The tech giant’s largest union escalated its dispute with management after failing to reach an agreement over pay and working policies.Unionized workers at Samsung Electronics said Wednesday they would go on an indefinite strike, an escalation of a rare labor dispute that could disrupt the technology giant’s world-leading chip business.An estimated 6,500 workers walked off the job on Monday for a planned three-day strike over pay and working conditions. The Nationwide Samsung Electronics Union decided to extend the strike after “hearing no word” from the company, according to Lee Hyun Kuk, the vice president of the union, which represents 28,000 workers, or a fifth of the Samsung’s global work force.Samsung, South Korea’s biggest private employer, has long been the world’s largest maker of memory chips, which help computers and other electronics equipment store information. The company is also a leading manufacturer of logic chips, which make computers run, behind only Taiwan Semiconductor Manufacturing Company.The union said it has been negotiating with Samsung since January over vacation days and wages. The union said its work stoppage this week has slowed some Samsung operations and production. A Samsung representative said the strike has not affected production and that the company remained “committed to engaging in good faith negotiations with the union.”In June, workers went on a one-day strike, the first in the company’s history.Union workers are demanding a wage increase by 3.5 percent, improved bonus policies and an extra day of vacation. It also wants Samsung to agree to compensate workers for any lost wages during the strike.“We won’t go back until all of the demands are met,” Mr. Lee said.Last week, Samsung said that it would report a larger-than-expected jump in operating profit for the second quarter, of $7.5 billion. The company’s stock has recently set a series of multiyear highs as demand for chips to power A.I. applications has soared.For decades, Samsung was known for its aversion to organized labor, and unions have organized workers at the company only in the past several years.Labor strikes in South Korea are not uncommon. Since February, over 10,000 doctors walked off the job in protest of government plans to increase the number of admitted medical students. Last spring, thousands of construction workers rallied over discontent with the country’s labor policies. More