* ASMI sells 12 pct of ASM Pacific for 422 mln euro
* Investors had hoped for a larger stake sale
* ASMI shares fall as much as 16 percent (Recasts with final terms of share placement, analyst quote)
By Sara Webb
AMSTERDAM, March 13 (Reuters) - Dutch semiconductor equipment maker ASM International NV sold a smaller-than-expected stake in its Hong Kong-listed unit, disappointing investors who had hoped a break-up of the firm might create more money for shareholders.
ASMI said late on Wednesday it had raised 422 million euros ($547 million) by selling 12 percent of ASM Pacific Technology to institutional investors in a share placement, leaving it with a 40 percent stake in the Hong Kong business.
ASMI shares in Amsterdam fell as much as 16 percent to their lowest since November when the firm announced the share placement during trading hours, and closed down 10 percent.
The ASM Pacific shares in the placement were sold at HK$90.00 each, a discount of 6.7 percent to Wednesday's closing price of HK$96.45 in Hong Kong. HSBC and Morgan Stanley were joint bookrunners on the deal.
Amsterdam-listed ASMI consists of its own front-end processing, or production, of silicon chips, and the back end - the dicing and packaging of microchips - held by ASM Pacific.
The Dutch company has been at war with some investors over its valuation since 2006 because its majority stake in ASM Pacific has consistently been worth more than ASMI's market capitalisation.
ASMI's shares also trade at a substantial discount to those of its peers, according to StarMine Estimates, based on measures including the ratio of price to net asset value, the ratio of price to cash flow, and the ratio of enterprise value to EBITDA (earnings before interest, tax, depreciation and amortisation).
ASMI's founder and largest shareholder, Arthur del Prado, told investors in May 2012 that he favoured splitting up the group, and there were few synergy benefits in keeping ASMI combined with ASM Pacific.
Since then, ASMI has spent several months looking into how best to unlock its full value for investors.
On Wednesday it said that it had considered several options including a full or partial placement or sale of its stake in ASM Pacific, a spin-off of shares in ASM Pacific, and several merger alternatives.
"Expectations were high and they need to do more than this," said Robin van den Broek, analyst at ABN Amro, adding that the sale of such a small stake would not resolve the problem of the holding company discount.
ASMI said it plans to distribute about 65 percent of the cash proceeds from the placement, equal to about 4.25 euros per ordinary share, to shareholders.
This is "a really poor halfway house solution, and not enough of the proceeds are being returned to ASM shareholders," said Olivetree Financial Group in a note on the deal. ($1 = 7.7568 Hong Kong dollars) ($1 = 0.7722 euros) (Reporting by Sara Webb; Editing by Mark Potter and Kenneth Barry)