JP2006043875A - Drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drill capable of preventing a shift in position of an opened hole or formation of an uneven part on an inner wall of the hole. <P>SOLUTION: A torsion angle θ1 of a chip discharge groove 20 of the drill 10 is specified to be 30-50°. Thus, a shift in position of an opened through hole can be reduced. In addition, since drill chips are appropriately discharged, the drill is not interfered with the chips when making an opening, and a printed board excellent in electrical connection and reliability can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drill for a printed wiring board, and more particularly to a drill for a copper-clad laminate in which copper foils on both sides of a resin board constituting a printed wiring board are laminated.

A through hole is formed in order to establish conduction between the front and back of the printed wiring board. As an example, a double-sided copper clad laminate is formed with an opening penetrating with a drill, a conductor layer is formed in the opening by plating or the like, and etching is performed as necessary to form a circuit. Thereby, the printed wiring board which has a conductor circuit and enables conduction | electrical_connection of front and back is manufactured. A plurality of these wiring boards are prepared and a multilayered printed wiring board is obtained through a prepreg. Alternatively, an interlayer insulating layer is formed using a wiring board having a through hole as a core to obtain a multilayered printed wiring board. In recent years, with the demand for higher density of printed wiring boards, it has been studied to further reduce the diameter of through holes.
In order to meet these requirements, a miniaturized drill for opening a small-diameter through hole is required. Such miniaturized drills are disclosed in, for example, Japanese Utility Model Laid-Open No. 7-33514 and Japanese Patent Application Laid-Open No. 2004-82318.
In JP-A-2004-82318, only one chip discharge groove is provided and a drill that is 5/100 or less with respect to the maximum outer diameter of the cutting edge portion is used to increase the rigidity of the drill and obtain good hole accuracy. ing.
Japanese Utility Model Publication No. 7-033514 JP 2004-82318 A JP 2004-34213 A

  However, in the drill of the conventional example, the position accuracy of the hole to be opened may be lowered due to changes in various conditions such as the material of the base material to be opened and the conditions for opening. That is, the position shifts from the desired position. In addition, inadvertent irregularities may be formed in the opened inner wall portion. Therefore, applying a conductor layer in a misaligned opening or an opening with irregularities to form a through hole reduces electrical connectivity and reliability, and performs reliability tests such as heat cycle and high temperature exposure. If done, it may deteriorate early.

  In the drilling with a drill, a plurality of printed wiring boards are overlapped and opened simultaneously in order to increase processing efficiency. It is desirable that the same shape be obtained at the same position regardless of the number of printed wiring boards during simultaneous processing. Although the printed wiring board placed on the upper side can form a relatively good opening, the lower printed wiring board has generated misalignment and unevenness.

In addition, when the drill is used frequently (the number of shots to be opened increases), for example, a drill that is replaced when 6000 holes are drilled, and the defect described from the time when 4500 holes, which are the end of life, were drilled, It appears even more prominently.
Further, as the opening diameter becomes smaller, the frequency of occurrence of the defect has increased particularly when opening with an opening diameter of 400 μm or less.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a drill that does not form a positional deviation in the opened hole or unevenness in the inner wall of the hole. .

  It is another object of the present invention to propose a drill that does not deteriorate the electrical connectivity and reliability without causing problems such as misalignment of the formed through hole even if the frequency of use of the drill is increased.

  As a result of the inventor's diligent research, in order to rotate and open the work piece, in the drill in which the tip blade part and the body chip discharge groove are formed, the body chip discharge groove is continuous, It turned out that it is good to use the drill whose twist angle of the chip | tip discharge groove | channel is 30-50 degrees.

  When a drill having a twist angle in the range of 30 to 50 ° is used, the positional deviation of the open through hole is small. In other words, the hole forming accuracy is improved. Moreover, since the chips of the drill are appropriately discharged, the printed wiring board having excellent electrical connectivity and reliability can be obtained because the chips are not obstructed by the chips when opening. Moreover, since wear of the drill accompanying use can be suppressed, the number of times that the drill can be used can be increased as compared with the conventional case, and the accuracy of the shape and the shape of the hole to be opened is difficult.

