CAYOM CA-4 vs. BOLIGO Z980 Thermal Pastes Review – More than just similar bargains?

1 - Introduction and overview 2 - Shear behavior, microscopy, and chemical composition 3 - Lab measurements, interface resistance and bulk thermal conductivity 4 - Real performance on CPUs, notebook chips, and GPUs 5 - Durability (pump-out), summary, and conclusion

Paste condition after the tests

The two images show the condition of the pastes after a large number of test cycles, i.e. under realistic thermomechanical loads. I can easily see how stable the inner structure of a paste remains and whether weaknesses in the dispersion or in the binder-filler ratio become apparent. The first picture shows the CA-4. The surface appears slightly roughened after the numerous load changes and shows a finely granulated texture. This indicates that the binder has retracted somewhat during the cycles and the fillers are more exposed. At the same time, however, the layer remains largely closed, with no visible cracks or open contact points. The paste shows a homogeneous displacement pattern, which indicates sufficient internal cohesion. Although I can see the first signs of incipient segregation at the edges, which may have increased due to the repeated pressure load, the CA-4 appears remarkably stable overall for an entry-level paste. Such a slightly porous surface is typical of many oxide-filled pastes and does not necessarily lead to a loss of performance as long as the contact surface remains closed.

The second image shows the Z980, which appears much more dusty and grainy on the surface. The finely distributed, almost powder-like deposits indicate that the fillers have less binding within the matrix. The surface appears matt and more homogeneously structured than with the CA-4, which indicates a stronger migration of the binder. At the same time, however, it should be positively emphasized that the layer does not show any cracks or local breakouts. Here too, the contact surface remains closed and stable. The uniform, almost powder-like texture may indicate a somewhat softer binder medium, which was more strongly displaced from the upper layers by the thermal stress. For an inexpensive paste, the Z980 nevertheless shows acceptable resistance, as neither pump-out nor visible edge delamination occur.

It can be deduced from both pictures that both pastes have a certain basic stability, even if their long-term behavior does not come close to that of high-quality industrial formulations. The CA-4 seems to remain somewhat more cohesive, while the Z980 ages more smoothly and softer. For private users, this means that both pastes will probably work for a long time in normal everyday CPU use, although differences may become apparent under extreme conditions or several cooler changes.

In future, I will also carry out standardized durability tests on an industrial scale as soon as a paste qualifies for this and provides sufficiently stable initial data. This includes defined temperature change cycles, long-term constant load tests and reproducible visual inspections under standardized conditions. Only such tests allow a real statement to be made about the ageing mechanisms and long-term reliability, which goes far beyond simple performance measurements.

Summary and evaluation

The CA-4 shows itself in the measurements as a paste with solid, but not outstanding thermal conductivity, whose strength clearly lies in its very good compressibility. The minimum achievable layer thickness of around 14 µm is extremely low and thus compensates for many of its disadvantages on the material side. Microscopy shows a fine and predominantly uniformly dispersed particle distribution, with oxidic fillers dominating, which are thermally stable but not maximally conductive. The structured surface formation after many test cycles indicates a slightly thinning binder medium without any relevant cracks or tears forming. The layer also remains homogeneous and stable in terms of behavior, which ensures sufficient internal cohesion. Overall, CA-4 is a technically unagitated, mechanically good-natured paste that scores with its low BLT and predictable behavior.

The Z980 shows a slightly higher effective thermal conductivity than the CA-4 in the measured values and confirms this with a lower Rth gradient on average. Its compressibility is slightly higher than that of CA-4, but remains within the range of similarly favorable pastes. Under the microscope, the higher carbon content and the somewhat coarser particle structure are noticeable, resulting in a duller, flatter texture. While the CA-4 tends to show a more granular surface ageing, the Z980 appears more binder displaced with a fine, almost powdery surface character. Despite these differences, the contact surface remains undamaged and completely closed even after many cycles. Mechanically, it is also stable, but somewhat less cohesive than the CA-4. Thermally, it is supported by its slightly higher bulk values, which are visible in the test stand.

A direct comparison of the two pastes shows that the CA-4 clearly demonstrates its strengths in terms of mechanical compressibility and the unusually low minimum BLT for this price range. The Z980, on the other hand, tends to have better thermal conductivity and a flatter Rth curve, which gives it a slight advantage in the temperature comparison. Both pastes remain sufficiently stable in terms of durability, but show different ageing patterns, which are characteristic of their respective filler systems.

Compared to the Arctic MX-6, both pastes are surprisingly close behind, with the MX-6 achieving a consistently better balance of compressibility, effective conductivity and Rth curve. It benefits above all from its slightly higher bulk conductivity and its well-balanced binder-filler system, which allows for thin layers and hardly loses any efficiency even with larger BLT. The CA-4 comes closest to the MX-6 in terms of low BLT, while the Z980 is thermally closer to it.

For the user, this means that both the CA-4 and Z980 offer surprisingly good technical performance for the price. Nevertheless, the MX-6 remains the most balanced choice, while the CA-4 has its own niche advantages due to its thinness and the Z980 due to its slightly better conductivity.