DI Water in Electronics Manufacturing: What Grade Do You Actually Need?

# DI Water in Electronics Manufacturing: What Grade Do You Actually Need?

Water is the most-used consumable in electronics manufacturing. It’s also the most misunderstood. The grade of water you use directly affects cleaning quality, equipment longevity, and regulatory compliance — but not every process step requires the same purity. Here’s a practical guide to water grades and where each one belongs.

What DI Water Is

DI (Deionized) water is regular water that has been stripped of dissolved mineral ions — calcium, magnesium, sodium, chloride, sulfate — through ion exchange or reverse osmosis. The result is water that conducts almost no electrical current, which is exactly what you want when it touches electronic assemblies.

Why purity matters: Dissolved ions are conductive. If they remain on a circuit board after cleaning, they create leakage currents between traces, promote corrosion, and cause dendritic growth — tiny metal filaments that grow between conductors and eventually short circuits out. Even microscopic ionic contamination that you can’t see, feel, or measure without lab equipment can cause field failures months or years later.

How purity is measured: Water purity is measured in resistivity — the higher the resistivity, the fewer ions present. The theoretical maximum for pure water at 25°C is 18.2 MΩ·cm, meaning zero measurable dissolved ions.

The Water Grade Spectrum

Municipal / Tap Water

Resistivity: 0.01–0.05 MΩ·cm

Full of minerals, chlorine, and organic compounds. Used for general facility purposes — cooling towers, restrooms, initial equipment rinses. Never touches a circuit board directly in any quality-conscious facility.

RO (Reverse Osmosis) Water

Resistivity: 1–15 MΩ·cm

RO membranes remove 90–99% of dissolved ions, particles, and some organics. Good enough for pre-rinse stages where you’re washing away bulk chemistry before the final DI rinse. Not pure enough for final rinse on production assemblies — the remaining ion concentration is still too high for electronics.

DI (Deionized) Water

Resistivity: 12–18 MΩ·cm

The workhorse grade for electronics manufacturing. Ion exchange resin beds remove the remaining dissolved ions to near-zero levels. This is what SMT cleaning machines use for the final rinse after flux chemistry has done its dissolving work.

DI water is critical for post-reflow PCBA cleaning, stencil rinsing, and any process step where the water contacts the board surface and must leave no ionic residue behind.

UPW (Ultrapure Water)

Resistivity: 18.2 MΩ·cm

The purest water you can produce — zero measurable ions, zero particles above specification, zero organics. Used in semiconductor wafer fabrication: photolithography rinsing, gate oxide cleaning, CMP post-rinse, and virtually every wet process step on the wafer fab floor.

A semiconductor fab can consume 2,000–10,000+ gallons per minute of UPW in continuous recirculation loops. The purification systems are dedicated plants within the plant — continuous monitoring, redundant purification stages, and real-time resistivity measurement. No semiconductor facility buys UPW; they all generate it on-site because the volume and purity requirements make any other approach impractical.

Where Each Grade Is Used

Semiconductor wafer fabrication (upstream):

UPW (18.2 MΩ·cm) — highest volume, highest purity requirement
Used in every wet processing step on silicon wafers

Microelectronics packaging (die attach, wire bonding, flip-chip):

Vapor-phase machines typically use solvents, not water — this is a water-free process
If water is used, DI grade for rinse steps

SMT board assembly (solder paste print → reflow → clean):

DI water is the final rinse in aqueous cleaning machines
RO water may be used for the first rinse stage to conserve DI water
Chemistry (saponifiers, surfactants) dissolves flux residue; DI water rinses the chemistry away

Stencil and screen cleaning:

DI water rinse after chemistry, same as PCBA cleaning

Conformal coating / potting preparation:

Surfaces must be clean before coating; DI water rinse is a common pre-step

On-Site Generation vs. Purchasing

This is where the economics get interesting for SMT and PCBA operations:

Purchasing DI water in bulk containers:

Delivered in 55-gallon drums or totes
Cost includes transportation, storage, and handling
Contamination risk during transfer and storage — drums must be clean, capped, and stored properly
Supply chain dependency — if delivery is delayed, production may stop

On-site RO/DI generation:

Dedicated purification unit connected to facility water supply
Produces DI water on demand at the required resistivity
Eliminates delivery logistics and contamination risk
Higher upfront capital cost but lower ongoing consumable cost
Payback period depends on volume — facilities running multiple cleaning machines typically see payback within 1–2 years

The Purbest LDSJ-250L-CS is an example of an integrated RO/DI system designed for electronics manufacturing facilities. It takes municipal water input and produces DI water at the resistivity grades needed for cleaning processes, with built-in monitoring and storage.