  If the drill is obstructed by chips when the drill is opened, the position of the hole is displaced and bumps are formed on the inner wall of the hole. As a result, the electrical connectivity and reliability may be reduced. Since it becomes easy to apply excessive stress to the drill, the wear of the drill is accelerated.

  When the twist angle is less than 30 ° or when the twist angle exceeds 50 °, it becomes difficult to discharge chips. For this reason, the chips obstruct the drilling of the opening by the drill, cause the positional deviation of the hole, or form bumps (unevenness) on the inner wall of the hole, thereby reducing the electrical connectivity and reliability. Further, the wear of the drill progresses due to the chips that are not discharged. For this reason, the drill deteriorates with a small number of uses.

  More preferably, the twist angle is in the range of 35 to 45 °. Within this range, chips can be discharged efficiently regardless of drill opening conditions such as the number of rotations and drill entry speed. For this reason, it is difficult to cause problems such as a positional deviation of the hole and a bump on the inner wall of the hole. Moreover, since the wear of the drill is small, it can be used for a longer period of time, and the accuracy of the opened hole is not reduced.

  The torsion angle refers to the angle at which the body forming the drill and the groove intersect. That is, it means an angle formed by the leading edge and a straight line parallel to the drill axis passing through one point on the leading edge.

The groove in the body portion is for discharging chips such as a base material, and the tip angle of the tip blade portion is preferably 110 to 150 °.
If the tip angle is in the above range, it is difficult to cause positional deviation, and the shape of the hole to be formed is also desired. Even if a plurality of copper-clad laminates are overlapped to form an opening, the upper copper-clad laminate and the lower copper-clad laminate have the same position and shape.
Moreover, even if the number of drills used increases, it becomes difficult to reduce the electrical connectivity and reliability of the through hole.

  If the tip angle of the tip blade portion is less than 110 °, the inner wall of the opened hole is likely to be uneven (uneven). If the unevenness (unevenness) is subjected to a desmear treatment, the unevenness is further promoted, and the width of the unevenness is increased. When a conductor layer is applied to the opened hole and a through hole is formed, unevenness may be caused by the unevenness of the conductor layer. Therefore, electrical characteristics (impedance, through-hole resistance value, etc.) are degraded.

  Further, if the tip angle of the tip blade portion exceeds 150 °, the opened hole is easily displaced from a desired position. In particular, when a plurality of copper-clad laminates are overlaid, the tendency of positional deviation appears more remarkably in the lower copper-clad laminate. For this reason, when the hole is formed as a through hole, the electrical connection with the other conductor layer is lowered. In addition, when a reliability test is performed, deterioration starts early.

  It is more desirable that the tip angle of the tip blade portion is between 120 and 140 °. This is because during this time, it is difficult to cause deformation and displacement of the hole.

  The tip angle of the blade refers to the angle of the gap where there is no metal part formed with a single blade when the drill is viewed from the tip. This means the angle when the cutting edge is projected in parallel to a plane parallel to the axis of the drill.

It is desirable that the second clearance angle of the blade portion at the tip is 30 to 50 °.
As shown in FIG. 2 (A), the tip flank of the drill of the present invention has a multi-step shape composed of a plurality of flat flank surfaces, and is a flat surface from the cutting edge toward the drill rotation direction. Certain first to fourth flank surfaces are sequentially arranged along the circumferential direction. Of these, it is desirable to set the relief angle of the second flank (the angle formed by the cross section perpendicular to the axis and the flank in the outer corner) to 30 to 50 °.

As for a drill, it is desirable for the front-end | tip outer diameter of a blade part to be 350 micrometers or less.
The diameter has an advantage that the hole position accuracy is easily improved, and the hole shape is also desired, so that it is difficult to cause a decrease in electrical connectivity and reliability.

