ST. PAUL (AP) _ A federal arbiter on Tuesday awarded Minnesota Mining and Manufacturing Co. $107 million in damages, ruling that Johnson & Johnson infringed on 3M's patents for a new fiberglass medical casting tape.

Former federal magistrate Janice Symchych found that Johnson & Johnson copied 3M's Scotchcast Plus in order to produce a nearly identical fiberglass tape that unfairly competed with 3M's.

Symchych set damages to Maplewood-based 3M at $53,636,348, but she said Johnson & Johnson's willful infringement in 1987 warranted doubling the amount. Symchych's order effectively forces Johnson & Johnson to take its product off the market or pay royalties.

The five-month trial that ended in late December centered around a tape that allows technicians to immobilize broken bones quickly. Johnson & Johnson, of New Brunswick, N.J., maintained that the patents granted 3M for its orthopedic casting tape were adapted from research that predated 3M's patent filing.

But Symchych found that: ''3M's research and development scientists created and steadily improved upon a whole new generation of fracture immobilization products. 3M opened a whole new market in casting products.

''After a thorough challenge to the validity and enforceability of these patents ... the court believes that the patents must stand. Had (Johnson & Johnson) not infringed, 3M could have exploited this market it created. The damage award and injunction are necessary to make 3M whole, and to restore the rights 3M may claim as a patent holder.''

Attorneys for the two companies could not immediately be reached for comment.