Drill bit machining apparatus

Abstract

The objective of this invention is to provide a drill bit processing apparatus that can easily detect the depth of a conductor layer, thereby improving processing efficiency. The drill bit processing apparatus of this invention includes: a rotating shaft that rotates a drill bit; a drive mechanism that enables the rotating shaft to move along its axial direction; a position detection sensor that detects the position of the rotating shaft in the axial direction; and a control device that performs hole-making processing (forming through-holes) and back-drilling processing on a multilayer printed circuit board. The control device includes: a conductor layer detection unit that outputs a detection signal detecting that the drill bit contacts the surface of the conductor layer during hole-making processing (forming a detection hole at a location different from the through-hole on the multilayer printed circuit board); a memory unit that stores position information when the detection signal is output; and a depth calculation unit that calculates the processing depth of the conductive plating removed by back-drilling based on the position information.

Description

Technical Field

[0001] This invention relates to a drill bit processing apparatus for hole drilling using a drill bit. Background Technology

[0002] Previously known drilling apparatuses utilize drill bits to create openings in printed circuit boards (PCBs). In multilayer PCBs, through-holes extending along the stacking direction of the PCB are formed, and the through-holes are plated, thereby connecting the internal wiring layers to each other. As disclosed in Patent Document 1, a technique for back-drilling to remove excess plating applied to the through-holes is also disclosed as a drilling apparatus.

[0003] Patent Document 1 uses a multilayer printed circuit board (PCB) comprising a circuit forming region having an internal wiring layer (conductor layer) and a reference depth detection region having a reference depth detection layer arranged in the same order as the internal wiring layer. The drill bit processing apparatus described in Patent Document 1 includes a continuity detection unit that applies voltage between the reference depth detection layer and the drill bit, and a position detector that detects the position of the drill bit. It performs drilling processing on the reference depth detection region. After the drill bit reaches the reference depth detection layer, the continuity detection unit outputs a detection signal, and the depth of the reference depth detection layer can be determined based on the position of the drill bit when the detection signal is output. Furthermore, it calculates the ratio of the depth of the reference depth detection layer in the reference depth detection region to the overall thickness of the substrate, and uses this ratio to determine the depth of the inner wiring layer in the circuit forming region. In other words, it calculates the processing depth to remove excess plating through back drilling.

[0004] [Existing technical documents] [Patent Literature] [Patent Document 1] Japanese Patent Application Publication No. 2016-122825. Summary of the Invention

[0005] [The problem the invention aims to solve] However, in the drill bit processing apparatus described in Patent Document 1, drilling is required to determine the depth of the reference depth detection layer. Therefore, when back-drilling internal wiring layers (conductor layers) of different depths, multiple drilling operations must be performed in the reference depth detection area to determine the depth of the reference depth detection layer separately. Consequently, back-drilling results in reduced processing efficiency due to the time and effort involved.

[0006] The purpose of this invention is to provide a drill bit processing device and a back-drilling processing method that can easily detect the depth of the conductor layer and improve processing efficiency.

[0007] [Problem-solving methods] To achieve the above objectives, the drill bit processing apparatus of the present invention is a back-drilling apparatus for removing excess conductive plating from a multilayer printed circuit board. The multilayer printed circuit board has multiple conductor layers and insulating layers. To connect predetermined conductor layers among the multiple conductor layers to form a through-hole, and to apply conductive plating to the through-hole, the drill bit processing apparatus is characterized by comprising: a rotating shaft having a holding portion for holding the drill bit, allowing the drill bit held by the holding portion to rotate; a drive mechanism capable of moving the rotating shaft along its axial direction; a position detection unit for detecting the position of the rotating shaft in the axial direction; a conductor layer detection unit that outputs a detection signal detecting contact between the drill bit and the surface of the conductor layer when drilling towards the conductor layer by rotating the drill bit and moving the rotating shaft using the drive mechanism; a memory unit that stores position information obtained by the position detection unit when the detection signal is output; and a control unit that, during back-drilling, acquires the position information at the time of outputting the detection signal from the memory unit and calculates the drilling depth of the drill bit based on the acquired position information.

[0008] [The effects of the invention] According to the present invention, the depth of the conductor layer can be easily detected, thereby improving processing efficiency. Attached Figure Description

[0009] [ Figure 1 [1] is a schematic diagram of the drill bit processing device of the first embodiment.

[0010] [ Figure 2 [] is a vertical cross-sectional view showing the structure of a multilayer printed circuit board.

[0011] [ Figure 3 [Illustration 1] is a schematic block diagram showing the electrical configuration of the drill bit processing apparatus according to the first embodiment.

[0012] [ Figure 4 [ ] indicates the positions of the drill bit when the drill bit processing apparatus of the first embodiment performs hole processing on the conductor layer detection area. Figure 4 Timing diagrams of (A) to (E) and the shaft voltages corresponding to each position of the drill bit ( Figure 4 (F)).

[0013] [ Figure 5 [ ] is a flowchart illustrating the process of the drill bit processing apparatus 1 of the first embodiment performing the back drilling processing step.

[0014] [ Figure 6 [Illustration] is a block diagram illustrating the electrical configuration of the drill bit processing apparatus according to the second embodiment.