On the other hand, if the outer diameter of the tip exceeds 350 μm, the chip to be discharged becomes large, so that it is difficult to improve the hole position accuracy. In addition, if it is 50 micrometers or less, a drill will be easy to bend and the laser processing has an advantage. Here, as for the diameter of a drill, 50 micrometers-350 micrometers are desirable, and 75 micrometers-300 micrometers are especially suitable.
Also, a drill of 100 μm or less is likely to cause drill breakage with a low frequency of use depending on processing conditions. In this case, while reducing the total thickness at the time of processing by reducing the thickness of the insulating layer of the substrate to be processed and reducing the number of stacked substrates, the above hole position accuracy is ensured. , Can increase the frequency of use.

 In the so-called undercut drill, a neck constricted in a cylindrical shape is formed in the body. A portion from the tip of the blade portion to the neck is referred to as a margin portion. It is desirable that the chip discharge groove formed in the body is on the inner side with respect to the end portion of the margin portion. That is, it is preferable that the chip discharge groove does not reach the neck. In particular, the distance is more desirably 100 μm or more from the end. As a result, chips can be discharged properly and no stress is applied, so that the hole position accuracy and the shape of the hole to be formed are not reduced.

The length of the margin portion indicates the distance from the tip to the neck, that is, the length excluding the length of the neck from the length of the body. The length of the margin part is desirably 0.1 to 0.3 mm. In particular, when the tip outer diameter of the drill is 200 μm or less, the length of the margin portion is more preferably 0.1 to 0.3 mm.
When the length of the margin portion is less than 0.1 mm, a region where a groove for discharging chips is formed becomes small, so that stress is easily applied to the drill. For this reason, since the stress cannot be buffered, the frequency of occurrence of bending or bending of the drill increases. Also, the hole position accuracy may be lowered.

If the length of the margin part exceeds 0.3 mm, the hole position accuracy is lowered.
An undercut type having a neck is suitable for forming a small-diameter hole. That is, it is suitable for opening a hole of 400 μm or less, and more particularly suitable for opening a hole of 200 μm or less.

However, if the undercut type has one groove for discharging chips, it may be difficult to discharge the chips.
That is, if the position where the groove is formed is applied to the neck, it is difficult for chips to be discharged, and an excessive force is applied to the drill itself. Therefore, it becomes easy to cause a decrease in positional accuracy and the shape of the hole to be formed.

As shown in FIG. 18, the printed wiring board drilling apparatus 100 according to the present application includes an XY table 90 on which a copper-clad laminate or a multilayer printed wiring board 60 is placed. The XY table 90 includes a table driving mechanism 114 that can move to the X axis and the Y axis, respectively. Further, a spindle mechanism 106 for rotating the drill 10 and a spindle drive mechanism 112 for driving the spindle mechanism 106 are provided. These spindles 106 are fixed with a single drill discharge groove, and are provided with an opening 66 penetrating the printed wiring board 60 at a rotational speed / feed speed of the drill. These rotational speeds are preferably at least 100 Kprm. More preferably, it is 200 Kprm or more.

The table driving mechanism 114 and the spindle driving mechanism 112 are also driven in accordance with the drilling timing and the exact position of the drilling is adjusted. Interlocking with the computer 110 that accurately controls these is performed. The processing data 108 is input to the computer 110.

As the material of the XY table 90, a material generally used in a processing apparatus can be used. However, it is more desirable to use a material that is not easily affected by heat during processing. The number of the substrates 60 placed on the XY table 90 may be one, or a plurality of two or more substrates are stacked (for example, four substrates are stacked as an example), and drilling is performed. May be. About the number of this board | substrate, it adjusts timely with the shape of a drill, a board | substrate, and the hole to open.

Also, the feed rate of these drills is preferably at least 30 inches / min. More desirable is 40 inches / min or more. The aforementioned rotation speed and feed speed ensure productivity and stabilize the opening shape of the substrate. That is, the connectivity and reliability as a substrate are not easily lowered.

As the drill 10 used in the spindle mechanism 106, it is desirable to use a drill whose twist angle of one discharge groove is 30 to 50 ° in the body. Chips are efficiently discharged. In addition, even when a plurality of substrates are stacked, the problem of hole formation is less likely to occur. In addition, even when a plurality of substrates are stacked, the problem of hole formation is less likely to occur.

