Established in Hong Kong in 1978, Yet Chong Electric Co. (YCEC) offers a full line of quartz clocks and alarm clocks, electromagnetic and piezoelectric buzzers, ferrite permanent magnets, and various coils for many kinds of electronic devices. YCEC is also one of the very few companies in the world which specialize in the related technology transfer. These technologies are especially suitable for firms in developing countries, where quality of products can sometimes be affected by the lack of stable sources of high quality components and raw materials. YCEC's proven technology and know-how specialize in decreasing such problems. YCEC offers the following technology transfer:


Clock Movement Technology


a. Quartz Alarm Clock Movement      


b. Quartz Clock Movement



.Electro-magnetic Buzzer Technology     



.Piezoelectric Buzzer Technology



.Ferrite Permanent Magnet Technology



.Spring Coil Winding Machine Technology



.Radio Coil Package       


1.     Clock Movement Technology

Since the emergence of the first quartz clock several decades ago, technology advances have made precision time keeping with quartz clocks an essential and affordable part of the every day modem fife. The accuracy of a quartz clock, unmatched by almost any mechanical clock, is maintained by the extremely high stability of the quartz oscillator. Unlike ordinary electric clocks, which are essentially mechanical clocks powered by household electricity and hence, easily affected by its fluctuation and interruption, an energy efficient quartz clock offers precise and uninterrupted time keeping, up to more than one year with only one small AA battery. Most quartz clocks also have alarm functions.

However, much like other high-tech industries, quartz clock manufacturing has been dominated by a few corporations in developed countries, which control most of the clock markets. This is mainly due to the technological complexities involved in the manufacturing of clock movements, the central piece of a quartz clock.  A well designed and manufactured quartz alarm clock requires a combination of


1)     well-built electronic components, such as quartz oscillators, integrated circuits and alarm components;

2)     high quality stepping motors (and their components, such as ferrite permanent magnets and FeNi alloy );

3)     high precision gear box building and plastic molding technology and;

4)     sophisticated clamping and other auxiliary apparatus as well as quality controlled assembling procedures and final product calibration.



2.   Electro-magnetic Buzzer Technology

In addition to applications in alarm clock movements, these buzzers are also widely used in many other electronic devices and products, such as household appliances, toys and instruments. The package includes:

A)    Blueprints of the molds for plastic components, punch molds for metal parts and other hardware of YB - 12 GP / AP and YB - 12 GW / AW and related manufacturing know-how.

B)     Blue prints of unique clamping and other auxiliary apparatus.

C)    Assembly line demonstration (for validation).

D)    A 6 day on-site training program taught by two YCEC engineers.

3. Piezoelectric Buzzer Technology

Structure, Chemical Composition and Working Principle

Piezoelectric buzzer is a compact, energy efficient sound producing device, which is an assembly of a vibration mechanism attached to a piezoelectric ceramic plate with two electrodes on both sides. When AC electricity of a given frequency is applied to the electrodes, an audible vibrating sound with the same frequency is produced by the assembly. The materials used to manufacture the buzzer plates are derivatives of lead zirconium-titanate (PZT) with a general chemical formula: Pd x Sry (MZr. NTi)z0n + Nba0b.

Manufacturing Procedure

a)     Preparation of powder material

The proper starting ingredients are mixed thoroughly, ground and made into small cakes, which are then heated in a high temperature furnace. The following main reaction takes place:

PbTiOn + PbO + ZrOm- ------------------ > Pb(MZr, N Ti)Om The heated cakes are then further finely ground into a powder form.

b) Shaping

The powder thus obtained is mixed with PEG binder and pressed into a thin film, from which the product blanks with desired shapes are prepared.

c)     Binder removal and sintering

The product blanks are then heated to remove the binder and then sintered to give piezoelectric ceramic plates.

d)     Polarization and testing

Both sides of the ceramic plate are then coated with silver electrodes, which are further strengthened through a polarization process. The resonance resistance of the piezoelectric ceramic plates thus obtained should be below 4.8 ohms.

e)     Buzzer assembling and QC

The piezoelectric ceramic plates are then attached to the vibration mechanisms with epoxy resin to give the buzzers. The product QC of the buzzers obtained through the above sophisticated manufacturing process is carried out with special instruments. The major electroacoustic parameter, Kp, should be better than 60%

4. Ferrite Permanent Magnet Technology

These affordable magnets are widely used in many electronic devices and products, such as loudspeakers, household appliances, toys and medical instruments

Chemical composition and working principle

Ferrite permanent magnets are made of ferrimagnetic materials. In a magnetic field, the atoms in these ferrimagnetic materials can adopt and maintain an orderly arrangement. Once they become magnetized, they possess a high magnetic remanence even after the external magnetic field is removed. There are two commonly used ferdmagnetic materials. ferroxdure (BaFe12O19) and ferrostrontium (SrFel2Ol9). The latter has a higher magnetizability, but costs about 50% more.

Manufacture of ferrite permanent magnets

a) Preparation of powder material:

The proper starting ingredients are mixed thoroughly, ground and made into small balls, which are then heated in a high temperature furnace. The heated ball are then @her finely ground into a powder material.

b) Shaping

Two methods of shaping are most widely used: dry pressing and magnetic field assisted pressing. In dry pressing, the powder material is mixed with binder and compressed in a mold to give (Square) magnet blanks. In magnetic field assisted pressing, the powder material is suspended in water and the suspension is compressed in a mold under a magnetic field to give -9i@magnet blanks. In addition to these, magnetic field assisted injection molding has also been developed.

c) Sintering

After being dried, the product blanks are sintered in a high temperature continuous furnace.

d ) Polishing

Sintered (Square) magnet blanks are then polished, ultrasonically cleaned and dried in a stove while sintered 4ktk magnet blanks require mechanical grinding to achieve precise sizes, followed by ultrasonic cleaning and drying in a stove.

e)        Magnetization and final product QC

Ferrimagnetism materials are usually magnetized in a magnetic field with special equipment. The final product QC includes measurements of product size and major magnetic properties with special instruments.

5. Spring Coil Winding Machine Technology