MAY 2017

Investor Presentation

Safe HarborThis presentation contains, or may be deemed to contain, "forward-looking statements" (as defined in the US Private Securities Litigation Reform Act of 1995) which reflect our current views with respect to future events and financial performance. We use words such as "anticipates,", “projection”, “outlook”, “forecast”, "believes," "plan," "expect," "future,"' "intends," "may," "will," "estimates," "predicts," and similar expressions to identify these forward-looking statements. Forward looking statements included in this presentation include our expectations about achieving our longer-term revenue and profitability goals and with respect to our second quarter 2017 outlook. All forward-looking statements address matters that involve risks and uncertainties. Accordingly, the Company’s actual results may differ materially from the results predicted or implied by these forward-looking statements. These risks, uncertainties and other factors also include, among others, those identified in "Risk Factors”, "Management's Discussion and Analysis of Financial Condition and Results of Operations'' and elsewhere in our annual report on Form 10-K for the year ended December 30, 2016 as filed with the Securities and Exchange Commission and subsequently filed quarterly reports on Form 10-Q. Ultra Clean Holdings, Inc. undertakes no obligation to publicly update or review any forward-looking statements, whether as a result of new information, future developments or otherwise unless required by law.

Management uses non-GAAP net income and non-GAAP net income per diluted share to evaluate the Company's operating and financial results. The Company believes the presentation of non-GAAP results is useful to investors for analyzing our core business and business trends and comparing performance to prior periods, along with enhancing investors' ability to view the Company's results frommanagement's perspective. The presentation of this additional information should not be considered a substitute for results prepared in accordance with GAAP. Tables presenting reconciliations of non-GAAP results to U.S. GAAP results are included in the Appendix.

2

Non-GAAP

3

UCT Highlights

* Non-GAAP reconciliation in the Appendix

Q1 2017 delivered yet another record in revenue and profitability

• Q1’17 revenue of $205M– 17.2% increase quarter-over-quarter

– 82.3% increase year-over-year

– Semiconductor up 22.4% quarter-over-quarter

• Q1’17 GAAP diluted EPS of $0.42 and non-GAAP* diluted EPS of $0.47

• Q2’17 guidance of $210-220M and GAAP EPS of $0.46-0.52Q1'16 Q2'16 Q3'16 Q4'16 Q1'17

$112$130

$146$175

$205

0.8%4.0%

6.1%8.7%

10.3%

13.0%14.7%

16.1% 17.4%18.3%

Revenue (in M)

GrossMargin

OperatingMargin*

4 Main Drivers for 2017– 2017 WFE spending to increase on 3D NAND & node transitions in 10nm Logic & 1x DRAM

– Our primary customers are concentrated in Deposition & Etch; fastest growing areas of WFE

– High OEM factory capacity utilization driving strong push for expanded outsourcing

• Share gain opportunities for the strongest suppliers with the broadest capabilities

• Ability to manufacture major modules across a customer’s entire tool is fueling strong growth

– Ability to meet shortfalls in capacity across the supply base, filling additional demand

4

UCT Drivers

Leading outsourcing manufacturer for the semiconductor capital equipment industry

20152016

2017(F)2018(F)

$31.5

$35.0

$38.0 $40.0

5

Wafer Fab Equipment Spending Reaching New Highs

($B)

5%

8%

Source: Gartner April 2017

Deposition & Etch Outperforming WFE Market

2017 WFE Estimate: $38B

>80%of UCT Semi

Sales

Dep & Etch CapEx Spend 12-15% CAGR 2013 - 2018

Total CapExSpend~8% CAGR 2013 - 2018

Thermal & Implant

5% Deposition23%

Removal27%

Lithography27%

Metrology & Inspection

12%

Other6%

Source: Gartner April 2017, SEMI WSEMS and UCT estimates6

OEM Component Suppliers

34%

OEM Integration In-Sourcing

44%

UCT5%

For example: Flex, Celestica, Benchmark, etc.

Specialty Contract Manufacturers

7

Inflection:OEM Outsourcing Accelerating Dramatically

Source: UCT estimates as of Feb 2017.

