What is the difference between QFN and QFP?
Quad flat package (QFP) is also a surface mount integrated circuit package. In QFP, unlike QFN, the leads extend out in a gull-wing shape (L-shaped). This provides a good footing for the package during the PCB assembly process.
What is solder mask expansion?
It is the expanded distance between SMT pads and solder mask layer. In the production of printed circuit board there should be some space for pads on solder mask layer, which avoid the overlapping of solder mask layer and pads.
What is the minimum solder mask sliver?
0.1 mm
Minimum “Solder Mask Sliver” means the pip of Soldermask between the pads. In our specifications we declared the thickness with a minimum of 0.1 mm. In example for PCB-POOL orders: The applied solder pad is increased 0.075 mm around the copperpad.
What is silk to solder mask clearance?
Summary. This rule checks the clearance between any silkscreen primitive and any solder mask primitive, or exposed copper-layer primitive (exposed through openings in the solder mask). The check ensures that the distance is equal to, or greater than, the value specified in the constraint.
What is solder mask clearance?
Solder mask clearance is a tolerance to decide how close the solder mask can be to the PCB surface features. The purpose of this tolerance/clearance is to provide adequate spacing known as solder dams between surface features that receive solder. This prevents the formation of solder bridges.
Which is the best way to solder a QFN package?
For QFN package soldering, hot air method or IR hot air combined method is recommended. If only IR is used, solder and the terminals on the bottom surface of the QFN are hard to obtain enough heat for soldering, because IR might be blocked by the molded package body, especially for large size QFN packages.
How are the pins arranged in a QFN package?
QFN and DFN packages are plastic encapsulated lead- frame-based packages, which are near Chip Scale Package (CSP) with a low profile (< 1.0 mm). This pack- age type uses perimeter lands/pins on the bottom of the package to provide electrical contacts to the PCB. Perimeter pins can be arranged in dual-in-line (DFN) or quad (QFN) configuration.
How does voiding occur in a QFN pack?
Voiding in QFNs. Voiding in QFNs occurs readily as volatiles become entrapped underneath the pad upon reflow. Unlike Quad Flat Packs (QFPs), QFNs contain no leads and therefore no standoffs to allow for stress absorption and volatile escape.
Can you reduce stencil thickness on QFN solder?
Nevertheless, it is important to note that reducing stencil thickness can have a negative impact on solder connections on the I/O pads. Placement and Pad Design. Even and consistent placement pressure as well as depth is imperative to successful QFN soldering. The component should be under tension on all sides to aid soldering.
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