PCB drilling process failure and solution

Drilling is an important process in the PCB process. It looks simple, but it is actually a very critical process. In the manufacturing industry, the production of defective products cannot be separated from the five factors of people, machines, objects, laws, and rings. In the same way, this is also true in the drilling process. The following is a list of factors affecting drilling with fishbone diagrams.

First, in the many stages of influencing the drilling process, various projects are inspected. The following lists the common inspection categories and items for PCB board drilling.

 (1) Substrate inspection before drilling, items include: name, number, specification, size, copper and platinum thickness; no scratches; no bending, no deformation; no oxidation or oil contamination; And wrinkles.

 (2)、Drilling operator's independent inspection, the project is: aperture; approved front; depth penetration; whether there is a hole; check the hole, hole deformation; porous hole; burr; if there is a hole; Hole; entire plate shift.

Second, the detailed breakdown of faults often occurs in the drilling process

1, broken drill Tsui

 The reasons are:

Spindle deflection excessive;

Incorrect drilling of the CNC drilling rig;

Drill nozzle is not suitable for use; the rotational speed of the drill is insufficient and the feed rate is too high;

There are too many layers of laminated plates; there are debris between the plate and the plate or under the cover plate;

The depth of the main shaft during drilling is too deep to cause hang-death on the drill nozzle.

Drill tip grinding too often or exceeding life expectancy;

Scratches, wrinkles, and uneven bending plates

When fixing the substrate, the tape is too wide or the cover plate and the plate are too small;

Infeed speed is too fast to cause extrusion;

When the hole is not properly handled, the cover plate is seriously clogged with ash;

The center of the weld tip is offset from the centre of the drill shank.

Solution: 

(1) Instruct the machine to repair the spindle or replace the spindle.

(2) A. Check the pressure of the beriberi pipe for clogging;

B. Adjust the pressure of the pressure foot according to the state of the drilling nozzle and check the pressure data when the pressure foot is pressed. Normally 7.5 kg;

C. Check the spindle speed variation and whether there is copper wire in the clip to affect the uniformity of the speed;

D. Detect the change of the spindle speed and the stability of the spindle when the drilling operation is performed; (can be used as a comparison between the spindle and the spindle)

E. Carefully adjust the state between the pressure foot and the drill bit. Do not drill the tip of the nozzle to expose the pressure foot. Allow only the drill tip to be within 3.0 mm of the pressure foot.

F. Detect the parallelism and stability of the drilling table.

Parallelism and stability.

(3) To test the geometry of the drill tip, wear conditions and to select a suitable drill tip for the length of the flute. (4) Select a suitable feed rate to reduce the feed rate.

(5) Reduce to a suitable number of laminates.

(6) Clean the surface of the board and the debris under the cover plate while keeping the board and keep the board surface clean.

(7) Inform the machine to adjust the drilling depth of the main shaft and maintain a good drilling depth. (The depth of normal drilling should be controlled to 0.6mm.)

(8) Control the grinding frequency (performed by job instructions) or strictly according to the parameter settings in the parameter table.

(9) Choose a suitable cover and backing plate with suitable surface hardness.

(10) Carefully check the state and width of the adhesive tape, replace the aluminum plate, and check the plate size.

(11) Reduce the feed rate appropriately.

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

(13) A. Check the height of the presser foot and the exhaust groove of the presser foot are normal;

B, suction is too large, you can properly adjust the suction.

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

2, hole damage

The reason is:

After breaking the drill nozzle, take the drill nozzle;

No aluminum sheet or clip anti-backplate when drilling;

Parameter error;

Drill nozzle elongated;

The effective length of the drill nozzle can not meet the thickness requirement of the drilling plate stack;

Hand drilling

Special plate, caused by the front.

Solution: 

(1) According to the previous question 1, check the cause of the broken knife and make correct treatment.

(2) The aluminum sheet and the bottom plate all play a role in the protection of the ring of holes. They must be used during production, separated from the available and unusable bottom plates, and placed in the same direction. Then they should be checked again before they are placed on the plate.

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

(4) The drill rig picks up the drill bit and checks whether the position of the drill bit is correct and then turns on. When the machine is turned on, the drill nozzle cannot generally exceed the pressure foot.

(5) Visually measure the effective length of the drill tip before drilling the machine on the machine, and perform a measurement check on the stack of available production plates.

(6) Manual drilling and cutting accuracy, speed, etc. cannot meet requirements and manual drilling is prohibited.

