What are QFN/DFN packages?

Quad-flat no-leads (QFN) and dual-flat no-leads (DFN) packages are used to physically and electrically connect integrated circuits to PCBs. They are leadframe based chip scale packages with pads instead of legs or pins for their electrical connections.

• Quad because they have connections to all four sides of the package. Quad is a word of latin origin that means four or fourth.
• Flat because it is a flatpack surface mount component. Flat packages are defined as rectangular or square packages with leads parallel to the base plane, attached on two opposing sides of the package periphery. In our case it is on all four sides. Hence the Quad. That's also where DFNs or Dual flats come in. They are describing pretty much the same thing.
• No lead because they don't have any pins, legs, however you want to call them.

Epoxy molding compounds for QFN/DFN packages.

Molding compounds for QFN packages don't just need to be high end with high filler loading. They also need to have low stress, low moisture absorption, high adhesion, low viscosity and more.

For example a lower release force of a product from the GR 900 product line can help the production line with more continuous mold shots. Or a good adhesion force post mold cure and after MSL testing makes sure that we will have a good delamination performance.

We want to make sure that the packages will pass all Reliability tests such as SAT, PCT, TCT, HTST and THT without any defects. The products need to have excellent copper wire compatibility, good fluidity to avoid wire sweeping and also meet UL94 V0 rating.

To add to this list of requirements, MSL3-MSL1 260°C is a plus and also the material needs to be "Green" without Br/Sb and comply with Rohs. Simple, right?

That's why we singled out some products that we recommend to mold a QFN package and they are:

• Hysol GR900C
• Hysol GR900 Q1L4
• Hysol GR900 HD6/HD3A which are under development

These are high end epoxies with high spherical silica loading. Their excellent properties such as low CTE, lost stress, low water absorption, low shrinkage and low ionics ensure the package reliability.

Hysol GR900 Series is a black semiconductor-grade epoxy molding compound, designed for the encapsulation and protection of quad-flat no-leads (QFN) and dual-flat no-leads (DFN). GR900 has been formulated to provide the best possible moldability and to have a very low internal stress to reduce warpage, as well as low moisture absorption to increase MSL performance.

Moldability

• Good continuous moldability performance

• Good fluidity to prevent wire sweep (W/S) failures

Reliability

• Good reliability performance on QFN package. 

• Excellent compatibility with Copper wire

• Meet MSL3~MSL1/260°C requirement

Other

• Meet UL94 V-0 flammability rating at 1/8 inch (3mm) thickness

• Contains no Bromine (Br) or Antimony (Sb) to comply with ROHS

Presentations

Die attach for QFN & DFN packages

Die attach pastes for QFN applications