Discounting the sophisticated image of high technology here in the Silicon Valley, the Immigration and Naturalization Service claims that as much as one-quarter of the work force in this capital of the computer industry is made up of illegal aliens.
In opening a new base of operation here last week - a full-service INS office - the federal agency announced it will conduct a minimum of two raids a week in search of undocumented aliens on the job in local high-tech firms.
''High technology is a sophisticated industry, and it's difficult to make people realize that because of the nature of the industry, illegal aliens are working here,'' says John Senko, officer in charge of the new office. ''Almost every business with 40 or more employees has some illegals.''
''We strongly believe that 25 percent of the total combined work force is in the illegal-alien category,'' says Howard Ezell, a commissioner for the service's western region. The work force he speaks of also includes the service and agricultural industries in the area. (The edges of the Silicon Valley, well over 400 miles from the Mexican border, are still a checkerboard of plowed fields, where aliens have traditionally found work.) But the focus of the raids has been at high-tech firms. Two raids last week netted 27 illegal aliens, each making $5.50 to $7.50 an hour.
The INS assertions have raised complaints from civil rights and minority groups, who claim that 25 percent is an exaggerated figure used to justify INS contentions that undocumented workers are filling jobs that might be taken by unemployed Americans. They also note that the new publicity coincides with scheduled congressional discussion this month of the Simpson-Mazzoli immigration reform bill, which the INS favors. Critics further argue that the new raids will be aided unfairly by last week's US Supreme Court ruling that said INS officers may block workplace exits in order to question workers inside about their citizenship - a procedure long disputed as a violation of the United States Constitution's prohibition of unreasonable searches and seizures.
''I haven't seen anything to indicate there are growing numbers'' of illegal aliens in high-tech, says Joaquin Avila, president of the Mexican American Legal Defense and Education Fund in San Francisco. ''If that were the case, all the aliens in Los Angeles would be up in San Jose. By focusing on high-tech, it's (the INS's) way to blow the numbers out of proportion.''
But the fact is that INS raids consistently find illegal aliens on the job in this industry. And the pay in high-tech is considered better than in other areas for the unskilled and semiskilled positions often taken by aliens.
''Twenty-five percent does not surprise me at all,'' says Patricia Fernandez-Kelley, a research associate with the Center for US-Mexican Studies at the University of California at San Diego. ''They are accurate to say there is a large percentage of undocumented aliens in this industry.''
But Dr. Fernandez-Kelley's reasoning differs from that of the INS. She regularly interviews employers and aliens alike and concludes that the high-tech industry needs undocumented aliens as a source of cheap labor that is difficult to find among American citizens. The INS claims that aliens displace Americans in jobs.
''It's a mistake to assume the kind of work done in high-tech is sophisticated,'' Dr. Fernandez-Kelley asserts. ''Yes, electronics requires very specialized technicians and engineers, but the integrated circuits that are changing our lives are assembled by hand. The manufacture of these very complicated gadgets is labor-intensive.''
She notes that many electronics firms have their manufacturing arms overseas, where they can pay as little as 35 cents an hour for labor. It stands to reason, she says, that any company wanting to be competitive is going to want the cheapest labor it can find. ''We find a lot of home work, women assembling electronic parts in their kitchens. And I know of several cases of companies that have moved to San Diego County because of the availability of cheap labor, '' says Dr. Fernandez-Kelley. (She would not identify the companies, because of the confidentiality promised in exchange for the research she does on site.)
She says these facts should be better-known, in light of the eagerness of many communities to snare high-tech business, which is considered the ''avant-garde of economic development.'' The Simpson-Mazzoli bill is a reflection of unreasoned public fear of the pressures in Mexico and Latin America. She says the direction of immigration reform flies in the face of economic reality, which points to the need in the near future for a growing labor force.
The Simpson-Mazzoli bill would give the United States a stiffer approach to the problem by allowing amnesty for aliens already here, providing for a national identity card, and punishing employers for hiring illegal aliens that don't have that form of identification.
Last month, 46 aliens, or 10 percent of the work force, was apprehended at General Technology, one of the largest printed-circuit and testing companies here.
Becky Lowe, who handles the hiring for General Technology, says that when a brown-skinned, non-English-speaking jobseeker hands her a social security card, a green card (an alien registration card), and a California driver's license, there's no way to tell if he can legally work in the US.
She routinely calls in the names of alien numbers to an Immigration and Naturalization Service computer center to verify them when hiring employees. But while acknowledging that 10 percent of General Technology's plant force was arrested in an INS raid here last month, she says, ''We're not investigators.''
General Technology vice-president Tom Kruse suggests that given all the precautions employers already take, Simpson-Mazzoli provisions would not be much more effective and would appear to penalize employers unfairly.