(7) When drilling special plate setting parameters, select the appropriate parameters according to the quality conditions. The feeding should not be too fast.

3, hole position deviation, shift, alignment inaccurate

The reason is:

Deviation of drill bit during drilling;

Improper selection of cover material, hard and soft discomfort;

Substrate shrinks and causes hole deviation;

Used mating positioning

Improper use of tools;

Improper setting of the presser foot when drilling, hit the pin to move the production board;

Resonance occurs during operation of the drill bit;

The spring collet is not clean or damaged; the production plate, panel bias hole position or full stack position offset;

The drill bit slips when it touches the cover plate;

Scratches or creases on the aluminum surface of the cover plate, causing deviations when guiding the drill tip to drill;

There is no hitting pin;

The origin is different;

The adhesive tape is not stuck;

Drilling machine's X, Y axis movement deviation;

There is a problem with the program.

Solution: 

(1) A. Check whether the main shaft is deflected;

B, to reduce the number of stacks, usually the number of double-sided stacking is 6 times the diameter of the drill bit and the number of stacked layers of the multi-layered plate is 2 to 3 times the diameter of the drill;

C. Increase the rotational speed of the drill or reduce the feed rate;

D. Check whether the drilling nozzle meets the technological requirements, otherwise it will be sharpened again;

E. Check whether the drill tip and the drill shank have a good concentricity;

F. Check whether the fixing state between the drill bit and the collet chuck is tight;

G. Detect and correct the stability and stability of the drill table.

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

(3) According to the characteristics of the plate, baking treatment (usually 145 °C ± 5 °C, baking 4 hours) before or after drilling.

(4) Check or check the tool hole size accuracy and position of the upper positioning pin.

(5) Check the height of the presser foot. The height of the normal presser foot from the board surface is 0.80mm, which is the optimum presser foot height.

(6) Select the appropriate bit speed.

(7) Clean or replace the collet chuck.

(8) The panel is not loaded with a pin, the pin of the control board is too low or loose, and the replacement pin needs to be repositioned. (9) Choose the proper feed rate or drill with better bending strength.

(10) Replace the flat aluminum plate with no creases.

(11) Perform nailboard operations as required.

(12) Record and verify the origin.

(13) Apply a 90o right angle to the edge of the tape.

(14) Feedback, informing the machine repair and repair drilling rig.

(15) Check the verification and inform the project to modify it.

4, hole, hole, aperture distortion

The reason is:

Drill tip specifications are wrong;

Incorrect feed speed or speed;

Drill tip excessive wear;

The number of re-grinding of the drill nozzle is too much or the length of the retracting groove is lower than the standard;

The spindle itself is excessively deflected;

The tip of the drill tip collapses and the borehole diameter becomes larger;

Misperception

No hole diameter measured when changing the drill tip;

Drill bit arrangement error;

When changing the drill nozzle, the position is wrong;

The aperture map is not checked; the spindle cannot be placed under the knife, resulting in a pressure knife;

The wrong number was entered in the parameter.

Solution:

(1) Before the operation, check the drill size and whether the control system has an instruction error.

(2) Adjust the feed rate and rotation speed to the optimal state.

(3) Replace drill tips and limit the number of drilled holes per drill. Generally, 3000~3500 holes can be drilled according to double panels (four stacks per stack); 500 holes can be drilled on high-density multilayer boards; 3000 holes can be drilled for FR-4 (three stacks per stack); and harder FR-5, an average reduction of 30%.

(4) Limit the number of re-grinding drills and regrind size changes. For drilling multi-layered plates with 500 holes each drilled once, allowed to sharpen 2~3 times; 1000 holes per drill can be sharpened once; for each double-faced plate 3000 holes, sharpen once, then drill 2500 holes; regrind Drill 2000 holes at a time. The re-grinding of the drill bit can increase the number of re-grinding and increase the life of the drill. Through tool microscopy, the depth of wear should be less than 0.2 mm over the entire length of the two main cutting edges. Reground 0.25mm. The shank bit can be reground 3 times; the spade bit regrind 2 times.

(5) Feedback to maintenance The dynamic deflection tester checks the deflection of the spindle during operation, and is repaired by a specialized supplier in severe cases.

(6) Before drilling, check the face with a 20-fold mirror to sharpen or scrap the defective drill tip.

(7) Multiple checkups and measurements.

(8) The replaced drill tip can be measured when replacing the drill tip. The first drill hole has been drilled to measure the drilled hole.

