CN103987195A - Hole drilling method for printed circuit boards - Google Patents

Abstract

A hole-drilling method for a printed substrate, which can efficiently utilize a laser and a drill without being limited to the number of overlapping substrates, and perform hole-drilling with high precision, convenience, and efficiency. In this method, after the process (S10) of forming a peripheral hole (2) for positioning and fixing at a predetermined position on the peripheral portion of the substrate (1), laser light is used at a predetermined position outside the peripheral portion. A step of processing the blind hole (5) on the substrate (1) (S20). Next, each substrate (1) processed with blind holes is alternately stacked to form a workpiece (W) of a superimposed body, and a lamination pin is inserted into a peripheral hole (2) of the workpiece (W) of a superimposed body, and each substrate ( 1) After the process (S30) of stacking and concentrating (workpiece (W)), perform a drill with a diameter (representing the diameter of the hole on the entrance side of the blind hole (5)) larger than the diameter of the blind hole (5) to the workpiece ( W) A step of processing through holes (S40).

Description

Hole drilling method for printed circuit boards

The patent application for the present invention is a divisional application of the patent application for invention with the application number 201010217581.6 and the name "Method for Perforating Printed Substrates".

technical field

The present invention relates to a method of drilling holes in a printed wiring board (hereinafter referred to as "printed board") for drilling holes with high precision and efficiency.

Background technique

Now, when electrically connecting the conductive layers arranged on the front and back sides with an insulator sandwiched between the printed board, holes for connecting to the front and back conductive layers (hereinafter referred to as connection holes) are opened in the printed board, Conductive plating is applied to the inside of the connection hole to electrically connect the positive and negative conductive layers. With recent miniaturization and high-density mounting of electronic devices, the diameter of connection holes on printed circuit boards mounted on electronic devices has been in the size range of about 0.15 to 0.08 mm. Such connection holes are usually drilled or laser drilled.

Fig. 7 is the explanatory drawing of the workpiece when adopting drill bit to carry out the processing of connecting hole with prior art, Fig. 7 (a) is the top view of this workpiece, Fig. 7 (b) is the side view of this workpiece, Fig. 7 (c) is A partial enlarged view of the region A of Fig. 7(b).

Referring to FIGS. 7( a ) to 7 ( c ), in this printed circuit board 1 , the conductive layer 1 a is arranged on the front side and the conductive layer 1 b is arranged on the back side so as to sandwich the insulating layer 1 z. The insulating layer 1z is made of resin 1j and glass fiber 1g. When using a drill to process the connection holes of the printed circuit board 1 , in order to improve the processing efficiency, it is common practice to perform drilling processing on a superimposed body of multiple printed circuit boards 1 . In addition, the connecting hole at the time of drilling with a drill is a through hole (through hole).

When drilling a through hole, the peripheral hole 2 for positioning and fixing is processed at a predetermined position on the peripheral portion of the printed circuit board 1, and the lamination pin 3 is inserted into a stacked body in which a plurality of printed circuit boards 1 are stacked. (Japanese: stockpin). Usually, the cross-sectional shape of the peripheral hole 2 in the direction of the board surface is circular, and in order to prevent the overlapping printed circuit boards 1 from shifting each other, each printed circuit board 1 is provided with two or more places (in this case, two places) Peripheral hole 2. In addition, the outer diameter of the lamination pin 3 is slightly larger than the diameter of the peripheral hole 2. If the lamination pin 3 is inserted into the peripheral hole 2 and engaged with them, it is possible to fabricate a printed circuit board 1 with a plurality of laminated sheets 1 (eight in this case). Zhang) formed by overlapping body as a workpiece W. As is well known, the lamination pin 3 also functions as a positioning pin for positioning the workpiece W on the machining table (for example, refer to Patent Document 1).

If the processing of opening a through hole is carried out with a drill bit as described above, since the surface roughness of the inner wall of the hole can be set as 2 μm or less, a plated layer with a uniform thickness can be formed when the conductive plating layer is electroplated on the inner wall of the hole, and can be The conductor layer 1a is reliably electrically connected to the conductor layer 1b.

Fig. 8 is an explanatory view of the workpiece when the laser is used to process the connection hole in the prior art, Fig. 8(a) is a top view of the workpiece, and Fig. 8(b) is a partial enlargement of the B region of Fig. 8(a) picture.