The spindle mechanism 106 adjusts the drill rotation speed, and the spindle drive mechanism 112 described above controls the drill feed speed, the drill raising / lowering, the drill movement, etc. in a timely and accurate manner. For this reason, the computer 110 is linked.
A drill having a diameter of 300 μm or less may be used. As a result, a small-diameter hole can be accurately drilled.

The computer 110 that controls the processing apparatus controls the XY table and the spindle and performs drilling to a predetermined position when processing, and in some cases, drives the mechanisms of these processing apparatuses. Control the timing.

The processing apparatus 100 according to the present application includes an XY table 90 on which one or two or more printed circuit boards 60 for punching are stacked, and a spindle mechanism 106 that holds the drill 10 having one groove. A mechanism 112, 114 for driving the XY table 90 or the spindle mechanism 106, and a computer 110 for controlling driving, drilling positioning, and the like are provided.

As other mechanisms, a mechanism for positioning the substrate is provided. This includes a camera 102 that images the positioning mark 61 on the substrate 60, an image processing device 104 that performs image processing on an image captured by the camera 102, and a computer 100 that calculates the position. An accurate machining position is calculated based on the position of the positioning mark 61, and the XY table 90, the spindle mechanism 106, and the like are driven.

Also, a mechanism for counting the number of drilled shots and the like may be provided in order to grasp the drill replacement time. A temperature control device may be provided to keep the inside of the processing device at a constant temperature. It is desirable that the processing equipment should be provided with an enclosure in consideration of the safety aspect that prevents damage to the human body such as bending of the drill and scattering of chips, and the manufacturing aspect of preventing contamination of foreign substances such as dust and temperature management. .

(Drill)
First, the manufacturing process of the drill according to the first embodiment will be described with reference to FIG.
1. Preparation of drill material The metal used in the drill of the present invention is an alloy containing iron, cobalt, nickel and the like. A cylinder 50 in which these metals are equal to or larger than the diameter of the shank of the drill is prepared (FIG. 3A). It is more desirable to use a cemented carbide.

2. Drilling In the prepared cylinder 50, grinding is performed to form the drill body 40 (FIG. 3B). That is, grinding is performed until a desired tip outer diameter is obtained. Thereby, the shank 12 and the body 40 of a drill are comprised. At this time, if necessary, in the body, an undercut drill may be formed by forming a neck (a portion constricted in a cylindrical shape) on a part of the body.

  Next, in the body 40 of the drill, the chip discharge groove 20 for chip discharge is formed in a spiral shape (FIG. 3C). The groove 20 is formed by one, and at this time, the twist angle at the intersection of the groove 20 and the body 40 is set as desired. The angle at this time is more preferably 30 to 50 °. At this time, the interval between the groove 20 and the groove 20 may be uniform, or the groove interval may be gradually changed. This is determined in a timely manner depending on the diameter of the opening and the material used for opening.

  Next, the blade 30 that is the tip of the drill is processed (FIG. 3D). The processing order is not particularly limited, but the first angle and the second clearance angle forming the blade portion are processed, and then each groove portion is ground, and each portion called the clearance angle is flat or conical. The shape is processed. Thereby, the 1-blade drill which consists of the blade part 30, the body 40, and the shank 12, and was formed in the body 40 with one chip discharge groove 20 for chip discharge can be obtained.

FIG. 1 shows a side view of the drill 10, FIG. 2A shows a front view of the tip of the drill, and FIGS. 2B and 2C show enlarged views of the tip of the drill.
As shown in FIG. 1, the tip diameter D1 of the blade part 30 of the drill 10 is set to 0.115 mm, and the diameter D2 of the shank 12 is set to 2 mm. The cutting edge length L1 is set to 1.8 mm, the body length L2 is set to 2.0 mm, the total length is 31.75 mm, the margin length L4 is set to 0.25 mm, and the relief length L5 is set to 1 mm. On the other hand, the twist angle θ1 of the chip discharge groove 20 is set to 40 °.

  The groove width L6 shown in FIG. 2C is set to 0.145 mm. The tip angle θ2 shown in FIG. 2B is set to 150 °.

