Areas that should not be soldered may be covered with solder resist (solder mask). One of the most common solder resists used today is called "LPI" (liquid photoimageable solder mask). A photo-sensitive coating is applied to the surface of the PWB, then exposed to light through the solder mask image film, and finally developed where the unexposed areas are washed away. Dry film solder mask is similar to the dry film used to image the PWB for plating or etching. After being laminated to the PWB surface it is imaged and develop as LPI. Once common but no longer commonly used because of its low accuracy and resolution is to screen print epoxy ink. Solder resist also provides protection from the environment.
What solder resist with a four-word name is a popular choice in the industry?
liquid photoimageable solder mask

Evidence of wheeled vehicles appeared in the mid 4th millennium BC, near-simultaneously in Mesopotamia, the Northern Caucasus (Maykop culture) and Central Europe. The wheel initially took the form of the potter's wheel. The new concept quickly led to wheeled vehicles and mill wheels. The Sumerians' cuneiform writing system is the oldest (or second oldest after the Egyptian hieroglyphs) which has been deciphered (the status of even older inscriptions such as the Jiahu symbols and Tartaria tablets is controversial). The Sumerians were among the first astronomers, mapping the stars into sets of constellations, many of which survived in the zodiac and were also recognized by the ancient Greeks. They were also aware of the five planets that are easily visible to the naked eye.
What form did wheels initially take?
potter's wheel

The Samoan word for dance is siva with unique gentle movements of the body in time to music and which tells a story, although the Samoan male dances can be more physical and snappy. The sasa is also a traditional dance where rows of dancers perform rapid synchronised movements in time to the rhythm of wooden drums (pate) or rolled mats. Another dance performed by males is called the fa'ataupati or the slap dance, creating rhythmic sounds by slapping different parts of the body. This is believed to have been derived from slapping insects on the body.
What does "siva" mean in Samoan?
dance