Masking and Underfill Dispensing for Medical Devices

Case Study

Masking, Underfill Dispensing for medical photo

In one of our medical applications projects, the customer wanted to dispense a mask to protect gold leads and an underfill on a silicon substrate with a clear test die. The substrates were Dymax X-499-91-C for Masking and Epoxibond-106M-1 for Underfill Dispensing.

Recommended Dispensing Process:

A conveyorized MAX Series System equipped with a Precision Auger Dispense Pump and a time pressure system were used for the evaluation. The Precision Auger Pump was selected to dispense small volumes of material accurately. The Underfill material was specified with a noticeably short pot life which allowed us to dispense the material directly from the syringe with controlled air pressure and a disposable needle. If the material had had a longer pot life a different pump would have been selected.

Dispense Parameters:

The substrate was programmed using our proprietary FLOware software. Dispensing accurately and repeatedly requires a combination of precise needle positioning and total control of the gantry and pump action.

Due to the size of the substrate and alignment points a 2X magnifier was added to the camera. This allowed us to use the small alignment marks in the corners and the substrate edge for precise alignment. The mask had excellent dispensing properties and held its form very well after dispensing, even without a UV flash. The mask covered the leads completely without noticeable flow leaving space enough for the underfill process. After the masking material had cured, the underfill process was programmed and run with similar heights to that of the dispensed mask.

Dispense SettingsHeightVelocityValve SpeedAir Pressure / Vacuum
Mask0.002 in0.14 in/sec14,000 cts/sec8 PSI / 0.0 PSI
Underfill0.008 in.100 in/secN/A13 PSI / -3.0 PSI

Conclusions: Masking and Underfill Dispensing for Medical Devices

Both dispensing processes were successful for the testing as described. Adjusting the masking line widths and lengths optimized control for the underfill spread. The positioning of the mask was critical to make sure that sufficient space was allocated for the underfill epoxy.

Final Dispensing Equipment Recommendation:

Dispense SystemMAX Series System with auto vision, red/blue illuminator, autocalibration station – backlit, needle wiper
Dispense PumpPrecision Auger Pump & Time Pressure System
Material (1)Dymax X-499-91-C for Masking
Material (2)Epoxibond-106M-1 for Underfill Dispensing
Needle Size and Type25G Precision needle
Needle Size and Type0.25 inch long plastic hub 25G needle

GPD Global offers dispensing system customization and in-house application evaluations with our customers. Call 1.970.245.0408 or email

Read more about fluid dispensing applications