DEV Community: MUHAMMAD SAEED

How Are SMD Resistors Made? Inside the Manufacturing Process of the Tiny Components on Every PCB

MUHAMMAD SAEED — Sat, 06 Jun 2026 21:43:35 +0000

Take a look at almost any modern electronic device. Whether it's a smartphone, laptop, router, or smartwatch, you'll find dozens—or even hundreds—of tiny rectangular components soldered onto the circuit board.

Many of those components are SMD resistors.

Despite their small size and low cost, SMD resistors are the result of a highly controlled manufacturing process that combines ceramic engineering, precision printing, laser trimming, and automated testing.

Let's take a closer look at how these tiny components are made.

What Is an SMD Resistor?

An SMD (Surface-Mount Device) resistor is a resistor designed to be mounted directly onto the surface of a printed circuit board (PCB).

Unlike traditional through-hole resistors with wire leads, SMD resistors are compact, lightweight, and suitable for automated assembly.

Common package sizes include:

1206
0805
0603
0402
0201

As electronic devices continue to shrink, resistor packages become smaller as well.

Step 1: Creating the Ceramic Substrate

The manufacturing process starts with a ceramic substrate.

Most chip resistors use high-purity alumina ceramic because it provides:

Excellent electrical insulation
Mechanical strength
Good heat resistance
Stable performance over time

Large ceramic sheets are produced and prepared for further processing.

At this stage, the material does not yet have any resistance value.

Step 2: Depositing the Resistive Film

A thin resistive layer is applied to the ceramic substrate.

Depending on the resistor type, manufacturers may use:

Ruthenium oxide compounds
Metal oxide materials
Thick-film resistive pastes

The resistive material is screen-printed onto the ceramic surface.

This printed layer will eventually determine the resistor's electrical resistance.

The printed sheets are then fired in a furnace at high temperatures to permanently bond the resistive material to the ceramic.

Step 3: Printing Conductive End Areas

Next, conductive terminals are added to both ends of the resistor structure.

These terminal areas provide electrical connection points.

Special conductive pastes containing silver, palladium, or other conductive materials are deposited and fired onto the substrate.

The resistor now has:

A ceramic body
A resistive element
Conductive end terminations

It is beginning to resemble the final component.

Step 4: Laser Trimming for Precision

At this stage, the resistor value is close to the target resistance but not yet precise enough.

Manufacturers use laser trimming systems to adjust the resistance.

A computer-controlled laser removes tiny portions of the resistive film.

As material is removed, resistance increases.

The trimming process continues until the exact resistance value is reached.

This step allows manufacturers to achieve tolerances such as:

±5%
±1%
±0.5%
±0.1%

Without laser trimming, precision resistors would be difficult to manufacture economically.

Step 5: Applying Protective Coatings

The resistor is then coated with protective materials.

These coatings help protect the component from:

Moisture
Mechanical damage
Contamination
Environmental stress

The coating also improves long-term reliability.

Step 6: Adding Terminal Plating

The end terminations receive additional metal plating layers.

Typical layers may include:

Nickel
Tin

These layers improve solderability and protect the conductive terminals from corrosion.

This is what allows the resistor to be reliably soldered onto a PCB during assembly.

Step 7: Marking the Resistor

Larger SMD resistors may receive printed markings.

Examples include:

103
472
1001
EIA-96 codes such as 24C

Very small packages like 0402 and 0201 are often left unmarked because there simply isn't enough space.

In those cases, identification relies on packaging labels and manufacturing records.

Step 8: Electrical Testing

Every production batch undergoes electrical testing.

Manufacturers verify:

Resistance value
Tolerance
Temperature characteristics
Power handling capability

Automated inspection systems quickly sort components that fail specifications.

Only parts meeting the required standards continue to packaging.

Step 9: Cutting and Packaging

Large ceramic panels contain thousands of resistors.

The panels are separated into individual components using precision cutting processes.

The finished resistors are then packaged into tape-and-reel systems for automated PCB assembly machines.

A single reel may contain thousands of identical resistors ready for production use.