Wastewater Considerations

Aqueous cleaning generates wastewater that contains dissolved flux residue, cleaning chemistry, and whatever the DI water picked up during the process. This wastewater must be treated before discharge:

pH adjustment — cleaning chemistry is often alkaline; discharge must be neutralized
Heavy metals — depending on the flux and board metallurgy, trace metals may be present
BOD/COD — organic content from flux residue
Local discharge permits — facilities must comply with municipal or industrial discharge limits

Wastewater treatment adds ongoing operational cost to aqueous cleaning. Vapor-phase solvent cleaning sidesteps this entirely — closed-loop solvent systems generate no wastewater, require no treatment infrastructure, and produce no discharge permits.

For facilities evaluating cleaning technology: the total cost of ownership includes not just the equipment and consumables, but the water treatment infrastructure, permits, monitoring, and regulatory compliance that aqueous cleaning requires.

Practical Guidance

If you run aqueous SMT cleaning: On-site DI water generation is almost always more cost-effective and reliable than bulk purchasing for any facility with more than one cleaning machine.
If you’re expanding capacity: Factor DI water generation into the facility plan early — retrofitting plumbing and treatment after the fact is more expensive.
If you’re evaluating vapor-phase vs. aqueous: Remember that vapor-phase eliminates the water treatment equation entirely — no DI generation, no wastewater treatment, no discharge permits.

This article is part of Akrivis’s technical resources for electronics manufacturing process evaluation. For equipment specifications, application reviews, or process consultation, contact the Akrivis team.

Have a question about water purity for your cleaning process? Contact the Akrivis team for an application review and equipment recommendation for your specific process requirements.

Published by Akrivis Components and Tools — North American distributor for PurBest electronics manufacturing process equipment.

# DI Water in Electronics Manufacturing: What Grade Do You Actually Need?

Water is the most-used consumable in electronics manufacturing. It’s also the most misunderstood. The grade of water you use directly affects cleaning quality, equipment longevity, and regulatory compliance — but not every process step requires the same purity. Here’s a practical guide to water grades and where each one belongs.

What DI Water Is

DI (Deionized) water is regular water that has been stripped of dissolved mineral ions — calcium, magnesium, sodium, chloride, sulfate — through ion exchange or reverse osmosis. The result is water that conducts almost no electrical current, which is exactly what you want when it touches electronic assemblies.

Why purity matters: Dissolved ions are conductive. If they remain on a circuit board after cleaning, they create leakage currents between traces, promote corrosion, and cause dendritic growth — tiny metal filaments that grow between conductors and eventually short circuits out. Even microscopic ionic contamination that you can’t see, feel, or measure without lab equipment can cause field failures months or years later.

How purity is measured: Water purity is measured in resistivity — the higher the resistivity, the fewer ions present. The theoretical maximum for pure water at 25°C is 18.2 MΩ·cm, meaning zero measurable dissolved ions.

The Water Grade Spectrum

Municipal / Tap Water

Resistivity: 0.01–0.05 MΩ·cm

Full of minerals, chlorine, and organic compounds. Used for general facility purposes — cooling towers, restrooms, initial equipment rinses. Never touches a circuit board directly in any quality-conscious facility.

RO (Reverse Osmosis) Water

Resistivity: 1–15 MΩ·cm

RO membranes remove 90–99% of dissolved ions, particles, and some organics. Good enough for pre-rinse stages where you’re washing away bulk chemistry before the final DI rinse. Not pure enough for final rinse on production assemblies — the remaining ion concentration is still too high for electronics.

DI (Deionized) Water

Resistivity: 12–18 MΩ·cm

The workhorse grade for electronics manufacturing. Ion exchange resin beds remove the remaining dissolved ions to near-zero levels. This is what SMT cleaning machines use for the final rinse after flux chemistry has done its dissolving work.

DI water is critical for post-reflow PCBA cleaning, stencil rinsing, and any process step where the water contacts the board surface and must leave no ionic residue behind.

UPW (Ultrapure Water)

Resistivity: 18.2 MΩ·cm

The purest water you can produce — zero measurable ions, zero particles above specification, zero organics. Used in semiconductor wafer fabrication: photolithography rinsing, gate oxide cleaning, CMP post-rinse, and virtually every wet process step on the wafer fab floor.

A semiconductor fab can consume 2,000–10,000+ gallons per minute of UPW in continuous recirculation loops. The purification systems are dedicated plants within the plant — continuous monitoring, redundant purification stages, and real-time resistivity measurement. No semiconductor facility buys UPW; they all generate it on-site because the volume and purity requirements make any other approach impractical.

