process common problems and solutions of PCB mechanical drilling

First, the drilling file (Drill File) introduction

Common drilling and meaning:

PTH - PTH: A hole in the wall of the hole that is used to attach metal to the conductive pattern in the middle or outer layer.

NPTH - Non-plated through hole: Apertures that are used for mechanical mounting or mechanical fixing of the components of the cell wall without plating the metal.

VIA - Vias: Electrical connections (eg, buried vias, blind vias, etc.) used to electrically conductive patterns in different layers of the board, but not through the through holes of the module legs or other reinforcement.

Blind Hole: A via that extends only to one surface of the board.

Buried hole: does not extend to the printed circuit board surface vias.

Common format:

S & m

Exel.drl

Unit system:

METRIC (mm)

ENGLISH (inch or mil)

Unit Conversion:

1 inch = 1000 mil = 2.54 cm = 25.4 mm

1 mm = 0.03937 inch = 39.37 mil

Coordinate format:

LEADING ZERO SUPPRESS: 0 in front of the coordinates of an integer omitted, the number of decimals is not enough to fill 0.

TRAILING ZERO SUPPRESS: 0 after the coordinates of small digits omitted, the number of digits is not enough to fill 0.

NONE ZERO SUPPRESS: Enough numbers and decimal places are all padded with 0s.

FORMAT (decimal point hidden): There are ten formats.

Second, drilling plate (DRILL RACK) introduction

The main description of the drill bit used in the file size, some also shows the hole is PTH or NPTH.

The drilling plate generally starts with M48 and is arranged in front of the drilling file. There are also separate documents.

DRILL RACK + DRILL FILE = Complete bore pattern

Common fields:

Tool: Bit number

Size: aperture size

Pltd: PTH or NPTH instructions

Feed: Next speed

Speed: speed

Qty: the number of holes

Third, the camera file (Apeture File) introduction

The lens file mainly describes the shape and size of the lens used for the corresponding Gerber File.

Apeture File + Gerber File = complete PCB Layout graphics.

Common fields:

D_Code: D code, the lens number

Shape: Lens shape

Size: Lens size

1, cut off Tsui

The reasons are: excessive deflection of the spindle; improper operation of the CNC drilling machine when drilling; improper use of the drill bit; insufficient speed of the drill bit, too much feed rate; too many layers of lamination; Drilling too deep spindle lead to drill bit chip bad hanged; drill Tsui grinding too much or life expectancy; cover scratches and wrinkles, pad bending uneven; tape fixed substrate too wide Or cover plate aluminum plate is too small; feed rate is too fast cause extrusion; fill hole improper operation; cover plate aluminum block serious ash; welding drill tip center and drill stem center deviation.

Solution: 

(1) Inform the mechanics to overhaul the main shaft or replace the main shaft.

(2) A, check the pressure beriberi pipeline is blocked; B, adjust the pressure foot pressure according to the state of the drill tip, check the pressure data when the pressure foot is compressed, the normal is 7.5 kg; C, check the spindle speed variation and the grip Within the copper wire affect the speed uniformity; D, drilling operation is detected when the spindle speed changes and spindle stability; (spindle and spindle can be compared between) E, carefully adjust the pressure between the foot and the drill State, the tip of the drill tip can not be exposed presser foot, only allow the drill tip 3.0mm at the presser foot; F, testing drilling table parallelism and stability.

(3) Check the geometry of the drill Tsui, wear and choose the appropriate length of the tip of the drill tip.

(4) Select the appropriate amount of feed, reduce the feed rate.

(5) Reduce to the appropriate number of lamination.

(6) Clean the surface of the board and cover the debris, keep the board clean.

(7) Notify the machine to adjust the drilling depth of the spindle to maintain a good drilling depth. (The normal drilling depth should be controlled at 0.6mm.)

(8) control the number of grinding (according to operating instructions) or strictly according to the parameter table parameter settings.

(9) Select the appropriate surface hardness, flat cover, pad.

(10) carefully check the adhesive tape fixed state and width, replacement cover aluminum, check the size of the plate.

(11) Properly reduce the feed rate.

(12) Pay attention to the correct fill hole position during operation.

(13) A, check the presser foot height and presser foot exhaust groove is normal; B, suction is too large, you can properly adjust the suction force.

(14) Replace the drill bit in the same center.

2, hole damage

The reason is as follows: after cutting the drill bit, the drill bit is taken; when drilling, there is no aluminum plate or clip counterplate; the parameter is wrong; the drill bit is elongated; the effective length of the drill bit can not meet the requirement of the thickness of the drilling stack plate; Special, approved Feng caused.

Solution: 

(1) According to the previous question 1, the reasons for the investigation broken knife, to make the right deal.

(2) aluminum plate and the bottom plate play a role in protecting the hole ring, must be used in production, available and can not be separated from the bottom plate, the direction of a unified place, check again before the board.

(3) Before drilling, it is necessary to check whether the drilling depth is correct and whether the parameters of each drill are set correctly.