(9) Make sure the position of the tool magazine is clear when arranging the drill tip.

(10) Observe the serial number when changing the drill tip.

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

(12) Clean the nipples and carefully measure and inspect the surface of the knives after pressing.

(13) Check the tool number repeatedly.

5、Drilling hole

The reasons are:

Broken drill nozzle (unidentified);

Suspended halfway;

Procedural error

Humans do not intend to delete the program;

The rig leaks when reading data.

Solution: 

(1) Deal with the broken drill plates separately and check them one by one.

(2) After restarting after being paused midway, it is necessary to rewind 1~2 holes to continue drilling.

(3) Once it is determined that it is an engineering process error, immediately notify the engineering change.

(4) During the operation, the operator should try not to change or delete the program at will, and notify the project if necessary.

(5) After reading the file through CAM, change production and notify the machine for repair.

6. Feng Feng

The reasons are:

Parameter error;

Drill wear is serious and the cutting edge is not sharp;

The density of the bottom plate is not enough; there are impurities between the substrate and the substrate, the substrate and the bottom plate;

The bending deformation of the substrate forms voids;

Without cover plate;

Special plate material.

 Solution: 

(1) When setting parameters, strictly follow the parameter table, and check and verify after setting.

(2) When drilling, control the service life of the drill, and do not exceed the service life setting.

(3) Conduct a density test on the bottom plate.

(4) Clean up the substrate debris when nailing the board, and clean the board surface with a rag when stacking the boards.

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

(6) The cover plate is used for protection and guide drilling. Therefore, aluminum must be added when drilling. (For bored aluminum sheets drilled)

(7) When drilling special plate setting parameters, select the appropriate parameters according to the quality conditions. The feeding should not be too fast.

7, the hole is not drilled (do not penetrate the substrate)

The reasons are:

Inappropriate depth;

Drill nozzle length is not enough;

Uneven board

Uneven thickness of the pad;

Broken knife or drill nozzle broken half, the hole is not clear;

After the batch of holes infiltrated into the hole, the copper did not pass through.

The main shaft clamp is loose and the drill nozzle is pressed short during drilling;

No back plate;

Two pads were added to the first plate or hole, and no changes were made during production.

 Solution: 

(1) Check if the depth is correct. (minute total depth and spindle depth)

(2) Measuring whether the drill bit length is enough.

(3) Check if the platen is flat and adjust it.

(4) Measure whether the thickness of the pad is consistent, feedback and replace the pad.

(5) Positioning and refilling the borehole.

(6) Examine and eliminate the source of the batch front according to the front, and polish the batch front.

(7) Adjust the looseness of the spindle to clean or replace the nozzle.

(8) Check whether there is a bottom plate before the board on the double-sided board.

(9) Make a mark. Drill the first board or fill in the hole to change it back to its normal depth.

8. The curled debris on the panel is broken.

The reasons are:

The cover plate or drilling process parameters have not been selected properly.

Solution: 

(1) Appropriate cover plates should be used.

(2) Reduce the feed rate or increase the bit speed normally.

9, plug hole (plug hole)

The reasons are:

The effective length of the drill bit is not enough;

The depth of the drill bit into the plate is too deep;

Substrate material problems (moisture and dirt);

Repetitive use of the plate;

Inappropriate processing conditions, such as insufficient suction power;

The structure of the drill nozzle is not acceptable;

Drilling tip feed speed is too fast and mismatched with the rise.

Solution: 

(1) Selecting the appropriate drill bit length based on laminate thickness can be compared with the production board laminate thickness.

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

(3) Good quality substrate material should be selected or baked before drilling (normally 145°C±5 baking for 4 hours). (4) Replace the pad.

(5) The best processing conditions should be selected, and the suction power of the drill hole should be properly adjusted to 7.5 kg per second.

(6) Replace drill supplier.

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

10, rough hole wall

The reasons are:

The amount of feed changed too much;

Feed rate is too fast;

Improper selection of cover material;

Insufficient vacuum of fixed drill (pressure);

Retraction rate is not suitable;

The leading edge of the drill bit's cutting edge is broken or damaged;

Spindle deflection is too large;

Chip discharge performance is poor.

Solution: 

(1) Maintain the optimum feed rate.

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

(3) Replace the cover material.

(4) Check the numerical control rig vacuum system (air pressure) and check if there is any change in spindle speed.

(5) Adjust the retraction rate and drill bit speed to the best condition.

(6) Check the use of the drill bit or replace it.

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