PCB drilling
2022-9-9
1.1 Overview
The production of single-sided or double-sided PCBs is to directly drill non-conductive holes or through-holes after blanking, and multi-layer boards are drilled after the platen is completed. In addition to the simple distinction of conduction or not, the types of traditional holes can be divided into different functions: part hole, tool hole, through hole (Via), blind hole (Blind hole), buried hole (Buried hole) (later hole) The two are also a type of via hole). In recent years, the development trend of electronic products' light, thin, short, small, fast. has made drilling technology leap forward, machine drilling, laser hole burning, photosensitive hole forming, etc. The equipment technology is applied to different levels of boards. This article only introduces the YSA spindle machine drilling part.
1.2 process
Sizing → drilling → rounding → edging → grinding
Slicing refers to cutting the sheet into a work board of a specific size as required by the order; rounding is to process the originally right-angled board corners into rounded corners to facilitate subsequent processing; the purpose of edging is to polish the edge of the work board to prevent cuts. ; And grinding is the burr around the hole.
1.3 Aperture parameters
The minimum via hole accepted by general customers is 0.3mm, and the maximum drilling hole is 6.3mm. However, the 0.3mm via hole is not the limit of drilling machine drilling, the limit of machine drilling is0.15mm.In view of the production cost and process difficulty, try to avoid 0.1mm and 0.2mm in pcb design. Because not only is it easy to break the drill, but also the difficulty of the process increases the cost, and at the same time, the number of unqualified boards increases. Therefore, it is suggested here that the via design≥0.35mm,The requirements for YSA drilling spindles are extremely high.
1.4 PINprocess:
During drilling operations, in addition to drilling blind holes, or very high-level board hole position accuracy requirements are very strict, in addition to single-piece drilling, usually multi-piece drilling, which means two or more pieces per stack. As for several pieces of one piece Drilling depends on 1. The required accuracy of the board 2. The minimum hole diameter 3. The total thickness 4. The total number of copper layers. The pinning machine (pinning maching) executes it. The double-sided board is very simple, most of them use the side-by-side method, and the punching and pinning are completed at one time. The multi-layer board is more complicated, and a special PIN machine for the multi-layer board is required.
1.5 Drilling tools and equipment
driller:
There are many types of drilling machines and their equipped functions. The following List evaluates the key points.
A. Number of axes: directly related to output
B. Effective drill plate size
C. Drilling machine table: choose a material with low vibration and good strength.
D. Spindle selection YSA high-precision ER chuck spindle
E. Drill disc: automatic replacement of drill bits and the number of drill bits
F. Pressure foot
G. X, Y and Z axis transmission and size: accuracy, X, Y move independently
H. Dust collection system: with pressure foot, good chip removal, and cooling drill function
I. Ability of Step Drill
J. Broken Needle Detection
K. RUN OUT
Grooving knife:
The minimum slotting knife is 0.65mm, and the slotted hole is called a connecting hole. Compared with the "drill nozzle", the groove knife is relatively difficult to break. But not less than 0.65mm when designing the slot.
1.6 Drilling room environment design
A. Temperature and humidity control
B. Clean environment
C. The weight of the floor
D. Insulation Grounding Considerations
E. External vibration interference
1.7 Material introduction
The materials that will be used in drilling operations include drill bits, back-up boards, cover boards (Entry boards), etc. The following are introduced one by one: Figure 6.1 is a schematic diagram of several materials in drilling operations.
6.4.2.1 Drill Bit, or drill bit,
Its quality has a direct and immediate impact on the quality of the borehole. The following will briefly describe its material, appearance, and management.
A. Drill needle material There are three main materials for the drill needle:
a. Tungsten Carbide (WC) with high hardness and strong wear resistance
b. Cobalt with good impact resistance and hardness
c. Organic adhesives.
After the three powders are uniformly mixed in proportion, they are sintered in a mold at a high temperature in a precision-controlled incinerator. The composition is about 94% is tungsten carbide, and about 6% is cobalt. Wear resistance and hardness are the key points of drill evaluation. The finer alloy particles can improve the hardness and are suitable for drilling small holes. Usually, the alloy particles are less than 1 micron.
B. External structure
1. Grip (Shank)
The part clamped by the Spindle clamp is made of stainless steel to save material.
The overall shape of the drill has 4 shapes:
(1) Straight Shank with the same thickness as the handle,
(2) The drill part thicker than the trunk is called Common Shank.
(3) Large-hole drills with a drilled portion larger than the handle
(4) Thick and thin progressive drill pin for small hole.
C. Drill inspection and regrinding
a. Inspection method 20~40 times solid microscope inspection
b. Re-Sharpping of the drill bit is the life of the drill bit for the quality of the hole wall, and the re-sharpening management can be done according to the table below. Generally speaking, the life of the drill can reach 5000-6000 hits (Hit) with three highs of the four-layer board, and it can be reground three times in total. (should re-grind the number table)
summary:
Use YSAHigh-speed spindleFor the drilling accuracy requirement of 0.15MM, the actual measured hole position deviation is 0.05, and the inner circle of the cut hole is smooth and free of burrs, which has a great accuracy advantage for precision drilling of PCB boards.