If referring to Fig. 8 (a), Fig. 8 (b), then when carrying out the processing of connection hole with laser, form the blind hole 5 (Japanese: bottom) that arrives at the surface of conductor layer 1b from conductor layer 1a on single printed substrate 1 pay ki point). When processing blind holes, the printed circuit boards 1 are processed one by one, but as we all know, since the time required to process one hole is about 10 to 100 times shorter than that of processing with a drill, there is no advantage in processing speed (processing time). Problems occur (for example, refer to Patent Document 2). However, when processing with a laser, as shown in Figure 8(b), the shape of the blind hole 5 is a truncated cone due to the conical shape in the axial direction (due to the energy distribution of the laser beam), and the diameter of the hole bottom is much larger than that of the truncated hole. smaller than the diameter of the hole on the inlet side.

In addition, the case where the peripheral hole 2 is provided on the printed circuit board 1 is also exemplified here. However, when processing the connection hole with a laser, due to the difference between the printed circuit boards 1 when a plurality of printed circuit boards 1 are stacked to form a superimposed body, There is no need to take countermeasures against the deviation, so the printed circuit board 1 may be positioned on the table by other methods such as setting a positioning mark instead of providing the peripheral hole 2 .

Patent Document 1: Japanese Patent Laid-Open No. 63-306847

Patent Document 2: Japanese Patent Laid-Open No. 2002-335063

FIG. 9 is a partially enlarged cross-sectional view of main parts when a through-hole is processed on a workpiece W of a superimposed body using a conventional drill.

If referring to Fig. 9, when the workpiece W of the superimposed body is drilled with a drill bit, the axes L and N of the through hole 4 as the target object will be opposite to each other in the middle due to the rigidity of the superimposed body during the drilling process. A straight line perpendicular to the surface of the printed circuit board 1 is inclined (not shown), or curved from the middle as shown in the drawing. In this state, the accuracy of the hole positions of the through-holes 4 in the lower printed circuit board 1 may be lowered and the allowable value may not be satisfied. Therefore, generally, the number of laminated printed circuit boards 1 of the laminated body is reduced, and the drilling process is performed. For example, in the case of the example shown in FIG. 9 , in order to improve the accuracy of the hole positions of the through holes 4 , it can be seen that the number of superimposed printed circuit boards 1 in the superimposed body should be controlled to four or less.

Specifically, as the printed circuit board 1, the copper foils of the surface layer and the back layer sandwiching the glass fiber-doped resin layer are each 18 μm, and when it is assumed that the printed circuit board 1 with a plate thickness of 0.1 mm is opened, the diameter is 0.1 mm. When processing the through-holes 4, if it is desired to control the accuracy of the hole position of the lowermost through-holes 4 to ±30 μm, overlapping four sheets is the limit.

In short, in conventional hole drilling using a drill, there is a problem that efficient hole drilling cannot be performed because it is necessary to control the number of stacked printed circuit boards in order to maintain hole processing accuracy.

FIG. 10 is an enlarged cross-sectional view of main parts in the thickness direction of a workpiece (printed substrate 1 ) when processing connection holes with a laser in the prior art.

Referring to Figure 10, when using a laser to open a connecting hole, the time required to process one hole is much shorter than when processing a hole with a drill, but if the energy intensity of the laser is set to be able to cut 1g of glass fiber If the value is smaller, the resin 1j will be melted excessively, which will not only deteriorate the surface roughness of the inner wall of the blind hole 5, but also cause the glass fiber 1g to protrude from the inner wall of the blind hole 5 in some cases. If the surface roughness of the inner wall of the blind hole 5 is deteriorated as described above, the thickness of the plating layer formed in the electroplating process of the conductive plating layer will vary, thereby reducing the reliability of the electrical connection between the conductor layer 1a and the conductor layer 1b. reduce.

In short, in conventional laser drilling, since it is necessary to strictly manage the set value of the laser energy intensity in order to maintain the machining accuracy of the hole, there is a problem that the drilling cannot be performed conveniently.

Contents of the invention

The present invention was invented to solve the above problems, and its technical problem is to provide a method that can effectively utilize lasers and drills without being limited to the number of overlapping sheets of substrates and perform hole drilling with high precision, convenience, and efficiency, and A hole-drilling method for a printed circuit board that can maintain the surface roughness of the inner wall of the hole well.