  As shown in FIG. 2 (A), the tip flank of the drill has a multi-step shape composed of a plurality of flat flank surfaces, and extends from the cutting edge 31 in the drill rotation direction (counterclockwise direction in the figure). The first flank 32A, the second flank 32B, the third flank 32C, and the fourth flank 32D, which are flat surfaces, are sequentially arranged along the circumferential direction. Moreover, the reverse side 1st flank 32E and the reverse 2nd flank 32F which are flat surfaces are arrange | positioned in the axial vicinity. Adjacent to the fourth flank 32D and the reverse second flank 32F, a second picking surface 33 having a substantially arc-shaped cross section is provided. The clearance angle of the first flank 32A is set to 10 °, and the clearance angle of the second flank 32B is set to 40 °.

(Drilling method of printed wiring board)
1. Copper-clad laminate As an insulating base material to be opened with the drill of the present invention, any organic insulating base material can be used. Specifically, an aramid nonwoven fabric-epoxy resin base material, a glass cloth epoxy resin base material , Aramid nonwoven fabric-polyimide substrate, glass cloth bismaleimide triazine resin substrate, glass cloth polyphenylene ether resin substrate, rigid (hard) laminated substrate selected from FR-4, FR-5, or polyphenylene ether (PPE) ) It is desirable to be one kind selected from a flexible substrate made of a film such as a film or polyimide (PI).

  The insulating resin base material has a thickness of 10 to 800 μm, preferably 20 to 400 μm, and most preferably 50 to 300 μm. This is because if the thickness is smaller than these ranges, the strength is reduced and handling becomes difficult, and if it is too thick, formation of a small-diameter through hole and formation of a conductor layer are difficult.

The thickness of the copper foil of the insulating substrate is 5 to 50 μm, preferably 8 to 30 μm, and more preferably 12 to 25 μm. The reason is that, when forming a through-hole with a small diameter by drilling, if it is too thin, the pattern formation is inhibited. Conversely, if it is too thick, it is difficult to form a fine pattern by etching.
Those prepared as a single-sided or double-sided copper-clad laminate are used.

2. Processing conditions In order to perform processing with the drill 10, as shown in FIG. 6, on the XY table 90, a backing plate (bake plate) 92 larger than the laminated plate for processing is placed, and on that, One or a plurality of single-sided or double-sided copper-clad laminates 60 are stacked. On top of that, if necessary, an entry sheet 94 in which a swelling layer is impregnated with acrylic and a metal layer such as aluminum is provided on the surface layer may be placed on the copper clad laminate and processed. . The swelling agent in the entry sheet 94 serves as a lubricant when the drill is opened.

At this time, as drilling conditions,
Rotational speed: 100-500krpm
Feed rate: 30-200 inch / min.
It is desirable to use up to 2000 shots or more.

Here, if the rotational speed is less than 100 krpm, the processing cannot be performed efficiently. On the other hand, if the rotational speed exceeds 500 krpm, the life is shortened due to the heat generated by the drill.
If the feed rate is less than 30 inch / min., It cannot be efficiently processed. On the other hand, when the feed speed exceeds 200 inches / min., The load on the drill increases and the breakage tends to occur.
In particular, a rotational speed of 100 to 300 krpm and a feed rate of 40 to 120 inch / min. Are more desirable from the viewpoint of processing efficiency and drill life.

  A substrate on which through holes, lands of through holes and conductor circuits are formed is formed on a copper clad laminate having a drill opened by a sub-tracing method or tenting method.

  Further, in order to make a multilayer, substrates may be laminated by a press method or the like, or a substrate on which the through hole is formed may be used as a core substrate to be multilayered by an additive method.

[Example 1]
1. Preparation of drill material Prepare a metal made of an alloy such as iron or cobalt. This was made thicker than the diameter of the drill that forms a circle, and prepared according to the diameter of the processing device that rotates the drill.