8

Winning StrategyPrimary Focus on Semiconductors

Broaden CriticalProcess Capabilities

Make StrategicInvestments

Increase UCT Content on Platforms

Deepen Engagementwith Existing Customers & Add New Customers

GAS

FOUNDING CAPABILITY

9

Expanding Critical Capabilities to Capture New Opportunities

Chemical Delivery Sub-Systems

Complete Assemblies

LIQUID DELIVERY

ASSEMBLYINTEGRATION

& TEST

ManufacturedComponents

FRAMES PROTOTYPE MACHINING

MACHININGMETALS

PLASTICMODULES

SHEET METAL FORMING

THERMAL PRODUCTS

10

UCT Expert Outsourcing Partner

MANUFACTURING

INTEGRATION & TESTPROTOTYPING/ DEVELOPMENT

MANUFACTURINGENGINEERING

SUPPLY CHAIN MANAGEMENT

Design for manufacturability (DFM) Partnering with customers for new product requirements Network of global, strategic suppliers Comprehensive new product introduction process Sub-system through full tool integration

External Use11

Now Addressing Major Modules in Semiconductor Equipment

Wafer transfer: 10 – 20% 15 – 30%Factory InterfaceVacuum Transfer

Process Chamber: 55 – 70% 50 – 75%

Gas Panel: 15 – 20% 0 – 10%

TYPICAL CVD & ETCH TOOL COST OTHER PROCESS TOOL TYPES

Source: UCT estimates.

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UCT Strong Growth in Semiconductor EquipmentStrategy to focus on semiconductor successful• Q1 2017 Semi revenue increased 22.4% q/q

– Strong Etch & CVD markets– New module and component wins

• Q1 2017 Semi revenue 93.4% of total• Strong core gas panel business + new modules

driving further growth

Non-semi dominated by Display• Display equipment spending reaching

unprecedented levels• OLED and build-out of Gen 10.5

20122013

20142015

2016

$345$390

$423 $433

$508

(in $M)

($M) Q1’16 Q2’16 Q3’16 Q4’16 Q1’17

Revenue $112.2 $129.8 $146.2 $174.5 $204.6

Gross Margin 13.0% 14.7% 16.1% 17.0% 18.3%

GAAP Net Income (loss) ($3.2) $0.7 $2.6 $10.0 $14.3

GAAP Diluted EPS ($.10) $0.02 $0.08 $0.30 $0.42

Non-GAAP* Net Income (loss) ($0.0) $3.2 $5.7 $12.0 $15.9

Non-GAAP* Diluted EPS ($0.0) $0.10 $0.17 $0.36 $0.47

Cash $45.5 $44.1 $47.3 $52.5 $54.9

13

Select Trailing Financial Data

* Non-GAAP results exclude intangible asset amortization and non-recurring expense items

• Outperforming a growing Semiconductor WFE market

• Rapidly expanding opportunities in customer’s major modules

• Delivering what customers need (OTD, quality, cost)

• Industry trends reinforce leading position as a supply chain consolidator

• Key partner to top customers

14

Compelling UCT Opportunity

WinningStrategy

StrongMargins

Improved Profitability

Solid Cash Generation

Thank You

(in thousands) Q1’16 Q2’16 Q3’16 Q4’16 Q1’17

Reported net income (loss) on a GAAP basis $(3,239) $723 $2,614 $9,953 $14,341

Amortization of intangible assets (1) $1,440 $1,440 $1,438 $1,439 $1,231

Executive transition costs (2) - - $925 - -

Restructuring charges (3) $177 $70 $(105) $109 -

Impairment of “Held for Sale” Assets (4) - - - $666 -

Termination of Contractual Obligation (5) - - - $438 -

Income tax effect of non-GAAP adjustments (6) $(385) $(406) $(574) $(549) $(256)