[0015] [ Figure 7 [] is a block diagram showing the structure of the electrostatic capacitance detection section.

[0016] [Explanation of Labels in the Attached Images] 1.51: Drill bit processing device 10: Multilayer printed circuit board 10a: Circuit Formation Region 10b: Conductor layer detection area 11: Device base 12: Processing table 12a: Locating pin 13: Gantry-type column 15: Cross slider 16: Shaft 17: Drill bit 17A: Outer Peripheral Surface 17a: Front end 17b: Base end 17c: Insulator 18: Secondary clamp 19: Supply tool column 20: Discharge tool column 21: Drill bit box 22: Drill Bit Inspection Tool 25, 55: Control device 26: Display Section 27: Memory Department 31: Rotor shaft 32: Collet Chuck 33: Motor 33a: Rotor 33b: Stator 33c: Coil 35, 52: Electrode components 41: Vertical drive control unit for rotating shaft 42: Shaft Control Unit 43: XY Direction Drive Control Unit 44: Shaft voltage detection unit (conductor layer detection unit) 45: Conductor Layer Determination Section 46: Depth Calculation Department 47: Vertical drive mechanism of rotating shaft 48: XY Direction Drive Mechanism 49: Position Detection Sensor 52: Electrode components 53: Electrostatic Capacitance Detection Section (Conductor Layer Detection Unit) 61: Capacitor 62: Transformer 63: Oscillator Circuit 64: Resonance Detection Circuit 101, 101A, 101B, 101C, 101D, 101E: Conductor layers 102: Insulation layer 103: Through hole 104: Conductive plating 105: Positioning hole 106: Inspection Hole G: Grounding wire VC: Variable capacitor. Detailed Implementation

[0017] [First Embodiment] [Composition of Drill Bit Processing Equipment] like Figure 1 As shown, the drill bit processing apparatus 1 of this embodiment includes an apparatus base 11, a processing table 12, and a gantry column 13. The processing table 12 is driven on the apparatus base 11 by an XY direction drive mechanism 48 (see reference). Figure 3 Driven along the X direction. Multiple (two in this embodiment) multilayer printed circuit boards 10, which become the workpieces, are placed on the processing table 12.

[0018] A gantry column 13 is mounted on the device base 11. The gantry column 13 is configured to span the machining table 12, and a cross slide 15 driven along the Y direction by an XY direction drive mechanism 48 is mounted on one of the vertical surfaces of the gantry column 13. Multiple rotating shafts 16 are provided on the cross slide 15.

[0019] The rotating shafts 16 correspond to the multilayer printed circuit boards 10 placed on the processing table 12 and are mounted in a manner that allows them to slide relative to the gantry column 13. The multiple rotating shafts 16 are connected by a rotating shaft vertical drive mechanism 47 (see reference). Figure 3 They are driven synchronously along the vertical direction (Z direction).

[0020] A drill bit 17 is held on a pivot 16. The drill bit 17 is used for drilling holes in the multilayer printed circuit board 10 and for back drilling as described below. A chuck 18 is mounted on the pivot 16. The chuck 18 moves together with the pivot 16 in the Z direction. Furthermore, a feed tool post 19, a discharge tool post 20, a drill bit holder 21, and a drill bit inspector 22 are respectively provided on the processing table 12. The drill bit holder 21 stores new drill bits separately from old drill bits. The drill bit inspector 22 has the function of detecting the diameter or tip position of the drill bit 17 held on the pivot 16, and is operated by inserting the drill bit 17 from above. The feed tool post 19, the discharge tool post 20, the drill bit holder 21, and the drill bit inspector 22 are each provided near the multilayer printed circuit board 10 to be processed, corresponding to the pivot 16.

[0021] [Structure of the multilayer printed circuit board 10] like Figure 2 As shown, the multilayer printed circuit board 10 has multiple (five in this embodiment) conductor layers 101 and insulating layers 102 alternately stacked. Furthermore, in this specification, when distinguishing the conductor layers 101 according to the stacking direction of the multilayer printed circuit board 10, A, B, C… are appended to the end of the numbers from top to bottom. Figure 2 In the embodiment shown, since there are 5 conductor layers 101, they are arranged sequentially from top to bottom as conductor layers 101A, 101B, 101C, 101D, and 101E. When referring to them collectively, they are arranged as conductor layers 101 that are only labeled with numbers.

[0022] Furthermore, the multilayer printed circuit board 10 is provided with a circuit forming region 10a and a conductor layer detection region 10b. In the circuit forming region 10a of the multilayer printed circuit board 10, a circuit pattern formed by a conductor layer 101, a through-hole 103, and a conductive plating 104 are formed. The through-hole 103 penetrates the multilayer printed circuit board 10 along the stacking direction of the conductor layer 101 and the insulating layer 102. The through-hole 103 is formed to connect a predetermined conductor layer 101 among a plurality of conductor layers 101. The conductive plating 104 is applied to the inner peripheral surface of the through-hole 103.

[0023] The drill bit processing apparatus 1 in this embodiment performs back drilling processing on the multilayer printed circuit board 10 to remove excess portions of the conductive plating 104. Furthermore, in Figure 2 In the example shown, a multilayer printed circuit board 10 has a through hole 103 and a conductive plating 104 formed in only one place, which is the object of back drilling. However, it is not limited to this. The multilayer printed circuit board 10 may also form multiple through holes 103 and conductive plating 104.