2. Drilling First, the part that forms the body of the drill is processed. Thereby, the shank and body part of the drill are formed. At this time, the outer diameter of the tip of the blade portion for the body is adjusted to a preset diameter.
Thereafter, one chip discharge groove is formed to discharge the chips. At this time, the twist angle of the drill is set to be a preset angle.
Then, in order to form a single blade, the first angle and the second clearance angle are formed, and then the respective clearance angles are formed. Created a drill. In Example 1, as shown to FIG. 4 (A), the straight type drill without an undercut was used.

3. Drilling (1) Drilling Double-sided copper-clad laminate (material: glass epoxy resin or polyimide resin: thickness of insulating layer 62: 200 μm; thickness of copper foil 64 on one side: 12 μm) 60 shown in FIG. As shown in FIG. 6, four sheets were stacked on an XY table 90 for drilling in a drilling device (product number: ND-N series manufactured by Hitachi Via). A discard board (backup board) 92 was placed below the double-sided copper-clad laminate 60. An entry sheet 94 for drilling was placed on the upper side of the double-sided copper-clad laminate 60.
In that state, an opening with an opening diameter of 100 μm was performed under the drill conditions shown below. At this time, every time four sheets were processed, the number of drill shots was converted to 1 Shot.

<Drilling conditions>
Rotation speed: 160krpm
Feeding speed: 40inch / min.
Drill shape: Drills shown in Table 1 Number of evaluation shots 3000 Shot 6000 Shot
Thus, a through hole 66 having an opening diameter of 100 μm was provided in the substrate 60 (see FIG. 5B).
After drilling, the double-sided copper-clad laminate was desmeared with permanganic acid or the like.

4). A conductor-forming electroless plating film 66 and an electrolytic plating film 68 in the through hole were provided in this order, and a conductor layer was formed on the inner wall of the through-hole 66 and the surface layer of the laminated plate 60 (see FIG. 5C). The plating conditions at this time were as follows.
Electroless plating (electrolytic copper plating aqueous solution)
NiSO ₄ : 0.003 mol / l
Tartaric acid: 0.200 mol / l
Copper sulfate: 0.030 mol / l
NaOH: 0.050 mol / l
α, α′-bibilidyl: 100 mg / l
Polyethylene glycol: 0.10 g / l

[Electroless plating conditions]
It was immersed for 40 minutes at a liquid temperature of 50 ° C.
Electrolytic plating (electrolytic copper plating aqueous solution)
Sulfuric acid: 160 g / l
Copper sulfate: 77 g / l
Additive (product name: Kaparaside GL, manufactured by Atotech Japan)
: 1 ml / l
[Electrolytic plating conditions]
Current density: ² A / dm 2
Time: 30 minutes Temperature: 25 ° C

5. Circuit formation An etching resist is formed on the conductor layer, a mask on which wiring is drawn is placed, and exposure and development are performed. Thereby, a through hole (including land) and a conductor circuit are formed by the resist. Thereafter, the resist non-formation portion was etched with an etching solution such as sulfuric acid, and the etching resist was peeled off. Thereby, the through hole, the land of the through hole 72, and the conductor circuit 74 were formed (see FIG. 5D).

6). Filling Through Holes Through holes 72 were filled by printing using a thermosetting resin or a photocurable resin as the hole filling resin 76 (see FIG. 5E). At this time, a mask having an opening in the through hole portion may be used. After filling a hole-filling resin excessively with respect to the through-hole and semi-curing or curing, grinding was performed to smooth the substrate surface. Thereby, the through hole was filled and a smoothed substrate was obtained.

7). Formation of Solder Resist Layer A solder resist 76 was formed on both surfaces of the substrate 60 with openings corresponding to the terminals of the portion to be subjected to the continuity test.

[Example 2]
Example 2 and Reference Example 2 were substantially the same as Example 1, but the drills used for drilling were those shown in Table 2.

[Example 3]
Example 3 and Reference Example 3 were almost the same as Example 1, but the drills used for drilling were those shown in Table 3.

[Example 4]
Example 4 and Reference Example 4 were almost the same as Example 1, but the drills used for drilling were those shown in Table 4.

[Example 5]
Example 5 and Reference Example 5 were substantially the same as Example 1, but the drills used for drilling were those shown in Table 5.

