PCB drilling and vias

2019-11-18 17:21Writer: qyadminReading:

PCB drilling guide


1. The role of drilling process

Used for PCB hole for plug-in and conduction operation.

2. pcb drill bit Process includes:

Feeding- Needle drill set - -high speed Drilling –Inspection- Delivery

3. Environmental requirements for PCB Drill:

Temperature: 20 + 2 C, Relative humidity: 50 + 5%

4. Main materials for drilling:


4.1 Backup board (2.5mm):


4.1.1 Function:

a. Prevent damage to 
micro drill bed;
B. Reduce drill burrs;
C. Reduce bit twisting;
D. Reducing drill temperature;
E. Clean the glue residue in the groove of drill needle.

4.1.2 Backup Types:

A. Composite materials - like paper substrates. But based on sawdust and mixed with acid or salt adhesives. They pressed and hardened at high temperature and pressure. To form an integrated board 
carbide pcb with high hardness.
B. Phenolic resin board - the price is more expensive than the above-mentioned board. that is, the general single-panel material.
C. Aluminum foil - the same as entry board.
D. Vbu backup board - refers to Vented Back up board, the upper and lower sides of the aluminum foil. The middle layer of pure aluminum foil with the same flexure, during which air can flow. Such as asbestos waves.
The choice of backup board is also evaluated according to the conditions of each factory. The key points are: no organic grease, soft chip, hard surface. Uniform and even thickness of the board. Etc. Operating CNC to control existing CAD/CAM workstations. Can convert the language accepted by drilling machines.  As long as some parameters such as the aperture represented by each hole code are set.

4.2 Aluminum sheet (0.18 mm), also known as entry board:


4.2.1 Function:

printed circuit drill Prevent pressure foot from crushing copper surface;
B. Make the drill point easy to center positioning;
C. Reducing imported drill burr
D. Favorable for heat dissipation;
E. Cleaning when drilling and retreating.

4.2.2 Material for entry board:

A. Composite material - made of wood pulp or paper, and phenolic resin as an adhesive by hot pressing. Its material is like that of single panel, which is the cheapest.
B. Aluminum foils laminating material. Pure sawdust with thin aluminum foil pressed on top. And bottom layers and filled with degreasing and dechemicals.
C. Aluminum alloy sheet - 5-30 mil, different alloy composition, and the most expensive.
The above materials should select according to the product level. Environment and management, cost considerations. And the quality standards must be smooth surface, flat board. No impurities, grease and good heat dissipation.

4.3 Drill Bit, or bit,

Has a direct impact on the drilling yield. The following will discuss its material and structure.

4.3.1 Drill Material:

printed circuit drill needle composition material has the following three points:
A. Tungsten carbide with high hardness and wear resistance;
B. Cobalt with high impact resistance and hardness;
C. Organic adhesives.
The three powders mixed and. then sintered in high temperature and mould in a precision controlled incinerator. About 94% of the powders are tungsten carbide and about 6% are cobalt. Wear resistance and hardness are the key points of drilling needle evaluation. The finer the alloy particles. The higher the hardness and the more suitable for drilling small holes. Usually the alloy particles are less than 1um.

4.3.2 Shape structure of drill tool:

The external structure of the drill needle can divided into three parts. The drill point, the drill handle and the spiral cutter (the retreating slot).

A. Drill point

I. Point Angle
First drill tip and angle, second 
print circuit face and angle, cross edge and rib
A -drill point consists of two narrow first drill points.  And two triangular second drill points.
The blade surface meets the drill point. And forms two short edges at the central junction. Also known as the transverse edge, where the plate is first touched. The transverse edge positioned and drilled into stack under pressure and rotation. Each side of the first drill tip has a prominent square strip called a margin. Which spirals upward along the part of the drill body? And is the contact part between the drill pin and the hole wall. The corner at the junction of the rib and the edge lip is very important to the quality of the hole wall. There is a long edge between the first drill tip and the second drill tip. The prominent point between the two long edges and the two transverse edges is the point. The angle formed by the two long edges called the point angle. Drilling FR4. The sharp corners of glass woven boards need to be blunt to 115 degrees, 135 degrees. And the most common is 130 degrees.
The angle between the horizontal plane of the first tip and the long edge is about 15 degrees. Which called the primary face Angle, while the secondang face Angle is about 30 degrees? And the angle between the edge and the lip called the Chisel Edge Angle.

