direction of the circuit pattern, and (b) projecting the beam onto the printed-circuit board so that a hole is formed in the printed-circuit board, whereby the circuit pattern is cut by the beam; 
   A method for cutting a circuit pattern inside a printed-circuit board comprising the steps of (a) adjusting a mask of a beam having a predetermined energy so that a projection area of the beam is formed on a surface of the printed-circuit board, the projection area being decided based on a narrowing ratio of the beam and a working area of the beam projected onto a surface of the circuit pattern to be cut, the narrowing ratio of the beam being a degree of narrowing of an area, to be worked by the beam having the predetermined energy, in materials on and over a surface of the circuit pattern, and (b) projecting the beam in which the mask thereof is adjusted on the printed circuit board so that a hole is formed in the printed-circuit board, whereby the circuit pattern is cut by the beam; 
   A method for cutting a circuit pattern inside a printed-circuit board comprising the steps of (a) removing a portion of the printed-circuit board by projection of a beam focused on a focal point, and (b) moving the focal point on which the beam is focused with moving of a working area of the beam inside the printed-circuit board caused by removal of the portion of the printed-circuit board, whereby the circuit pattern is cut by the beam; 
   A method for cutting a circuit pattern inside a printed-circuit board comprising the steps of (a) projecting a beam in which a mask thereof is adjusted so that a first projection area of the beam corresponds to an area covering the circuit pattern, a first portion at a first side of the circuit pattern and a second portion at a second side of the circuit pattern, a hole being formed by the beam until a predetermined depth is obtained, (b) projecting the beam in which the mask thereof is adjusted so that a second projection area of the beam corresponds to an area covering the circuit pattern and the first portion, and (c) projecting the beam in which the mask thereof is adjusted so that a third projection area of the beam corresponds to an area covering the circuit pattern and the second portion, wherein after the step (a) is completed, the step (b) and the step (c) are alternately repeated at predetermined intervals until the circuit pattern is cut by the beam; and 
   A method for cutting a circuit pattern inside a printed-circuit board comprising the step of projecting a beam on the printed-circuit board while a mask thereof is being adjusted so that a projection area of the beam is narrowed, a hole being formed in the printed-circuit board by projection of the beam, so that the circuit pattern is cut by the beam. 
   According to the cutting method of the present invention, the circuit pattern can be accurately cut while taking into consideration of a position of another circuit pattern such as the sheet-haped circuit pattern. 
   A third specific object of the present invention is to provide a printed-circuit board having an altered circuit pattern. 
   The above object of the present invention is achieved by a printed-circuit board comprising: a circuit device mounted on the printed circuit board; and a conductive body which is in a groove formed in the printed-circuit board so as to pass under the circuit device, the groove corresponding to a circuit path. 
   According to the printed-circuit board of the present invention, the printed-circuit board in which a circuit pattern has been altered can be obtained. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present invention will be apparent from the following description when read in conjunction with the accompanying drawings, in which: 
       FIGS. 1A ,  1 B,  1 C and  1 D are diagrams illustrating a process for altering a circuit pattern of a printed-circuit board according to an embodiment of the present invention; 
       FIG. 2  is a diagram illustrating an example of a worked hole or opening formed on the printed-circuit board to alter the circuit pattern on an inner layer; 
       FIG. 3  is a diagram illustrating another example of the worked hole or opening; 
       FIGS. 4A ,  4 B and  4 C are diagrams illustrating a process for connecting a wire to the exposed circuit pattern; 
       FIGS. 5A ,  5 B and  5 C are diagrams illustrating another process for connecting a wire to the exposed circuit pattern; 
       FIGS. 6A and 6B  are diagrams illustrating an example of a position at which the circuit pattern is exposed; 
       FIGS. 7A and 7B  are diagrams illustrating another example of a position at which the circuit pattern is exposed; 
       FIG. 8  is a diagram illustrating a position at which the circuit pattern under a sheet-shaped circuit pattern in the printed-circuit board is exposed; 
       FIGS. 9A and 9B  are diagrams illustrating a process for forming the hole through which the circuit pattern is exposed at the position shown in  FIG. 8 ; 
       FIGS. 10A ,  10 B and  10 C are diagrams illustrating a process for connecting a wire to the circuit pattern exposed through the hole as shown in  FIGS. 8 ,  9 A and  9 B; 
       FIG. 11  is a diagram illustrating a position at which the circuit pattern located under a sheet-shaped circuit pattern in the printed-circuit board is exposed; 
       FIGS. 12A ,  12 B and  12 C are diagrams illustrating a process for forming a hole through which the circuit pattern is exposed at the position shown in  FIG. 11 ; 
       FIGS. 13A ,  13 B and  13 C are diagrams illustrating a process for cutting the circuit pattern located under a sheet-shaped circuit pattern in the printed-circuit board; 
       FIG. 14  is a diagram illustrating examples of holes mechanically formed to cut the circuit pattern inside the printed-circuit board; 
       FIG. 15  is a diagram illustrating holes improved in comparison with the holes shown in  FIG. 14 ; 
       FIG. 16  is a diagram illustrating examples of holes formed using a high energy beam to cut the circuit pattern inside the printed-circuit board; 
       FIG. 17  is a diagram illustrating holes improved in comparison with the holes shown in  FIG. 16 ; 
       FIG. 18  is a diagram illustrating holes having widths which are acceptable to cut the circuit pattern inside the printed-circuit board (1st); 
       FIG. 19  is a diagram illustrating holes having widths which are acceptable to cut the circuit pattern inside the printed-circuit board (2nd); 
       FIG. 20  is a cross sectional view illustrating a structure of a hole formed to cut the circuit pattern inside the printed-circuit board; 
       FIG. 21  is a cross sectional view illustrating a hole formed using a beam and a focus point of the beam; 
       FIG. 22  is a cross sectional view illustrating a hole formed using a beam in which a focus point is adjusted; 
       FIGS. 23A and 23B  are diagrams illustrating an example of a mask for a beam used to cut the circuit pattern inside the printed-circuit board; 
       FIGS. 24 and 24B  are diagrams illustrating a procedure for adjusting a mask for a beam used to cut the circuit pattern inside the printed-circuit board; 
       FIG. 25  is a cross sectional view illustrating the circuit pattern cut by the beam for which the mask is adjusted as shown in  FIG. 24  (1st); 
       FIG. 26  is a cross sectional view illustrating the circuit pattern cut by the beam for which the mask is adjusted as shown in  FIG. 24  (2nd); 
       FIGS. 27A and 27B  are diagrams illustrating another example of a masking adjustment for the beam used to cut the circuit pattern inside the printed-circuit board and a cross sectional structure of a hole formed of the beam; 
       FIGS. 28A and 28B  are diagrams illustrating a mask for a beam used to remove metal powder from the hole formed to cut the circuit pattern as shown in  FIGS. 27A and 27B  and a cross sectional structure of the hole from which the metal powder is removed; 
       FIGS. 29A and 29B  are diagrams illustrating another example of a masking adjustment for the beam used to cut the circuit pattern inside the printed-circuit board and a cross sectional structure of a hole formed of the beam; 
       FIGS. 30A and 30B  are diagrams illustrating a mask for a beam used to remove metal powder from the hole formed to cut the circuit pattern as shown in  FIGS. 29A and 29B  and a cross sectional structure of the hole from which the metal powder is removed; 
       FIG. 31  is a diagram illustrating a structure by which a circuit wire passes under circuit elements mounted on the printed-circuit board; 
       FIG. 32  is a plan view illustrating a groove in which a circuit wire connecting circuit patterns exposed from the printed-circuit board is placed; 
       FIG. 33  is a plan view illustrating a groove which is filled with conductive material connecting circuit patterns exposed from the printed-circuit board; 
       FIGS. 34A and 34B  are diagrams illustrating a method for fixing the wire in the groove shown in  FIG. 32  (1st); and 
       FIGS. 35A and 35B  are diagrams illustrating a method for fixing the wire in the groove shown in  FIG. 32  (2nd). 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A description will be given of an embodiment of the present invention. 