[0024] A positioning hole 105 is formed in the conductor layer detection area 10b of the multilayer printed circuit board 10. The positioning hole 105 penetrates the multilayer printed circuit board 10 along the stacking direction. A plurality of positioning pins 12a (see reference) are inserted into the positioning hole 105 on the processing stage 12. Figure 4 Thus, the multilayer printed circuit board 10 is positioned on the processing stage 12. In other words, the position of the multilayer printed circuit board 10 in the X and Y directions relative to the processing stage 12 is restricted by inserting the positioning pin 12a into the positioning hole 105.

[0025] [Electrical Configuration of Drill Bit Processing Equipment] Then, use Figure 3 The electrical configuration of the drill bit processing device 1 will be explained. For example... Figure 3 As shown, each part of the drill bit processing apparatus 1 is controlled by a control device 25. The control device 25 is implemented, for example, by a programmable processor. Furthermore, a display unit 26 is connected to the control device 25. The display unit 26 displays various information to be transmitted to the operator.

[0026] The control device 25 includes a memory unit 27. The memory unit 27 stores programs, display data, and predetermined thresholds, for example, non-volatile memory. The control device 25 acquires position information of the rotating shaft 16 when detecting the conductor layer 101 of the multilayer printed circuit board 10 and stores it in the memory unit 27. During back drilling, the control device 25 reads the position information from the memory unit 27 and calculates the drilling depth of the drill bit 17. The control performed by the control device 25 will be described below. Furthermore, the memory unit 27 stores the X and Y directions of the through hole 103 and the conductive plating 104, which are the targets of back drilling.

[0027] [Composition of pivot 16] The rotating shaft 16 includes a rotor shaft 31, a collet chuck 32, a motor 33, an air bearing 34, and an electrode component 35. The rotating shaft 16 is controlled by a control device 25.

[0028] The rotor shaft 31 is supported rotatably by an air bearing 34. A circular pressure-bearing portion 31a is externally fitted to the upper end of the rotor shaft 31. The air bearing 34 is composed of multiple nozzles (not shown) that spray compressed air radially toward the rotor shaft 31 and multiple nozzles (not shown) that spray compressed air vertically toward the pressure-bearing portion 31a. The air bearing 34 supports the rotor shaft 31 radially and vertically by spraying compressed air onto the rotor shaft 31 and the pressure-bearing portion 31a.

[0029] An electrode member 35 is fixed inside the air bearing 34 via an insulating member (not shown). The electrode member 35 is arranged such that a gap is formed between it and the pressure-bearing portion 31a of the rotor shaft 31. Thus, the electrode member 35 forms a capacitor between itself and the pressure-bearing portion 31a.

[0030] The motor 33 is composed of a rotor 33a and a stator 33b. The rotor 33a is coupled to the rotor shaft 31 and can rotate relative to the stator 33b. The rotor 33a is located at the center of the rotor shaft 31. The stator 33b is located opposite the rotor 33a. The stator 33b has a coil 33c formed by windings. The coil 33c is electrically connected to the shaft control unit 42 of the control device 25.

[0031] The collet chuck 32 is located at the lower end of the rotor shaft 31. The rotor shaft 31, the collet chuck 32, and the drill bit 17 are arranged coaxially. Therefore, from now on, the axial direction of the rotor shaft 31, the collet chuck 32, and the drill bit 17 will be simply referred to as the "axial direction". Furthermore, from now on, the side of the axial direction from the rotor shaft 31 toward the drill bit 17 mounted on the collet chuck 32 will be defined as "below", and the opposite side will be defined as "above".

[0032] The collet chuck 32 is variable between an open state, in which its radial dimension expands, and a closed state, in which its radial dimension shrinks, via a switching mechanism (not shown). In the open state, the inner diameter of the collet chuck 32 expands, thereby separating it from the outer circumferential surface of the drill bit 17 and releasing it from its grip. Conversely, in the closed state, the inner diameter of the collet chuck 32 shrinks, thereby bringing it into close contact with the outer circumferential surface of the drill bit 17 and holding it downwards. As a result, the rotor shaft 31 rotates integrally with the drill bit 17. "Downwards" means that the front end portion 17a of the drill bit 17 is positioned below, while the base end portion 17b held by the collet chuck 32 is positioned above.

[0033] [Composition of Drill Bit 17] like Figure 4 As shown, in this embodiment, the surfaces of the drill bit 17, except for the front end 17a and the base end 17b, are covered by an insulator 17c. The front end 17a and the base end 17b are electrically connected via an internal conductor (not shown). The base end 17b is the portion held by the collet chuck 32. The drill bit 17 is constructed, for example, by applying a shield to the front end 17a and the base end 17b, and forming a film of diamond or ceramic, etc., as the insulator 17c by CVD or PVD. The base end 17b of the drill bit 17 is held by the collet chuck 32, and the portion of the drill bit 17, except for the insulator 17c, is electrically connected to the rotor shaft 31.