B. Spiral knife, also known as flute:

The structure of drill needle composed of entity and chip removal groove. The outer edge of the solid is the rib. Which keeps a small gap between the solid part of the drill pin and the hole wall to reduce heat. The spiral angle on the side section of the spiral chip removal groove called spiral angle. The spiral angle rate is small, the threads are scarce, and the distance of the scrap removal is fast. But, the resistance to scrap withdrawal and the entry of drill needle is large. So it is easy to accumulate heat at the tip and form resin softening to form smear on the hole wall. When the screw angle is large, the friction resistance of the drill needle entering. And debris removing is small, and it is not easy to get fever. But the material returning is too slow.

C. Shank:

The part clamped by the spindle clamp made of stainless steel to save cost.

D. Types of drill pins:

I. Diameter score: every 0.05 mm / 
bit 0.9mm  is the diameter, the diameter of common drill needle is from 0.2 to 6.5 mm;
II. According to type
II. According to the type, it can divide into: micro-type below 0.45mm;
0.5-1.25 mm is small.
1.3-3.15 mm is medium-sized.
Over 3.2mm is large

Bit parameters:

I. Diameter tolerance of drill shank: 3.175 (0.00-0.015) mm;
II. Diameter tolerance of drill bit: D (0.01-0.0254) mm;
(iii) The length of the drill bit: 21.00-21.20 mm;
IV. Rings: Internal diameter 3.175 mm and External diameter 7.6 mm
F. Inspection and re-grinding of drill pins:
I. Examination methods: 20-40 times solid microscopy examination. Its shortcomings are the following items:
Big head; Small head; Separation; Overlapping;
_inner arc; _outer arc; _large surface; _long and short surface;
Notch; _center is not straight; 011 rounded corner; 0112 bright spot
II. Re-grinding: There are two main wear points of the drill needle, i.e. the drill tip and the edge belt. In the former, the cutting edge of the leading edge of the first side broken or blunt. The edge angle of the outer edge rounded, and even the drill point flattened. All these can improve by re-grinding. But the edge band of the outer edge of the whole drill cannot grinded again. The most important thing is that the edge corner circle will increase the fever. Causing nail head, hole wall digging. And other problems. Usually a new drilling needle drills FR-4 plate under the stack of three layers. After 3000 drills, it must be re-grinded. Because of the material changes, it is necessary to have a good quality hole wall. After first grinding, it can only drill 2000 drills when used again. And after second grinding, it can only use 1000 drills. As a result, new drill pins are usually used in multi-layer boards. And re-grinded drill pins degraded to double boards. And worse drill pins used in holes without PTH plating on single boards.
Both sides of the drill point are roughly and ground twice. The surface of the first side is finer than that of the second side. The residual glue in the chip removal tank should clean. And washed with 1% sodium phosphate Na3PO4. Under the energy of ultrasonic wave to keep the original smoothness. The spade-shaped drill bits for multi-layer plates. Should grinded with special brackets supporting the details. After grinding, they should examined under 20-40 x microscope before reuse.

5.1 The functions and precautions of PCB drill process:


5.1.1 Feeding:

 The main function is to send the base plate or the multi-layer plate tool set . After the feeding to the drilling area for drilling. Matters needing attention in feeding.

The Board processing telecommunications  sent to the drilling area to drilled must inspected for feeding. The inspection of feeding includes the following aspects:
A. Material number: Full inspection, material number and work order consistent;
B. Quantity: Full inspection, consistent with the work order data;
C. Sampling 20% of the panel surface, for the following items:
I. Poor positioning. Whether the main target position of PCB 
metal processing  positioning hole. is in the center position in press milling;
II. Depression: Depth less than 0.2 mm, diameter less than 0.5 mm, not more than 10 points;
III. Scratch: invisible base material, not on its line, does not affect the line length < 0.5mm;
IV. Bubbles: Copper foil is not bonded with P P and cannot enter the forming zone;
V. Oxidation: No large area of severe oxidation and fingerprints;
VI. Drawing edge into molding: not available;
_. Copper skin tear: not into the forming area;
_. Plate bending < 0.5mm.