   A printed-circuit board which should be altered is formed as shown in FIG.  1 A. Referring to  FIG. 1A , a first circuit pattern  101  which is line-shaped and a second circuit pattern  102  which is sheet-shaped are formed inside a printed-circuit board  100  (made of, for example, glass-epoxy resin). The second circuit pattern  102  is located under the first circuit pattern  101 . The first circuit pattern  101  is used for transmission of signals, and the second circuit pattern  102  is used for a power line or a ground line. Lands  104  and  125  are formed on an insulating body  103  (e.g., insulating material or resist) covering the first circuit pattern  101 . Via-holes  104  and  124  respectively extending from the lands  105  and  125  to the first circuit pattern  101  are formed in the printed-circuit board  100 . The via-holes  104  and  124  are respectively filled with pins  12  and  22  of electronic components  11  and  21  (e.g., LSI devices). The pins  12  and  22  electrically contact the first circuit pattern  101 , and are fixed onto the printed-circuit board  100  by solder lumps  106  and  126  on the lands  105  and  125 . 
   The first circuit pattern  101  located over the second circuit pattern  102  inside the printed-circuit board  100  as described above is altered in accordance with a procedure as shown in  FIGS. 1B ,  1 C and  1 D. 
   First, as shown in  FIG. 1B , holes  107  and  127  are respectively formed at positions adjacent to the lands  105  and  125  so as to pass through the first circuit pattern  101 . As a result, the first circuit pattern  101  is cut, so that the electrical connection between the pins  12  and  22  of the electronic components  11  and  21  through the first circuit pattern  101  is cut off. The first circuit pattern  101  may be mechanically cut using a drill, and may be cut, in a non-contacting manner, using a high energy beam such as a laser beam or an electron beam. The detailed description of cutting of the circuit pattern will be given later. 
   After the first circuit pattern  101  is cut as described above, the insulating body  103  is partially removed so that pattern exposure holes  108  and  128  are formed. Parts of the first circuit pattern  101  which electrically contact the pins  12  and  22  of the electronic components  11  and  22  are partially exposed through the pattern exposure holes  108  and  128 . The pattern exposure holes  108  and  128  may be mechanically formed using an end mill and may be formed, in a non-contacting manner, by using a high energy beam such as a laser beam or an electron beam. The depth of each of the pattern exposure holes  108  and  128  can be known from design data of the printed-circuit board  100 . The depth of a cut by a mechanical cutting tool such as the end mill is controlled in accordance with the design depth. The power of the laser beam which is pulsed and the number of projections of the laser beam are controlled so that the holes having the above depth are formed. 
   For example, the laser beam emitted by an excimer laser unit is masked so that the laser spot is squarely shaped. The laser beam is then projected onto the insulating body  103  of the printed-circuit board  100 , so that the insulating body  103  is removed in square as shown in FIG.  2 . That is, a square-shaped pattern exposure hole  108  through which the first circuit pattern  101  is exposed is formed. The mask of the laser beam is adjusted so that the width of the square-shaped pattern exposure hole  108  is slightly greater than the width of the first circuit pattern  101 . 
   As shown in  FIG. 3 , a wire connecting pad  101   a  may be formed on a part of the first circuit pattern  101 , near the via-hole  104 , covered with the resist layer (the insulating body  103 ). In this case, the resist layer is removed in a square by the laser beam from the excimer laser unit. As a result, the wire connecting pad  101   a  is exposed through the square-shaped pattern exposure hole  108 . The mask of the laser beam is adjusted so that the spot area of the laser beam is slightly greater than the area of the wire connecting pad  101   a.    
   After the parts of the first circuit pattern  101  connected with the pins  12  and  22  of the electronic components  11  and  21  are partially exposed as described above, electric connection bodies  109  and  129  are respectively formed on the exposed parts of the firs circuit pattern  101  (the pattern exposure holes  108  and  128 ). The electric connection bodies  109  and  129  are then connected to each other by a wire  30 . As a result, the pins  12  and  22  of the electronic components  11  and  21  are electrically connected to each other via the wire  30 . That is, the first circuit pattern  101  is altered so that the pins  12  and  22  of the electronic components  11  and  21  are disconnected from other electronic components connected to the first circuit pattern  101  and are directly connected to each other. 
   Each of the electric connection bodies  109  and  129  is formed in the pattern exposure hole through which the first circuit pattern  101  is exposed, as shown in  FIGS. 4A ,  4 B and  4 C.  FIGS. 4A ,  4 B and  4 C show a case where the electric connection body is formed in the pattern exposure hole  108 . The electric connection body is also formed in the pattern exposure hole  128  in the same manner as in this case. 
