PCB Tech - What are the secondary holes in the circuit board? What are the common problems with circuit board drilling?

Circuit board drilling is a process of PCB plate making, and it is also a very important step. It is mainly to punch the board, the wiring needs, a via hole, the structure needs, and a hole for positioning or something; the multi-layer board is not punched at one time, some holes are buried in the circuit board, and some are in the board. The board is opened up, so there will be one drill and two drills. The following editor will explain in detail what are the common problems of secondary drilling and drilling in circuit boards.

Introduction to the secondary hole of the circuit board
The second-drilled holes are holes that do not require copper, such as screw holes, positioning holes, heat sinks, etc., these holes do not need copper. The second drill must be after the first drill, that is to say, the process is separated.

One-drilling requires a copper sinking process, that is, plating the hole with copper so that the upper and lower layers can be connected, such as vias, original holes, etc.

Common problems of PCB drilling
1, broken drill nozzle

The reasons are: excessive deflection of the spindle; improper operation of the CNC drilling machine; inappropriate selection of the drill tip; insufficient drill speed and too large feed rate; too many layers of laminate; debris between the plate and the plate or under the cover plate ; The depth of the spindle during drilling is too deep, causing poor chip evacuation of the drill tip to cause strangulation.

Too many grinding times of the drill tip or over-life use; the cover plate is scratched and wrinkled, the backing plate is bent and uneven; when the substrate is fixed, the tape is too wide or the cover plate aluminum sheet or plate is too small; the feed speed is too fast to cause extrusion ; Improper operation when filling holes; serious dust clogging under the aluminum sheet of the cover plate; the center of the welding drill tip is deviated from the center of the drill shank.

2, hole loss

The reasons are: take the drill nozzle after the drill nozzle is broken; there is no aluminum sheet or the base plate is clamped when drilling; parameter error; the drill nozzle is elongated; the effective length of the drill nozzle cannot meet the needs of the thickness of the drilling stack; hand drilling; plate Special, caused by the Feng Feng.

3, hole position deviation, shift, misalignment

The reasons are: the drill bit shifts during the drilling process; the cover material is not properly selected, and the soft and hard are uncomfortable; the base material expands and shrinks and the hole position is deviated; the matching positioning tool used is not used properly; the presser foot is set incorrectly when drilling, Hitting the pin to make the production board move; resonance occurs during the operation of the drill.

The collet chuck is not clean or damaged; the production board and the panel are offset or the entire stack is offset; the drill bit slides when it touches the cover plate; scratches or creases on the aluminum surface of the cover plate are used when guiding the drill bit to drill down Deviation occurs; there is no pin; the origin is different; the adhesive tape is not firmly attached; the X and Y axis of the drilling machine move deviation; there is a problem with the program.

4, the hole is big, the hole is small, the hole is distorted

The reasons are: wrong specifications of the drill tip; inappropriate feed speed or speed; excessive wear of the drill tip; too many regrind times of the drill tip or lower than the standard specification; excessive deflection of the spindle itself; tip collapse of the drill tip. The hole diameter of the drilling hole becomes larger; the hole diameter is wrong; the hole diameter is not measured when the drill nozzle is changed; the drill nozzle arrangement is wrong; the position of the drill nozzle is inserted wrongly; the hole diameter diagram is not checked; .

5, leak drilling

The reasons are: broken drill tip (unclear identification); pause in the middle; error in the program; delete the program accidentally; the drilling rig misses the reading while reading the data.

6, Pian Feng

The reasons are: parameter error; serious wear and tear of the drill tip, and the blade is not sharp; the base plate density is not enough; there is debris between the base plate and the base plate, the base plate and the base plate; the base plate is bent and deformed to form a gap; the cover plate is not added; the plate material is special.

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

The reasons are: improper depth; insufficient length of the drill tip; uneven platen; uneven thickness of the backing plate; broken knife or half of the drill tip, and the hole is not penetrated; the batch blade enters the hole and the copper is not penetrated; the spindle jaw is loose. During the drilling process, the drill nozzle was shortened; the bottom plate was not clamped; two backing plates were added when the first plate was made or the hole was patched, and there was no change during production.

8. There are crimp-shaped debris with broken lotus roots on the panel

The reasons for are: not using a cover plate or improper selection of drilling process parameters.

9, plug hole (plug hole)

The reasons are as follows: the effective length of the drill bit is not enough; the depth of the drill bit into the backing plate is too deep; the substrate material problem (with moisture and dirt); the backing plate is reused; improper processing conditions, such as insufficient dust suction; drilling The structure of the nozzle is not good; the feed rate of the drill nozzle is too fast and the rise is not properly matched.

10, the hole wall is rough

The reasons are: too large change in the feed rate; too fast feed rate; improper selection of the cover material; insufficient vacuum (air pressure) of the fixed drill bit; inappropriate retraction rate; cracks or breaks in the cutting edge of the top corner of the drill bit. Damaged; the deflection of the spindle is too large; the chip discharge performance is poor.

11. A white circle appears on the edge of the hole (the copper layer of the hole is separated from the base material, and the hole is blasted)

Causes: Thermal stress and mechanical force during drilling cause local breakage of the substrate; the size of the glass cloth weaving yarn is relatively thick; the quality of the substrate material is poor (paperboard material); the feed rate is too large; the drill tip is loose and not tightly fixed; Too many layers.