NOMACON ™ KPTD-1

TCEI - Thermally Conductive Elastic Insulating Material RTV2 - Two Components of Room Temperature Vulcanized Silicone Rubber Compound

Qualitative indicators:

KPTD-1 / 1L-1.00 (K1 / 50)

KPTD-1 / 1L-1.50 (K1 / 70)

KPTD-1 / 1L-2.50 (K1 / 90)

KPTD-1 / 1T-5.50 (K1)

KPTD-1 / 1T-8.50 (K3)

KPTD-1 / 1T-12.5 (K4)

KPTD-1 / 2L-6.50 (K2)

KPTD-1 / 2T-12.5 (K5)

KPTD-1 / 3T-10.5 (K6)

KPTD-1 / 3T-15.0 (K7)

• Pouring and enveloping compounds KPTD-1 polymerize at room temperature into a solid rubber-like material with high dielectric properties, resistant to vibration and shock loads, ultraviolet rays, atmospheric oxygen, water vapor and most chemical compounds.
• The use of compounds is carried out by full or partial filling of products or by application to the surface, while the thickness of the compound layer is not limited, and linear shrinkage does not exceed 0.1-1.5%
• Pot life (fluidity) when poured is 10-40 minutes at room temperature, the time for complete polymerization (vulcanization) is no more than 24 hours at room temperature and no more than 2 hours at a temperature of plus 70 ºС
• Materials do not emit harmful substances during the polymerization process and during further operation
• Does not cause corrosion of metals and alloys, have good adhesion to metal, glass and ceramics
• Heavy-duty compounds can be used as adhesives when pre-applied to the bonded surfaces of undercoats (primers) to improve adhesion
• Provide effective heat dissipation and electrical insulation due to the increased heat-conducting and dielectric properties of ceramic fillers, comfort to contact surfaces and pronounced thermal relaxation.

Full or partial filling of the electronic board in the housing is the main application of the KPTD-1 compounds.

The maximum thickness of the compound layer during pouring, as a rule, does not exceed 4-6 mm. With the correct selection of the filling viscosity and the technology of applying the compound, it is possible to pour gaps between the board and the case with a width of 0.1-0.3 mm.

The main operations of the technological process of filling products in the housing:

• preparation of the surfaces of the case and the board (cleaning, degreasing, applying a primer-subcoat);
• preparation of the compound: kneading components A and B in the original container to a uniform consistency, dosing components A and B by weight into the container for preparing the compound, mixing;
• pouring the prepared compound into a housing with an electronic board;
• when filling the electronic board in the housing, as a rule, the latter is processed on a vibration table to fill the micro-slots with the compound and release air bubbles (filling the gas cavities), processing in a vacuum chamber to release micro-air bubbles, holding in a heat chamber at 60-85 ° С for fast curing compound.

When choosing a grade of compound for housing casting, the developers are faced with the question of assessing the heat-conducting properties of KPTD-1 (see example 1 from the previous section).

Example 2.

Let us determine the criterion for choosing a compound when pouring, depending on the thermal conductivity and the pouring viscosity. When using the compound KPTD-1 / 1L-2.5 (K1 / 90), it is possible to shed design gaps between the board and the case with a width of 0.35 mm, and when using KPTD-1 / 1T-12.5 (K4) at least 1 mm, because pouring viscosity K1 / 90 is five times lower than K4. The thermal conductivity of K4 is 1.6 times higher than that of K1 / 90 (see the table of technical characteristics). Let us estimate the specific thermal resistance to heat transfer when using these compounds (see example 1): for the K1 / 90 compound with a layer thickness of 0.35 mm R = 7.17 (K⋅ m²) / W , for compound K4 with a layer thickness of 1.0 mm R = 12.72 (K⋅ m²) / W.

In the processes of pouring and encapsulation, where the thickness of the protective layer is normalized and does not depend on the filling viscosity, the amount of heat removal directly depends on the thermal conductivity of the compound.

The selection criterion given above in example 2 is confirmed by the statistics of compound sales in recent years: there is a steady increased demand for KPTD-1 / 1L-2.5 (K1 / 90) and KPTD-1 / 1T-5.5 (K1) for body casting , as well as KPTD-1 / 3L-10.5 (K6) and KPTD-1 / 3T-15.0 (K7) for filling with standardized gaps and encapsulation.

In the conditions of mass production with significant dimensions of the poured products, the advantages of encapsulation are obvious: the lowest compound consumption compared to full filling in the body, full control of the coating quality after curing, the ability to remove the encapsulated product from the body to check its operability and replace. Experience with complete encapsulation of electronic boards shows that KPTD-1 coating provides IP68 enclosure protection (long-term operation under water at a depth of more than 1 m).

The main operations of the technological process of encapsulating products:

• preparation of the surface of the board and electronic elements: cleaning, degreasing, applying a primer-subcoat, drying;
• preparation of the compound: kneading components A and B in the original container to a uniform consistency, dosing components A and B by weight into the container for preparing the compound, mixing;
• dosing of the compound for each board;
• distribution of the compound on the board with a special automatic dosing head, or manually with a brush;
• keeping the coated board in a heat chamber at 60-85 ° С for fast curing of the compound;
• continuous visual quality control of the coating;
• selective ultrasonic control of coating thickness.

