A U.S. judge told Japanese chipmaker Elpida Memory Inc he was "troubled" by the firm's inadequate efforts to keep creditors informed about its bankruptcy process, and warned he may upend its proposed sale to U.S. rival Micron Technology Inc. Elpida's main bankruptcy proceeding is being handled by a district court in Tokyo, but Christopher Sontchi, the Delaware Bankruptcy Court judge overseeing Elpida's parallel U.S. case, said the company was taking a risk by not keeping creditors better informed. "I don't have a problem tanking a case," judge Sontchi said at a court hearing in Wilmington on Wednesday. Sontchi will eventually have to approve the transfer of U.S. assets after a sale is cleared by the Japanese court. Elpida, the last of Japan's dynamic random access memory (DRAM) chipmakers, was driven into bankruptcy by falling chip sales and foreign competition. The company proposed a $2.5-billion sale to Micron, based in Boise, Idaho, as a way to repay creditors. That deal would catapult Micron into the No. 2 spot in the global market for DRAM chips, behind Samsung Electronics. Bondholders, led by hedge funds Linden Advisors, Owl Creek Asset Management and Taconic Capital Advisors, have said the $2.5-billion price tag grossly undervalues the firm, arguing that Elpida is worth 300 billion yen ($3.78 billion). Saying the planned sale to Micron has lacked transparency, failed to involve creditors and not gone through meaningful competitive bidding, the bondholders have proposed their own restructuring plan to the Tokyo court. The Tokyo court has appointed a neutral examiner to review the two bankruptcy plans and to make a recommendation. Read more.