[0034] [Electrical configuration of control device 25] like Figure 3 As shown, the control device 25 controls each part of the drill bit processing device 1 by reading and executing the control program pre-memorized in the memory unit 27. The control device 25 includes a spindle vertical drive control unit 41, a spindle control unit 42, an XY direction drive control unit 43, a spindle voltage detection unit 44 (conductor layer detection unit), a conductor layer determination unit 45, and a depth calculation unit 46 (depth calculation unit).

[0035] The vertical drive control unit 41 controls the drive of the vertical drive mechanism 47. The vertical drive mechanism 47 is a mechanism that moves the shaft 16 upward or downward along the axial direction, and is, for example, composed of an electric cylinder.

[0036] The XY direction drive control unit 43 controls the drive of the XY direction drive mechanism 48. As described above, the XY direction drive mechanism 48 drives the machining table 12 along the X direction and drives the cross slide 15, on which the rotating shaft 16 is provided, along the Y direction. In other words, the XY direction drive mechanism 48 changes the relative positions of the rotating shaft 16 and the machining table 12 in the X and Y directions.

[0037] The shaft control unit 42 controls the motor 33 and the switching mechanism of the shaft 16. In other words, the shaft control unit 42 controls the rotation of the rotor shaft 31 and the switching of the collet chuck 32. The shaft control unit 42 includes an inverter circuit. The inverter circuit converts a commercial AC voltage (not shown) input from a three-phase AC power supply into a higher frequency three-phase AC voltage.

[0038] If a three-phase AC voltage is supplied to the coil 33c of the stator 33b via the shaft control unit 42, the stator 33b generates a changing magnetic field (rotating magnetic field), causing the rotor 33a (rotor shaft 31) to rotate. The rotation of the rotor 33a is transmitted to the drill bit 17 held by the collet 32 ​​via the rotor shaft 31 and the collet chuck 32.

[0039] On the other hand, if a three-phase AC voltage is supplied to the coil 33c of the stator 33b, the stator 33b generates a certain amount of so-called zero-phase voltage. This zero-phase voltage induces an induced voltage (hereinafter referred to as shaft voltage) V1 (approximately several V) between the coil 33c and the rotor 33a. Then, if the shaft voltage V1 is induced, a voltage is also induced in the electrode member 35, which forms a capacitor with the rotor shaft 31. The electrode member 35 is electrically connected to the shaft voltage detection unit 44. Therefore, the shaft voltage detection unit 44 can detect the shaft voltage V1 of the rotor shaft 31.

[0040] The positioning pins 12a and processing table 12 of the aforementioned positioning multilayer printed circuit board 10 are made of metal such as iron, and the conductor layer 101 of the multilayer printed circuit board 10 is grounded via the positioning pins 12a. Therefore, if the tip 17a of the drill bit 17 contacts the surface of the printed circuit board 2, the potential of the rotor shaft 31 becomes 0, and the electrode member 35 no longer induces a voltage. The shaft voltage detection unit 44 is connected to the conductor layer determination unit 45. The shaft voltage detection unit 44 is configured to detect the shaft voltage V1, and when the rotor shaft 31 is grounded and the shaft voltage becomes 0, output a detection signal to the conductor layer determination unit 45.

[0041] The conductor layer determination unit 45 acquires the detected position of the rotating shaft 16 in the axial direction from the position detection sensor 49. The position detection sensor 49 is, for example, a magnetic sensor. Furthermore, not limited to this, when the rotating shaft vertical drive mechanism 47 is an electric cylinder, the position of the rotating shaft 16 can also be calculated based on the rotation angle of the rotating body constituting the electric cylinder. In this case, a rotation angle sensor is provided to detect the rotation angle of the rotating body. The rotation angle sensor is, for example, a rotary encoder.

[0042] Based on the detection signal output by the self-axis voltage detection unit 44, the conductor layer determination unit 45 determines that the tip 17a of the drill bit 17 has reached the surface of the conductor layer 101 of the multilayer printed circuit board 10, and acquires the position information of the rotating shaft 16 in the axial direction detected by the position detection sensor 49 when the detection signal is output. The conductor layer determination unit 45 stores the acquired position information in the memory unit 27.

[0043] During back-drilling, the depth calculation unit 46 calculates the processing depth of the conductive plating 104 removed by the back-drilling process based on the position information stored by the memory unit 27 and the connection information of the conductor layer 101. The connection information of the conductor layer 101 refers to the information of the conductor layers 101 constituting the multilayer printed circuit board 10 that are connected by the conductive plating 104. This connection information is specified by the user through an input device not shown.

[0044] [Hole drilling] In the drill bit processing apparatus 1, during the step of manufacturing the multilayer printed circuit board 10, the drilling process to form through holes 103 is first performed. As a preparation stage for the drilling process, a positioning pin 12a is inserted into the positioning hole 105 to position the multilayer printed circuit board 10 (before forming the through holes 103) on the processing table 12. Furthermore, the XY direction drive mechanism 48 is driven by the XY direction drive control unit 43 to move the processing table 12 along the X direction and the rotating shaft 16 along the Y direction, so that the position where the through holes 103 should be formed is aligned with the position of the rotating shaft 16.