5.1.2 Needle preparation:

The main function is to prepare the inspected OK cnc drill needle. according to the material number of the plate to drill. and the aperture and the number of holes required by the customer. After preparing OK, the needle will distribute to the starter. According to the needle acquisition procedure for production. Notes in needle preparation:

A. When preparing needles, the material number. and version number of the plate to drill must saw first.
B. Check the customer specifications. according to the material number and version number of the board. and understand the customer's 
cnc drill diagrams, aperture and number of holes;
C. According to the customer's drilling diagrams. the required aperture. and the number of holes to prepare the drill needle after full inspection of OK;
D. Distribution and recovery of drill needles must follow the procedures. for distribution and recovery of drill needles.

5.1.3 Drilling:

The main function is to connect the upper and lower parts of the circuit board and to install the parts.

Notes for drilling

After drilling the directional hole, check the hole position with Map map. then continue about 10 holes after OK, and check the hole after OK again.
B. Patrol every 5 minutes to see if there is dirt on the board, whether the tape is falling off. whether drilling is abnormal, if there is a problem, stop the machine in time. and notify the foreman and engineer.
C. Calculate the life of the drill pin in operation, collect the drill pin in time. and prohibit the phenomenon of stopping the machine and waiting for the pin or using the drill pin. again without grinding.
D. When changing the 
pcb cnc bits tool needle, the diameter of the drill needle must measured. and the insertion must be correct.
E. Drilling parameters should be consistent with the parameter table at any time. 
large diameter

5.1.4 Inspection:

The main function is to inspect. whether the drilled plate meets the customer's requirements. according to drilling inspection standards and customer specifications. Inspection steps:

A. Measuring aperture: large aperture, small aperture;
B. Film shooting: porous, leaky, displaced, not perforated, not penetrated;
C. Visual inspection: hole loss, avalanche, cap, plug hole, scratch, glue mark, burning. Notices for inspection:

A. All the boards sent to IPQC by Film OK, and the boards inspected. The inspection standards based on Drilling Inspection Code and Customer Inspection Code.
B. When checking the board, the action of holding the Board. must be under the Code for Drilling and Handling Industry;
C. Record all inspection information. and inform the foreman and engineer of the bad condition in time. The aperture of the same material number should measured once every two times. and the aperture must measured when changing the material number.
D. When the film checked, the film hole aligned first, and then the PIN pin inserted .
E. Film is flat, wrinkle-free and must confirmed by IPQC and quality engineer before it can used.
F. The film used must be longer than the edge length of the plate.

5.1.5 Delivery:

The main function is to drill OK board. after confirmation by drilling QC, IPQC, all aspects. can meet customer's quality requirements. and then transfer to the next process for processing. Notices for shipment:

A. Store on the roller rack in 120PNL/L-RACK unit;
B. When shipping, the process card must signed by IPQC. and affixed with the certificate of qualification.
C. and urge the next process to be over-counted in time.

5.2 Process control process parameters:

Borehole Temperature: 22 +3 Temperature
Drilling indoor humidity: RH 50 +10%
HITAHI Drilling Machine:
Air pressure: 6.5 + 0.5kg/cm2 Spindle pressure: 5.5kg/cm2
Pressure foot pressure: 3.5 + 0.5kg/cm2 air clamp pressure: 5 + 0.5kg/cm2
Rum-out test: <15um hole position accuracy test: 25.0um
SPINDLE upper and lower limits:
Double panel: up: 11 + 2um
Dowm: 2 + 0.2um
Multilayer board: up:22+3um
Dowm: 14 + 0.2um
Condenser: Cooling Oil Temperature, 20 +2 Celsius
Cooling oil quantity, calibration line more than 1/3
Dust collector: Dust collector vacuum pressure, 1000MNAQ or more.