(4) The drill grabbed the drill bit, check whether the position of the drill bit is correct and then turn on the machine, and the drill bit should not exceed the presser foot when turning on the machine.

(5) Measure the effective length of the drilling nozzle before drilling the machine and inspect the stacks of available production plates.

(6) manual drilling cutting accuracy, speed, etc. can not meet the requirements, prohibit the use of human hand drilling.

(7) When drilling the special board to set the parameters, according to the quality of the appropriate parameters, the feed should not be too fast.

3, hole position deviation, shift, right alignment

The reason is as follows: the drill bit is offset during drilling; the material of the cover is improperly selected, the hardware and software are not suitable; the base material is caused by the shrinkage and shrinkage of the hole, which leads to the improper use of the matched positioning tools; , Hit the pin to move the production plate; drill resonance during operation; the spring collet is not clean or damaged; production board, the panel partial hole or the stack of bit offset; drill in contact with the cover slip; cover Board aluminum surface scratches or creases, drilling in the guide drill deviation; no pin; origin is different; adhesive tape is not firmly; drilling machine X, Y axis deviation occurs; the program has a problem.

Solution: 

A, check the spindle is deflected;

B, to reduce the number of stacks, usually double the number of double-sided laminated drill bit diameter of 6 times the number of laminated multilayer drill bit diameter of 2 to 3 times;

C, increase drill speed or reduce the feed rate;

D, check whether the drill tip meets the technical requirements, or resharpened;

E, check the drill tip and drill Tsui handle with good concentricity;

F, check whether the fixed state between bit and collet is tight;

G, testing and correction of drilling table stability and stability.

(2) Select a high density 0.50mm lime cover or replace the composite cover material (the upper and lower layers are 0.06mm thick aluminum foil, the middle is the fiber core, the total thickness of 0.35mm).

(3) according to the characteristics of the plate, bake plate processing before drilling or after drilling (usually 145 ℃ ± 5 ℃, baking 4 hours whichever is).

(4) check or test tool hole dimensional accuracy and location of the pin on whether there is offset.

(5) check and reset the presser foot height, the normal presser foot height 0.80mm from the board to drill the best presser foot height.

(6) Select the appropriate bit speed.

(7) Clean or replace a good collet.

(8) the panel is not loaded with pins, the control board pin is too low or loose, you need to reposition the replacement pin.

(9) Select the appropriate feed rate or choose a better bending strength drill bit.

(10) replacement of flat surface without crease cover aluminum sheet.

(11) nail board operations as required.

(12) record and verify the origin.

(13) The adhesive tape and the board into a 90o right angle.

(14) Feedback, notify the machine repair maintenance drilling rig.

(15) Check to verify, notify the project to be modified.

4, holes, holes, aperture distortion

The reason is as follows: Drill bit specification error; Infeed speed or speed is not appropriate; Drill bit excessive wear; Drill bit excessive grinding or retreating the end of the length of the bottom is lower than the standard; Spindle itself is too deflected; Drill hole diameter becomes larger; wrong hole diameter; drill hole when not measured when the hole; Drill nozzle alignment error; drill when the wrong position; did not check the aperture map; the spindle put the knife, resulting in pressure knife; .

Solution: 

(1) Check the drill before operation and control system whether the instruction error.

(2) Adjust the feed rate and speed to the best condition.

(3) Replace the drill bit, and limit the number of drill holes per drill. Typically 3,000 to 3,500 holes can be drilled in double-sided panels (four in each stack); 500 holes in a high-density multilayer board; 3,000 holes in a FR-4 (three in each stack); and for harder FR-5, an average reduction of 30%.

(4) limit the number of drill re-grinding and regrinding size changes. Drill multi-hole drilling for each hole 500 times, allowing sharpening 2 to 3 times; 1000 holes per drill can be sharpened once; for double-sided board per hole 3000, sharpening once, and then drill 2500 holes; Drill 2000 holes at a time. Drill timely resharpening, can increase the number of bit re-grinding and increase bit life. Through the tool microscope measurement, wear depth of less than 0.2mm in the two main cutting edge length. When grinding to wear to 0.25mm. Fixed shank bit can be re-grinded 3 times; shovel-shaped bit re-grinding 2 times.

(5) feedback to the maintenance of dynamic deflection tester to check the deflection of the spindle running process, in serious cases by a professional supplier to repair.

(6) 20 times before drilling with a mirror face, the bad drill sharpening or scrapped.

(7) Checked and measured many times.

(8) It is possible to measure the drill bit that has been changed while changing the drill bit. The first hole drilled has been changed.

(9) to arrange the drill when the number of clear magazine location.

(10) Change the drill when see the serial number.

(11) Check the actual aperture of the aperture map one by one while preparing the knife.

(12) cleaning clamp Tsui, resulting in pressure gauge after careful measurement and check the knife face situation.

(13) Check repeatedly when entering the tool number.

