15. Benefit Plans

We have retirement plans covering substantially all our employees. The principal plans are our defined contribution plan that covers substantially all of our employees in the United States and the multi-employer pension plan for hourly union employees in Pennsylvania. Expense related to both plans is insignificant.

Defined Contribution Plan – Domestic employees of Amtech and its subsidiaries who meet certain eligibility requirements may participate, at the employee’s option, in the 401(k) Plan. The 401(k) Plan is a defined contribution plan subject to the provisions of ERISA. We match employee contributions to the 401(k) Plan equal to 60% of the participants' elective deferrals, up to 3.6% of the participants’ eligible compensation each payroll period. Employees are auto-enrolled upon eligibility at a 6% contribution rate, however, an employee may opt out at their election. The match expense was $0.4 million in 2022 and $0.3 million in 2021 and 2020.

Pension Plan – Our hourly union employees in Pennsylvania participate in a multi-employer pension plan, the NIGPP, in accordance with the union agreement between PR Hoffman and the United Automobile, Aerospace and Agriculture Implement Workers of America. The agreement was renewed in 2022 for a three-year term that expires September 30, 2025. Every company participating in the plan pays a contribution per hour worked for each employee of the company that is eligible to participate in the NIGPP. Our contributions to the NIGPP were $38,000, $39,000 and $44,000 in 2022, 2021 and 2020, respectively.