Hot Air Bonding

Hot Air bonding is achieved during the winding process by means of a jet of hot air. The temperature of the hot air at the winding, usually between 140°C and 230°C, is dependent upon the wire size, winding speed, and the size and shape of the winding. This method is recommended for the majority of applications. It is cost effective for fine wire and is recommended for sizes 0.010 - 0.14mm (58 - 35 AWG)

Advantages

DisadvantagesRisks
Hot air bonding- fast
- stable and easy process
- easy to automate
- not suitable for heavy wire- tool contamination

Solvent Bonding

Solvent bonding is achieved by applying suitable solvents, (i.e. denatured alcohol), during the winding process. The solvent can be brushed, sprayed or wicked onto the winding.  Typically ethanol or methanol solvent is recommended. The solvent can be diluted with water, but the bonding process becomes more difficult as more water is used.

Advantages

DisadvantagesRisks
Solvent bonding- simple machinery / process

- solvent emission

- difficult to automate

- remaining solvents can harm insulation

- coils with many layers are difficult to dry inside, therefore often an oven is used after bonding to evaporate solvents completely

Oven bonding

Oven bonding is achieved by a thermal treatment of the finished winding in a heat chamber. Dependent upon the size of the winding, heating times of 5 to 30 minutes in a temperature of 130°C to 220°C are necessary in order to obtain uniform heating of the windings. Because of the longer times needed, oven bonding can be uneconomical for some applications.

Advantages

DisadvantagesRisks
Oven bonding

- post baking process included

- possible for coils with many layers

- costly

- time-consuming

- tool contamination

Resistance bonding

Resistance bonding is achieved by means of an electric current (resistance heating). Current intensity is dependent upon wire size and winding size. Resistance bonding is recommended for sizes heavier than 0.10 mm (38 AWG) but care should be taken no to overheat the centre of the winding because overheating could crack or destroy the base insulation, resulting in short circuits.

Advantages

DisadvantagesRisks
Resistance bonding

- fast and energy efficient process

- easy to automate

- hard to find best process parameter

- not suitable for wire ≤ 0.10mm

- application of to much current, results in too high temperatures