[Example 6]
Example 6 and Reference Example 6 are substantially the same as Example 1, except that the drill used for drilling is an undercut type provided with a neck 42 as shown in FIG. 6 was performed.

[Example 7]
Example 7 and Reference Example 7 were almost the same as Example 1, but the drills used for drilling were those shown in Table 7.

[Example 8]
Example 8 and Reference Example 8 were almost the same as Example 1, but the drill used for drilling was of the undercut type, and the one shown in Table 8 was used.

[Example 9]
Example 9 and Reference Example 9 were almost the same as Example 1, but the drill used for drilling was performed with the tip outer diameter shown in Table 9.
In Example 9, the drill having a tip outer diameter of 100 μm or less was evaluated in the same manner by drilling two or three double-sided copper-clad laminates.

[Comparative example]
The comparative example is almost the same as in Example 1, but the drill used for drilling was the one shown in Table 10.

<Evaluation items>
(1) Hole Position Accuracy Number of Shots 3000Shot 6000Shot was evaluated for the positions where through holes are formed. That is, the positional deviation distance of the center point of the through hole formed at the center portion with the land was compared.
○: Position deviation range within 35 μm △: Position deviation range within 50 μm ×: Position deviation range over 50 μm

(2) Number of cross-sectional shots of through-holes Cross-cuts were made on the cross-sections of through-holes in 3000 Shots and 6000 Shots, and the presence or absence of irregularities on the side surfaces of the conductor layers was examined.
◯: Maximum height of irregularities in opening is within 8 μm △: Maximum height of irregularities in opening is within 10 μm ×: Maximum height of irregularities in opening is over 10 μm

(3) Conductivity measurement of through hole The presence / absence of conduction on both sides of the through hole in the number of shots 3000 Shot 6000 Shot was confirmed.
○: Conduction ×: Conduction abnormality

(4) Reliability test The heat cycle test (125 ° C / 3min.６５-65 ° C / 3min.) Is taken as one cycle, and repeated until the number of cycles where continuity abnormality is confirmed, and reliability is evaluated by continuity tests such as disconnection. went. The maximum cycle was 3000. A continuity test was performed every 1500 cycles, 2000 cycles, and 3000 cycles.
Those that cleared 2500 cycles did not cause any problems in practical use.

(5) Evaluation of drill breakage About Example 9 and Comparative Example 9, the presence or absence of breakage of the drill in 1000 Shot 3000 Shot 6000 Shot (○: no breakage ×: with breakage) was evaluated. Moreover, when the tip outer diameter of the drill in Example 9 was 100 μm or less, the same evaluation was performed when the number of stacked sheets was 3 or 2.

  Here, the evaluation results of Example 1 and Reference Example 1 are shown in FIG. 7, the evaluation results of Example 2 and Reference Example 2 are shown in FIG. 8, the evaluation results of Example 3 and Reference Example 3 are shown in FIG. 10 and FIG. 11 show the evaluation results of Example 4 and Reference Example 4, FIG. 11 shows the evaluation results of Example 5 and Reference Example 5, FIG. 12 shows the evaluation results of Example 6 and Reference Example 6, and Example 7 and Reference Example 7 FIG. 13 shows the evaluation results of Example 8, FIG. 14 shows the evaluation results of Example 8 and Reference Example 8, FIG. 15 shows the evaluation results of Example 9 and Reference Example 9, and FIG. 15 shows the damage results of Example 9 and Reference Example 9. 16 shows the evaluation results of the comparative example.

  From the above evaluation results, it can be seen that when the twist angle of the chip discharge groove of the drill is in the range of 30 to 50 °, the positional deviation of the opening through hole is small. In addition, it was found that the number of usable times can be increased, and it is difficult to reduce the accuracy and shape of the opening hole.

  When the twist angle is less than 30 ° or when the twist angle exceeds 50 °, the electrical connectivity and reliability are deteriorated. It was also found that the drill deteriorates with a small number of uses.