[0045] In the hole-making process, firstly, the control device 25 rotates the drill bit 17 under the control of the spindle control unit 42, and moves the spindle 16 towards the multilayer printed circuit board 10 downward in the Z direction (axial direction) under the control of the spindle vertical drive control unit 41. The control device 25 lowers the spindle 16 to a position that penetrates the multilayer printed circuit board 10, forming a through hole 103.

[0046] [Steps for forming conductive plating 104] After the hole-making process, the multilayer printed circuit board 10 is removed from the processing table 12, and a conductive plating 104 is formed in the through hole 103. The conductive material is plated on the entire area (the whole in the axial direction) of the through hole 103, thereby forming the conductive plating 104.

[0047] Then, referring to Figure 4 and Figure 5 The inspection hole-making and back-drilling processes in the drill bit processing device 1 are described. Figure 4 This indicates the positions of the drill bit 17 during the drilling process of the drill bit processing device 1 for drilling the conductor layer detection area 10b. Figure 4 (A) ~ Figure 4(E)), and timing diagrams of the shaft voltages corresponding to each position of drill bit 17 ( Figure 4 (F)). Furthermore, at Figure 4 (A) ~ Figure 4 In (E), the drill bit 17 is shown in different positions for ease of illustration, but in reality, it represents the positions of the drill bit 17 when performing inspection hole processing on the multilayer printed circuit board 10 at the same position in the X and Y directions. Figure 5 This is a flowchart illustrating the process of the drill bit processing device 1 performing inspection hole drilling and back drilling.

[0048] [Drilling for Inspection] In the drilling process of the drill bit processing apparatus 1, an inspection hole 106 is formed at a position different from the through hole 103 on the multilayer printed circuit board 10. The inspection hole 106 is a hole used to inspect the conductor layer 101. During the inspection drilling process, as a preparation stage, a positioning pin 12a is inserted into the positioning hole 105 to position the multilayer printed circuit board 10 on the processing table 12. Furthermore, the XY direction drive mechanism 48 is driven by the XY direction drive control unit 43 to move the processing table 12 along the X direction and the rotating shaft 16 along the Y direction, aligning the conductor layer inspection area 10b with the position of the rotating shaft 16. In other words, the rotating shaft 16 is moved to a position different from the through hole 103.

[0049] In the drilling process for inspection, firstly, the control device 25 rotates the drill bit 17 under the control of the shaft control unit 42, and moves the shaft 16 towards the multilayer printed circuit board 10 downwards in the Z direction (axial direction) under the control of the shaft vertical drive control unit 41. Next, the control device 25 operates the shaft voltage detection unit 44 to begin detecting the shaft voltage of the rotor shaft 31 (ST1). At this time, an AC voltage is supplied to the coil 33c, and a shaft voltage is induced in the rotor shaft 31. The moment T0 when the shaft voltage detection unit 44 begins detecting the shaft voltage is called the shaft voltage V1.

[0050] like Figure 4 As shown in (A), when the front end 17a of the drill bit 17 reaches the uppermost conductor layer 101A (time T1), the rotor shaft 31 is grounded, and the shaft voltage switches from V1 to 0. At this time, the shaft voltage detection unit 44 outputs a detection signal to the conductor layer determination unit 45. The conductor layer determination unit 45 acquires the position information in the axial direction of the rotating shaft 16 detected by the position detection sensor 49 at the time the detection signal is output (time T1). In other words, the conductor layer determination unit 45 acquires the position information corresponding to the conductor layer 101A.

[0051] Furthermore, while the drill bit 17 is lowered, the inspection drilling process continues. At time T2, the front end 17a passes through the conductor layer 101A, and the rotor shaft 31 is no longer grounded. Therefore, the shaft voltage switches from 0 to V1. Furthermore, while the drill bit 17 is lowered, the inspection drilling process continues. At time T3, as... Figure 4 As shown in (B), the front end 17a of the drill bit 17 reaches the second conductor layer 101B from above, the rotor shaft 31 is grounded, and the shaft voltage switches from V1 to 0. At this time, the shaft voltage detection unit 44 outputs a detection signal to the conductor layer determination unit 45. The conductor layer determination unit 45 acquires the position information in the axial direction of the rotating shaft 16 detected by the position detection sensor 49 at the time of outputting the detection signal (time T3). In other words, the conductor layer determination unit 45 acquires the position information corresponding to the conductor layer 101B.

[0052] Furthermore, while the drill bit 17 is lowered, the inspection hole-making process continues. At time T4, the front end 17a passes through the conductor layer 101B, the rotor shaft 31 is no longer grounded, and the shaft voltage switches from 0 to V1.

[0053] Then, similarly, while lowering drill bit 17, the drilling for inspection continues, such as... Figure 4 (C) ~ Figure 4 As shown in (E), at times T5, T7, and T9, the front end 17a of the drill bit 17 reaches the 3rd to 5th conductor layers 101C to 101E from above, respectively, and the shaft voltage switches from V1 to 0. Consequently, the shaft voltage detection unit 44 outputs detection signals to the conductor layer determination unit 45 at times T5, T7, and T9. The conductor layer determination unit 45 acquires the position information in the axial direction of the rotating shaft 16 detected by the position detection sensor 49 at the times the detection signals are output (times T5, T7, and T9). In other words, the conductor layer determination unit 45 acquires the position information corresponding to conductor layers 101C to 101E.

