Case Sharing: Manual Soldering Causes Damage to IC and Peripheral Components

The linear regulator IC and peripheral components are mounted on a PCB (Printed Circuit Board) by soldering. In mass production, the soldering temperature and time are managed by automatic equipment, so there are usually no problems. However, in the case of trial production or rework, manual soldering with an electric soldering iron may be used, which may damage the IC and peripheral components, resulting in the power circuit not starting (not working).

Key takeaways from this article

▶ One of the reasons why the power supply circuit does not start up (doesn’t work) is damage to the IC and peripheral components due to hand soldering.
▶ When mounting ICs and peripheral components on a circuit board by hand soldering, it is necessary to observe the recommended conditions for hand soldering of each component.
▶ When components are in surface mount form, and the smaller the component size, the easier it is to be damaged by the thermal and mechanical stress of hand soldering.

Case 1: Damage to IC and peripheral components caused by manual soldering

The linear regulator IC and peripheral components are mounted on a PCB (Printed Circuit Board) by soldering. In mass production, the soldering temperature and time are managed by automatic equipment, so there are usually no problems. However, in the case of trial production or rework, manual soldering with an electric soldering iron may be used, which may damage the IC and peripheral components, resulting in the power circuit not starting (not working).

The installation conditions of the IC will be provided in the “Installation Specifications” in the “Packaging and Quality Data” under the relevant product page of the product official website (eg: ROHM official website link). For packages that can be hand soldered with a soldering iron, recommended soldering conditions are provided and soldering needs to be done in accordance with these conditions. Examples of conditions are as follows.

Example of recommended conditions for soldering iron soldering in TO252-3 package

☆ Soldering iron temperature: below 380℃
☆ Soldering time: less than 4 seconds (each pin)

Case Sharing: Manual Soldering Causes Damage to IC and Peripheral Components

However, if this condition value is exceeded, the IC may be damaged due to problems such as cracking of the package or peeling of internal bonding wires. In addition, if it is a package that is not recommended for mounting with an electric soldering iron, the risk of damage will increase in the case where an electric soldering iron has to be used during trial production, so careful soldering is required in a short period of time, when the circuit does not start (operate) normally , it is possible to suspect that the IC is damaged.

In addition, not only ICs can be damaged by hand soldering, but also surface mount components that constitute peripheral circuits, such as resistors and ceramic capacitors. Recommended conditions for manual soldering are provided in the technical specifications and other materials of each component, and soldering should be performed according to these conditions. Examples of conditions are as follows.

Examples of recommended conditions for manual soldering of resistors

☆ The temperature of the soldering iron tip: 350℃
☆ Welding time: 4s Max
☆ Times: 1 time
☆ Power: 20W Max
*Except 0603 (0201), 0602 (01005) size products

Basically, the smaller the size of the component, the more easily damaged it is when soldered with a soldering iron. In particular, components under 1005 (0402) size are susceptible to external stress, and the lead electrodes may peel off due to overheating or external force from the soldering iron tip, resulting in an open circuit failure. This problem occurs especially when the same product is used repeatedly. The peeling of the lead electrode is difficult to judge with the naked eye. If the output voltage set by the voltage divider resistor does not work properly, or an abnormal waveform appears, it can be suspected that the peripheral components are damaged.

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