Stock-Based Compensation

6 Months Ended

Jun. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

6. Stock-Based Compensation

The Company uses the Black-Scholes option pricing model to calculate the fair value of stock option awards and options granted under the Vicor Corporation 2017 Employee Stock Purchase Plan (“ESPP”) as of their grant date. Stock-based compensation expense, net for the three and six months ended June 30 was as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Cost of revenues	$	59	$	38	$	115	$	72
Selling, general and administrative		957		215		1,499		395
Research and development		164		34		302		74

Total stock-based compensation	$	1,180	$	287	$	1,916	$	541

The overall increase in stock-based compensation between the 2018 and 2017 periods was due to an increase in stock options granted between July 1, 2017 and June 30, 2018. The increase in selling, general and administrative stock-based compensation for the three and six months ended June 30, 2018, compared to the same periods in 2017, was also due to increased expense for certain Vicor stock options held by a non-employee. The fair value of these stock options, and related stock-based compensation, are adjusted monthly based on changes in the assumptions under the Black-Scholes option pricing model, including the price of the Company’s common stock, in accordance with the accounting for stock options granted to non-employees.

Compensation expense by type of award for the three and six months ended June 30 was as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Stock options	$	1,005	$	287	$	1,598	$	541
ESPP		175		—		318		—

Total stock-based compensation	$	1,180	$	287	$	1,916	$	541