17. Read the advertisement. Make everybody trust the method described.

Advertisement.

Customers provide the vacuum impregnator with parts that are molded, finished and ready for assembly. The parts are placed in baskets and put in the vacuum chamber. Air is evacuated, opening fine leak paths within the parts and making the pores receptive to filling. The chamber is then pressurized, forcing liquid resin into the components. After passing through several rinses to clear excess resin from external surfaces, the remaining resin inside the part is left to catalyze into a polymer, leaving behind a hard yet flexible seal. The fundamental process is relatively quick – typical impregnation times are only 20–25 minutes.

A vacuum impregnation seal is permanent, will not crack or degrade and offers better quality control and quicker turnaround rates than other sealing methods. The impregnation process does not alter external surfaces, so electronic components require no additional tooling or shaping after sealing. The seal itself, an anaerobic resin composed of methacrylate monomers, is formulated differently from conventional metal seal ants. It is designed to seal at the interface between two dissimilar materials, such as plastic and metal, and withstand these materials' differing coefficients of expansion at various temperatures. The chemical is non-toxic and leaves no residue, so it has no adverse effects on solderability or electrical conductivity.

At room temperature, the resin cures in a matter of hours. Alternatively, the resin can be cured at 150F, which speeds up the process to completely dry the product in about 1 hr. There have been cases where parts were dropped off in the morning and before noon the truck was returning to the supplier loaded with completely sealed and dried parts.

The resin is formulated to withstand a wide range of temperatures from –40–150 °C. It is effective in filling surface pores as well as “through porosity” – cracks and holes that penetrate the component walls. Normally, parts with such flaws would be scrapped, but after vacuum impregnation they can be properly sealed and used.

Over time, O-rings (уплотнительные кольца) tend to get dry and brittle, eventually cracking. A good seal will not do that.

18. Puzzle: “Find the Physicist’s First Name.” Decide whose name of the two physicists from the above units is hidden in the following definitions-words. The answers are all related to the field of physics. The first letters of the answers are taken in the same order as clues.

(1) The distance between two adjacent wave crests. [10]

(2) The effect that results in areas of cancellation or reinforcement when two or more sets of waves meet. [12]

(3) A device that causes rays of light to diverge or converge as they pass through it. [4]

(4) The region of the electromagnetic spectrum, wavelength range ca 400–800nm that produces a visual sensation in the human eye. [5]

(5) The angle between a ray of light and the normal to the surface of the substance it is entering. [9]

(6) The maximum displacement of an oscillator from it equilibrium position. [9]

(7) A highly polished surface that reflects light rays. [6]