Mau said boom grew out of a competitive product review when executives at the credit union realized they could create a card that would resonate with some consumers by eliminating negatives such as fees and dispensing with features some consumers now find archaic such as paper checks.

"Many prepaid cards charge high fees," Mau said. "We did not want to and we know that makes our card more attractive."

As for the name, Mau said boom means "just like that" and that is how easy it is to use boom to make purchases.

"We developed the card internally, using our own resources," he noted. "It really is no more complicated than developing a checking product. The development was not difficult."

A prepaid card expert who asked for anonymity citing unfamiliarity with boom, said it was highly unusual for an institution of Heritage Grove's size to build its own card.

Unlike some prepaid cards, applicants for a boom account must meet minimal creditworthiness standards, according to Mau. With boom, the credit union plans to "attract consumers with whom we can build relationships."

"Our income with boom is earned through the interchange fees," Mau said. "And, we develop relationships. They come back to us for their loan needs."

That means eventually boom account holders may want a conventional checking account, credit card, car loan and so forth. It is in those products that Heritage Grove believes it will find revenue in its boom accounts.

Mary Monahan, EVP and research director of mobile with Javelin Strategy + Research, said pursuing a plan to upsell members into products such as auto loans is a good strategy.

Millennials, in particular, seem attracted to prepaid cards and that generation is crucial to credit union survival, she added.

"They need the younger consumers or credit unions will die," Monahan said.

So far, Heritage Grove has opened 117 boom accounts, Mau said.

In its promotions, the credit union stressed that boom is similar to highly rated prepaid cards such as Green Dot and Bluebird.

Mau said Heritage Grove has focused on raising awareness of boom at Willamette University, which is also in Salem. The credit union has also promoted the card in the Salem Weekly.