5.3 Quality Detection and Processing:

Remarks on Processing Method of Benchmark for Sequence Number Detection
1 deviated hole < 2mil scrap
2 Pifeng <0.05 mm Grinding
3 Plug Hole No Air Gun Blowing Hole
No heavy work without penetration
5 Porous can not scrapped
No heavy work for small holes
7 holes must not scrapped
8 No scrap allowed for burning coke
9-hole 0.05mm patch/scrap
10-hole small-0.05mm heavy industry
11 Scratches and Invisible Material Waste
Twelve hole wall roughness < 1mil change
13 Shift must not scrapped


6.1 PCB DRILL Quality Detection and Processing:

Remarks on Processing Method of Benchmark for Sequence Number Detection
1 deviated hole < 2mil scrap
2 Pifeng <0.05 mm Grinding
3 Plug Hole No Air Gun Blowing Hole
No heavy work without penetration
5 Porous can not scrapped
No heavy work for small holes
7 holes must not scrapped
8 No scrap allowed for burning coke
9-hole 0.05mm patch/scrap
10-hole small-0.05mm heavy industry
11 Scratches and Invisible Material Waste
Twelve hole wall roughness < 1mil change
13 Shift must not scrapped

6.2 Technical staff:


6.2.1 Borehole Start-up Technician Responsibilities: According to the production management schedule. prepare all related materials and tools in time. and complete the production task with quality and quantity. Input of the program of changing material number each time. setting of parameters and making good batch control; Fill in the production situation every two hours and report to the foreman. Report abnormal situations in the production process to the foreman immediately. and prohibit good self-determination; responsible for the timely cleaning and maintenance of the "5S" area. and do a good job of daily machine spot inspection projects; Operating in strict accordance with the operational specifications; Careful and detailed succession work.

6.2.2 Work responsibilities of drilling board technicians: First of all, understand the quality of working drill boards . and the situation of drill boards on each platform of this shift. Measure and record the aperture of the first plate of each machine. Make the aperture of the plate once every two times. Inspection board and measuring aperture must gloved. The middle and bottom plates should separated and placed, and the quality engineer. or foreman should reported immediately if there are leaks, holes, perforations or failures. and then sent to each machine for clarification and heavy work. The inspection items of each board must recorded . It forbidden for bad boards to flow into IPQC or the next process. and the bad boards should tracked and recorded. Films should stacked and put in a filming cabinet without filming. Report the abnormal situation of the drilling plate in this class. Check whether the number of measuring needles is OK before leaving work.

6.2.3 Drilling in and out technicians are responsible for: Understand work stock and on-site production; Prepare the required magnets and substrates; When feeding, attention should paid to the inspection of feeding, and the batch. and return of bad and unqualified boards should carried out. achieve the consistency of material number, version and work order, and the quantity must also be correct. Double panels, multi-layer panels, gaskets. and aluminium sheets placed , and the material number marked. and pushed into the storage area of the drilling plate. Delivery must be timely, the quantity must be correct, not less or more plates, excessive number must be timely; Work orders stacked behind the temporary plate L frame or on the board of W cart according to the material number. The quantity of work orders must be by the work orders. Prepare adequate L-rack, do well in workshop "5S", at least 3-4 times a day; Distinguish semi-waste gaskets and all-waste gasket. pack and stack all-waste gaskets and aluminium sheets on the shelf; Fill in the incoming and outgoing record form of the class without any mistakes. Reporting to the foreman about the output, input. and stock of the day, and handing over OK to the off-duty shipper before leaving work.

6.3 RE-Work Flow of Bad Plate:

Bad boards sorting out and classifying heavy industry QC inspection IPQC inspection shipment

6.3.1 Hole Small Heavy Work Step: uses a needle to measure the diameter of the drill and confirm which type of hole is small. Put all orifice plates in place and prepare corresponding drill pins. All the small holes in the plate repaired.
After hole filling, QC used to measure the aperture.
6..1.5 is finally checked by IPQC and shipped after OK.

6.4 Plug hole rework steps:

6.4.1 Mark the plug hole with chalk.
6.4.2 Stand the plug orifice plate on the desktop, hold the board with one hand. and blow holes at the plug orifice with an air gun in one hand.
6.4.3 After blowing off the fibre powder of the plug, it can submitted to QC for full examination.
6.4.4 QC and IPQC shipped after full OK inspection.