   The pattern exposure hole  108  though which the first circuit pattern  101  is exposed is filled with soldering paste  300  (a conductive connecting body) (see FIGS.  4 A and  4 B). A core  32  projecting from a cover  31  of the wire  30  is then inserted into the soldering paste  300  (see FIG.  4 B). In this state, the soldering paste  300  is melted by hot-air heat, CO 2  laser beam or the like. After this, the soldering paste  300  which has been melted is hardened (see FIG.  4 C). As a result, the electric connection body  109  having a structure in which the core  32  of the wire  30  is electrically connected to the first circuit pattern  101  by the solder  300  is formed in the pattern exposure hole  108 . 
   Solder wire, solder ribbon, solder plate and solder ball may be used in place of the soldering paste  300 . Further, conductive adhesive may be used as the conductive connecting body in place of the solder. 
   The electric connection body may be formed in accordance with a procedure shown in  FIGS. 5A ,  5 B and  5 C. 
   In this case, a solder lump  300  is attached to the core  32  projecting from the cover  31  of the wire  30  in accordance with a method of the screen deposition. The solder lump  300  has a volume which can be placed in the pattern exposure hole  108  and is enough to form a pertinent electric connection body. The tip end of the wire  30  to which the solder lump  300  is attached is inserted into the pattern exposure hole  108  through which the first circuit pattern  101  is exposed (see FIGS.  5 A and  5 B). In this state, the solder lump  300  is heated so as to be melted in the pattern exposure hole  108  (see FIG.  5 C). The solder which has been melted is hardened, so that the electric connection body is formed in the pattern exposure hole  108 . 
   As has been described above, a circuit pattern is partially exposed to alter the circuit pattern of the multi-layer printed-circuit board (forming of the pattern exposure holes  108  and  128 ). In this case, care must be taken that other circuit patterns located near the circuit pattern to be altered are not damaged.  FIG. 6A  shows a portion near a position at which the pattern exposure hole is formed.  FIG. 6B  is a cross sectional view taken along line A—A shown in FIG.  6 A. In a case shown in  FIGS. 6A and 6B , other circuit patterns  111  and  112  are located over the circuit pattern  101  which is to be exposed. If a pattern exposure hole H is formed at a position near a pin of an electronic component inserted into the via-hole  104 , the pattern exposure hole H interferes with the circuit pattern  111 . Thus, the pattern exposure hole H can not be formed at the position. In this case, it is decided, based on the design data of the printed-circuit board  100 , that a pattern exposure hole  108   a  is formed at a position in an area between the other circuit patterns  111  and  112 . 
   When design changes regarding the power line or the ground line are made, the sheet-shaped circuit pattern  102  used for the power line or the ground line is altered. In this case, the sheet-shaped circuit pattern (the second circuit pattern)  102  is partially exposed and an exposed part of the sheet-shaped circuit pattern  102  is connected to a desired portion by a wire in the same manner as in the case of the first circuit pattern  101 . 
   Since the sheet-shaped circuit pattern  102  has a relatively wide area, a position at which the pattern exposure hole should be formed can be roughly decided in comparison with the case of the line-shaped circuit pattern (the first circuit pattern)  101 . However, in a case where the sheet-shaped circuit pattern  102  is located in a deep layer, line-shaped circuit patterns may be complicatedly located over the sheet-shaped circuit pattern  102 . Thus, care must be taken that circuit patterns located over the sheet-shaped circuit pattern are not damaged. 
     FIG. 7A  shows a portion near a position at which the pattern exposure hole for the sheet-shaped circuit pattern  102  is formed.  FIG. 7B  is a cross sectional view taken along line A—A shown in FIG.  7 A. If a pattern exposure hole H is formed at a position near a pin of an electronic component inserted into the via-hole  104 , the pattern exposure hole H interferes with the circuit pattern  101  and  111  located over the sheet-shaped circuit pattern  102 . Thus, the pattern exposure hole H can not be formed at the position. In this case, it is decided, based on the design data of the printed-circuit board  100 , that a pattern exposure hole  108   a  is formed at a position in an area surrounded by circuit patterns  111 ,  112 ,  101  and  101 ′. 
   For example, a circuit pattern located under the sheet-shaped circuit pattern  102  is partially exposed, an exposed part of the circuit pattern is connected to another portion by the wire. In this case, the pattern exposure hole for the circuit pattern passes through the sheet-shaped circuit pattern  102  and reaches the circuit pattern. The pattern exposure hole may be formed by the laser beam from the excimer laser unit. When the laser beam passes through (partially removes) the sheet-shaped circuit pattern  102 , metal powder caused by the abrasion of material (copper) of the sheet-shaped circuit pattern  102  is adhered to an inner wall of the pattern exposure hole. Thus, if the pattern exposure hole is formed so as to reach the circuit pattern to be exposed straight out, the sheet-shaped circuit pattern  102  and the circuit pattern which is located under the sheet-shaped circuit pattern  102  and is to be exposed may be short-circuited by the metal powder (insulation defects). 
   To prevent the short circuit between the sheet-shaped circuit pattern  12  and the circuit pattern to be exposed, it is preferable that the pattern exposure hole for the circuit pattern located under the sheet-shaped circuit pattern is formed in accordance with a procedure as shown in  FIGS. 8 ,  9 A and  9 B.  FIG. 8  is a plan view showing a portion in which the pattern exposure hole should be formed.  FIGS. 9A and 9B  are cross sectional views taken along line A—A shown in FIG.  8 . 
   A position on a plane at which the pattern exposure hole  108  for a circuit pattern  114 , located under the sheet-shaped circuit pattern  102 , is decided as shown in  FIG. 8 , based on the design data of the printed-circuit board  100 . That is, the position of the pattern exposure hole  108  on the plane is decided so that the pattern exposure hole  108  does not interfere with all the circuit patterns  111 ,  112 ,  101  and  101 ′ located over the sheet-shaped circuit pattern  102 . 
   The laser beam from the excimer laser unit is masked so as to have a square-shaped beam spot. The pulsed laser beam is projected at the position, decided as described above, on the surface of the insulating body  103  of the printed-circuit board  100 . The mask of the laser beam is adjusted so that the laser beam spot formed on the surface of the insulating body  103  has a first area. The insulating body  103  is removed by the pulsed laser beam projected from the excimer laser unit onto the insulating body  103 . As a result, as shown in  FIG. 9A , a first hole  108 ( 1 ) having a square-shaped cross section is formed. That is, the laser beam passes through the sheet-shaped circuit pattern  102 , and the first hole  108 ( 1 ) having a predetermined depth D 1  is formed. The intensity of the laser beam and the number of times which the laser beam is projected (the number of pulses) are decided, based on the material of the insulating body  103  and the sheet-shaped circuit pattern  102 , so that the depth D 1  of the first hole  108 ( 1 ) is slightly greater than the length between the surface of the insulating body  103  and the sheet-shaped circuit pattern  102 . 
