Carlsbad, CA -- Asymtek (www.asymtek.com) has developed a method for applying solder ball reinforcement material to semiconductor packages that can eliminate the need for dispensing secondary underfill in PCB assembly. 

The company's DispenseJet DJ-9000 shoots a fluid stream of underfill adhesive as small as 100 micrometers wide between balls on CSPs and other BGA packages during the semiconductor packaging process. Other methods of pre-applied underfill have resulted in contaminating the solder balls or have been too costly to ramp into production.

Jetting the underfill prior to board assembly without contaminating the solder balls allows semiconductor packaging companies to offer packages with improved reliability without the cost of traditional underfilling.

Typically, CSPs or other BGA packages require adhesive underfill to glue the component rigidly to the PCBA to prevent failures due to shock. If the primary failure of a non-underfilled CSP or other BGA package occurs at the ball-package interface, the pre-applied solder ball reinforcement reduces the probability of joint failure at that interface.

The cured reinforcement material relieves the stress at the ball-substrate interface by reducing the geometric stress concentration factor at that point. Therefore, the solder joint withstands more load during shock-loading or thermal cycling.

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