PCB Tech - What preparations need to be made before drilling multilayer circuit boards?

What preparations need to be made by the machine before drilling in a multi-layer circuit board factory

Multi-layer circuit board factories need to make the following preparations before drilling. Making high-quality circuit boards is no longer a problem!

1. The multilayer circuit board factory regularly cleans magnetic heads and other components:

For paper tape drives, tape drives or floppy disk devices, the heads must be cleaned up on time. In addition, the light bulbs, lenses, light-emitting tubes and photoelectric tubes of the paper tape machine must also be cleaned regularly.

2. The multi-layer circuit board factory sets the parameters reasonably:

The main parameters of the equipment include coordinates, metric system/imperial system, absolute/incremental, EIA code/ASC2 code, leading zero/post zero, etc.

The basic parameters of the drill include T (1/2/3), drill diameter, feed, speed, etc.

3. Multi-layer circuit board factory preheating equipment in advance:

The spindle of the ball bearing must be warmed up in advance every time the ball bearing is started. If it is more than 1 hour away from use, it must be reheated. The oil mist lubricated spindle is a special case and does not require preheating. The above preheating operation can keep the CNC drilling machine safe and stable. Insufficient preheating will produce more low-quality boreholes.
Multilayer Circuit Board Factory

So how to preheat the spindle? In fact, the drill bit is inserted into the spring chuck, the drill bit rate is controlled at 15 thousand per minute, and it must continue to rotate for a quarter of an hour. If there is a special preheating program then the efficiency will be very high. Remember that if the spring chuck rotates at a high speed without a drill bit, it will inevitably destroy the spindle. Everyone must pay attention to this!

4. The drilling quality of the multi-layer circuit board factory is closely related to the radial runout of the drill shaft, so it must be tested on time. The method is still very simple: put the standard rod into the collet chuck, the dial gauge measuring head is placed about 19 mm away from the lower end of the collet chuck, and then slowly rotate the drill shaft, at this time the dial gauge moves the radial direction The amount of runout has been measured. Each drill shaft of some CNC drilling machines is equipped with a laser measuring instrument, which can measure the diameter, radial runout and axial size of the drill bit. If there is this kind of equipment, the efficiency will be improved a lot. Under normal circumstances, the replacement cycle of the spring chuck is half a year, which should be paid attention to.

5. The drill bit of the multilayer circuit board factory should be controlled at about 1.3 mm lower than the drill shaft presser foot pad. The sequence of drilling steps is as follows:

1. The presser foot pad first presses the laminated board of the base plate;

2. Drill down the drill bit;

3. Remove the drill bit when retracting;

4. The presser foot pad leaves the base plate stack.

The presser foot pressure of the cylinder and spring should be controlled at 21-42N/㎡. When the diameter of the drill bit is less than half a millimeter, it is better to use a rigid presser foot pad.

6. Drilling depth measured by multi-layer circuit board factory

Generally speaking, all drilling thresholds are that the tip of the drill bit is exactly on the surface of the table. Everyone is familiar with the standard drill bit installation size is 0.8 inches, but there are other specifications. We generally adjust the drilling threshold to exactly 1 mm deep into the backing plate or one-half of the thickness of the backing plate. There are two reasons:

If it is too shallow, it is easy to make it difficult to drill through the substrate on the backing surface.

If it is too deep, the wear rate of the drill bit will be higher.
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