   Next, the mask of the laser beam is adjusted so that the area of the laser beam spot is changed from the first area to a second area which is narrower than the first area. In this state, the pulsed laser beam is further projected onto a bottom surface of the first hole  108 ( 1 ). As a result, as shown in  FIG. 9B , a second hole  108 ( 2 ) expanding from the bottom surface of the first hole  108 ( 1 ) to the circuit pattern  114  is formed. The depth D 2  of the second hole  108 ( 2 ) corresponds to the difference between the length from the surface of the insulating body  103  to the circuit pattern  114  and the depth D 1  of first hole  108 ( 1 ). Thus, the intensity of the laser beam and the number of times which the laser beam is projected (the number of pulses) decide the depth of the second hole  108 ( 2 ) is equal to D 2  corresponding to the above difference. 
   The aperture area of the second hole  108 ( 2 ) (corresponding to the second area of the laser beam spot) is decided, as shown in  FIG. 8 , so as to have enough area to form the electric connection body on the exposed portion of the circuit pattern  114 . The aperture area of the first hole  108 ( 1 ) (corresponding to the first area of the laser beam spot) is decided so as to be slightly greater than the second area. Thus, the pattern exposure hole  108  through which the circuit pattern  114  located under the sheet-shaped circuit pattern  102  is exposed has a structure in which there is a step in a boundary between the first hole  108 ( 1 ) and the second hole  108 ( 2 ). 
   In the case where the pattern exposure hole  108  (the first and second holes  108 ( 1 ) and  108 ( 2 ) is formed by switching the laser beam spot area in two steps, the metal powder of the sheet-shaped circuit pattern  102  may be adhered to the wall of the first hole  108 ( 1 ). However, since after the first hole  108 ( 1 ) passes through the sheet-shaped circuit pattern  102 , the second hole  108 ( 2 ) is formed, the metal powder is not adhered to the wall of the second hole  108 ( 2 ). Thus, the insulation defects between the circuit pattern  114  and the sheet-shaped circuit pattern  102  located above the circuit pattern  114  can be prevented. 
   After the pattern exposure hole  108  through which the circuit pattern  114  located under the sheet-shaped circuit pattern  102  is exposed is formed as described above, the electric connection body is formed on the exposed potion of the circuit pattern  114  in accordance with a procedure as shown in  FIGS. 10A ,  10 B and  10 C. The electric connection body is fixed with a tip end of a wire used to electrically connect to another portion. 
   The core  32  projecting from the cover  31  of the wire  30  is plated with solder so that a solder plating layer  301  covers the core  32  of the wire  30 . The core  32  projecting from the cover  31  is bent at 90°. In this state, the core  32  of the wire  30  is inserted into the pattern exposure hole  108  formed as described above (see FIGS.  10 A and  10 B). The core  32  which is bent at 90° and plated with solder is pressed against the circuit pattern  114  by the reflow-chip  400 . In this state, the core  32  is heated by hot-air (see FIG.  10 C). The solder plating layer  301  covering the core  32  is thus melted. After the hot-air supplied to the core  32  is stopped, the solder which has been melted is hardened. As a result, the core  32  is electrically connected to the circuit pattern  114  by the solder  301 . The wire  30  connected to the circuit pattern  114  is drawn out of the pattern exposure hole  108 , and another end of the wire  30  is connected to a predetermined portion of the printed-circuit board  100 . 
   In the above case, the second hole  108 ( 2 ) has to have enough aperture area to insert the core  32  which is bent into the second hole  108 ( 2 ). The depth D 2  of the second hole  108 ( 2 ) is decided so that the core  32  projecting from the cover  31  of the wire  30  is not in contact with the sheet-shaped circuit pattern  102 . 
   To positively prevent the metal powder generated when the sheet-shaped circuit pattern  102  is partially removed by the laser beam from causing the insulation defects between the sheet-shaped circuit pattern  102  and the circuit pattern  114 , the pattern exposure hole  108  may be formed in accordance with a procedure as shown in  FIGS. 11 ,  12 A,  12 B and  12 C.  FIG. 11  is a plan view showing a portion near a position at which the pattern exposure hole is formed.  FIGS. 12A ,  12 B and  12 C are cross sectional views taken along line A—A shown in FIG.  11 . 
   A position on a plane at which the pattern exposure hole should be formed is decided so that the pattern exposure hole does not interfere with all circuit patterns located over the sheet-shaped circuit pattern  102  (see FIG.  11 ), in the same manner as in the case shown in FIG.  8 . The pulsed laser beam from the excimer laser unit is masked so as to have the square-shaped spot of the first area. The pulsed laser is projected at the position, decided as described above, on the insulating body  103 , so that the first hole  108 ( 1 ) is formed (see FIG.  12 A), in the same manner as in the case shown in FIG.  9 A. The first hole  108 ( 1 ) passes through the sheet-shaped circuit pattern  102 . 
   After this, as shown in  FIG. 12B , the first hole  108 ( 1 ) formed as described above is filled with insulating resin  150 . The mask of the laser beam from the excimer laser unit is adjusted so that the laser beam spot is changed from the first area to the second area which is narrower than the first area. In this state, the pulsed laser beam is projected on to the insulating resin  150 . A portion of the insulating resin  150  corresponding to the laser beam spot having the second area is removed by the laser beam. As a result, a hole is formed concentric with the first hole  108 ( 1 ). After the laser beam passes through the insulating resin  150 , the projection of the laser beam is continued. A second hole  108 ( 2 ) having an aperture of the second area is formed from the bottom surface of the insulating resin  150  to the circuit pattern  114  (see FIG.  12 C). 
   As the result of the above process, the first hole  108 ( 1 ) in which the inner surface is coated with the insulating resin  150  and the second hole  108 (2) in which the inner surface is not coated with the insulating resin form the pattern exposure hole  108 . 
