One-Step Underfill 688

One-Step Underfill 688 Description:

A non-odorous, low surface tension, one component epoxy resin designed as a one-step underfill for flip chip, CSP, BGA and uBGA assemblies.

One-Step Underfill 688 is a low surface tension, one component epoxy resin designed as a one-step no-flow underfill for flip chip, CSP, BGA and micro-BGA assemblies. One-Step Underfill 688 improves product reliability through high Tg, low CTE, and good fill with no voiding. Even though One-Step Underfill 688 does not require flux, it is compatible with no-clean flux residues and provides excellent adhesion.

One-Step Underfill 688 can be dispensed directly following solder paste printing, after which components are placed and the entire assembly is reflowed and cured simultaneously in a standard lead-free reflow process. This eliminates the need for a second assembly process and separate cure cycle. The result of this is faster throughput and higher yields that are achieved in one step through excellent capillary action, fast reflow characteristics, and rapid cure speeds.

One-Step Underfill 688 may be reworked at 120° C and the viscosity of the product remains stable through out its shelf life. This product wets solder to OSP, ENIG, immersion silver, and immersion tin board surfaces.

Features:

• Excellent Capillary Function for Fast Reflow
• Compatible with No-Clean Flux Residues
• Odorless During Printing and Curing
• Flux Action to Make Solder Connections
• Non-Hygroscopic
• Reworkable
• Good Storage Properties
• No Voiding
• Cures in Lead-Free Profile

Application:

• Curing: Standard lead-free solder profile (RSS), maximum temperature 255° C (491° F).
• Rework: Flows at 120° C – 140° C (248° F – 284° F).
• Print your solder paste, dispense One-Step Underfill 688, place the components, and finally reflow all in one assembly line. One-Step Underfill 688 is designed to solder on its own without the need for solder paste.
• The dispense pattern for small die applications 6.35mm (.25”) is typically single center dot only, with no secondary dispense or final perimeter bead required. Ensure that all pads are covered with One-Step Underfill 688.
• The low viscosity and excellent wetting characteristics of the product allow the material to “self-fillet” along the edges of the die. For larger pads, multiple dots or x patterns may be required to ensure that all pads are covered.
• The dispense pattern for larger die applications is typically dot pattern from the center out. Since the product improves solder wetting there is no need to avoid solder pads. Cover all pads to be soldered to on the board and place the component.
• One-Step Underfill 688 is reworkable by heat. The suggested rework procedure is to heat the part to be removed to its standard reflow temperature and removing it with a flat spatula. Using a soldering wick and a soldering iron, soak up excessive epoxy. Scrub the pads clean, and if necessary, clean with a small amount of solvent, such as methyl ethyl ketone or isopropyl alcohol.

Recommended Reflow Profile

One-Step Underfill 688 is designed for lead-free processing. If a lead-free profile is not run or longer curing is needed, a 150° C (302° F) soak can be added. Twenty minutes is recommended, however the length of time is dependent on the density of the board.

Handling and Storage

• One-Step Underfill 688 has a work life of 2 months at 5°C or 3 months at 0°C.
• One-Step Underfill 688 has a frozen shelf life of 3 months.