LOCTITE ABLESTIK QMI3555
- Wide processing window
- Silver/Vanagium glass
- Reworkable at less than 350°C
LOCTITE ABLESTIK QMI3555 is formulated using a Polymodal Metal Flake distribution technology which utilizes a combination of specifically selected silver flakes that, in conjunction with a unique glass, maximizes adhesion to gold while simultaneously enhancing rheological properties of the paste. It is a No-Dry paste that possesses rheological properties which optimize dispensability during die attach and it is reworkable at less than 350°C.
LOCTITE ABLESTIK QMI3555 incorporates a patented silver/vanadium glass at a metal to glass ratio of 6.5:1 by weight. The paste is completely resinless and 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.
A thin bondline combined with its excellent thermal properties make QMI3555 attractive for use in high power devices. Because of its wide processing range, one common low temperature firing profile can be used for both solder and glass sealed packages with nearly all die sizes.
| 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.
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
The viscosity of a material can be decreased with an increase in temperature in
order to better suit an application
| 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.
QMI 3555 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 at least be 14 minutes above 300ºC when the peak is <325ºC. Higher peak temperatures require less dwell time. The material is completely resinless and contains only low boiling solvents that are involved during the early stages of the firing process.
See the Technical Data Sheet for Firing profiles.
Can you pack QMI3555 in smaller syringes?
Henkel is supplying such "silver glass type of QMI 3555" 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 3555 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 3555, 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.
tl;dr no QMI 3555 in syringes available, but process can be optimized using (vacuum) centrifuging equipment ….