   According to the above manner in which the pattern exposure hole  108  for the circuit pattern  114  located under the sheet-shaped circuit pattern  102  is formed, even if metal powder is generated while the first hole  108 ( 1 ) is being formed, the cutting surface of the sheet-shaped circuit pattern  102  and the generated metal powder are covered with the insulating resin  150 . Thus, even if the hole is formed from the insulating resin  150  to the surface of the circuit pattern  114  to be exposed, the electrical insulation between the circuit pattern  114  and the sheet-circuit pattern  102  is reliably maintained. 
   Further, in a case where the circuit pattern  114  located under the sheet-shaped circuit pattern  102  is cut, it is preferable that the circuit pattern  114  is cut by forming a stepped hole in the same manner as in the case shown in  FIGS. 9A and 9B . 
   As shown in  FIGS. 13A ,  13 B and  13 C, the pulsed laser beam, having a square-shaped beam spot, from the excimer laser unit is projected onto the surface of the insulating body  103  covering the sheet-shaped circuit pattern  102 . First, the mask of the laser beam is adjusted so that the square-shaped beam spot has a first area. A first hole  107 ( 1 ) which passes through the sheet-shaped circuit pattern  102  is formed (see FIGS.  13 A and  13 B). After this, the mask of the laser beam is adjusted so that the square-shaped beam spot has a second area less than the first area. In this state, the pulsed laser beam is further projected onto the insulating body  103 . As a result, a second hole which cuts the circuit pattern  114  is formed (see FIG.  13 C). 
   As has been described above, a cutting hole for cutting the circuit pattern  114  located under the sheet-shaped circuit pattern  102  is formed of the first hole  107 ( 1 ) which passes through the sheet-shaped circuit pattern  102  and the second hole  107 ( 2 ) having an aperture area less than that of the first hole  107 ( 1 ). As a result, the insulation defects between the sheet-shaped circuit pattern  102  and the circuit pattern  114  which is cut can be prevented. 
   In a case where a circuit pattern of the printed-circuit board is altered, the circuit pattern is generally cut. The circuit pattern (formed on or inside the printed-circuit board) is cut by using a mechanical tool (e.g. a drill) or by using a high energy beam such as the laser beam or the electron beam in the non-contact manner. A detailed description will now be given of high-quality methods for cutting the circuit pattern of the printed-circuit board. 
   As shown in  FIG. 14 , in a case where a circuit pattern  117  between circuit patterns  115  and  116  is mechanically cut by using a tool such as a drill, it is ideal that the center of a cutting hole  131   a  formed by the tool is positioned on the center line of the circuit pattern  117 . In this ideal case, a gap between cut ends of the circuit pattern  117  has a uniform value of W 1 . However, when the center of a cutting hole  131   b  formed by the tool is shifted by δ from the center line of the circuit pattern  117 , the gap between the cut ends of the circuit pattern  117  is non-uniform as shown in FIG.  14 . For example, at a side of the circuit pattern  117 , the gap has a value of W 21 , and at an opposite side of the circuit pattern  117 , the gap has a value of W 22  greater than W 21 . If the center of the cutting hole  131   b  is shifted too much from the center line of the circuit pattern  117  a side of the circuit pattern  117  may not be completely cut. 
   Thus, to cut the circuit pattern  117  so that the gap between the cut ends of the circuit pattern  117  is uniform even if the center of a cutting hole is slightly shifted from the center line of the circuit pattern  117 , the cutting hole in which a cross section is worked into an extended-circular shape is formed as shown in FIG.  15 . In this case, data regarding positions, widths, inclinations and the like of the circuit pattern to be cut are extracted from design data of the printed-circuit board, image recognition results, results of direct observation or the like. An insert start position, an insertion depth, a moving direction and a moving distance of the tool such as the drill are then decided based on the above extracted data. After this, drilling work starts at the insert start position. After the tool reaches the decided insertion depth, the tool is moved in the decided moving direction by the decided moving distance. The printed-circuit board may be moved, instead of the tool, in a direction opposite to the decided moving direction. As a result, the cutting hole  132   a  has a cross section which is an extended-circular shape as shown in FIG.  15 . The circuit pattern  117  is cut by the cutting hole  132   a.    
   The moving direction is set, for example, so as to be parallel to the width direction of the circuit pattern  117  to be cut. In this case, even if the center of the cutting hole  132   a  is slightly shifted (by δ) from the center line of the circuit pattern  117 , the gap between the ends of the cut circuit pattern  117  is uniform (W 1 =W 2 ). 
   The moving direction may not be parallel to the width direction of the circuit pattern  117 . The moving direction is decided so that the circuit pattern is completely cut by the tool moved by the decided distance. In addition, the moving distance is not less than the width W 1  of the circuit pattern  117  to be cut as shown in FIG.  18 . The moving distance is decided so that other circuit patterns located in the same layer as the circuit pattern  117  and located over the circuit pattern  117  are not broken by the cutting hole. That is, the moving distance is decided so that the length L 2  of the aperture of the cutting hole  132  ( 132 ′) is less than the distance W 2  between the circuit patterns  115  and  116  between which the circuit pattern  117  to be cut is positioned, as shown in FIG.  18 . 
   As shown in  FIG. 16 , in a case where a bent circuit pattern  120  put between bent circuit patterns  119  and  118  is cut using a laser beam in the non-contact manner, it is ideal that the center of the square-shaped beam spot  133   a  of the laser beam is positioned on the center line of the circuit pattern  120 . In this ideal case, the gap between cut ends of the circuit pattern  120  is uniform (W 1 ) at both sides of the circuit pattern  120 . However, if the square-shaped beam spot  133   b  of the laser beam is shifted by δ from the center line of the circuit pattern  120 , the gap (W 21 ) of the cut ends of the circuit pattern  120  in a side differs from the gap (W 22 ) of the cut ends of the circuit pattern  120  in an opposite side (W 12 =W 22 ). That is, the gap between the ends of the circuit pattern  120  is non-uniform at both sides of the circuit pattern  120 . If the center of the square-shaped beam spot of the laser beam is shifted too much from the center line of the circuit pattern  120 , a side of the circuit pattern  120  may not be completely cut. 
