Low stress epoxy resin for electronic encapsulation is a formulation answer to one failure mode: package cracking at solder reflow. The cause is a thermal mismatch, because the resin, copper, and silicon expand at different rates. Yolatech meets this with the DOPO-HQ modified phenolic epoxy series.
A potting compound does not fail from mechanical load. It fails because it is restrained. The resin wants to shrink on cooling, the die does not move with it, and the mismatch shows up as warpage, interfacial delamination, or a crack that starts at the corner of the silicon.
Two material properties drive that stress: coefficient of thermal expansion and water absorption. Water matters because absorbed moisture flashes to steam during reflow at 260 °C, and the resulting pressure is what pops the package.
DOPO-HQ modified phenolic epoxy attacks both. Its densely crosslinked aromatic backbone keeps expansion low, and the polar groups responsible for moisture uptake are fewer than in conventional bisphenol A systems.
| Grade | EEW (g/eq) | Viscosity @25 °C (mPa·s) | N.V. (%) |
| YLDP-320-K70 | 300–340 | <1,000 | 70 ± 1 |
| YLDP-275-K70 | 250–300 | <1,000 | 70 ± 1 |
| YLDP-255-M80 | 240–270 | 1,000–7,000 | 80 ± 1 |
| YLDP-230-MCS80 | 210–250 | 1,000–4,000 | 80 ± 1 |
The two K70 grades hold below 1,000 mPa·s at 70 % solids, which matters when you are impregnating glass cloth or filling a narrow gap. YLDP-230-MCS80 has the lowest EEW at 210–250 g/eq — the highest crosslink density of the four, and therefore the stiffest cured network.
These resins are used as the base of an encapsulant or laminate varnish, not as a standalone. Typical loading is 40–70 % of the total resin solids, blended with a multifunctional epoxy to tune flow and a latent catalyst to control cure onset.
Because DOPO-HQ carries phosphorus in the backbone, flame retardancy comes from the resin itself. Halogenated additives are not required, which keeps the formulation free of the corrosive by-products that brominated systems release on combustion. Exact loading and cure schedule should be confirmed against our TDS.
Applications include IC packaging, copper-clad laminate for high-frequency boards, and encapsulants for automotive power modules. Anywhere the thermal budget is tight — 260 °C reflow, repeated thermal cycling — this is the low stress epoxy resin class to start from.
DOPO-HQ modified phenolic epoxy resin — grade table and specifications. Send us your target Tg and CTE and we will recommend a grade. For halogen-free flame retardancy in laminates, see also DOPO modified phenolic epoxy resin.
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