FAQ; ADIS16475 Underfill Process Example

Q:

Do you have any recommendations for using under-fill to strengthen the attachment of the ADIS16475 to a printed circuit board?

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A:

Yes, we can offer some suggestions, for a process that we have used in the past.  The intent of this document to offer our customers with a starting point, for developing a process that is able to support all qualification and application level environments. 

1. After installing the ADIS16475, dry-bake the printed circuit board (PCB), which includes the ADIS16475, for 2 hours, at +125C.
2. Place the PCB on to the surface of a 90C hot plate
3. Use Henkel FP4470, in 10cc syringes
4. Thaw syringes per the instructions in the Henkel TDS
5. Attach a pink, 20 gauge EFD/Nordson needle (0.023" ID) to the syringe
6. Set the EFD dispenser pressure to 30 psi
7. Start in one corner of the ADIS16475 and apply a continuous bead of the material between the PCB and the substrate of the ADIS16475
8. Use an "L shape" pattern, while applying the material to only two adjoining sides of the IMU/PCB gap
   (NOTE: Application of the material on all four sides can cause entrapment of air bubbles, which will weaken the attachment strength)
9. Allow the material to flow out to the other two sides of the IMU/PCB interface (which did not receive application of the material from the syringe)
10. Cure the material, using a two-stage process:
    1. +125C, 30 minutes
    2. +165C, 90 minutes

Acknowledgement to Ed Bradshaw and Tom Richards, for organizing and documenting this process, so that we could share it with this community.