   Thus, to cut the circuit pattern  120  in a state where the gap between the cut ends of the circuit pattern  120  is uniform even if the beam spot of the laser beam is slightly shifted from an ideal position, the laser beam is projected onto the circuit pattern  120  as shown in FIG.  17 . Referring to  FIG. 17 , the angle of the mask of the laser beam is adjusted so that a projection area of the laser beam on the circuit pattern  120  is not changed even if the square-shaped beam spot of the laser beam is slightly shifted in a predetermined direction. In an example, data regarding the width, the inclination and the like of the circuit pattern  120  to be cut are extracted from the design data of the printed-circuit board, image recognition results, results of direct observation or the like. The size and the angle of the mask of the laser beam is adjusted so that the length of the beam spot in a direction parallel to the width direction of the circuit pattern  120  is uniform. In a case shown in  FIG. 17 , the angle of the mask is adjusted so that two sides of the square-shaped beam spot are parallel to the sides of the circuit pattern  120  to be cut and two other sides of the square-shaped beam spot are perpendicular to the sides of the circuit pattern  120 . In this case, even if the square-shaped beam spot is slightly shifted (δ) in a horizontal direction, the projection area of the laser beam on the circuit pattern  120  is almost not changed. Thus, in the case where the circuit pattern  120  is cut by the laser beam for which the mask is adjusted as described above, even if the beam spot of the laser beam is slightly shifted, the gap between the cut ends of the circuit pattern  120  can be uniform (W 1 =W 2 ). 
   Further, in the case where the circuit pattern is cut by a laser beam in the non-contacting manner, the circuit pattern may be scanned by the laser beam having the square-shaped spot. In this case, as shown in  FIG. 19 , a scanning range (length) of the laser beam is decided so as to be greater than the width W 1  of the circuit pattern  120  to be cut. In addition, the scanning range of the laser beam is decided so that other circuit patterns in the same layer as the circuit pattern  120  to be cut and over the circuit pattern  120  are not damaged. That is, the scanning range of the laser beam is decided so that the length L 2  of a projection area  133  ( 133 ′) is less than the distance W 2  between the circuit patterns  118  and  119  between which the circuit pattern  120  to be cut is positioned. 
   In a process in which the insulating body and the circuit patterns are partially removed by using a high energy beam such as a laser beam or an electron beam, the deeper in the printed-circuit board, the narrower the region (the area) to be worked by the high energy beam. The reason for the above is that the high energy beam is diffracted inside the printed-circuit board. The degree of variation (narrowing) of the region to be worked by the high energy beam depends on material of the region. Thus, in a case where the multi-layer printed-circuit board is worked, the projection area (the mask size) of the beam on the surface of the printed-circuit board is decided based on the thicknesses of the respective layers and the degrees of narrowing of regions to be worked in the respective layers. 
   For example, a multi-layer printed-circuit board is formed as shown in FIG.  20 . Referring to  FIG. 20 , the printed-circuit board has a first layer made of material A (e.g., a resist layer), a second layer made of material B (e.g., an insulating layer), a third layer (a circuit pattern) made of material C (e.g. copper) and a fourth layer made of material D. The first layer has the thickness of T A , the second layer has the thickness of T B , and the third layer has the thickness of T C  (T=T A +T B +T C ). The degree of narrowing of the region to be worked in the respective layers has been previously measured by using a laser beam which is actually used to work the printed-circuit board. The degree of narrowing of the region to be worked is represented by a narrowing coefficient (ratio) K. The narrowing coefficient (ration) K in a structure (the first, second and third layers) to be worked is defined by
 
 K=δ/T 
 
where T is the thickness of the structure to be worked and δ is the difference between a position of the edge of the projection area of the laser beam on the surface of the first layer and a position of the edge of a region to be worked on the bottom surface of the third layer.
 
   In a case where the circuit pattern of the third layer in the printed-circuit board structured as described above is cut so that a gap of W 2  is formed between cut ends of the circuit pattern, the width W 1  of the projection area (the mask size) of the laser beam (the excimer laser beam) on the surface of the printed-circuit board (the surface of the first layer) is decided as follows. 
               W1   =       W2   +     2   ⁢   δ       =       ⁢     W2   +     2   ⁢     (       δ   A     +     δ   B     +     δ   C       )                       =       ⁢     W2   +     2   ⁢     (       K   A     ×     T   A       )       +     2   ⁢     (       K   B     ×     T   B       )       +     2   ⁢     (       K   C     ×     T   C       )                         
 
   That is, the mask of the laser beam is adjusted so that the projection area of the laser beam on the surface of the printed-circuit board has the width of W 1 . 
   In addition, a working rate R of the laser beam, which is actually used to work the printed-circuit board, with each of materials of the respective layers has been measured. The working rate R is defined as
 
 R=d/N 
 
where d is the depth of a hole formed by the laser beam and N is the number of times which the laser beam is projected onto the material or a time for which the laser beam is projected onto the material. The number of times which the laser beam is projected on to each layer (the number of pulses) or the times for which the laser beam is projected onto each layer is controlled based on the working rate R with respect to the material of each layer.
 
   The laser beam or the electron beam used to cut the circuit pattern is focused, as shown in  FIG. 21 , on the surface of the printed-circuit board  100  by a lens  160  having a focal length L f . If the circuit pattern to be cut is placed at a deep position in the printed-circuit board, while the region which is worked by the laser beam or the electron beam is being moved inside the printed-circuit board  100 , the degree of out-of-focus of the laser beam or the electron beam on the worked region is increased. Thus, while the worked region is being moved inside the printed-circuit circuit board, the energy density of the laser beam or the electron beam on the worked region is decreased, so that substantial narrowing coefficient (ratio) K of the worked region is increased. The amount of insulating material which is removed from the worked region by the laser beam is reduced, so that the bottom of the worked hole  134  formed by the laser beam is narrow and curved. As a result, the gap between cut ends of the circuit pattern located at a deep position in the printed-circuit board  100  is small. That is, the gap is varied in accordance with the position of the circuit pattern in the depth direction. 
   To eliminate the above disadvantage, as shown in  FIG. 22 , the lens  160  or a laser head emitting the laser beam is moved in synchronism with the movement of the region which is worked by the laser beam in the printed-circuit board  100 . As a result, while the printed-circuit board  100  is being worked by the laser beam, the laser beam is always focused on the worked region. The movement of the lens  160  or the laser head is controlled based on the working rate R of the laser beam with respect to the material of each of the layers in the printed-circuit board  100 . 
   According to the above control of the lens  160  or the laser head, the bottom of the worked hole  134  can be flat as shown in FIG.  22 . As a result, the variation of the gaps formed in cut circuit patterns in the respective layers of the printed-circuit board can be reduced. 
