Aaron Liang From my understanding of the directive, there is no need to perform testing although if it is required to produce evidence to demonstrate conformity it should be done. That being said it is up to the manufacturer to perform the due diligence to show conformity and if assessing the methods of manufacturer and the materials involved is sufficient, there shouldn't be a reason why a declaration of conformity isn't sufficient. In your case you could structure it such that all of your RoHS components have documented declarations of conformity and rolling it up to your finished device to demonstrate it is compliant too.

Mauricio G. Pincilotti Thank you very much Aaron. Until this moment I have demonstrated conformity with RoHS Directive in this way, but surfing on the web I found laboratories that offer the service of RoHS verification or something like that, which made me hesitate about the requirements to demonstrate conformity and the necessity of perform a test with a third party laboratory.
Thank you again for share your thoughts and experiences!

Jim Kandler Correct, there is no explicit statements in the directive that requires chemical testing of parts. Collection, analysis and evaluation of supplier declaration is the most commonly used method of compliance to RoHS.
The directive does require that a quality system is implemented. In an effective quality system audits must be performed periodically and where there is concern. If that function is applied to RoHS then you must audit your supplier parts and declarations at some time, and you must verify correctness of declarations that are questionable. Laboratory testing is the only way that I know of to do these effective challenge and mitigate concerns. There are survey level tests that can be performed inexpensively by XRF that indicate presence or absence, and the more expensive chemical tests which indicate the actual levels of substance present.

Jim Kandler Part of the response was cut off.
Audits of the supplier practices is also a potential means of doing this, but an onsite audit might be needed to uncover potential issues that could not be observed remotely.
The finished device rollup is also important, since a part of your CE Mark Technical File for each finished product there must be a RoHS Declaration of Conformance. This rollup is the evidence to support the DoC.

Jim

Mauricio G. Pincilotti Thank you very much Jim for sharing your experience and thoughts!
Mauricio

Bob Parsons If the components in the device are made to print and the specs require ROHS compliance, you can review your MFG process and if not introducing non-compliant materials,

Bob Parsons you can write a declaration of conformance stating you have manufactured product in compliance with ROHS.

Bob Parsons At some point you'll need to verify the components are indeed ROHS compliant through supplier auditing.