Is link exchange a part of black hat SEO?

As i think reciprocal link is not a good way to promote the site.

Where as I know, when your website has a link of your created website in your portfolio and a backlink of your website on that website as signature the developer of website. then it is not part of blackhat.

It is kinda sad people have begun talking of link exchanges as black hat (I don't blame the OP though because what counts is what Google thinks) because the net started with sites doing link exchanges. See http://misvblog.com/the-history-of-natural-links/

Link exchange is part of off page optimization but when follow some basic criteria and rules then it is what hat SEO otherwise it is consider as Black hat SEO.

*Link must be relevant
*the outbound link less than 50 at link or resource page
*Link adding only at link page and partner pages.
*Link page must be PR0 or above
*Link page index by Google Recently
* Link should be try way not Reciprocal

I agreed that link building is not a part of black hat SEO, but doing copy of some one post and artical is part of black hat SEO, so please do unique thing. We found lots of thing which help us for Off page SEO but  we cant do same thing which was done by others...

No Link exchange is not black hat seo. but you remember if you are using niche site

 when exchange link from non relevant site there will be no chance of traffic but only the waste of your own link juice. Bulk link exchange will triggers search engines that site having some un natural behavior.