Just as in Switzerland's three previous ties, Bencic and Wawrinka were the heart and soul of Saturday's epic 2-1 victory over Belgium at Ken Rosewall Arena.
After surviving a third-set tiebreaker to defeat Elise Mertens 6-3 4-6 7-6 (7-0) in the opening singles match, Bencic teamed with Jakub Paul to win their third decisive mixed doubles match of the tournament in a rollercoaster encounter stretching almost eight hours.
Unbeaten in four singles and four mixed matches this week, Bencic - the Tokyo Olympic gold medallist and former world No.4 - teamed with Paul for a 6-3 0-6 10-5 victory after regrouping from a second-set collapse when they won just 12 points.
The mixed victory was necessary after Zizou Bergs continued his impressive campaign with a 6-3 6-7 (7-4) 6-3 triumph over Wawrinka to level the tie as the temperature exceeded 40 degrees during Sydney's summer heat wave.
Despite Wawrinka's defeat, Bencic and Paul credited the 40-year-old triple grand slam winner as the inspiration behind their unlikely march to the final of the $17 million mixed teams' showpiece.
The former Australian, French and US Open champion needed endless ice packs and towels to stay on court but pushed Bergs for two and a half hours before succumbing.
"He's just doing an amazing job to give us the energy," Paul said.
"A great job from Stan to keep Zizou as long as possible on the court.
"So we try to give him back as much as possible. He's just a role model for him to play three hours and then be here (supporting courtside) for the first point of the doubles.
"And it's just great to play with Belinda. Just hats off to her to play almost three hours and then come out again for the doubles.
"That's amazing."
Switzerland will face either Coco Gauff's defending champion USA outfit or Iga Swiatek's Poland in Sunday night's final.
Poland took the early lead in the second semi-final when Hurbert Hurkacz rebounded brilliantly from a sapping three-set loss on Friday night to local hero Alex de Minaur to edge out Tayor Fritz 7-6 (7-2) 7-6 (7-1) in a serving shootout.
Hurkacz's triumph piled the pressure on Gauff to beat Swiatek in a blockbuster battle of grand slam giants to keep the tie alive for America.
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