[0054] Before the conductor layer 101A reaches the conductor layer 101E from the topmost conductor layer 101A of the multilayer printed circuit board 10 (not in ST2), the control device 25 repeatedly performs shaft voltage detection and position information acquisition. This forms the detection hole 106 (see reference). Figure 4 Then, when the control device 25 reaches the bottom conductor layer 101E of the multilayer printed circuit board 10 and obtains position information (ST2), it stops supplying AC voltage to the coil 33c, stops the rotation of the rotor shaft 31, and stops the detection of shaft voltage.

[0055] Subsequently, the control device 25, under the control of the vertical drive control unit 41, causes the rotating shaft 16 to rise toward the multilayer printed circuit board 10 along the Z direction (axial direction), and the memory unit 27 stores the position information (ST3) corresponding to each conductor layer 101A to 101E acquired by the conductor layer determination unit 45, and ends the hole opening process for detection.

[0056] [Back Drilling Processing] After the inspection hole is drilled, the control device 25 begins back drilling (ST4). More specifically, the control device 25 operates the depth calculation unit 46, which reads from the memory unit 27 the position information corresponding to the through hole 103 and conductive plating 104 that are to be back drilled, as well as the connection information of the conductor layer 101, and calculates the drilling depth of the drill bit 17 that removes the conductive plating 104 through the back drilling. Based on the position information and connection information, the depth calculation unit 46 calculates the depth from the upper surface of the multilayer printed circuit board 10 to the uppermost conductor layer 101 connected by the conductive plating 104 as the drilling depth.

[0057] When the depth calculation unit 46 calculates the processing depth, for example, if it specifies, as connection information for conductor layer 101, that the fourth conductor layer 101D from the top will be connected only to the bottom conductor layer 101E, the depth calculation unit 46 reads the position information corresponding to the conductor layer 101D. Based on the position information, the depth calculation unit 46 calculates the depth from the upper surface of the multilayer printed circuit board 10 to the top conductor layer 101D connected by the conductive plating 104 as the processing depth. At the same time, the memory unit 27 also reads the position information of the through hole 103 and the conductive plating 104 in the X and Y directions, which are the targets of back-drilling.

[0058] Based on the X and Y direction position information of the through hole 103 and conductive plating 104 read from the memory unit 27, the control device 25 drives the XY direction drive mechanism 48 under the control of the XY direction drive control unit 43, causing the processing table 12 to move along the X direction and the rotating shaft 16 to move along the Y direction, so that the positions of the through hole 103 and conductive plating 104 are aligned with the position of the rotating shaft 16. Then, based on the calculated processing depth, the control device 25 rotates the drill bit 17 under the control of the rotating shaft control unit 42, and moves the rotating shaft 16 towards the multilayer printed circuit board 10 downward in the Z direction (axial direction) under the control of the rotating shaft vertical drive control unit 41.

[0059] In the specific example described above, during back drilling, the control device 25 lowers the spindle 16 from the upper surface of the multilayer printed circuit board 10 to the uppermost conductor layer 101D connected by the conductive plating 104. This removes excess material from the conductive plating 104 by the amount of machining depth calculated by the depth calculation unit 46, and back drilling is performed. Afterward, the same steps are repeated for all the through holes 103 and conductive plating 104, and the back drilling process is completed (ST5).

[0060] [Effects of the First Embodiment] According to this embodiment, in the detection hole-making process where a detection hole 106 for detecting conductor layers 101A to 101E is formed at a position different from the through hole 103, a detection signal is output to detect that the front end 17a of the drill bit 17 contacts the surface of the conductor layers 101A to 101E. Based on the position information when the detection signal is output, the processing depth of the conductive plating 104 removed by back drilling is calculated. Therefore, the depth of the conductor layer can be easily detected, and the processing efficiency of back drilling is improved.

[0061] Furthermore, when the drill bit processing device 1 performs a single inspection hole-making process, the shaft voltage detection unit 44 outputs a detection signal each time it contacts the surface of each conductor layer 101A to 101E, and stores the position information corresponding to the multiple conductor layers 101A to 101E in the memory unit 27. Therefore, even when back-drilling conductor layers of different depths, it is not necessary to perform multiple hole-making processes in advance, which can save the time spent on back-drilling and improve processing efficiency.

[0062] Furthermore, the rotor shaft 31, which is electrically connected to the drill bit 17 and rotates integrally with the drill bit 17, induces a shaft voltage V1. The shaft voltage detection unit 44 detects the shaft voltage V1 of the rotor shaft 31, and outputs a detection signal when the shaft voltage of the rotor shaft 31 becomes 0 due to grounding via the drill bit 17 and the conductor layer 101. Therefore, the position of each conductor layer 101 can be reliably detected, improving the processing efficiency of back drilling.

[0063] Furthermore, the depth calculation unit 46 reads the connection information of the conductor layer 101 connected by the conductive plating 104. Based on the position information and connection information, it calculates the depth from the upper surface of the multilayer printed circuit board 10 to the uppermost conductor layer 101 connected by the conductive plating 104 as the processing depth. Therefore, during back drilling, the processing depth can be calculated with high accuracy, improving processing efficiency.

