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#329 Know-how on automation: Pressurized heating technology

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February23, 2018

Of production technologies, a processing method where heat treatment is conducted while a constant level of pressure is being applied is widely used for processes of adhesive/bonding and transcription (deformation).This section describes pressurized heating technology and automation.

(1)Description of pressurized heating technology

Pressurized heating (hot pressing) technology is used for the following machining processes:
1)Adhesive of the machined workpiece and machining fixture for precision machining (cutting, grinder polishing, etc.) (Fig. 1 a)
2)Adhesive of two glass substrates with a gap of some µm (LCD devices, etc.)
3)Mount bonding of COG (Chip On Glass), etc.
4)Transcription process of fine pattern (micro/nano imprint, etc.) (Fig. 1 b)

[Fig. 1] Example of pressurized heating method

Pressurized heating technology is being expected to meet the following requirements for precision and productivity:
a)Applying homogeneous and high precision pressure onto the area of the object workpiece
b)Control program capable of ensuring homogeneous and high precision distribution of temperature, and accurate temperature rise, steady temperature, and temperature fall
c)Pressurized heating method with high productivity (at a constant cycle)

(2)Instrumentation of pressurized heating

・This section describes hot pressing technology mentioned above in 2).
・For the pressurized heating process, it is commonly practiced that instrumentation of the process is carried out by dividing it into two processes: pressurizing and heating.
・Pressurizing process is of two types of process design: (1) process of final pressurizing only, and (2) process of preliminary pressurizing and final pressurizing. The latter is used in the case where positioning precision is required.
・Fig.2 shows an example of mechanism of pressurizing process.The basic structure is the same as that of a press machine. The pressure is applied by moving the pressurization plate in parallel with the base plate using the four guide columns.
・Even if the two opposing surfaces of the base plate and the pressurization plate are kept exactly in parallel, a deformation of the mechanism as a whole cannot be avoided due to the load of pressurization plate applied. As a countermeasure for this deformation, the pressure is often applied through the pressurization buffer material (rubber elastic body, etc.).
・Heating treatment is often adopted in tunnel furnaces, because control of temperature rise from room temperature to the level for treatment or temperature fall, and also heating treatment for a given period of time are required.A box furnace is more appropriate for processes for high-mix production.
・From the viewpoint of productivity, it is desirable to place several workpieces in the pressurization mechanism, shown in Fig.2, to conduct the pressurized heating process.

[Fig. 2] Example of pressurization mechanism