It's not the quality of the workers in China, it's the quality of the product specifications as set by the company (in the US, or Europe, etc). Apple, and many other companies, have shown that if you specify a quality product - and are willing to pay for it - you will get a quality product from the factories in China. And if a company specifies that cheap parts be used, and is willing to accept low quality products being delivered... then the factories in China are happy to give you what you pay for.
The FoxConn factories have a lower suicide rate than the US national average. People commit suicide in China for the same reasons all people do. For lost love, for embarrassing incidents, for gambling debts, for all sorts of tragic events in their lives for which they can not find a way out.
Keep in mind that people line up for jobs in these factories. That these jobs are considered plums, and that people will often retire and return home to their villages on their savings. Or perhaps they will continue working, sending the bulk of their pay cheque to their extended in their village. Life is hard in rural areas of China. These factory jobs are often all that prevent rural families from falling into total abject poverty. Because of these jobs, many villages have enough money coming from those villagers in the factories that the village itself can start modernizing.