[0064] Furthermore, in the above embodiment, a motor 33 is exemplified by supplying a three-phase AC voltage to the coil 33c of the stator 33b to induce a shaft voltage in the rotor shaft 31. However, it is not limited to this. Any motor that induces a shaft voltage in the rotor shaft is acceptable. It can be a magnetic synchronous motor that uses a permanent magnet or an electromagnet (magnetic field winding) on ​​the rotor. Similarly, it can also be a DC motor that uses brushes to provide AC voltage (AC voltage in the sense that the direction of the current flowing through the winding is reversed) to drive the rotor.

[0065] [Second Embodiment] Reference Figure 6 and Figure 7 The drill bit processing apparatus of the second embodiment of the present invention will now be described. Furthermore, detailed descriptions of the common configurations with the drill bit processing apparatus 1 of the first embodiment will be omitted, and the description will focus on the differences. The difference between the drill bit processing apparatus 1 of the first embodiment and the drill bit processing apparatus 51 of the second embodiment is that, in the drill bit processing apparatus 51 of the second embodiment, the conductor layer detection unit does not include the shaft voltage detection unit 44, but includes the electrostatic capacitance detection unit 53. Furthermore, in the drill bit processing apparatus 51, similar to the drill bit processing apparatus 1 of the first embodiment, the multilayer printed circuit board 10 is positioned on the processing table 12, and the conductor layer 101 of the multilayer printed circuit board 10 is grounded via the positioning pin 12a.

[0066] like Figure 6 As shown, the drill bit processing apparatus 51 includes an electrode component 52 and an electrostatic capacitance detection unit 53. The electrode component 52 is disposed close to the rotor shaft 31. The electrode component 52 is fixed inside the air bearing 34, for example, via an insulating member (not shown). The electrode component 52 and the rotor shaft 31 are maintained at a distance that allows for electrostatic coupling as described below. The electrode component 52 constitutes the capacitor 61 described below.

[0067] The electrostatic capacitance detection unit 53 is included in the control device 55. Furthermore, the control device 55 has the electrostatic capacitance detection unit 53 instead of the shaft voltage detection unit 44, and otherwise has the same configuration as the control device 25 in the first embodiment described above. The electrostatic capacitance detection unit 53 is electrically connected to the electrode member 52 and outputs a detection signal to the conductor layer determination unit 45 to detect that the drill bit 17 is in contact with the surface of the conductor layer 101.

[0068] Figure 7This is a block diagram showing the detailed structure of the electrostatic capacitance detection unit 53. The electrostatic capacitance detection unit 53 is electrically connected to the capacitor 61. The electrostatic capacitance detection unit 53 mainly includes a transformer 62, an oscillation circuit 63, and a resonance detection circuit 64. The capacitor 61 is composed of an electrode component 52, a grounding wire G, and a variable capacitor VC. The variable capacitor VC is electrically connected to both the electrode component 52 and the grounding wire G. The grounding wire G is connected, for example, to the metal casing of the control device 55, serving as a reference potential.

[0069] When the tip of drill bit 17 contacts the surface of the conductor layer 101 of the multilayer printed circuit board 10, a change in the electric field occurs between the rotor shaft 31 and the conductor layer 101, and the electrode member 52 is electrostatically coupled to the rotor shaft 31. In the case of electrostatic coupling as described above, current flows from the electrode member 52 to the rotor shaft 31 side, thus reducing the electrostatic capacitance (capacitance) stored in capacitor 61. In other words, the electrostatic capacitance stored in capacitor 61 varies significantly depending on whether the tip of drill bit 17 is in contact with the conductor layer 101 of the multilayer printed circuit board 10 or not, decreasing in the former case (not reaching a predetermined threshold).

[0070] The secondary coil of transformer 62 is connected to electrode component 52 (capacitor 61), and the primary coil is connected to oscillation circuit 63. Oscillating circuit 63 causes alternating current oscillation at a predetermined frequency. The predetermined frequency of oscillation in oscillation circuit 63 is set to the value at which capacitor 61 resonates in parallel when the tip of drill bit 17 contacts the surface of conductor layer 101 of multilayer printed circuit board 10, in other words, when the electrostatic capacitance accumulated in capacitor 61 decreases (below a predetermined threshold).

[0071] The resonance detection circuit 64 detects the voltage across the primary winding of the transformer 62. When capacitor 61 resonates in parallel, the impedance of the primary winding of the transformer 62 increases. In other words, when capacitor 61 resonates in parallel, the voltage across the primary winding of the transformer 62 decreases. Therefore, the resonance detection circuit 64 outputs a detection signal S when the voltage across the primary winding of the transformer 62 decreases.

[0072] Next, the inspection hole-making process in the drill bit processing apparatus 51 will be described. Furthermore, the back drilling process in the drill bit processing apparatus 51 is the same as the back drilling process in the drill bit processing apparatus 1 in the first embodiment described above, so the description is omitted.

