Figure 1. Four failure modes account for most potted electronic component failures - and each points to a specific design decision. | Fong Yong Chemical Co., Ltd.
Fong Yong Chemical Co., Ltd. - a clear epoxy potting compound manufacturer in Taiwan - produces six formulas for electronic component encapsulation. Selection comes down to four variables: (1) whether the assembly needs stress-accommodating flexibility or rigid protection; (2) whether heat curing equipment is available on the production line; (3) whether potting volume is large enough for exothermic heat to become a design concern during cure; and (4) whether the finished encapsulation has an appearance requirement. For assemblies subject to thermal cycling, vibration, or dynamic stress: E-750/H-750 (Shore A 65). For LED encapsulation above 100°C: E-600/H-600 (heat cure required). For production without oven equipment: E-120/H-100. For large-volume low-exotherm applications: E-190/H-190. For appearance-sensitive or protective coating applications: E-132/H-100. For general-purpose rigid potting: E-700/H-190.
Selecting the right clear epoxy potting compound for electronic components comes down to four variables: whether the cured encapsulant needs to be rigid or flexible, whether you can heat cure or must use room temperature, whether the potting volume is large enough for exothermic heat to be a design concern, and whether the application has an appearance requirement - cured surface quality or decorative coating duty.
All six formulas in this clear epoxy potting compound selection guide produce a clear, electrically insulative encapsulation after cure. The differences are not in basic function but in where each formula is the correct specification. Working through four questions in sequence identifies the right product without comparing every specification in parallel.
Four Selection Variables - Jump to Section
Variable 1: Rigid or Stress-Relieving After Cure?
Variable 2: Room Temperature Cure or Heat Cure Required?
Variable 3: Is the Potting Volume Large Enough to Create an Exotherm Concern?
Variable 4: Does the Application Have an Appearance Requirement?
→ Go straight to the routing table
Variable 1: Does the Cured Encapsulant Need to Accommodate Stress?
Figure 1. Rigid encapsulant (Shore D) accumulates stress at the substrate interface under thermal cycling - leading to cracking. Flexible encapsulant (Shore A 65) accommodates the same expansion without cracking.
This is the first question because it eliminates the largest selection error in electronic potting: applying a rigid encapsulant to an assembly that will experience thermal cycling, vibration, or mechanical movement in service.
Rigid epoxy potting compounds - Shore D 80 to Shore D 90 - protect against moisture, impact, and electrical breakdown. They do not absorb cyclic mechanical stress. When a rigid-potted assembly expands and contracts through repeated thermal cycles, stress accumulates at the interface between the epoxy and the substrate. Over time this produces cracking or delamination, and once the encapsulant cracks, moisture protection is compromised.
If the assembly will experience any of the following, a Shore A formulation should be evaluated before a Shore D product is specified:
Outdoor installation with wide day-night temperature swings
Automotive or industrial environments with engine or motor vibration
Power cycling that generates significant internal temperature change
Substrates with very different coefficients of thermal expansion bonded together
Important - Shore A vs Shore D are different measurement scales: Shore A 65 and Shore D 80 are measured on different instruments and cannot be compared numerically. Shore A 65 describes a soft, flexible material. Shore D 80 describes a hard, rigid material. They are not close to each other in stiffness.
Variable 1 Routing
| Requirement | Formula |
|---|---|
| Assembly will experience thermal cycling, vibration, or dynamic stress | E-750 / H-750 - Shore A 65, stress-accommodating encapsulation |
| Assembly requires rigid protection - moisture, impact, electrical insulation | Continue to Variable 2 → E-700, E-190, E-132, E-120, or E-600 |
Variable 2: Is Heat Curing Equipment Available on Your Production Line?
Within the rigid formulas (Shore D 80–90), one product requires heat curing and cannot be cured at room temperature: E-600/H-600, the LED encapsulation formula. All other rigid formulas in this range can cure at room temperature.
The distinction matters in two directions. If your application is LED encapsulation and you have heat curing capability, E-600 is the only formula in this range with the optical and thermal properties required for that application. If your production does not have oven infrastructure and the application is standard electronic potting, E-120/H-100 is the formula specifically formulated around RT cure as its primary pathway - not RT cure as a fallback with reduced performance.
Variable 2 Routing
| Cure Condition | Formula |
|---|---|
| No oven available - RT cure is the only option, and full mechanical performance at RT is required | E-120 / H-100 - RT cure as primary design pathway, 13,000 psi flexural strength |
| Heat cure available, application is LED encapsulation or requires 140°C+ service temperature | E-600 / H-600 - LED encapsulation, heat cure required (100°C), 140–150°C service |
| RT cure or heat cure both acceptable - standard rigid potting | Continue to Variable 3 → E-700, E-190, or E-132 |
Variable 3: Is the Potting Volume Large Enough for Exothermic Heat to Be a Design Concern?