Why Are SMD Resistors So Cheap?

One reason SMD resistors cost fractions of a cent in large quantities is manufacturing scale.

Modern production lines can manufacture millions of resistors per day using highly automated equipment.

The combination of screen printing, laser trimming, automated testing, and reel packaging makes large-scale production extremely efficient.

Final Thoughts

Although an SMD resistor appears to be one of the simplest components on a PCB, its manufacturing process involves advanced materials science and precision engineering. From ceramic substrates and resistive films to laser trimming and automated testing, every step is carefully controlled to ensure accuracy and reliability.

The next time you see a tiny resistor marked "103" or "24C" on a circuit board, remember that a surprisingly sophisticated manufacturing process went into creating that tiny component.

Why EIA-96 SMD Resistor Codes Don't Match Their Resistance Values

MUHAMMAD SAEED — Sat, 06 Jun 2026 21:18:56 +0000

The first time I encountered an EIA-96 resistor, I assumed the marking would tell me the resistance value directly.

I was troubleshooting a PCB and found a resistor marked 24C. Naturally, I expected some relationship between "24" and the actual resistance. After measuring and checking the datasheet, I discovered the resistor was 17.4 kΩ.

That raised an obvious question:

Why doesn't the code match the resistance value?

The Problem With Traditional SMD Codes

Most electronics enthusiasts learn resistor markings through familiar examples:

103 = 10 kΩ
472 = 4.7 kΩ
681 = 680 Ω

These markings are straightforward. The first digits are significant figures and the last digit is a multiplier.

The system works well for common resistor values, especially 5% tolerance components.

However, things become complicated when manufacturers need to identify large numbers of precision resistor values on extremely small packages.

Enter the EIA-96 Series

Precision resistors often use the E96 preferred value series.

Instead of having only a handful of values per decade, the E96 series contains 96 standardized resistance values between powers of ten.

Some examples include:

100 Ω
102 Ω
105 Ω
107 Ω
110 Ω
113 Ω

Notice how closely spaced these values are.

Trying to represent all of them with traditional three-digit markings would quickly become messy and inconsistent.

A Different Approach

Rather than printing the resistance value directly, EIA-96 uses an index system.

Each number from 01 to 96 corresponds to one of the standard E96 values.

For example:

Code	Base Value
01	100
24	174
68	499
96	976

A letter is then added to indicate the multiplier.

So the resistor marking becomes:

Number + Letter

Instead of:

Resistance Value

Example: Decoding 24C

Let's break down 24C.

First, look up the base value:

24 → 174

Next, decode the multiplier letter:

C → ×100

Now calculate:

174 × 100 = 17,400 Ω

Final resistance:

17.4 kΩ

At first glance, nothing about "24C" resembles 17.4 kΩ, but that's because the code is functioning as a compressed lookup reference rather than a direct value.

Why Manufacturers Prefer It

The EIA-96 system offers several practical advantages:

Fits on tiny resistor packages
Supports the entire E96 precision series
Reduces printing space requirements
Works consistently across manufacturers
Simplifies automated assembly and inspection

For engineers designing dense PCBs, saving even a few characters on component markings matters.

Common Misconceptions

One mistake I frequently see is assuming the first two digits are the resistance value.

For example:

01A ≠ 1 Ω

The "01" is simply an index that points to the E96 base value of 100.

Without the lookup table and multiplier letter, the marking has no direct meaning.

Why This Still Confuses Engineers

The EIA-96 system solves a manufacturing problem, not a human readability problem.

Traditional codes are easy to understand once you know the formula.

EIA-96 requires a reference table, which means the markings appear cryptic unless you're familiar with the standard.

That's why EIA-96 resistor calculators remain popular tools for technicians, repair specialists, and hobbyists.

Final Thoughts

EIA-96 resistor markings were never intended to display resistance values directly. Instead, they provide a compact way to identify all 96 preferred values in the E96 precision resistor series.

Once you understand that the number is an index and the letter is a multiplier, the system becomes surprisingly logical.

The challenge is that the logic is optimized for manufacturing efficiency rather than human intuition.