   The working rate R of the laser beam depend on the material onto which the laser beam is projected. The working rate R with respect to resin of an insulating body is two or three times as large as the working rate R with respect to metal (e.g., copper) of the circuit pattern. In view of complete cutting of the circuit pattern, as shown in  FIG. 23A , the width of the projection area E p0  of the laser beam used to work the printed-circuit board may be greater than the width of the circuit pattern  117  to be cut. In this case, since the working rate with respect to the circuit pattern  117  is smaller than that with respect to the resin of the insulating body, parts of the resin beside the circuit pattern  117  are removed sooner than the circuit pattern  117 . 
   As a result, immediately after the circuit pattern  117  is cut, as shown in  FIG. 23B , a protruding portion corresponding to the gap between cut ends of the circuit pattern  117  is formed on the bottom surface  135   a  of the worked hole  135 . In an extreme case, before the circuit pattern  117  is completely cut, the circuit pattern  101  located under the circuit pattern  117  to be cut is corroded by the laser beam which passes through portions at the sides of the circuit patterns  117 . 
   To eliminate the above disadvantage, the projection area of the laser beam is controlled as follows. 
   Until the surface of the circuit pattern  117  is exposed, the laser beam in which the mask thereof is adjusted so that the projection area E p0  is obtained as shown in  FIG. 23A  is projected onto the printed-circuit board  100  at the working rate R based on the material of the insulating body  103 . As a result, as shown in  FIG. 25 , a worked hole  135 , having the depth of D 11 , in which the bottom surface is flat is formed. 
   After this, as shown in  FIG. 24A , the mask of the laser beam is adjusted so that the projection area E p1  covering the circuit pattern  117  and only a portion at a first side of the circuit pattern  117  is obtained. In this state, the laser beam is further projected onto a predetermined number of times the bottom surface of the worked hole  135  at the working rate R with respect the resin of the insulating body  103 . 
   Next, as shown in  FIG. 24B , the mask of the laser beam is adjusted so that the projection area E p2  covering the circuit pattern  117  and only a portion at a second side of the circuit pattern  117  is obtained. In this state, the laser beam is further projected onto the bottom surface of the worked hole  135  a predetermined number of times at the working rate R. 
   After this, every time the laser beam is projected a predetermined number of times, the projection area is switched between E p1  shown in  FIG. 24A and E   p2  shown in FIG.  24 B. The switching operation of the projection area is continuously performed until the circuit pattern  117  is completely cut. During the projection of the laser beam with the switching operation of the projection area, the depth of the worked hole  135  is increased by D 12 . 
   According to the projection control of the laser beam, the laser beam is projected onto the circuit pattern  117  at a rate twice as large as a rate at which the laser beam is projected onto both the positions at the first and second sides of the circuit pattern  117 . In a case where the working rate with respect to the resin of the insulating body  103  is twice as large as that with respect to the metal of the circuit pattern  117 , when the circuit pattern  117  is completely cut, positions of worked surfaces corresponding to the circuit pattern  117  and the portions at the first and second sides of the circuit pattern  117  in the depth direction are theoretically the same as each other (D 11 +D 12 ). As a result, the protruding portion as shown in  FIG. 23B  is not formed on the bottom surface  135   a  of the worked hole  135  which is formed to cut the circuit pattern  117 . In addition, the circuit pattern  101  located under the circuit pattern  117  is prevented from being corroded by the laser beam before the circuit pattern  117  is completely cut. 
   In the above example, to change the projection area, the mask of the laser beam is changed. On the other hand, a relative position of the printed-circuit board to be worked with respect to the laser beam may be changed in a state where the mask of the laser beam is fixed. 
   Furthermore, in a case where the working rate with respect to the resin covering the circuit pattern  117  to be cut is greater than twice the working rate with respect to the circuit pattern  117 , a time at which the projection area of the laser beam is switched is controlled based on the difference between the working rates. That is, a switching position SP at which the projection area of the laser beam is switched in the printed-circuit pattern is decided so that the bottom surface  135   a  of the worked hole  135  is substantially flat when the circuit pattern  117  is completely cut. As shown in  FIG. 26 , until the bottom surface of the worked hole  135  reaches the switching position SP (the depth of D 21 ), the printed-circuit board is worked by the laser beam having the projection area E p0  which covers, as shown in  FIG. 23 , the circuit pattern  117  and the portions at both sides of the circuit pattern  117 . After this, in a range between the switching position SP (the depth of D 21 ) and a position of the depth of D 22 , the projection area E p1  shown in FIG.  24 A and the projection area E p2  shown in  FIG. 24B  are alternately switched in the same manner as in the case described above. 
   As a result of the switching control of the projection area described above, even if the working rate with respect to the insulating body  103  covering the circuit pattern  117  to be cut is greater than twice the working rate with respect to the circuit pattern  117 , the bottom surface  135   a  of the worked hole  135  can be flat when the circuit pattern  117  is completely cut. 
   In the cases, as described above, where the circuit pattern is cut by using the high energy beam such as the laser beam or the electron beam in the non-contacting manner, the metal powder caused by the abrasion of the circuit pattern is adhered to the inner surface of the worked hole. As a result, the isolation between the cut ends of the circuit pattern may not be sufficiently maintained. 
   To prevent such the matter, the projection area of the high energy beam such as the laser beam or the electron beam is controlled as follows. In a case where the circuit pattern in a layer inside the printed-circuit board is cut by using the excimer laser, as shown in  FIG. 27A , the work starts using the laser beam having the projection area E p1  which is greater than the projection area E p3  used to finally cut the circuit pattern  117 . The phased adjustment of the mask of the laser beam is performed so that every time the laser beam is projected a constant number of times, the projection area is narrowed (E p1 →E p2 ). Finally, the circuit pattern  117  is cut by using the laser beam having the projection area E p3 , so that the circuit pattern  117  is divided into pattern parts  117   a  and  117   b.  According to the phased control of the projection area as described above, the worked hole  136  is, as shown in  FIG. 27B , narrowed by stages. In this state, the metal powder caused by cutting of the circuit pattern  117  may be adhered to the inner surface of the worked hole  136 . 
   Next, the mask of the laser beam is adjusted so that the width of the projection area E p4  is slightly greater than the width of the projection area V p1  controlled at the start of the work, as shown in FIG.  28 A. The laser beam having the projection area E p4  is then projected onto an area between the pattern parts  117   a  and  117   b  a predetermined number of times. Due to the work using the laser beam with the projection area E p4 , as shown in  FIG. 28B , a slot  136   a  deeper than the worked hole  136  which had been formed is formed. The worked hole  135  is divided into a pattern part  117   a  side portion and a pattern part  117   b  side portion by the slot  136   a.    