For the remaining rigid, RT-capable formulas - E-700, E-190, and E-132 - the primary differentiator for E-190 is exotherm management, not temperature rating. All epoxy systems generate heat during cure; in large or deep potting volumes, this exothermic heat can accumulate faster than it dissipates, creating thermal stress or dimensional distortion in the cured part.
E-190/H-190 is formulated for low exotherm output, making it the appropriate choice when potting volume is large enough for heat accumulation during cure to be a design consideration. As a secondary property, E-190 carries a rated service range of −30°C to +90°C (Tg 75°C) - useful where the application also requires a defined upper service temperature specification.
For standard small- to medium-volume potting where exothermic heat dissipates normally, E-700 and E-132 are the remaining options. Volume and component geometry, not temperature alone, determine whether E-190 is required.
Variable 3 Routing
| Potting Condition | Formula |
|---|---|
| Large or deep potting volume where exothermic heat accumulation during cure is a concern; or application requires rated service temperature to −30°C / +90°C | E-190 / H-190 - low exotherm formulation, Tg 75°C, rated −30°C to +90°C |
| Standard potting volume - exotherm is not a design consideration | Continue to Variable 4 → E-700 or E-132 |
Variable 4: Does the Application Have an Appearance Requirement?
At this point in the selection, the two remaining formulas are E-700/H-190 and E-132/H-100. Both are rigid, RT-capable, and suited to standard indoor electronic service. The selection between them turns on whether the finished encapsulation has an appearance requirement - or whether the product will be used in a dual role as a protective coating in addition to potting.
E-132/H-100 delivers a non-foggy, high-gloss cured surface with the lowest water absorption in this range (0.06%). Its specification notes suitability for decorative and protective coatings in addition to potting. Where the appearance of the cured surface is visible in the finished product - display devices, instruments with visible potted components, or housings where surface quality is a commercial consideration - E-132 is the appropriate specification.
Where appearance is not a factor and the requirement is straightforward electrical insulation and moisture protection at lowest complexity, E-700/H-190 is the default choice.
Variable 4 Routing
| Requirement | Formula |
|---|---|
| Cured surface appearance matters - high gloss, non-foggy; or dual use as protective coating | E-132 / H-100 - high-gloss surface, water absorption 0.06%, decorative/protective coating capability |
| No special requirement - general electrical encapsulation and moisture protection | E-700 / H-190 - default general-purpose rigid potting when no other variable applies |
Complete Product Routing Table - All Six Formulas
Figure 2. Six clear epoxy potting compound formulas - positioned by hardness, cure method, and primary application. Each formula occupies a distinct position in this matrix: no two formulas serve the same requirement.
Already know your application requirements? Use the routing table below to identify the appropriate formula directly.
| If your situation is… | Specify this formula | Key property |
|---|---|---|
| Assembly will experience thermal cycling, vibration, or dynamic mechanical stress | E-750 / H-750 | Shore A 65 - accommodates thermal expansion and vibration stress |
| LED encapsulation requiring heat resistance above 100°C and high transparency | E-600 / H-600 | Shore D 90, 140–150°C service, refractive index 1.534, heat cure required |
| No oven available - RT cure must deliver full mechanical performance | E-120 / H-100 | Shore D 82, 13,000 psi flexural strength, low exotherm, RT cure as primary pathway |
| Large-volume or large-component potting where exothermic heat during cure is a design consideration | E-190 / H-190 | Shore D 80, Tg 75°C, rated −30°C to +90°C, low exotherm design for large pours |
| Cured surface appearance matters, or dual use as decorative / protective coating | E-132 / H-100 | Shore D 80, high-gloss non-foggy surface, water absorption 0.06% |
| General electrical encapsulation - no special mechanical, thermal, or appearance requirement | E-700 / H-190 | Shore D 80 - default choice when no other variable applies |
All data from published TDS documents, Fong Yong Chemical Co., Ltd. Properties tested under laboratory conditions at 25°C. Application suitability should be verified in representative service conditions before production commitment.
Request Samples or Technical Data
All six formulas are available for sample evaluation. Contact Fong Yong to discuss your application requirements, production conditions, and cure schedule.
Clear Epoxy Potting Compound Product Pages
E-750 / H-750 - Stress-Relieving Flexible Potting (Shore A 65)
E-600 / H-600 - LED Encapsulation Epoxy (140–150°C, Heat Cure)
E-120 / H-100 - RT-Cure Potting, 13,000 psi Flexural Strength
E-190 / H-190 - Low Exotherm for Large Component Potting
E-132 / H-100 - Appearance-Sensitive Encapsulation and Protective Coating
E-700 / H-190 - General-Purpose Electronic Potting Compound
Related Knowledge
Why Potted Electronic Components Fail: Cracking, Delamination, and Moisture Ingress
Does Your Production Line Really Need an Oven? RT vs Heat Cure in Electronic Potting Epoxy
