What are the specific requirements for self-locking tuning screws in the filter cover?

Specific requirements of filter cover plate for self-locking tuning screws

A, size and precision requirements

High thread precision

Generally m2 ~ M4 fine thread (commonly M2.5, M3).

Accuracy grade: 6H/6g or higher, ensuring smoothness and no sticking.

Matching with the threaded bottom hole of the cover plate

The diameter and depth of bottom hole are designed in strict accordance with screw specifications.

Small fit clearance, no shaking and eccentricity.

The length extending into the cavity is controllable.

The length tolerance of the tuning screw extending out of the cover plate is within 0.1 mm.

Avoid touching the resonant rod too long and the tuning range is too short.

Head size adaptation cover plate

The diameter and thickness of the head must not interfere with the adjacent tuning points.

Meet the batch butt size of automatic debugging equipment.

Second, the self-locking performance requirements (core)

Has stable positive self-locking force.

No looseness, no rebound and no drift after debugging.

The locking torque is consistent after vibration and high and low temperature cycles.

The torque range is controllable and the consistency is good.

Starting torque, running torque and locking torque are within the range specified in the drawing.

Torque difference in the same batch ≤ 0.5 kgf cm.

Repeated debugging without self-locking failure

Repeated screwing ≥50 times, the locking force does not decay and the teeth do not slip.

No additional locking parts

Self-locking is realized without nuts, gaskets and glue.

Pure structure self-locking (nylon insert/knurling/expansion/irregular teeth, etc.)

Third, the material and surface treatment requirements

material

Commonly used: brass, stainless steel, alloy copper.

Requirements: Good conductivity, easy cutting, no deformation and no rust.

surface treatment

Commonly used: silver plating, nickel plating and gold plating (according to shielding and conductive requirements)

Requirements: Uniform coating, strong adhesion, no peeling and no influence on threads.

Non-magnetic/low magnetic

Avoid affecting the high frequency performance of the filter.

Four, electrical and shielding performance requirements

Good electrical conductivity

Ensure low contact resistance between the cover plate and the screw.

Does not affect the shielding efficiency and increase the insertion loss.

No protruding tips and burrs

Prevent tip discharge and interfere with high frequency signals.

Good sealing performance

Cooperate with cover plate to realize cavity sealing

Outdoor models are required to be waterproof, dustproof and magnetic-proof.

V. Assembly and Process Requirements

Easy to assemble, no jamming, no biting.

Screw in smoothly, without astringency and teeth disorder.

Suitable for automatic production

The head is suitable for automatic feeding, automatic locking and debugging.

Welding/press fitting does not damage the self-locking structure.

If it is a riveting/welding screw, it must be resistant to high temperature and not deformed.

Do not loosen after debugging.

The frequency does not drift after aging and vibration test of the whole machine.

Six, environmental reliability requirements

High and low temperature resistance

The self-locking function is normal after cycling at-40℃ ~+85℃

Vibration resistance and impact resistance

Meet the vibration standard of communication base station/vehicle equipment.

corrosion-resistant

Salt spray test ≥ 48 ~ 96h without rust and failure.

Long-term use does not age.

When used outdoors for a long time, the self-locking structure is not brittle and ineffective.

Seven, appearance and structure requirements

The head has no deformation, burr and collapse angle.

Thread integrity, no crush, no disorderly teeth.

The self-locking structure is free from damage and falling off.

After being assembled with the cover plate, it is flush, not high and not sunken.