6.5 Beatles  RE Work Steps:

6.4.1 Make the board into a certain angle and visual plane to judge the degree of batch front.
6.4.2 Use a certain amount of strength, sandpaper to polish the shawl plate;
6.4.3 QC and IPQC shipped after full OK inspection.

6.6Rubber Track Reengineering Steps:

6.6.1 The glue marks around the visual board will put in order.
6.6.2 Use sandpaper to polish off the glue marks.
6.6.3 QC and IPQC shipped after full OK inspection.

6.6.1Unperforated, impermeable and leaky rework steps:

6.6.1 When the broken needle alarms, record the number of holes in the display.
6.6..2 After drilling the board, take a red film. and find out the location of the holes that are not perforated. not penetrated and leaked, and mark them with an oil pen.
6.6.3 According to the procedure of repairing non-perforated. impermeable and leaky holes, all holes repaired.
6.6.4 QC and IPQC shipped after full OK inspection.

6.7 Maintenance Specification:

Number Maintenance Project Maintenance Frequency Maintenance Method Maintenance Baseline Inspection Operational Notes
Head Technician
1 Spindle chuck 1 time/shift cleaner clean, clean
2 Run-out test once a month with micrometer to measure <15um_
3-hole position accuracy testing machine < 25.0um_once a month
4 Condenser filter screen cleaned. by air gun blowing or water flushing once a shift without blockage
Clean the dust-proof cover of ventilator once a shift with alcohol and no dust
6 Workbench 1/shift vacuum cleaner, rag clean and dust-free
Clean and dustless with broom and mop once a shift in the surrounding environment

6.8 quality and Improvement Measures:


6.8.1 Poor drilling needle items;

A. Hole size: measured with a measuring needle less than 0.0254 mm of actual aperture. 2 mil larger than the actual aperture;
B. Small aperture: measured with a measuring needle less than 0.0254 mm of actual aperture. 2 mil smaller than the actual aperture;
C. Leakage: Film used to check, visual board surface. found that there are holes in the film and no holes in the board surface. and the same is true in the front check.
Porous: With Film Check, visual board surface. it found that Film has no holes while the board face has hole. and this phenomenon also exists in the frontal check.
E. Offset hole: Film check shows that the holes on the surface of the plate deviate in the same direction.
F. Shift: The holes on the board are offset in the same direction after checking with Film.
G. Not worn: check with film, look at the board surface, and find that there is no hole on the board surface and film has hole. no such phenomenon in the front check;
H. Impervious: When checking with Film. we can see that the holes on the plate surface are smaller than those on the film surface. and there is no such phenomenon on the front.
I. Cape: Visual board surface, the line of sight. and the board surface maintain a certain inclination. found around the hole there are small hair protuberances;
J. scorching: on the surface of the visual board. it found that the hole wall is white, and the copper foil and the base material melted by scorching.
K. Collapse tip: Visual board surface, positive light. found the hole wall whitening (large hole phenomenon);
L. Plug hole: It found that the hole blocked by foreign matter on the light Kanban surface.
M. Rubber trace: Visual board surface. found that there are black colloidal objects on the board surface;
N. Scratch: Copper foil scratched to expose the internal base material.

Drilling pcb holes

PCB drill hole is one of the important part for multilayer PCB. usually drilling cost account for 30% to 40% of the total cost in PCB fabrication.PCB Drill Room
PCB Drill Room
PCB Drilling Considerations

The drill press consists of a high-speed spindle, which rotates at speeds of about 300k RPM. These speeds are essential to produce the required accuracy. for micron-level drilling on the PCB.
To maintain accuracy at high speeds, the spindle makes use of an air bearing and a direct drill bit assembly. which held by a precision collet chuck. Additionally, the vibration of the tip of the bit controlled within a 10-micron range. to maintain the exact position of the hole on the PCB, the drill mounted on a servo table.  which controls the motion of the table on the X and Y-axes. A tunnel actuator used to control the motion of the PCB in the Z-axis.
As the pitch of the holes in the PCB assembly line is decreasing. and the demand for higher throughput is increasing. the electronics to control the servo may lag behind at some moment. The use of laser drilling to create through holes for manufacturing. PCBs helps reduce or drop this lag and is the next generation’s need. 

