1990, a foreigner's invention was patented internationally and in many countries, but he didn't apply for a patent in China. Is his invention infringed in China?

Patents in the 1990s have not been applied in China, so they can't claim priority now, so they can't be authorized in China, and they can be used casually without patent right. A similar patent filed in China in 2005, if authorized, may hinder you, and you may infringe. Of course, you can also void it, which is also possible. If you fail, try to avoid it.

According to what you said, the domestic application is similar to the foreign application, so it is likely to be an improvement of the invention, which means that the domestic application is an improvement on the basis of the foreign application (in principle, the domestic application also violates the right to apply abroad). If that's the case, it's easy to avoid his patent protection, as long as I don't have to go to where he improved.

In short, I use your patented technology abroad, but it is not infringement to use or sell it at home, because you have no authorization from China Home Bureau. As long as I don't need to improve your domestic application, I can say that I use your patented technology abroad. Why, you bit me? !

There are many ways to avoid it, it depends!