5, drain holes

Produced due to: broken drill Tsui (identification is unclear); suspended halfway; procedural errors; man-made accidental deletion of the program; drill read data leakage read.

Solution: 

(1) Disconnected drill plate separately, check separately one by one.

(2) After the suspension in the midway start again, to be back 1 to 2 holes to continue drilling.

(3) Once the decision is an error in the engineering procedure, immediately notify the engineering change.

(4) In the operation process, operators try not to change or delete the program, if necessary, notify the engineering treatment.

(5) after CAM read the file, change machine production, notify the mechanized processing.

6, Feng front

Produced due to: parameter error; serious drill wear, blade is not sharp; floor density is not enough; substrate and substrate, substrate and substrate between the debris; substrate bending deformation to form voids;

Solution: 

(1) When setting parameters, execute it strictly according to the parameter list, and check and verify after setting.

(2) When drilling, control the life of drill, according to the life table set can not be used for life.

(3) The floor density test.

(4) When nailed plate cleaning debris between the substrate, the multi-layer laminated plate with rags for surface cleaning.

(5) Deformation of the base plate should be carried out to reduce the gap between the plates.

(6) The cover is to protect and guide the drill. Therefore, when drilling holes must be added aluminum. (For the impermeable aluminum sheet drilling)

(7) When drilling the special board to set the parameters, according to the quality of the appropriate parameters, the feed should not be too fast.

7, the hole is not drilled (not through the substrate)

Produced due to: improper depth; drill length is not enough; uneven platen; uneven thickness of the pad; Broken knife or drill Tsui half, the hole is not through; In the drilling process, the drilling nozzle is pressed short; not clamping the bottom plate; when adding the two plates for the first plate or back hole, no change is made in production.

Solution: 

(1) check the depth is correct. (Total depth and depth of each spindle)

(2) measure the length of the drill is enough.

(3) Check the platen is flat, to be adjusted.

(4) measuring the thickness of the pad is consistent, feedback and replacement pad.

(5) Positioning re-fill the hole.

(6) According to the source of the batches of the front to clear the exclusion, the first batch of grinding process.

(7) Adjust the spindle loose, clean or replace the nozzle.

(8) double-panel board before check whether there plus floor.

(9) Make a mark, drill the first board or make up the hole to be changed back to its normal depth.

8, appeared on the panel with silky crimples debris

The reasons are: do not use the cover or drilling process parameters selected improperly.

Solution: 

(1) Appropriate cover should be used.

(2) Usually should choose to reduce the feed rate or increase bit speed

9, plug hole (plug hole)

Produced due to: the effective length of the drill bit is not enough; Drill bit into the depth too deep; substrate material problems (with water and dirt); plate reuse; improper processing conditions, such as insufficient suction force; Tsui's structure does not work; drill Tsui's feed rate too fast with the rise with improper.

Solution: 

(1) According to the thickness of the stack to choose the appropriate length of the drill, plate thickness can be used to compare production.

(2) The drilling depth should be set reasonably (control the drill tip to drill into the backing plate 0.5mm).

(3) should choose good quality substrate material or bake before drilling (normal is 145 ℃ ± 5 bake 4 hours).

(4) should be replaced plate.

(5) should choose the best processing conditions, proper adjustment of the suction force of the drill, reaching 7.5 kg per second.

(6) replacement drill Tsui suppliers.

(7) Set the parameters strictly according to the parameter list.

10, rough hole wall

10, rough hole wall

The reasons for this are as follows: the change of the feed rate is too large; the feed rate is too fast; the material of the cover plate is improperly selected; the vacuum degree of the fixed drill bit is insufficient (air pressure); the retraction speed is not suitable; Damage; spindle deflection is too large; chip discharge poor performance.

Solution: 

(1) to maintain the best amount of feed.

(2) Based on experience and reference data to adjust the feed rate and speed, to achieve the best match.

(3) Replace the cover material.

(4) Check the CNC rig vacuum system (air pressure) and check if the spindle speed has changed.

(5) Adjust the tool retraction speed and bit speed to achieve the best condition.

(6) Check the drill status, or replace.

(7) Check and clean the spindle and collet chuck.

(8) to improve chip chip performance, check the status of chip flute and cutting edge.

11, the hole edge of the hole appears white (hole edge of the copper layer separated from the substrate, burst hole)

Reason: Drilling caused by thermal stress and mechanical fragmentation caused by local fragmentation; glass cloth woven coarse size; poor quality of the substrate material (cardboard material); feed is too large; Too many plies.

Solution: 

(1) Check drill wear, and then replace or re-grinding.

(2) Selection of fine glass woven into a glass cloth.

(3) Replace the substrate material.

(4) Check the set feed amount is correct.

(5) Check the drill handle diameter and the size of the main spring clamp folder is enough.

(6) According to the process of laminated data adjustment

The above is a common problem in the PCB mechanical drilling production, in practice, should be more measurement and more checks. At the same time, strictly regulate the operation of drilling quality control problems have great benefits to improve product quality, improve production efficiency, but also great help.