In order to solve the above-mentioned technical problems, the hole processing process of the printed substrate of the present invention adopts laser to process the holes on the printed substrate; stacks a plurality of the above-mentioned printed substrates processed with the above-mentioned holes; The drill bit further processes the above-mentioned holes of the above-mentioned printed substrates laminated in multiple sheets to process a hole with a desired diameter on the printed substrate. The printed circuit boards processed with holes were stacked alternately so that the printed circuit boards processed with holes by laser were located on the upper side.

According to the present invention, since the laser and the drill can be effectively used without being limited by the number of overlapping substrates, the drilling process can be performed with high precision, convenience, and high efficiency, and the surface roughness of the inner wall of the hole can be maintained well, so it can Improves the reliability of finishing when electroconductive plating is performed on the surface of the inner wall of the hole. That is, since there is a sequence of forming through-holes targeting each blind hole with a drill for the superimposed body stacked after forming blind holes on each printed board by laser, although the number of steps is smaller than that of the known method Although it has increased a little, the accuracy of the hole position can be maintained well even if the number of overlapping layers of the substrate is more than twice that of the conventional case in the drilling process using a drill, so the total required for the drilling process is only slightly increased. Time, is advantageous in industry.

Description of drawings

FIG. 1 is a flow chart showing the overall processing procedure of a method of drilling a printed circuit board according to Embodiment 1 of the present invention.

Fig. 2 is an explanatory view of the workpiece in the first half of the process of processing the connection hole with laser in the processing sequence illustrated in Fig. 1, Fig. 2(a) is a top view of the workpiece, and Fig. 2(b) is a side view of the workpiece , FIG. 2(c) is a partially enlarged view of the C region of FIG. 2(b).

Fig. 3 is an enlarged cross-sectional view of the main part of the workpiece in the plate thickness direction when the drill bit is used in the second half of the process of processing the connection hole described in Fig. 1. Fig. 3(a) is a diagram when one through hole is formed, FIG. 3( b ) is a view after forming two through holes.

4 is an enlarged cross-sectional view of a main part in the plate thickness direction showing a basic structure of a first modification example of a workpiece of a superimposed body to which the processing procedure described in FIG. 1 is applicable.

5 is an enlarged cross-sectional view of a main part in the plate thickness direction showing a basic structure of a second modified example of a workpiece of a superimposed body to which the processing procedure described in FIG. 1 is applicable.

6 is an enlarged cross-sectional view of a main part in the plate thickness direction showing a basic structure of a third modified example of a workpiece of a superimposed body to which the processing procedure described in FIG. 1 is applicable.

Fig. 7 is the explanatory drawing of the workpiece when adopting drill bit to carry out the processing of connecting hole with prior art, Fig. 7 (a) is the top view of this workpiece, Fig. 7 (b) is the side view of this workpiece, Fig. 7 (c) is A partial enlarged view of the region A of Fig. 7(b).

Fig. 8 is an explanatory view of the workpiece when the laser is used to process the connection hole in the prior art, Fig. 8(a) is a top view of the workpiece, and Fig. 8(b) is a partial enlargement of the B region of Fig. 8(a) picture.

Fig. 9 is a partially enlarged cross-sectional view of main parts when using a drill bit to process a through hole in a workpiece of a superimposed body in the prior art.

Fig. 10 is an enlarged cross-sectional view of the main part in the thickness direction of the workpiece when laser is used to process connection holes in the prior art.

(Symbol Description)

1, 11, 12 printed substrates

2 peripheral holes

3 Lamination Pins

4 through holes (through holes)

5 blind holes

5a, 5a' through hole

W, W1～W3 workpiece

Detailed ways

Hereinafter, the method of drilling a printed circuit board according to the present invention will be described in detail with reference to the drawings.

Example 1

FIG. 1 is a flow chart showing the overall processing procedure of the method of drilling a printed circuit board 1 according to Embodiment 1 of the present invention.

In this processing sequence, first, before using the laser beam of the laser processing machine to perform hole processing on the printed circuit board 1 having the same structure as that described in FIGS. The process of forming a peripheral hole 2 for positioning and fixing by using a drill bit at a predetermined position on the peripheral portion of 1. This is a step of processing the (peripheral) hole 2 on the printed circuit board 1 (step S10 ). In addition, this process is a preparatory process before carrying out the following 1st process.