   The worked hole  136  formed to cut the circuit pattern  117  is divided by the slot  136   a.  While the slot  136   a  is being formed, the metal powder adhered to the inner surface of the worked hole  136  is removed. As a result, there may be no metal powder inside the slot  136   a . Thus, the insulation between the pattern parts  117   a  and  117   b  (the cut ends of the circuit pattern  117 ) is prevented from deterioration. 
   The projection area of the laser beam may be continuously changed instead of the phased change of the projection area described above. 
   In this case, the work starts using the laser beam with the projection area E ps  greater than the projection area E pe  finally used to cut the circuit pattern  117 . After this, as shown in  FIG. 29A , the mask of the laser beam is adjusted so that the projection area is gradually narrowed in proportion to the number of projections of the laser beam. Finally, the circuit pattern  117  is cut using the laser beam with the projection area E pe , and the circuit pattern  117  is divided into the pattern parts  117   a  and  117   b . Due to the continuous control of the projection area, as shown in  FIG. 29B , the worked hole  137  is gradually narrowed. 
   In the above case, while the worked hole  137  is being worked, the laser beam is continually projected onto the inner surface of the worked hole  137 . Thus, the metal powder generated when the circuit pattern  117  is cut is immediately removed by the laser beam. As a result, the insulation between the pattern parts  117   a  and  117   b  can be improved. 
   To further improve the insulation between the pattern parts  117   a  and  117   b , after the pattern  117  is cut by the worked hole  137  formed as described above, the projection of the laser beam is performed again as follows. 
   The mask of the laser beam is adjusted again so that the width of the projection area E p2  is slightly greater than the width of the projection area E ps  controlled at the start of the work, as shown in FIG.  30 A. The laser beam having the projection area E p2  is then projected onto an area between the pattern parts  117   a  and  117   b  a predetermined number of times. Due to the work using the laser beam with the projection area E p2 , as show in  FIG. 30B , a slot  137   a  deeper than the worked hole  137  which has been formed is formed. The worked hole  137  is divided into a pattern part  117   a  side portion and a pattern part  117   b  side portion by the slot  137   a.    
   Thus, even if the metal powder is adhered to the inner surface of the worked hole  137 , the worked hole  137  formed to cut the circuit pattern  117  is divided and the metal powder is removed from the inner surface of the slot  137   a . As a result, the insulation between the pattern parts  117   a  and  117   b  is prevented from deteriorating by the powder adhered to the inner surface of the worked hole  137 . 
   In a case where circuit patterns are altered, a new circuit path is generally formed between electronic parts by using a wire. For example, in the case of alteration of the circuit pattern as shown in  FIGS. 1A ,  1 B,  1 C and  1 D, the wire connects the exposed circuit patterns to each other. If the location of the wire  30  is limited in the printed-circuit board, a path for electrical connection between two portions is formed in the printed-circuit board as follows. 
   As shown in  FIG. 31 , semiconductor devices  11  and  21  (e.g, LSIs) which are to be electrically connected are mounted on the printed-circuit board  100 . A semiconductor device  31  (e.g., LSI) which is located between the semiconductor devices  11  and  21  is closely mounted on the printed-circuit board  100 . A groove  131  is formed on the printed-circuit board  100  under the semiconductor  31  by using the laser beam or the electron beam. A wire  30  is placed in the groove  131 . Ends of the wire  30  are connected to predetermined pins of the semiconductor device  11  and  21  with solder. 
   Thus, the wire used for the alteration of the circuit pattern can be placed inside the printed-circuit board. 
   As shown in  FIG. 32 , circuit patterns  101 ( 1 ) and  101 ( 2 ) which are inside the printed-circuit board and respectively connected to pins  12  and  22  of semiconductor devices are respectively cut by worked holes  107  and  127 . A groove  132  is formed, by using the laser beam, on the printed-circuit board between the circuit pattern  100 ( 1 ) connected with the pin  12  and the circuit pattern  100 ( 2 ) connected with the pin  22 . At the ends E 1  and E 2  of the groove  132 , the circuit patterns  100 ( 1 ) and  100 ( 2 ) are partially exposed. The wire  30  is placed in the groove  132 . The ends of the wire  30  are respectively connected to the exposed portions of the circuit patterns  100 ( 1 ) and  100 ( 2 ) with solder. 
   In addition, as shown in  FIG. 33 , the groove  132  formed in the same manner as in the above case is filled with conductive material  310 , such as solder paste, solder wire, solder ribbon, solder balls or conductive adhesive. The whole printed-circuit or the groove is heated so that the conductive material  310  is melted and subsequently hardened. As a result, the circuit patterns  100 ( 1 ) and  100 ( 2 ) which are partially exposed at the ends E 1  and E 2  of the groove  132  are electrically connected by the conductive material  310  filling the groove  132 . 
   The wire  30  and the conductive material  310  provided in the groove  132  formed on the printed-circuit board are fixed in the groove  132 , insulated and protected as follows. 
   As shown in  FIG. 34A , the inner surface of the groove  132  is coated with fixing material  311 , such as adhesive, coating material or potting material. While the fixing material  311  is heated, the wire is placed in the groove  132 . As a result, as shown in  FIG. 34B , the wire  30  can be fixed, insulated and protected by the fixing material  311  (the adhesive, coating material or potting material). 
   Furthermore, after the wire  30  or the conductive material (e.g., the solder, the conductive adhesive or the like) is provided in the groove  132 , the groove  132  may be filled with the fixing material  311  (the adhesive, the coating material or the potting material). The fixing material filling the groove  132  is then hardened. In this case also, the wire  30  or the conductive material can be fixed, insulated and protected by the fixing material as shown in FIG.  34 B. 
   In addition, the wire  30  can be fixed in the groove  132  formed on the printed-circuit board as follows. 
   As shown in  FIG. 35A , the wire  30  which is coated with fusion material  312  is placed in the groove  132  formed in the printed-circuit board  100 . The fusion material  312  reveals adhesiveness when the fusion material  312  is heated or is provided with solvent. After the wire  30  is placed in the groove  132 , the wire  30  is heated or provided with the solvent. The fusion material  312  is thus softened and the wire  30  is fixed in the groove  132  by the fusion material  312 . 
   The present invention is not limited to the aforementioned embodiments, and other variations and modifications may be made without departing from the scope of the claimed invention.