PCB drilling process issue & solution

PCB drilling process issue & solution

The drilling is a process of PCB production, it’s very important. Major job is to drill the hole, if for need of connecting wire, it called via hole; if for need of structure, it called registration hole; multiple layer PCB drilling can not finish in one time, some holes are buried inside inner layer, some holes are through, therefore it had first-drill and second-drill.

 

What is the use of the PCB board drilling process

 

Drilling is to connect the outer layer circuit and the inner layer circuit, and the outer layer circuit is connected to the outer layer circuit. Anyway, the hole is drilled for the circuit connection between the layers. In the later electroplating process, the hole can be plated with copper. The lines of different layer are connected, and some drilling holes are screw holes, positioning holes, row holes, etc., and their uses are different.

Drilling is to drill the required vias on the CCL. Through-hole vias mainly provide electrical connection and are used for fixing or positioning of devices.

 

PCB vias are divided into:

a. Electroplated hole (PTH), also called metallized hole;

b. Non-plated hole NPTH): also called non-metallized hole.

According to the process, it is divided into:

a, blind hole (multilayer board);

b. Buried holes (multilayer boards).

PCB board drilling process

1. Drilling process of multi-layer board

2、drilling process of double side board

 

process capacity of PCB drilling

 

The quantity of each stack, have to consider below factors:

The accuracy that the panel required

Minimum hole diameter

Thickness

Copper layer quantity

 

The relationship btw Board thickness and stack quantity of drilling

PCB drilling process faults and solutions

1. drill bit broken

The reasons are: excessive deflection of spindle; improper operation of the CNC drilling machine; use wrong drill bit; insufficient rotation speed of the drill bit; too high feed rate; stack too many layers; debris between the panels or under the entry foil ;The drilling depth of the spindle is too deep, resulting in poor chip removal of the drill bit and hangs; the grinding times of the drill bit are too many or the life is exceeded; the entry foil is scratched and wrinkled, and the backup plate is not flat; the tape is too wide when fixing the substrate Or the aluminum sheet of the cover plate and the PCB panel are too small; the feed speed is too fast to cause extrusion; improper operation when filling holes; serious dust accumulate under the aluminum plate of the cover plate; the center of the welding drill tip is deviated from the center of the drill shank.

Solution:

(1) Inform the machine repairer to overhaul the spindle, or replace the spindle.

(2) Check the geometry and wear of the drill bit and select a drill bit with a suitable length of chip removal groove.

(3) Select the appropriate feed amount and reduce the feed rate.

(4) Reduce to an appropriate number of layers.

(5) Clean the board surface and the sundries under the cover when the board is on, and keep the board surface clean.

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

(7) Control the number of grindings (perform in accordance with the operation instructions) or strictly follow the parameter settings in the parameter table.

(8) Choose covers and pads with suitable surface hardness and flatness.

(9) Carefully check the fixed state and width of the adhesive tape, replace the aluminum sheet of the cover plate, and check the size of the plate.

(10) Appropriately reduce the feed rate.

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

(12) Replace the drill bit of the same center.

2. Hole damage

The reasons are: take the drill bit after the drill bit is broken; there is no aluminum sheet or a reverse plate when drilling; the parameters are wrong; the drill bit is elongated; the effective length of the drill bit cannot meet the thickness of the drilling slat; hand drilling; plate Special, caused by the front.

Solution:

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

(2) Both the aluminum sheet and the bottom plate play the role of protecting the aperture ring. They must be used during production. The usable and unusable plates are separated and placed in the same direction. Check again before the plate is installed.

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

(4) The drilling rig picks up the drill bit, checks whether the position where the drill bit is clamped is correct, and then starts the machine. Generally, the drill bit should not exceed the presser foot when starting up.

(5) At the drill tip. Visually check the effective length of the drill bit and measure the number of stacks of available production boards before starting the machine.

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

(7) When setting parameters for drilling special plates, select parameters appropriately according to the quality situation, and the feed should not be too fast

3. Hole offset, shift, misalignment

The reasons for this are: the drill bit is offset during the drilling process; the material of the cover plate is not properly selected, and the soft and hard are uncomfortable; the expansion and contraction of the base material causes the hole position deviation; the matching positioning used.

Improper use of tools; improper setting of the presser foot during drilling, hitting the pins and causing the production board to move; resonance during the operation of the drill bit; unclean or damaged spring chucks; production board, panel offset hole position or the entire stack position offset; The drill bit slides when it is in contact with the cover plate; the surface of the aluminum sheet of the cover plate has scratches or creases, and deviation occurs when guiding the drill bit to drill down; there is no dowel; the origin is different; the adhesive tape is not firmly attached; the X, There is a movement deviation in the Y axis; there is a problem with the program.

Solution:

(1) A. Check whether the spindle is deflected;

B. Reduce the number of laminates, usually the number of double-sided laminates is 6 times the diameter of the drill bit and the number of multi-layer laminates is 2 to 3 times the diameter of the drill bit;

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

D. Check whether the drill bit meets the process requirements, otherwise re-sharpen it; Ba. Check whether the top of the drill bit and the drill bit handle have good concentricity;

E. Check whether the fixed state between the drill bit and the spring chuck is tight;

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

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

(3) According to the characteristics of the plate, bake the plate before or after drilling (usually 145C+5℃, which is subject to baking for 4 hours).

(4) Check or detect the dimensional accuracy of the tool hole and whether the position of the upper positioning pin is offset.

(5) Check and reset the height of the presser foot. The normal height of the presser foot is 0.80mm from the board surface, which is the best height of the presser foot for drilling.

(6) Select the appropriate drill speed. Clean or replace the collet.

(8) The panel is not loaded with pins, the pins of the control board are too low or loose, and the pins need to be repositioned and replaced.

(9) Choose an appropriate feed rate or a drill with better flexural strength.

(10) Replace the aluminum sheet of the cover plate with a flat surface without creases.

(11) Carry out nail plate operations as required.

(12) Record and verify the origin.

(13) Stick the tape at a right angle of 900 to the edge of the board.

(14) Feedback, notify the machine repair to debug and repair the drilling rig.

(15) Check and verify, and notify the project for modification.