Next, a first step of processing a hole from the conductor layer 1a to the surface of the conductor layer 1b at a predetermined position of the printed circuit board 1 using a laser is performed. However, in the first step, the blind holes 5 are formed in the printed circuit board 1 by hole processing using a laser. (In this example, the blind hole 5 is in the shape of a truncated cone.) This is a step of processing the blind hole 5 on the printed circuit board 1 with a laser (step S20). In addition, it is practical to make the diameter of the blind hole 5 (indicating the diameter of the hole on the inlet side of the blind hole 5 ) about 20 to 30 μm smaller than the diameter of the designated connection hole as the target. Moreover, when positioning the printed circuit board 1 on the table of a laser processing machine, or when performing processing, processing can be performed using the peripheral edge hole 2 as a reference.

Next, a second step of forming a superimposed body by stacking a plurality of printed circuit boards 1 that have undergone hole processing in a state aligned with the axial direction of blind holes 5 is carried out. However, in the second process, the side of the printed circuit board 1 that does not expose the blind hole 5 and the side that exposes the blind hole 5 are abutted with each other (that is, the surface and the back surface of the printed circuit board after hole processing A step in which the overlapping workpieces W are overlapped with each other, and the positional displacement of each printed circuit board 1 is prevented by inserting lamination pins into the peripheral holes 2 of the overlapping workpieces W. This is a step of stacking and gathering a plurality of printed circuit boards 1 (work W) (step S30).

Next, by using a drill whose nominal diameter is larger than the diameter of the blind holes 5, the blind holes 5 on each printed substrate 1 of the stack are drilled in such a manner that they penetrate the blind holes 5 in the axial direction, Thereby, a third process of forming a through hole (through hole) having a diameter of a drill bit in the stacked body. This is a step of processing a through hole in the workpiece W with a drill (step S40 ). In addition, as the drill to be used, in order to improve the accuracy of the hole position of the through hole (through hole), it is desirable to use a drill with a tip angle of 110 degrees or less.

The processing procedure of the hole drilling process of the printed circuit board 1 (work W of the laminated body) is completed here, but a conductive plated layer is formed on the surface of the inner wall of the through hole (through hole) by electroplating.

FIG. 2 is an explanatory view of the workpiece W in the first half of the process of processing the connection hole with laser in the processing sequence here. FIG. 2( a ) is a top view of the workpiece W, and FIG. 2( b ) is a side view of the workpiece W. , FIG. 2(c) is a partially enlarged view of the C region of FIG. 2(b).

Referring to FIG. 2( a ) and FIG. 2( b ), it can be seen that a stacked body is formed by stacking a plurality of printed circuit boards 1 and inserting the lamination pins 3 into the peripheral holes 2 . When the laser is used for hole processing in the above-mentioned first process, since the positioning accuracy of the blind holes 5 is about ±10 μm, as shown in FIG. The axis and the stacking direction (direction perpendicular to the printed circuit board) are approximately in a straight line. In any case, the workpiece W of the superimposed body of the respective printed circuit boards 1 integrally structured by the lamination pins 3 is the target of the drilling process using the drill in the third step.

Fig. 3 is an enlarged cross-sectional view of the main part of the workpiece in the plate thickness direction when the drill bit 6 is used in the second half of the process of processing the connection hole in the above-mentioned processing sequence, and Fig. 3 (a) is when one through hole (through hole 4) is formed FIG. 3( b ) is a view after forming two through holes (through holes 4 ).

Here, in the above-mentioned third step, the form in which the through-hole 4 is processed on the workpiece W by the drill 6 having a bore diameter equal to the diameter of the connection hole whose nominal diameter is specified is shown. If referring to Fig. 3 (a), then, because the drill bit 6 perforates along the axis direction of the blind hole 5 processed on each printed circuit board 1, even when carrying out the processing of the printed circuit board 1 of the lowest layer, there is almost no hole on the drill bit 6. Bending occurs.

In this example, although the surface and the back surface of the printed circuit board after hole processing are stacked in such a way as to butt against each other, it is not limited to this, and when the holes processed by laser are symmetrical to the peripheral holes for positioning and fixing, it is also possible to The printed circuit board after the hole processing was bonded alternately between the front and the front, and the back and the back. However, in the latter case, since the thickness of the conductive layer without openings becomes substantially thicker, the hole position accuracy may be lowered.

