Solder Paste Stencils
Manual soldering was the way to go for most PCB hobbyist designers. However, it is really a nightmare to solder surface mount devices which are really tiny components. Under this condition, you need a more efficient way to get those components on your board. Solder paste stencil may be a good choice for you.
Solder paste stencil is the process of using a stencil made out of metal or a polymer to quickly apply solder paste to all of the pads on your bare board. This stencil contains a bunch of holes in it, which represents all of the SMD footprint pads on your board layout.
When you lay this stencil over your bare board, you can squeegee a layer of solder paste over it, leaving a nice, uniform layer of solder on all of your SMD pads.
The core component of solder paste stencil is, of course, the solder paste. This is used to attach components to your bare board, and hold your entire electronics project together. Besides, it serves three primary functions:
Binding. It helps to bind surface mount components to your circuit board during the assembly process.
Cleaning. When melting solder paste in a reflow or wave-soldering oven, the solder will clean the copper to help minimize any oxidation damage.
Connecting. It provides connectivity between every pad on your PCB and every pin on your components.
Solder paste comes in a variety of compositions, including:
Tin-lead or tin-silver-copper varieties for standard plastic component packages being assembled on an FR-4 epoxy circuit board.
There’s also tin-antimony solder paste which is used on PCBs that require greater resistance to tension and strain.
You’ll find lead-free solder as an alternative to traditional tin-lead. This requires a higher melting point and is harder to work with, but meets RoHS and reach regulations for lead-free electronics.
When purchasing solder paste for stenciling, two types for you to choose, one is no clean paste another is water soluble one.
No clean solder paste involves a rosin made from tree sap that makes it safe to leave solder residue on your PCB. If you get some of this paste on your board during the stenciling process, you won’t have to clean it off. However, if you need to clean any excess paste off of your board, then consider picking up a water soluble version, which can be removed by gently whipping it away with an IPA soaked kimwipe. This type is also known for its improved thermal stability, allowing higher soldering temperatures.