Where Each Grade Is Used

Semiconductor wafer fabrication (upstream):

UPW (18.2 MΩ·cm) — highest volume, highest purity requirement
Used in every wet processing step on silicon wafers

Microelectronics packaging (die attach, wire bonding, flip-chip):

Vapor-phase machines typically use solvents, not water — this is a water-free process
If water is used, DI grade for rinse steps

SMT board assembly (solder paste print → reflow → clean):

DI water is the final rinse in aqueous cleaning machines
RO water may be used for the first rinse stage to conserve DI water
Chemistry (saponifiers, surfactants) dissolves flux residue; DI water rinses the chemistry away

Stencil and screen cleaning:

DI water rinse after chemistry, same as PCBA cleaning

Conformal coating / potting preparation:

Surfaces must be clean before coating; DI water rinse is a common pre-step

On-Site Generation vs. Purchasing

This is where the economics get interesting for SMT and PCBA operations:

Purchasing DI water in bulk containers:

Delivered in 55-gallon drums or totes
Cost includes transportation, storage, and handling
Contamination risk during transfer and storage — drums must be clean, capped, and stored properly
Supply chain dependency — if delivery is delayed, production may stop

On-site RO/DI generation:

Dedicated purification unit connected to facility water supply
Produces DI water on demand at the required resistivity
Eliminates delivery logistics and contamination risk
Higher upfront capital cost but lower ongoing consumable cost
Payback period depends on volume — facilities running multiple cleaning machines typically see payback within 1–2 years

The Purbest LDSJ-250L-CS is an example of an integrated RO/DI system designed for electronics manufacturing facilities. It takes municipal water input and produces DI water at the resistivity grades needed for cleaning processes, with built-in monitoring and storage.

Wastewater Considerations

Aqueous cleaning generates wastewater that contains dissolved flux residue, cleaning chemistry, and whatever the DI water picked up during the process. This wastewater must be treated before discharge:

pH adjustment — cleaning chemistry is often alkaline; discharge must be neutralized
Heavy metals — depending on the flux and board metallurgy, trace metals may be present
BOD/COD — organic content from flux residue
Local discharge permits — facilities must comply with municipal or industrial discharge limits

Wastewater treatment adds ongoing operational cost to aqueous cleaning. Vapor-phase solvent cleaning sidesteps this entirely — closed-loop solvent systems generate no wastewater, require no treatment infrastructure, and produce no discharge permits.

For facilities evaluating cleaning technology: the total cost of ownership includes not just the equipment and consumables, but the water treatment infrastructure, permits, monitoring, and regulatory compliance that aqueous cleaning requires.

Practical Guidance

If you run aqueous SMT cleaning: On-site DI water generation is almost always more cost-effective and reliable than bulk purchasing for any facility with more than one cleaning machine.
If you’re expanding capacity: Factor DI water generation into the facility plan early — retrofitting plumbing and treatment after the fact is more expensive.
If you’re evaluating vapor-phase vs. aqueous: Remember that vapor-phase eliminates the water treatment equation entirely — no DI generation, no wastewater treatment, no discharge permits.

This article is part of Akrivis’s technical resources for electronics manufacturing process evaluation. For equipment specifications, application reviews, or process consultation, contact the Akrivis team.

Have a question about water purity for your cleaning process? Contact the Akrivis team for an application review and equipment recommendation for your specific process requirements.

Published by Akrivis Components and Tools — North American distributor for PurBest electronics manufacturing process equipment.

# DI Water in Electronics Manufacturing: What Grade Do You Actually Need?

Water is the most-used consumable in electronics manufacturing. It’s also the most misunderstood. The grade of water you use directly affects cleaning quality, equipment longevity, and regulatory compliance — but not every process step requires the same purity. Here’s a practical guide to water grades and where each one belongs.

What DI Water Is

DI (Deionized) water is regular water that has been stripped of dissolved mineral ions — calcium, magnesium, sodium, chloride, sulfate — through ion exchange or reverse osmosis. The result is water that conducts almost no electrical current, which is exactly what you want when it touches electronic assemblies.

Why purity matters: Dissolved ions are conductive. If they remain on a circuit board after cleaning, they create leakage currents between traces, promote corrosion, and cause dendritic growth — tiny metal filaments that grow between conductors and eventually short circuits out. Even microscopic ionic contamination that you can’t see, feel, or measure without lab equipment can cause field failures months or years later.

How purity is measured: Water purity is measured in resistivity — the higher the resistivity, the fewer ions present. The theoretical maximum for pure water at 25°C is 18.2 MΩ·cm, meaning zero measurable dissolved ions.

The Water Grade Spectrum

Municipal / Tap Water

Resistivity: 0.01–0.05 MΩ·cm

Full of minerals, chlorine, and organic compounds. Used for general facility purposes — cooling towers, restrooms, initial equipment rinses. Never touches a circuit board directly in any quality-conscious facility.