PCB Drilling
PCB drilling need
Considering many potential issues before submission can impact your board’s turnaround time. quality and cost. An important issue that sometimes doesn’t get the attention it warrants is PCB drill holes.
Most designers consider spacing and size as they relate to their performance objectives. but might not consider how they relate to the manufacturing process. Applying some simple PCB design for manufacturing (DFM) rules. and guidelines for drill holes can have a significant impact.
The most important DFM considerations for drill holes are generally. PCB drill hole tolerance and PCB drill aspect ratio. When determining these, there is much more to consider than the actual drill hole size.

Type of Pcb drill hole and pcb drill size


pcb drilling tolerance

function, the holes can divided into two categories. one used for electrical connection between each layers. The other used to fix or position the components.
technology in PCB manufacturing. the holes are generally divided into three categories, which are blind vias. buried vias and through holes.
Blind via located at the top layer and bottom layer surface of the printed circuit board. which used for the connection between surface layer and inner layer. the depth of the hole is usually not exceed a certain ratio.
Buried hole refers to connection hole that located. in inner layer of the printed circuit board. buried hole does not extend to the surface of the circuit board.
Through holes drilled through the whole printed circuit board. which can used for internal electrical interconnection. or used as a positioning hole to assemble components. Because the through holes are easier. to achieve in the pcb manufacturing. process with lower cost, so most of printed circuit boards choose to use. it rather than the other two holes (blind via and buried via).
Omit pcb design, the hole is consist of two parts. one is the drill hole in the center area, the other is the pad around the drill hole. The size of these two parts determine the hole size. , in the design of a printed circuit board with high speed and high density.  the designers always hope that the holes the smaller the better. so that it can leave more space for circuit layout. But the hole size decrease will bring the increase of the pcb fabrication cost, moreover. the hole size is impossible to decrease. because it's limited by the process of drilling and plating.
The smaller hole size, the longer drill time required, and the easier off center position. When the depth of hole is more than 6 times of hole diameter. the copper plating process won't guarantee that the hole wall could plate copper . For example, a standard 6 layer PCB with thickness (depth of the hole) about 50 mil. so the PCB manufacturer can provide the smallest hole diameter to 8 mil.

Drill Hole size

If your board needs to be IPC Class 2, then the annular ring must be at least 0.004” . larger than the drilled hole at every point. For example, if your hole is 0.006”, then the smallest pad size for the drilled hole would be 0.014”.
pcb drilling issue
In the PCB drilling process may have the following quality problems:
1, partial hole, porous & leak holes;
2, broken drill bits;
3, blocking the hole (hole with debris);
4, no drill through;
5, burr hole, rough, smudge;
6, the surface burrs.
Here is a quick solution of pcb  drilling quality problems. The method is from 1 to last to  find out the problems.
The program error of borehole 1.
(2) The use of drill bit is wrong;
(3) the run-out of drilling machine is too large;
(4) The collapse tip occurs in the drilling process;
_Broken needle filling produced. Use correct drilling program;
Change the correct drill bit;
(3) Run-out change of drilling machine;
(4) Tracing the quality of drill needles;
_Check the working conditions and methods of mending holes.
2 holes: 1. program error of drilling;
(2) The use of drill bit is wrong;
(3) too high grinding times of drill bits. Use correct drilling program;
Change the correct drill bit;
(3) Confirm the grinding range of the drill bit.
3. Programming errors in drilling holes;
(2) Broken needle;
(3) Operational errors. Use correct drilling program;
(2) Check the working conditions of hole mending;
(3) Education and training.
4. Small boreholes (1) Programming errors in boreholes;
(2) Broken needle;
(3) Too many screw cutters in drill bits;
(4) Operational errors. Use correct drilling program;
(2) Tracking the quality of drilling needles. and alarming the broken needle drilling machine;
(3) adjusting the helical knife with less use;
(4) Education and training.
5 bias holes: (1) improper parameter setting;
(2) too large run-out of drilling rig;
(3) Dirty matter with deviated holes;
(4) too many layers;
The pressure foot is uneven;
_Aluminum sheet is not uniform;
_too high grinding times of drill nozzle;
_There are viscera in the chuck. (1) follow the drilling parameter table;
(2) Adjust the run-out of the rig so that it is less than 15um;
(3) Clean up the dirt;
(4) The thickness of laminates should not exceed 4.0 mm;
(5) Replacement of pressure foot;
Replacement of aluminium sheets;
_Use low-wear drill needle;
_Clean the dirt of chuck .
6. Cape (1) Second use of cushion plate;
There are gaps between the plates.
The drill bit used too long. Don't reuse the cushion plate.
2. Tighten the board with tape and avoid cracks.
solid carbide micro  Use the drill bit according to the number of times it used;
7 displacement (1) PIN nail loosening;
(2) The floating origin of the machine is offset;
(3) Poor target hole. (1) Re-inserting 
drill press PIN nail;
(2) Investigate the causes of the deviation of the floating origin of the machine. and then plan corresponding improvement measures;
(3) Remilling the target position.
8. Unpenetrated and not penetrated. The lower limit is set too high.
(2) The length of the drill bit is too short;
(3) The tip of the drill bit collapses during drilling;
The thickness of cushion plate is not enough. (1) Setting appropriate lower limits;
(2) control the grinding times of drill bits;
(3) Tracing the quality of drill needles;
(4) Replace the appropriate cushion plate.