  More preferably, the twist angle is in the range of 35 to 45 °. If it is this range, it is possible to use it for a longer period, and it does not cause the fall of the precision of the opened hole.

  It is desirable that the tip angle of the tip blade portion is 110 to 150 °. Misalignment is less likely to occur, and the shape of the hole formed is also desired. Moreover, even if the number of drills used increases, it becomes difficult to reduce the electrical connectivity and reliability of the through hole.

  When the tip angle of the tip blade portion is less than 110 °, the electrical characteristics and reliability are deteriorated. On the other hand, when the tip angle of the blade portion at the tip exceeds 150 °, the opened hole is easily displaced from a desired position. For this reason, when the hole is formed as a through hole, the electrical connection with the other conductor layer is lowered. In addition, when a reliability test is performed, deterioration starts early.

  It has been found that if the tip angle of the blade portion at the tip is between 120 and 140 °, it is particularly difficult to cause positional deviation. It has also been found that the reliability does not decrease when the second clearance angle of the blade at the tip is in the range of 30 to 50 °.

  It can be said that when the tip outer diameter of the drill is between 100 μm and 350 μm, it is not damaged and does not have much influence on the printed wiring board. The number of stacked sheets could be used without any particular limitation. If it is less than 100 μm, the frequency of breakage also increased. However, it was confirmed that it can be used even in a large number of shots by changing processing conditions such as limiting the number of stacked sheets. However, it was confirmed that the thickness is not limited to 50 μm or less.

  In the embodiment described above, an example was given in which a drill was used for drilling a copper-clad laminate for printed wiring boards, but the drill of the present application is suitably used for drilling laminates of various resins and metals. To get.

It is a side view of the drill which concerns on embodiment of this invention. 2A is a front view of the tip side of the drill in FIG. 1, and FIGS. 2B and 2C are enlarged views of the tip portion of the drill. It is explanatory drawing of the manufacturing process of a drill. FIG. 4A is a side view showing a straight type drill, and FIG. 4B is a side view showing an undercut type drill. It is explanatory drawing of the manufacturing process of a printed wiring board. It is explanatory drawing of the drilling of the through-hole to a copper clad laminated board. 5 is a chart showing evaluation results of Example 1 and Reference Example 1. 6 is a chart showing evaluation results of Example 2 and Reference Example 2. 6 is a chart showing evaluation results of Example 3 and Reference Example 3. 10 is a chart showing evaluation results of Example 4 and Reference Example 4. 6 is a chart showing evaluation results of Example 5 and Reference Example 5. It is a graph which shows the evaluation result of Example 6 and Reference Example 6. 6 is a chart showing evaluation results of Example 7 and Reference Example 7. It is a graph which shows the evaluation result of Example 8 and Reference Example 8. It is a graph which shows the evaluation result of Example 9 and Reference Example 9. It is a graph which shows the damage result of Example 9 and Reference Example 9. It is a graph which shows the evaluation result of a comparative example. It is a block diagram of the processing apparatus for drilling of the printed wiring board which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drill 12 Shank 30 Blade part 31 Cutting edge 32A 1st flank 32B 2nd flank 32C 3rd flank 32D 4th flank 32E Reverse side 1st flank 32F Reverse 2nd flank 33 Second picking surface (theta) 1 Twist angle θ2 Tip angle

Claims (6)

In order to drill an opening in a copper-clad laminate with a plurality of layers, in a drill in which a chip discharge groove is formed in the blade part at the tip and the body,
The body has a single chip discharge groove,
The drill characterized by the twist angle of the chip discharge groove being 30 to 50 °. The drill according to claim 1, wherein a tip angle of the blade portion at the tip is 110 to 150 °. The drill according to claim 1 or 2, wherein a second clearance angle of the blade portion of the tip portion is 30 to 50 °. The drill according to any one of claims 1 to 3, wherein a tip outer diameter of the blade portion is 350 µm or less. The drill is an undercut drill with a neck,
The drill according to claim 1, wherein the chip discharge groove does not reach the neck. 6. The drill according to claim 5, wherein a length obtained by subtracting the length of the neck from the length of the body is 0.1 to 0.3 mm.

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