During last four years I've changed job thrice. Surely, it is bit suspicious for employer. ;-)
However, usually my goal was not only to increase salary (though it was quite important surely), but also to find more interesting projects or collectives where I could better grow in professional sense. So usually I told mainly about these ambitions, rather than about salary matters.
Anyway you should keep in mind that employers' HRs or tech-leads who holds interview are not "just fallen from the moon" and they understand two main reasons of changing job:
- salary lower than wishes;
- boring projects/bosses/colleagues.
Usually you'd better to avoid blaming your previous job, salary or colleagues. ;-)