The Importance of Installation
Early failures of power modules are often caused by improper installation. Incorrect installation can lead to excessively high junction temperature, significantly shortening the module's lifespan. Therefore, installation must be carried out strictly according to the correct procedures:
- Clean the surface
- Select the position
- Apply thermal grease
- Secure the module
- Connect the circuit
Cleaning the installation surface
Clean the installation surface: Ensure that the roughness of the substrate and heat sink surfaces is ≤ 10 μm, and the flatness (within 10 cm) is ≤ 20 μm. Avoid uneven force on the module, which may cause internal damage.
Selection of installation position
Single module: Center installation to reduce thermal resistance.
Multi-module: Distributed evenly according to heat generation
Application of thermal grease
The thermal grease (thermal resistance 60℃/W/in) is much better than air (1200℃/W/in), significantly reducing the contact thermal resistance.
However, the thickness should be controlled within 50-100 μm (with the grease line at the edge as the reference), too thick will increase the thermal resistance, and too thin will leave gaps.
Installation of Fixed Bolts
After applying the thermal grease, place the module correctly on the heat sink. First, evenly screw in (with a torque of approximately 0.5 N.m), with the insertion depth being about half of the total depth. Then, use a tool for tightening, generally controlling it within the range of 3 N.m to 6 N.m.
To achieve good thermal contact, the tightening of the bolts should be carried out in a diagonal sequence. As an example, SHYSEMI recommend tightening these 8 bolts in the following order:
Tighten the bolts by hand with a torque of approx. 0.5 N.m. in the following order:
2 → 6→ 3 → 7 → 4 → 8→ 1 → 5;
Tighten the individual bolts by hand with a torque of 3N.m to 6N.m in the same order:
2 →6→ 3 →7 →4 →8→ 1 →5.
During the first installation, ensure that the torque does not exceed 0.5 N.m. For the second installation, it should be completed using a manual torque wrench, whether for copper substrates or AlSiC substrates. Considering the penetration effect of the thermal grease, it is generally necessary to re-tighten the bolts after several hours.
This three-point fixed positioning requires ensuring that the edges of the module are not damaged during the installation process. Moreover, the insertion depth of the bolts needs to be controlled. Therefore, it is necessary to pay attention that the effective length of the bolts should be within the range of 6.5mm to 10mm.
Installation of self-tapping screws for fixing the PCB
On the upper part of some modules with a height of 17mm, there are self-drilling screw installation holes for fixing the PCB board. The matching self-drilling screws have a specification of M2.5 and a threaded effective length of 4-10mm. The effective length of the thread needs to be adjusted according to the thickness of the PCB board. The recommended example is as follows:
The effective length of the thread should be adjusted according to the thickness of the PCB, and the recommended examples are as follows:
Before installing the self-tapping screws, make sure that the PCB holes are aligned with the self-tapping screw mounting holes, and install the self-tapping screws vertically throughout the entire process. Since the upper 1.5mm depth of the self-tapping screw mounting holes is an imported hole structure, the initial PCB thickness plus the 1.5mm distance does not need to be subjected to any torque, and only needs to be forced to press it in; after completing the above steps, the self-tapping screws can be screwed into the mounting holes with the application of torque. Requirements for the entire process of installation torque can not exceed 0.5N.m.
Correct installation of self-tapping screws Incorrect installation of self-tapping screws
Other precautions:
- Avoid using excessively long screw threads to prevent damage to the internal structure of the module during installation; consult the data sheet for specific lengths.
- All the screws fixing the power busbar and power terminals should be tightened with the same torque, the specific size can be consulted in the datasheet.
- Do not use reflow soldering for main terminals and control terminals, and do not affect the module with heat, flux, cleaner, etc. when soldering other parts.
- please avoid drastic changes in temperature and humidity, especially the surface of the module can not be dew.
- Don't put in corrosive gas, dusty places.
- The installation of IGBT, IC is weak anti-static components, should avoid high-voltage static added to the main terminals, control terminals