At present, the processes of pouring into the body and encapsulation are quite automated with the use of special two-component dispensers for dosing by volume (mass), mixing and feeding the compound, as well as coordinate robots for positioning the dispensing head of the dispenser. The advantage of automated application systems is the ability to fully integrate into the conveyor line for mass production, as well as the ability to work in a semi-automatic mode with an operator and a dispensing device in the form of a hand gun.

Among the manufacturers of two-component dispensers, it is worth highlighting the SECMER equipment of the DOSAMIX series, the PU and RIM series, the PD44 and PR70 dispensing systems from Graco, the Liquid Control LC120FR dispensing systems, Liquid Control MINI, IJ30C, IJ40C from Fisnar Liquid Control.

The capabilities of the above dosing systems allow the use of components A and B with different viscosities, including silicones with various fillers, with a mixing ratio from 1: 1 to 100: 1.

The experience of using NOMACONTM KPTD-1 compounds in automated technological areas of pouring has shown their full compliance with the requirements of this dosing equipment in terms of mixing and dosing accuracy.

1. Components A and B of KPTD-1 compounds are mixed immediately before use. For compounds with a ratio of components A and B 1: 1 per 1 mass part of component A add 1 mass part of component B. For compounds with a ratio of components A and B 25-35: 1 per 25-35 mass parts of component A add 1 mass part of component B. If stored for more than 60 days from the date of manufacture, the pot life of the compound may change due to the partial loss of its properties by the catalyst. In this case, a preliminary check and correction of the pot life is necessary.
2. Before use, components A and B of compounds with a 1: 1 ratio of components, or component A of compounds with a ratio of 25-35: 1 must be thoroughly mixed in the manufacturer's container (see Figure 1). The presence of sediment, as well as age spots on the surface during storage is not a rejection factor. Sediment and pigment spots should be distributed and disappear with subsequent stirring. It is allowed to mix components A and B with solvent gasoline of the BR-2 type TU 38.401-67-108 or nefras C2-80 / 120 according to the manufacturer's TNLA to achieve the required filling viscosity (consistency) in a ratio of no more than 3 per 100 weight parts of component A or B parts by weight of solvent.
3. The mixing of components A and B during the preparation of the compound should be carried out with thorough mixing for at least 1-2 minutes. The technology of using KPTD-1 compounds should exclude the possibility of air bubbles, dust particles and other foreign inclusions entering the material when filling products.
4. The surfaces to be applied with KPTD-1 are thoroughly cleaned of dust, dirt and other debris with hair brushes, cloth napkins or by blowing with compressed air. To remove moisture, traces of mineral oils, as well as grease stains and other contaminants, the surfaces are degreased with a cloth moistened with BR-2 gasoline, C2-80 / 120 nefras or isopropyl alcohol TU 2632-015-11291058. After solvent treatment, the surfaces are immediately wiped dry with a dry, clean cloth, or dried in air and in an oven. Then, in the same order, secondary degreasing is carried out.
5. The compound is applied to the surfaces to be coated with a spatula, syringe, dosing head or other filling devices of various profiles (see Figure 2).
6. To achieve the specified bond strength of the compound with the surface during peeling, the surface of metal products must be prepared in accordance with GOST 21981. When applying KPTD-1 on the surface of other polymer or ceramic products, the adhesion properties are not standardized. In this case, the adhesion properties of KPTD-1 are consistent with the consumer, or are determined by the consumer independently.
7. The bond strength of the KPTD-1 materials with the surface can be increased by applying a sublayer (primer) of the P-11 or P-12E type to the previously prepared surface TU 38.103-04-06-90, SS4120, SS4155 from GE Silicones, Ambersil Primer No. 3 from Ambersil Silicones, Dow Corning 1200 RTV Prime Coat from Dow Corning.
   It should be borne in mind that the adhesive properties of the compounds are fully manifested within 2-14 days after polymerization.
8. In order to ensure the quality of the coating, polymerization of KPTD-1 before the loss of viability should be carried out mainly at room temperature, full polymerization should be carried out at temperatures from plus 15 ° C to plus 70 ° C.
9. The use of compounds is carried out by partial or complete filling of products (see Figures 3 and 4), as well as by applying to the surface in the form of a heat-conducting insulating layer from the external environment or a sealing layer - by encapsulation (see Figure 2). In this case, the thickness of the compound layer is, as a rule, 0.5-1.0 mm, and the linear shrinkage does not exceed 0.1-1.5 %.
10. Due to the residual elasticity and minimal shrinkage, even highly filled NOMAKON TM KPTD-1 compounds do not create residual stresses after polymerization, leading to mechanical damage to the components of electronic boards. Thus, the complete filling of products into housings (see Figure 4) guarantees reliable sealing from the external environment, additional electrical insulation, high resistance to vibration and shock loads, as well as effective heat dissipation simultaneously from all board elements through the compound to the product case and into the environment.
11. The use of NOMACON ™ KPTD-1 compounds does not exclude the possibility of repairing filled products. Due to its elasticity and relatively low mechanical strength, the compound layer can be easily opened with a plastic screwdriver or spatula, and also cut with a knife. The opening points and the restored elements are then again filled with a compound (preferably of the same brand) with guaranteed adhesion to the previous layer.