HR talent software vendor iCIMS has a new business partner and $35 million to spend on expansion. The company announced this morning that private equity fund Susquehanna Growth Equity has taken a minority stake in the firm.

“The company,” says today’s announcement, “plans to significantly increase investments in marketing, product development, and additional acquisitions that will further accelerate the organization’s rapid growth and expansion plans.”

Founded in 1999 by its CEO Colin Day, iCIMS offers SaaS-based talent acquisition, onboarding, performance and talent management tools. The company has made the inc. 5000 list of fastest growing companies for six consecutive years, finishing 2010 with revenue of $25.6 million (2011 rankings won’t be released until later this year).

The company has a strong presence in the SMB market, and says it added its 1,000th customer during 2011, though that’s a little fuzzy since the company has been claiming that milestone at least since 2008. Its client list includes Continental Airlines, FedEx, Liz Claiborne, Treasure Island Las Vegas, and eHarmony.

For years, even as equity funds began discovering HR tech, iCIMS eschewed outside investors. The press release announcing the Susquehanna investment makes the point that “iCIMS had been self-funded, highly profitable, and grown solely organically at 43% CAGR (compound annual growth rate) since 2003.”

The announcement doesn’t detail what led to the investment, and a company spokesperson hadn’t called back when this was posted. However, CEO Day did say in the press release, “We could have sustained our current rate of growth without an outside investment — but the timing was ideal to take iCIMS to the next level. This minority growth equity investment from SGE will help us dramatically accelerate our aggressive expansion plans. We look forward to offering deeper and broader services and support to our clients, and further penetrating the SMB marketplace with our high-value solutions and services.”

iCIMS said it expects to grow full-time staff by almost 25 percent this year. These employees will be spread throughout the United States and abroad and will be concentrated in marketing, sales, and technology.

The HR tech sector has been a hotbed of mergers and acquisition in the last few years. Taleo in particular has bought several companies in the HR sector to enhance and strengthen its product lineup. In the last few months, Taleo and Kenexa have seen their stock bid up, especially so since Oracle and SAP bought up vendors with strong SaaS products.