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MEMS inertial sensor welding process


PCB planning and layout are necessary to reduce pressure and add device functions.

The following are layout claims and requirements

Advocate to plan the PCB pad drawing as a non-solder mask definition (NSMD);

The area covered by the LGA package type must be defined as a "stop" area;

It is strongly recommended not to place metal drawings (eg, traces, pouring) or vias under the LGA package type (Figure 1). These structures will form irregular mechanical stress on the internal quality;

Components adjacent to the MEMS pad area may experience rated stress. It is strongly recommended not to place large penetration components (for example, shields, buttons, lid penetrations, screws) within 2 mm of the sensor package;

It is necessary to insist that the pin 1 indicator is not connected in order to use the device normally;

In order to achieve the best package type self-alignment on the planned PCB package type during solder reflow, it is necessary to pay attention to the symmetry of the pad traces (for example, the use of virtual traces even on pads that are not internally connected) .


                     

Figure 1. U1 shows the optimal wiring of the sensor in the LGA package type, while U2 shows that the layout rules are not followed.


Process Raiders

Regarding the correct device soldering, the drawing plan, solder paste thickness and reflow process curve should be considered;

The following are the process claims and requirements;

The thickness of the solder paste and the aperture of the solder paste should be properly confirmed, so as to properly clean the flux residue and allow the gap between the PCB and the package type;

The soldering data must not be reflowed on the package type side to prevent short circuit of the metal trace inside the LGA package type;

It is strongly recommended to clean the PCB after soldering to prevent leakage between adjacent pads due to flux residue;

The MEMS inertial sensor LGA package type meets the soldering heat resistance of JEDECJ-STD-020D humidity sensitivity level 3 specifications.

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