RO (Reverse Osmosis) Water

Resistivity: 1–15 MΩ·cm

RO membranes remove 90–99% of dissolved ions, particles, and some organics. Good enough for pre-rinse stages where you’re washing away bulk chemistry before the final DI rinse. Not pure enough for final rinse on production assemblies — the remaining ion concentration is still too high for electronics.

DI (Deionized) Water

Resistivity: 12–18 MΩ·cm

The workhorse grade for electronics manufacturing. Ion exchange resin beds remove the remaining dissolved ions to near-zero levels. This is what SMT cleaning machines use for the final rinse after flux chemistry has done its dissolving work.

DI water is critical for post-reflow PCBA cleaning, stencil rinsing, and any process step where the water contacts the board surface and must leave no ionic residue behind.

UPW (Ultrapure Water)

Resistivity: 18.2 MΩ·cm

The purest water you can produce — zero measurable ions, zero particles above specification, zero organics. Used in semiconductor wafer fabrication: photolithography rinsing, gate oxide cleaning, CMP post-rinse, and virtually every wet process step on the wafer fab floor.

A semiconductor fab can consume 2,000–10,000+ gallons per minute of UPW in continuous recirculation loops. The purification systems are dedicated plants within the plant — continuous monitoring, redundant purification stages, and real-time resistivity measurement. No semiconductor facility buys UPW; they all generate it on-site because the volume and purity requirements make any other approach impractical.

Where Each Grade Is Used

Semiconductor wafer fabrication (upstream):

UPW (18.2 MΩ·cm) — highest volume, highest purity requirement
Used in every wet processing step on silicon wafers

Microelectronics packaging (die attach, wire bonding, flip-chip):

Vapor-phase machines typically use solvents, not water — this is a water-free process
If water is used, DI grade for rinse steps

SMT board assembly (solder paste print → reflow → clean):

DI water is the final rinse in aqueous cleaning machines
RO water may be used for the first rinse stage to conserve DI water
Chemistry (saponifiers, surfactants) dissolves flux residue; DI water rinses the chemistry away

Stencil and screen cleaning:

DI water rinse after chemistry, same as PCBA cleaning

Conformal coating / potting preparation:

Surfaces must be clean before coating; DI water rinse is a common pre-step

On-Site Generation vs. Purchasing

This is where the economics get interesting for SMT and PCBA operations:

Purchasing DI water in bulk containers:

Delivered in 55-gallon drums or totes
Cost includes transportation, storage, and handling
Contamination risk during transfer and storage — drums must be clean, capped, and stored properly
Supply chain dependency — if delivery is delayed, production may stop

On-site RO/DI generation:

Dedicated purification unit connected to facility water supply
Produces DI water on demand at the required resistivity
Eliminates delivery logistics and contamination risk
Higher upfront capital cost but lower ongoing consumable cost
Payback period depends on volume — facilities running multiple cleaning machines typically see payback within 1–2 years

The Purbest LDSJ-250L-CS is an example of an integrated RO/DI system designed for electronics manufacturing facilities. It takes municipal water input and produces DI water at the resistivity grades needed for cleaning processes, with built-in monitoring and storage.

Wastewater Considerations

Aqueous cleaning generates wastewater that contains dissolved flux residue, cleaning chemistry, and whatever the DI water picked up during the process. This wastewater must be treated before discharge:

pH adjustment — cleaning chemistry is often alkaline; discharge must be neutralized
Heavy metals — depending on the flux and board metallurgy, trace metals may be present
BOD/COD — organic content from flux residue
Local discharge permits — facilities must comply with municipal or industrial discharge limits

Wastewater treatment adds ongoing operational cost to aqueous cleaning. Vapor-phase solvent cleaning sidesteps this entirely — closed-loop solvent systems generate no wastewater, require no treatment infrastructure, and produce no discharge permits.

For facilities evaluating cleaning technology: the total cost of ownership includes not just the equipment and consumables, but the water treatment infrastructure, permits, monitoring, and regulatory compliance that aqueous cleaning requires.

Practical Guidance

If you run aqueous SMT cleaning: On-site DI water generation is almost always more cost-effective and reliable than bulk purchasing for any facility with more than one cleaning machine.
If you’re expanding capacity: Factor DI water generation into the facility plan early — retrofitting plumbing and treatment after the fact is more expensive.
If you’re evaluating vapor-phase vs. aqueous: Remember that vapor-phase eliminates the water treatment equation entirely — no DI generation, no wastewater treatment, no discharge permits.

This article is part of Akrivis’s technical resources for electronics manufacturing process evaluation. For equipment specifications, application reviews, or process consultation, contact the Akrivis team.

Have a question about water purity for your cleaning process? Contact the Akrivis team for an application review and equipment recommendation for your specific process requirements.

Published by Akrivis Components and Tools — North American distributor for PurBest electronics manufacturing process equipment.