Management method of ultrasonic welding process for enclosures

The housings of AC/DC Power Adapters — Desktop & Wall-Mount are assembled using ultrasonic welding. This page introduces part of the thorough management methods for the ultrasonic welding process.

By reliably performing ultrasonic welding, it is possible to prevent accidents in which live components are exposed from the casing.

1. Preparation Before Start of Production

Production engineering staff will install and adjust the horn for the ultrasonic welding equipment and set the ultrasonic welding conditions according to the work instructions.
After the adjustment is complete, insert a dummy board into the casing and perform welding on one unit.
After welding, the IPQC (In Process Quality Control) staff will perform a drop test compliant with safety standards.
After the drop test, visually confirm that there are no cracks in the ultrasonic welded area of the casing.
Open the casing using a special tool, check the ultrasonic welded area, and confirm that more than 75% of the welded part is firmly fused.

After confirming the above, production will begin.

2. After Start of Production

1. Production Line

To prevent skipping the ultrasonic welding process, a checkpoint will be installed between the ultrasonic welding and the next process.
The operator of the ultrasonic welding process will visually inspect the ultrasonic welded area of all units after the welding is done.
In the next automatic electrical characteristic inspection process, before connecting the casing to the inspection equipment, verify for all units by striking the casing on the workbench that the welded area does not open.

2. IPQC

Every two hours, the IPQC staff will perform the following patrol sampling inspections from the production line:

After adjustment is complete, insert a dummy board into the casing and perform welding on one unit.
After welding, the IPQC staff will perform a drop test compliant with safety standards.
After the drop test, open the casing and check the welded area to confirm that more than 75% of the welded part is firmly fused.

After confirming the above, if any abnormalities are found in 2) or 3), all units will undergo rework processing by tracing back to the time of the previous IPQC patrol inspection in accordance with our company's ISO abnormality handling regulations.

3. OQC (Outgoing Quality Control)

Five units selected from the shipping lot will be tested using a thickness gauge to confirm that the gap between the upper and lower casing at the ultrasonic welded part is within the standard range.

Furthermore, in the case of 5W-class USB types where the ultrasonic welded line is particularly short, it is considered that the impact on the casing in a drop test compliant with safety standards may be small, and potential defects in the ultrasonic welding may not become apparent. Therefore, in order to apply a greater impact than the drop test, a weight-attached cable is connected to the casing, and a free-fall test is conducted from a company-specified height, simulating a steel ball drop test. The IPQC staff confirms on one unit every two hours that there are no damages to the ultrasonic welded part.