 How is pcb drill bits ?

      Shank diameter: approx. 1/8″ (3.175mm), bit 0.5mm
      The cutting edges avoid partial hole, ensure the quality. Sharp and twisted flute will make the drilling be more easy and effortless. Suitable for wood, aluminum, plastic, etc.
      The variety of sizes is nice and the collar makes fitting them into the chuck easy. Excellent product at great value. These are exactly what they say on the tin. For circuit boards. or even presumably for fine jewelry work, they are a good tool and quite affordable.
      These are for use in CNC or special drill press, or at least super sharp high quality one, with low vibration level. Depending on the size, these bits must run at roughly 6,000 to as much as 20,000 RPM or more.
      Drill has a large scraps discharge space, little resistance. and during the scraps discharge. The cutting edges avoid partial hole, ensure the quality.
Shank diameter: approx. 1/8″ (3.175mm). Use high-quality materials and fine grinding process. makes a bit more sharp cutting edge, reduce cutting force and broken drill. improve the quality of hole wall. Long life, it can drill 2000-5000 pcs under normal working conditions. also can return grinding 4-5 times.
      cnc pcb end mills No wobbles and sharp enough to do the job. nice color coded, have the sizes printed on the shafts, come in a handy storage case. The shafts are all the same size, does not need to use a needle-chuck. It makes these bits easier to use.
       The smallest one is so small it is hard to see with a magnifying glass. others are perfect for cleaning out small orifices. These are carbide and so you can shatter them if you don’t know how to respect carbide. Power hand drill is no steady enough to use these types of drills, use a drill press instead. And you need to be careful to not put much pressure on the bits when using them. and  careful that the only force you apply is along the bit and not to the side.
       You can use it to engrave on glass, wood, metal, about anything.
      Great drill bits at a great price.
       High-quality  PCB Drill Bits, Great for circuit board . Plastics, Fiberglass, Wood, Soft Metals, etc
Carbide rods and tungsten steel rods, with high hardness. high wear resistance, high strength, 1/8 shank depth setting, resistance to bending. anti-impairment and long tool life.
      Well packaged, has foam to protect cutting tips. Pretty standard in quality, they are rather fragile, most things under an mm in diameter would be. Great selection of sizes. These would work great in a drill press or CNC of some sort drilling tiny holes in circuit boards. Go well with Dremel tool. Perfect for drilling small holes into metal, glass, jewelry stones.
      The color-coded collar makes it easy to pick up when it’s on a flat surface. These are very sharp and precision drill bits.
      circuit board are excellent. They are sharp and strong. I use them for drilling FR2 and FR4 copper clad pcb print board carbide and these bits. make clean holes without any burr to clean off on the entry or exit side of the hole. I pushed the 0.9mm bit through an FR2 PCB using my drill press when the motor was off. and it made a clean hole through the board without breaking.
Sharp micro drills, pcb print board carbide work fine in a Dremel tool and drill-press. Short enough to make it easy to do a straight hole but long enough for doing what you need to. Perfect for small carving.
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pcb backup board
pcb back up board backup material