Altium Designer Lets You Easily Adjust Settings On Your PCB Solder Mask
What is solder mask?
Solder Mask is a covering that protects PCBs from contamination and solder bridging between exposed conductors on the outer surfaces of the PCB.
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Solder mask is a coating put onto the outer layer of a PCB to protect the surface materials from contamination. The surface materials include both conductive and nonconductive materials that benefit from protection to the surrounding environment. The coating is applied to all but conductive surfaces such as component pads and vias necessary to attach parts onto the boards with solder. Without the mask, adjacent conductive pads are more susceptible to solder bridging causing shorts and creating defective boards.
Define mask rule for expansion or contraction at the conductor
PCB software tools create a stencil layer within the Gerbers that is used during fabrication when applying the solder mask material. The stencil masks conductive pads and vias during application of solder resist coating. Stencils are specified for dimensioning the interface of solder mask to intended openings. Dimension requirements include specifying expansion to create the shape at each pad and via site to exclude from coating. Once the shape is defined, clearances are set up to define minimum clearance spacing.
Altium Designer provides easy access to menus for defining PCB solder mask in your design. Rules are set up with graphical interfaces that allow direct access to edit clearances. Clearances include minimum solder mask slivers and spacing minimums to adjacent objects such as conductive pads or silk screen. Tenting for vias may be setup as well, and final check is included before sending documents to PCB fabrication houses.
You want to protect your PCBs from contamination due to handling during manufacturing. PCBs go through a process that exposes them to environmental effects that negatively affect PCB materials. In addition, solder mask provides solder resist to avoid bridging between closely spaced conductive pads. Prevention of bridging maintains integrity of boards leading to high yields. High yields promote advancement to assembly and confidence that components will adhere to designed pad geometries during wave solder.
Set up minimum sliver dimension for solder resist requirements
Masking Techniques Manage Contamination and Avoid Bridging
Protection from contamination comes about by applying a coating to the outer layers of your PCB. Coating is applied during final stages of fabrication using a stencil placed over the PCB. The stencil masks out conductive pads and vias to ensure attachment of components when moving into wave solder during assembly. The openings in the stencil allow application of resin-based coating to the remaining areas of the PCB.
- Consider masking techniques for managing contamination.
- Analyze importance of solder mask in protecting PCBs.
- Complement component clearances with well designed solder mask stencils.
Once you’ve consulted with your fabricator to understand solder resist materials and their requirements, you are ready to prepare the solder mask stencil.
Circuit board software tools for PCB fabrication instructions include making a solder mask layer. The layer defines the stencil fabricators will generate to use when coating the boards with solder resist. Solder resist is used to coat all but the conductive pads where components will be attached to the board during PCB assembly. Vias are also designed to remain exposed for use as test points, although some exceptions include covering vias that could produce arcing when the board is energized. PCB software includes options for tenting critical vias.
Use clearance rules to ensure silkscreen stays off conductors
Solder Mask Stencils Cover Conductive Pads During Resist Coating
The gerber identifying solder mask layer defines a stencil to overlay on the PCB during resist application. Covering conductive pads and vias permits component attachment and test point accessibility further along in the PCB assembly and test process. The stencil masks pads where components will attach. It also masks vias that will be used in manufacture to test energized boards before placement into devices.
- Consider where solder masking fits into PCB fabrication processing.
- Understand solder mask layer specification within the stackup.
- Incorporate Solder Mask layers properly for manufacturing.
Your life improves with PCB layout tools that incorporate intuitive menus for specifying solder mask clearances. Let’s take a look at how Altium provides superior solder mask Rules management and easy output of the Mask Set for fabrication.
Altium Designer provides easy tools for specifying solder mask clearances. In two steps you are in the PCB Design Rules Reference that allows establishment of Masking and Manufacturing Rules for your solder mask. The rules allow definition of mask expansion, or contraction, with respect to each pad and via site. Once expansions are defined, you scope manufacturing rules to include minimum width restrictions for successful application of solder resist in narrow regions between pins and between other objects. Other objects include spacing to exposed copper or to adjacent silk screen.
Generate the Mask Set easily with Altium’s fabrication outputs command
Design Rules Manage Clearances To Set Mask Requirements
Manufacturing rules manage solder mask clearances for successful fabrication. Both masking and manufacturing rules are set using Altium’s PCB Design Rules Reference to navigate to editors. The editors provide production of masking layer in the Gerbers and readies the mask set for fabrication output.
- Visualize Altium’s Tools for setting solder mask design rules.
- Include your solder mask layer into modern, intelligent data formats.
- Embed solder mask gerber layers into document releases.
Altium Designer gives you intuitive command structures for designing solder mask sets. With easily accessible editors you can set solder mask expansions, or contractions, along with manufacturing clearances that define the stencil. With the stencil designed and available in the Gerber files, you’re confident that the board will be protected from contamination and free of solder bridges.