Hello Cove, I am a QA Tech for a medical manufacturing company. I would like to know who responsibility or Dept responsibility it is for investigating root causes on rma parts coming from the field on customer complaints?

Hello Cove, I am a QA Tech for a medical manufacturing company. I would like to know who responsibility it is for investigating root causes on rma products?
This sounds like a good question for your boss :D. Who has the responsibility in your company? In general, it depends on the size of the company. A small company might have a single person take care of RMAs in addition to other responsibilities, while a large company might have a dedicated department for it. Somewhere in the middle of those two extremes, it's usually a function of the Quality department.

My boss thinks QA should investigate the root cause, which would be me. I think each department should investigate the root cause. (i.e software problems should be investigated by the software engineer, circuit boards should be fowarded to the electrical engineer and so forth.) The only investigation I could start to give is that the product is bad or good after I have tested the product. To close the complaint properly, I need to know what is the root cause for this product not working if it tested bad and what will be done to prevent this from reoccuring in the future.

My boss thinks QA should investigate the root cause, which would be me. I think each department should investigate the root cause. (i.e software problems should be investigated by the software engineer, circuit boards should be fowarded to the electrical engineer and so forth.) The only investigation I could start to give is that the product is bad or good after I have tested the product. To close the complaint properly, I need to know what is the root cause for this product not working if it tested bad and what will be done to prevent this from reoccuring in the future.
FWIW: In my organization, we did not issue a Return Material Authorization (RMA) until we had confirmed samples were nonconforming. We expected a customer to segregate the suspect material at his location until the investigation confirmed the material was identified as unfit for use. Even then, if the material could not be repaired, we often authorized scrapping at the site, rather than paying to ship scrap back to us.

Well-run organizations have a multi-discipline Material Review Board (MRB) empowered to handle any and all issues surrounding suspect or non-conforming material. The MRB makes the decision whether to pursue root cause investigations and/or corrective action reviews. The MRB negotiates with the customer whether or not to return material, scrap material, wait for accompanying documentation (sometimes that's the only "nonconformance"), repair or sort it on site.

In small organizations, the MRB usually includes management, production, quality, and sales or purchasing because decisions sometimes involve "political" considerations with customers and suppliers.

The main thing is to avoid jumping to the conclusion that either supplier or customer is "usually" at fault. Each situation should be handled in a consistent, uniform manner without allowing either party to be intimidated or harrassed into taking an economic loss because of the attitude of the other party. This is the main reason the management should always be represented on an MRB.