In addition, the axis of the through hole 4 and the axis of the blind hole 5 may not necessarily be coaxial due to the deviation of the position of the blind hole 5 and the positioning of the axis of the drill bit 6 (permissible range of about ±10 μm). However, even when the deviation between the axis of the through hole 4 and the axis of the blind hole 5 increases (for example, when the cross-sectional shape in the horizontal plane direction is a tumbler shape (Japanese: Daruma shape)) or a part of the inner wall of the blind hole 5 is not processed If it remains, since the surface roughness of the inner wall of the through-hole 4 is formed small, it will not become a defective product, and a highly reliable plating layer can be formed in the electroplating process of the conductive plating layer.

(Modification 1)

4 is an enlarged cross-sectional view of a main part in the plate thickness direction showing the basic structure of a first modification example of a workpiece of a superimposed body that can be applied in the above-mentioned processing procedure.

As shown in FIG. 4 , the workpiece W1 of the superimposed body here is a printed circuit board 1 on which a blind hole 5 has been processed by a laser and a printed circuit board 1 not processed by a blind hole 5 in the previous first process. It is a structure in which printed circuit boards processed with blind holes 5 are arranged on top of each other and are sequentially stacked. Even if such a workpiece W1 is targeted, as in the case of the first embodiment, the drilling process of the through hole 4 can be performed using the drill 6 in the third step. At this time, since the processing time of the blind hole 5 in the first step can be reduced by half compared with the case where the blind hole 5 is processed for all the printed circuit boards 1 as in the workpiece W as the target in Example 1, Therefore, the processing efficiency up to the formation of the through hole 4 can be improved.

(Modification 2)

5 is an enlarged cross-sectional view of a main part in the plate thickness direction showing a basic structure of a second modified example of a superimposed workpiece W2 that can be applied in the above-mentioned processing procedure.

As shown in FIG. 5 , the workpiece W2 of the superimposed body here has a structure in which truncated conical through-holes 5 a are formed on each printed board 11 by laser and then stacked instead of blind holes 5 a formed on each printed board 1 in Example 1. Hole 5. That is, the through-holes 5a of the printed circuit boards 11 of the workpiece W2 are concentrated on the upper side on the entrance side (large diameter portion in the example of FIG. 5 ) and concentrated on the exit side (small diameter portion in the example of FIG. 5 ). The form that each concentrates on the lower side.

If the workpiece W2 with such a structure is used as an object, the efficiency of drilling the through hole 4 using the drill 6 in the third step can be improved more than in the case of Example 1. The through-holes 4 can be easily formed in the number of sheets.

(Modification 3)

FIG. 6 is an enlarged cross-sectional view of main parts in the plate thickness direction showing the basic structure of a third modification example of a stacked body workpiece W3 that can be applied in the above-mentioned processing procedure.

As shown in FIG. 6, the workpiece W3 of the stacked body here uses a printed circuit board 11 formed in Modification 2 as a core layer (Japanese: コアア layer), and one main surface side is configured as a core layer on both sides. The printed circuit board 12 of the insulating layer (composite layer (Japanese: ビルドパププ layer)) is a laminated substrate in which the conductive layer and the insulating layer are laminated and bonded in such a manner that they are in contact with each other. However, through-holes 5a' are formed in each assembly layer 12 here by using a laser in the first step. In the example of FIG. 6 , a laser is used to drill holes from the conductor layer side of each composite layer 12 , but the present invention is not limited to this, and blind holes may be formed from the insulating layer side of each composite layer 12 using a laser.

Even if the workpiece W3 having such a structure is used as the target, the efficiency of drilling the through hole 4 using the drill 6 in the third step can be improved more than that of the first embodiment, so even if the number of layers of the printed circuit boards 12 is further increased, The through-holes 4 can be easily formed in the number of sheets.

Claims (1)

1. A hole processing method for a printed substrate, Use laser to process holes on the printed substrate; stacking a plurality of printed substrates processed with the holes; further processing the holes of the laminated printed substrates by using a drill having a diameter larger than that of the holes to process holes having a desired diameter on the printed substrates, It is characterized in that, The printed boards processed with laser holes and the printed boards without holes were alternately laminated so that the printed boards processed with laser holes were located on the upper side.