Asymtek has developed an improved method for applying solder-ball reinforcement material to semiconductor packages that can eliminate the need for dispensing secondary underfill in board assembly. For this, the dispenser shoots a fluid stream of underfill adhesive as small as 100 micrometers wide between balls on CSPs and BGAs during the 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 the offering of packages with improved reliability without the cost of traditional underfilling. Typically, CSPs or other BGA-type packages require adhesive underfill to glue the component rigidly to the substrate to prevent failures due to temperature shock. If the primary failure of a non-underfilled CSP or other BGA occurs at the ball-package interface, the pre-applied solder ball reinforcement reduces the probability of joint failure at that location. The cured reinforcement material relieves the stress at the ball-substrate interface by reducing the geometric concentration factor at that point. Therefore, the solder joint withstands more load during shock-loading or thermal cycling.
EPP EUROPE 431
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