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LOCTITE ABLESTIK QMI3555R
- Wide processing window
- Low temperature profile
- Low stress on die
Product Description
LOCTITE ABLESTIK QMI 3555R is a low temperature processing, no dry, silver glass die attach adhesive for the attachment of integrated circuits in both solder seal and glass seal hermetic packages. It is designed for fast firing large die or small dies on either gold plated or bare ceramic substrates. The paste fires into a film that provides high thermal and electrical conductivity as well as excellent initial adhesion. It is extremely resistant to degradation during temperature cycling from -65°C to +150°C.
LOCTITE ABLESTIK QMI 3555R incorporates a patented silver/vanadium glass. Sub-350°C firing enhances the reliability of devices fabricated with sub-micron design rules. Also, in cofired package applications, nickel diffusion through gold plated seal rings and leadfinger pads are minimized at lower temperatures. QMI3555R low stress allows for a thin bondline, offering improved thermal performance for high power devices.
LOCTITE ABLESTIK QMI 3555R can be fired at temperatures between 300°C and 450°C on bare ceramic. On gold plated parts, the minimum peak should be 325°C. The minimum dwell time should be at least 14 minutes above 300°C when the peak is <325°C. Higher peak temperatures require less dwell time. There should not be any rapid spikes in the ramp that would volatilize the solvents and create voids.
Compared to LOCTITE ABLESTIK QMI 3555, the R in QMI 3555R stands for RESIN, so the QMI 3555R (resin) version contains ~0.1% by weight of resin added over QMI3555 to slow down solvent drying. Technically both products have comparable properties after cure.
Technical Specifications
| General Properties | |||||||||
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| Physical Properties | |||||||||
| Thixotropic index Thixotropic index Thixotropic Index is a ratio of a material s viscosity at two different speeds in Ambient temperature, generally different by a factor of ten. A thixotropic material s viscosity will decrease as agitation or pressure is increased. It indicates the capability of a material to hold its shape. Mayonnaise is a great example of this. It holds its shape very well, but when a shear stress is applied, the material easily spreads. It helps in choosing a material in accordance to the application, dispense method and viscosity of a material. | 10 | ||||||||
| Viscosity Viscosity Viscosity is a measurement of a fluid’s resistance to flow. Viscosity is commonly measured in centiPoise (cP). One cP is defined as the viscosity of water and all other viscosities are derived from this base. MPa is another common unit with a 1:1 conversion to cP. A product like honey would have a much higher viscosity -around 10,000 cPs- compared to water. As a result, honey would flow much slower out of a tipped glass than water would. The viscosity of a material can be decreased with an increase in temperature in order to better suit an application | 35,000 mPa.s | ||||||||
| Chemical Properties | |||||||||
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| Thermal Properties | |||||||||
| Thermal Conductivity Thermal Conductivity Thermal conductivity describes the ability of a material to conduct heat. It is required by power packages in order to dissipate heat and maintain stable electrical performance. Thermal conductivity units are [W/(m K)] in the SI system and [Btu/(hr ft °F)] in the Imperial system. | 80 W/m.K | ||||||||
Additional Information
What is the difference between QMI3555 and QMI3555R?
The R stands for RESIN, so the QMI 3555R (resin) version contains ~0.1% by weight of resin added over QMI3555 to slow down solvent drying. Technically both products have comparable properties after cure.
QMI 3555R can be fired at temperatures between 300°C and 450°C on bare ceramic. On gold plated parts, the minimum peak should be 325°C. The minimum dwell time should be at least 14 minutes above 300°C when the peak is <325°C. Higher peak temperatures require less dwell time. There should not be any rapid spikes in the ramp that would volatilize the solvents and create voids.
See the Technical Data Sheet for Firing profiles.
Can you pack QMI 3555R in smaller syringes?
Henkel is supplying such "silver glass type of QMI 3555R" die attach adhesives only in 2-ounce (155g) jars because of the silver settlement risk in the syringe and serious Free Thaw Voiding (FTV) issues in case such syringes would be stored at -40C and come back to ambient temperature. This will lead to microvoids in the syringe and consequently also in the bond line after dispensing.
One way to prevent this "micro voiding in the syringe" after down filling (if it happens) could be to add a centrifuging step on the syringes prior to dispensing :
- Use syringe kits from Nordson or similar (without the pistons inserted)
- Fit a tip cap, and hold the syringe vertical
- Pour some Ag glass into the syringe (it needs a steady hand and a bit of practice, but it’s not difficult)
- Insert a piston (white or beige should work OK, try to avoid getting QMI 3555R trapped between the piston & the syringe wall)
- Fit a top cap to seal the syringe
- Now – mix/degas the material in the syringe using "centrifuging equipment" as described below
- Thinky ARE-250 or ARE-310 mixer (available from Intertronics) or a “Speedmixer” from Synergy Devices would work well
- Vacuum versions of these mixers should be available, which will work better than non-vacuum versions but may not be needed
- The process takes about 5 mins, but parameters should be optimized by DOE at the customers' site
- Check the syringe, and push the piston down onto the surface of the QMI 3555R, if it lifted during the degassing
- The syringe is now ready to use and should be used within the same shift to prevent the settling of the silver in the syringe (or centrifuge again prior to use)
Such (vacuum) centrifuging equipment is commonly used in semiconductor back-end assembly.
Why do I need a jar roller?
There are numerous options available on the market, including single jar and multiple jar rollers. The primary purpose of using a jar roller is to homogenize the silver/glass paste prior to use. As specified on the TDS: "upon receipt, the paste must be immediately placed on a jar roller and continuously rolled for a minimum of 16 hours before opening the jar".
There are no specific brands recommended, the most important is to achieve the homogeneity of the paste before its use.