Income tax effect of valuation allowance (7) $1,876 $1,384 $1,391 $(49) $576

Non-GAAP net income (loss) $(131) $3,211 $5,689 $12,007 $15,892

16

Reconciliation: GAAP Net Income to Non-GAAP Net Income

(1) Amortization of intangible assets related to the Company's acquisitions of AIT, Marchi and Miconex(2) Represents expense for termination benefits paid to former executives of the Company(3) Adjustment to previous restructuring reserve related to the abandonment of one of the Company's facilities(5) Impairment of assets classified as “held for sale” related to our 3D printing business in Singapore

(5) Amount paid related to the termination of a long-term contractual obligation to our 3D printing business in Singapore(6) Tax effect on amortization of intangible assets, executive transition costs, restructuring charges, acquisition costs, impairment charges, and buy-out costs based on the non-GAAP tax rate(7) The Company's GAAP tax expense is generally higher than the Company's non-GAAP tax expense, primarily due to losses in the U.S. with full federal and state valuation allowances. The Company's non-

GAAP tax rate and resulting non-GAAP tax expense considers the tax implications as if there was no federal or state valuation allowance position in effect

(in thousands) Q1’16 Q2’16 Q3’16 Q4’16 Q1’17

Reported income (loss) from operations on a GAAP basis $(698) $3,719 $6,700 $12,670 $19,773

Amortization of intangible assets (1) $1,440 $1,440 $1,438 $1,439 $1,231

Executive transition costs (2) - - $925 - -

Restructuring charges (3) $177 $70 $(105) $109 -

Impairment of “Held for Sale” Assets (4) - - - $666 -

Termination of Contractual Obligation (5) - - - $438 -

Non-GAAP income from operations $919 $5,229 $8,958 $15,322 $21,004

17

Reconciliation: GAAP Income from Operations to Non-GAAP Income from Operations

(1) Amortization of intangible assets related to the Company's acquisitions of AIT, Marchi and Miconex(2) Represents expense for termination benefits paid to former executives of the Company(3) Adjustment to previous restructuring reserve related to the abandonment of one of the Company's facilities(4) Impairment of assets classified as “held for sale” related to our 3D printing business in Singapore(5) Amount paid related to the termination of a long-term contractual obligation to our 3D printing business in Singapore

Q1’16 Q2’16 Q3’16 Q4’16 Q1’17

Reported net income (loss) on a GAAP basis $(0.10) $0.02 $0.08 $0.30 $0.42

Amortization of intangible assets (1) $0.04 $0.05 $0.04 $0.04 $0.04

Executive transition costs (2) - - $0.03 - -

Restructuring charges (3) $0.01 $0.00 $0.00 - -

Impairment of “Held for Sale” Assets (4) - - - $0.02 -

Termination of Contractual Obligation (5) - - - $0.01 -

Income tax effect of non-GAAP adjustments (6) $(0.01) $(0.01) $(0.02) $(0.01) $(0.01)

Income tax effect of valuation allowance (7) $0.06 $0.04 $0.04 - $0.02

Non-GAAP net income (loss) $(0.00) $0.10 $0.17 $0.36 $0.47

Weighted average number of diluted shares (in K) 32,309 32,792 33,100 33,526 33,865

18

Reconciliation: GAAP Earnings Per Diluted Share to Non-GAAP Earnings Per Diluted Share

(1) Amortization of intangible assets related to the Company's acquisitions of AIT, Marchi and Miconex(2) Represents expense for termination benefits paid to former executives of the Company(3) Adjustment to previous restructuring reserve related to the abandonment of one of the Company's facilities(5) Impairment of assets classified as “held for sale” related to our 3D printing business in Singapore

(5) Amount paid related to the termination of a long-term contractual obligation to our 3D printing business in Singapore(6) Tax effect on amortization of intangible assets, executive transition costs, restructuring charges, acquisition costs, impairment charges, and buy-out costs based on the non-GAAP tax rate(7) The Company's GAAP tax expense is generally higher than the Company's non-GAAP tax expense, primarily due to losses in the U.S. with full federal and state valuation allowances. The Company's non-

GAAP tax rate and resulting non-GAAP tax expense considers the tax implications as if there was no federal or state valuation allowance position in effect