[0073] In the drilling process for inspection, similar to the first embodiment described above, the drill bit processing apparatus 51 forms an inspection hole 106 at a position different from the through hole 103 on the multilayer printed circuit board 10. In the inspection drilling process, firstly, the control device 55 rotates the drill bit 17 under the control of the shaft control unit 42, and moves the shaft 16 towards the multilayer printed circuit board 10 downwards in the Z-direction (axial direction) under the control of the shaft vertical drive control unit 41. Then, the control device 55 operates the electrostatic capacitance detection unit 53 and monitors the detection signal S based on the electrostatic capacitance of the capacitor 61.

[0074] When the tip 17a of the drill bit 17 reaches the uppermost conductor layer 101, as described above, the electrostatic capacitance accumulated in the capacitor 61 decreases, and the resonance detection circuit 64 outputs a detection signal S. The conductor layer determination unit 45, similar to the first embodiment described above, acquires the position information in the axial direction of the rotating shaft 16 detected by the position detection sensor 49 when the detection signal S is output. In other words, the conductor layer determination unit 45 acquires the position information corresponding to the uppermost conductor layer 101.

[0075] Then, while the drill bit 17 is lowered, the drilling for inspection continues. Then, upon reaching the second and subsequent conductor layers 101, the electrostatic capacitance accumulated in the capacitor 61 decreases, and the resonance detection circuit 64 outputs a detection signal S. The conductor layer determination unit 45 sequentially acquires the position information in the axial direction of the rotating shaft 16 detected by the position detection sensor 49 when the detection signal S is output. In other words, the conductor layer determination unit 45 acquires the position information corresponding to each conductor layer 101.

[0076] Then, when the control device 55 reaches the bottom conductor layer 101 of the multilayer printed circuit board 10 and obtains position information, it stops the rotation of the rotor shaft 31 and also stops the operation of the electrostatic capacitance detection unit 53. Subsequently, the control device 55 causes the rotor shaft 16 to rise toward the multilayer printed circuit board 10 along the Z direction (axial direction), and the memory unit 27 stores the position information obtained by the conductor layer determination unit 45 corresponding to each conductor layer 101, thus ending the hole-opening process for detection.

[0077] [Effects of the Second Embodiment] According to this embodiment, when the front end of the drill bit 17 contacts the conductor layer 101 of the multilayer printed circuit board 10, the electrostatic capacitance accumulated in the capacitor 61 decreases, and thus, the electrostatic capacitance detection unit 53 outputs a detection signal S. Therefore, similar to the first embodiment described above, the processing depth of the conductive plating 104 removed by back drilling can be calculated based on the position information when the detection signal is output. Thus, the same effect as the first embodiment described above can be obtained.

[0078] The above embodiments are examples illustrating the present invention, and are not intended to limit the scope of the invention to these embodiments. Those skilled in the art can make appropriate modifications without departing from the spirit of the invention.

Claims

1. A drill bit processing device, characterized in that... have: The shaft that causes the drill bit to rotate; A drive mechanism that enables the rotating shaft to move along the axial direction of the rotating shaft; A position detection sensor that detects the position information of the rotating shaft in the axial direction; and A control device controls the rotating shaft and the drive mechanism to perform hole drilling and back drilling on a multilayer printed circuit board with alternating layers of multiple conductor layers and multiple insulating layers. The hole drilling is to form through holes that extend along the stacking direction, and the back drilling is to remove excess portions of the conductive plating applied to the entire area of ​​the through holes. The control device includes: A conductor layer detection unit outputs a detection signal that detects the drill bit contacting the surface of the conductor layer during the hole-making process of forming a detection hole for detecting the conductor layer at a position different from the through hole on the multilayer printed circuit board. The memory unit stores the position information when the detection signal is output; and The depth calculation unit calculates the processing depth of the conductive plating removed by the back drilling process based on the position information stored in the memory unit.

2. The drill bit processing apparatus as described in claim 1, wherein, When the conductor layer detection unit performs the detection hole processing once, it outputs the detection signal each time it contacts the surface of the conductor layer; The memory unit stores the position information corresponding to the plurality of conductor layers.

3. The drill bit processing apparatus as described in claim 1, comprising: A positioning pin, which positions the multilayer printed circuit board by engaging with a positioning hole in the multilayer printed circuit board and grounds the conductor layer; A rotor shaft, electrically connected to the drill bit, and rotating integrally with the drill bit; and The stator induces a shaft voltage on the rotor shaft; The conductor layer detection unit detects the shaft voltage and outputs the detection signal when the rotor shaft is grounded and the shaft voltage becomes 0.

4. The drill bit processing apparatus as described in claim 1, comprising: A positioning pin, which positions the multilayer printed circuit board by engaging with a positioning hole in the multilayer printed circuit board and grounds the conductor layer; A rotor shaft, electrically connected to the drill bit, and rotating integrally with the drill bit; and Electrode components, arranged close to the rotor shaft, constitute a capacitor; The conductor layer detection unit outputs the detection signal when the current flows from the electrode component to the rotor shaft and the electrostatic capacitance accumulated in the capacitor decreases.

5. The drill bit processing apparatus as described in claim 1, wherein, The depth calculation unit Read the connection information of the conductor layers connected by the conductive plating among the plurality of conductor layers. Based on the location information and the connection information, the depth from the upper surface of the multilayer printed circuit board to the uppermost conductor layer connected by the conductive plating is calculated as the processing depth.

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