Development and design of PCBA, circuit boards, small home appliance circuit boards, scheme development, board copying and decryption

Common chemical properties of PCB

(1) Chemical properties:

1. Sulfuric acid: H2SO4- colorless oily liquid, with a specific gravity of 1.837 (1.84) at 15 ℃. Smoke at 30-40 ℃; Boil at 290 ℃. Concentrated sulfuric acid has strong water absorption, making it an excellent desiccant.

2. Nitric acid: HNO3- colorless liquid, with a specific gravity of 1.526 at 15 ℃ and a boiling point of 86 ℃. Red fuming nitric acid is a reddish brown, highly corrosive transparent liquid that vigorously emits smoke and absorbs moisture in the air.

3. Hydrochloric acid: HCl - colorless with a pungent odor, its specific gravity is 1.264 (for air) at 17 ℃. The boiling point is -85.2. Extremely soluble in water.

4. Gold chloride: Red crystal, easily deliquescent.

5. Silver nitrate: AgNO3- colorless diamond shaped flake crystal, melted at a specific gravity of 4.355108.5 ℃ and decomposed upon heating. If there is no organic matter present, light will not work, otherwise it will turn black. Easy to dissolve in water*** Ting D amaranth Yi Gao relies on the shape of a spear to pull the hub, Jia Xiao<negative locust Yi Guan lame mountain small S to unload the Jing?

6. Ammonium persulfate: (NH4) 2S2O8- colorless thin crystal with a slight greenish tint when shaken, soluble in water.

7. Tin (II) chloride: A colorless and semi transparent crystalline substance (rhombic crystal system) of SnCl2, with a specific gravity of 3.95. It melts at 241 ℃ and boils at 603.25 ℃. Can be dissolved in water, alcohol, ether, acetone, nitrobenzene, and ethyl acetate. It is quite stable in the air.

8. Potassium dichromate: needle or flake crystal of K2CrO7 orange red anhydrous triclinic system, with a specific gravity of 2.7, soluble in water. 9. Aqua regia: a colorless and rapidly yellowing liquid with strong corrosiveness and a chlorine odor. Preparation method: Mix 3 volumes of hydrochloric acid with a specific gravity of 1.19 and 1 volume of nitric acid with a specific gravity of 1.38-1.40. 10. Activated carbon: a black, fine particle (block) characterized by numerous pores. The surface area of 1 gram of activated carbon is approximately between 10 or 1000 square meters, which determines that activated carbon has a high degree of adsorption.

11. Sodium chloride: NaCl - white square crystal or small crystalline powder, with a specific gravity of 2 1675, melting point 800 ℃, boiling point 1440 ℃. Soluble in water but insoluble in alcohol.

12. Sodium carbonate: Na2CO3 • 10H2O - colorless and transparent monoclinic crystal system, with a specific gravity of 1.5; Soluble in water, with maximum solubility at 34 ℃.

13. Sodium hydroxide: NaOH - a colorless crystalline substance with a specific gravity of 2.20. It quickly absorbs carbon dioxide and water in the air and becomes sodium carbonate after deliquescence. Easy to dissolve in water.

14. Copper sulfate: Blue crystal of CuSO4 • 5H2O triclinic system, with a specific gravity of 2.29. When the temperature exceeds 100 ℃, it begins to lose crystalline water. At 220 ℃, anhydrous copper sulfate forms as a white powder with a specific gravity of 3.606, which is highly absorbent and forms hydrates.

15. Boric acid: H3BO3- is a hexagonal triclinic white small phosphorus sheet with pearlescence, with a specific gravity of 1.44. Can be dissolved in water, alcohol (4%), glycerol, and ether.

16. Potassium cyanide: KCN colorless crystalline powder with a specific gravity of 1.52, easily soluble in water. Toxic!

17. Potassium permanganate: KnMO4- easily forms light red purple nearly black diamond shaped crystals, with a metallic luster and a specific gravity of 2.71. A highly oxidizing agent that is soluble in water and appears deep purple in color.

18. Hydrogen peroxide: H2O2- colorless viscous liquid with a specific gravity of 1.465 (at 0 ℃), exhibiting weak acidic reactions.

19. Palladium chloride: PdCl2 • 2H2O - a reddish brown diamond shaped crystal that is prone to dehydration.

20. Hydrofluoric acid: HF - a colorless liquid with easy flow and strong hygroscopicity, with a specific gravity of 0.9879 at 12.8 ℃. Smoke in the air. Its steam has a strong corrosiveness and toxicity of ten centimeters!

21. Basic copper carbonate: CuC03 • Cu (OH) 2- amorphous powder with light green fine particles, specific gravity 3.36-4.03. Insoluble in water, but soluble in acid. It can also dissolve in aqueous solutions of cyanide, ammonium salts, and alkali metal carbonates to form copper complexes. 22. Ammonium dichromate: (NH4) Cr2O7 orange red monoclinic crystal system. Specific gravity 2.15. Easy to dissolve in water and alcohol. 23. Ammonia water: Ammonia water is a colorless liquid, lighter than water, with the unique odor and strong alkaline reaction of ammonia. 24. Potassium ferrocyanide (yellow blood salt): K4Fe (CN) 6 • 3H2O - a light yellow square or octahedral crystal with a specific gravity of 1.88. Stable in the air. 25. Potassium ferrocyanide (red blood salt): K3Fe (CN) 6-deep red diamond crystal: specific gravity 1.845. Soluble in water, the aqueous solution gradually decomposes when exposed to light to form K4Fe (CN) 6. It is a strong oxidizing agent in alkaline media. (2) Commonly used test paper properties: 1. Iodine starch test paper: turns blue when exposed to oxidants (especially free halides), so these substances can be checked. 2. Congo test paper: turns blue in acidic medium and red in alkaline medium (when pH=2-3, it changes from blue to red). 3. Litmus test paper: a light blue purple (blue) or purple rose color (red) test paper, which turns blue in acidic medium and red in alkaline medium. When pH=6-7, it changes color. 4. Lead acetate test paper: turns black in hydrogen sulfide (forming lead sulfide) and can be used to detect trace amounts of hydrogen sulfide. 5. Phenolphthalein test paper: White phenolphthalein test paper turns dark red in alkaline medium. 6. Orange I test paper: turns rose red in acidic medium, with an acid value of 1.3-3 Within the range of 2, the color changes from red to yellow. PCB Common Unit Conversion 1. Common Unit Conversion Table (1) ℃=(° F-32) x 5/9; (2) 1OZ/gal=7.49g/1; (3) 1ASF=0.1075A/dm2; (4) 1 psi=0.0704Kg/cm2; (5) 1ft2=12in; (6) 1mil=25.4 μ M; (7) 1 inch=2.54Cm=25.4Gmm; (8) 1Ib=453.6g; (9) 1Ib=16oz; (10) 1 gal=3.8573 1; (11) 1ft2=929cm2=0.0929m2; (12) 1m2=10.76ft2