The microscopic world of copper powder determines its macroscopic applications.

2026-03-11 14:23

In the previous installment, we discussed the preparation process of copper powder. In this one, let’s take a different angle: examining copper powder under an electron microscope.

Anyone who works with conductive materials knows a saying: The powder’s appearance determines the slurry’s fate. Particle size, morphology, and surface condition—these three factors determine where copper powder can be used and how well it performs.

1. Particle size: finer isn’t always better; the key is optimal matching.

When evaluating powder particle size, one should not rely solely on the D50 (median particle size). The D10 and D90 are equally important—they determine whether the particle-size distribution is “wide” or “narrow.”

The four models in the Cu‑H series not only cover a particle size range from 0.6 μm to 4.5 μm, but more importantly, they maintain exceptionally tight control over the span between D10 and D90:

Model number	D10 (μm)	D50 (μm)	D90 (μm)	Span (D90–D10)
Cu-H-07	0.18-0.6	0.6-0.9	1.0-1.8	~1.2 μm
Cu-H-20	1.1-1.6	1.8-2.4	2.6-3.8	~2.2μm
Cu-H-30	1.8-2.6	2.7-3.6	3.6-5.8	~3.2μm
Cu-H-40	2.1-3.2	3.6-4.5	5.0-6.5	~3.3μm

Looking at this span, even the largest Cu–H–40 bond is only about 3.3 μm. What does this mean?

A narrow particle size distribution makes formulation easier. If the D50 is 2 μm but the D90 reaches 10 μm, the larger particles in the slurry can clog the screen and compromise sintering uniformity.

The Cu-H series presses the D90 hard, precisely to help customers avoid this pitfall.

Looking at this graph, each curve is tightly peaked, indicating a narrow particle size distribution. What does this imply for the slurry formulation?

Solid content is easy to calculate, rheology is readily adjustable, and sintering behavior is predictable.

II. Morphology: Spherical—this is the “universal language” of conductive pastes.

Under the electron microscope, the Cu–H series gives the first impression: it’s round.

There are three advantages to a spherical shape:

1. Good liquidity: During printing, it flows smoothly through the screen and is less prone to clogging.

2. High bulk density: At the same solid content, the conductive network of spherical powder is more compact.

3. Uniform stress: During sintering, shrinkage is isotropic, making cracking less likely.

This is not a matter of chance. Chemical synthesis offers controllable reaction conditions and allows for the guided growth of crystals, resulting in uniformly spherical particles.

III. Surface: The “Last Mile” Before Shipment

Copper powder is prone to oxidation—this is common knowledge. However, oxidation doesn’t begin only when the customer receives the product; from synthesis and drying to storage and transportation, every step involves exposure to oxygen.

Our approach is: Perform surface modification before the powder leaves the factory. 。

This passivation layer is not a thick “coating”; rather, it operates at the molecular level. Its purpose is not to completely seal the copper, but to provide a temporary protective barrier that keeps the material active during storage and transport. When the customer prepares the slurry and proceeds to the sintering stage, this protective layer can be removed without compromising electrical conductivity.

IV. Application Recommendations

Based on particle size and morphological characteristics, the recommended applications for the Cu‑H series are as follows:

Model number	Recommended Apps	Reason
Cu-H-07	High-precision conductive pastes, fine-line printing	Small particle size, suitable for narrow linewidth.
Cu-H-20	General-purpose conductive paste	Well-balanced overall performance
Cu-H-30	Conductive ink, conductive adhesive	Great value for money
Cu-H-40	Thick-film printing, specific sintering process	Slightly larger particle size, with controllable shrinkage.

V. A Few Closing Remarks

Copper powder is nothing new, but achieving fine particle size, uniformity, and stability is a whole different story.

From silver‑plated copper to copper powder, Betely logic has remained unchanged: The powder is synthesized in-house, enabling quality control at the source. The same holds true for silver-plated copper, and for copper powder as well.

The Cu–H series represents another step forward in this research direction.

Fluctuations in copper prices are a matter for the market; doing our job well with copper powder is ours.

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