Classification of PCBs and Manufacturing Process of Copper Clad Laminates

1. Shri Sant Gajanan Maharaj College of EngineeringDepartment of Electronics & Telecommunications Engineering Electronic Devices & Components Unit – III Printed Circuit Board Manufacturing Process, Development Process and Soldering Techniques Classification ofPCBs and Manufacturing Process of Copper Clad Laminates

2. References Introduction to Printed Circuit Boards by Anand & Anand Printed Circuit Boards by Khandpur Electronic materials and Components by S. M. Dhir Many Internet Resources

3. Classification of PCBs According to Sides • Single Side PCB • Double Sided PCB • Multilayer PCB

4. Types of PCBs According to Sides Single Side PCB

5. Types of PCBs According to Sides Single Side PCB

6. Types of PCBs According to Sides Double Side PCB with PTH (Plated-Through Holes)

7. Types of PCBs According to Sides Double Side PCB without PTH

8. Types of PCBs According to Sides Multilayer PCB

9. Types of PCBs According to Sides Multilayer PCB

10. Types of PCBs According to Sides Multilayer PCB 6-layer PCB cross section Track Pad Insulator (e.g. Fiberglass laminate) Via

11. Types of PCBs According to Sides Multilayer PCB

12. Types of PCBs According to Sides Multilayer PCB

13. Types of PCBs According to Sides Multilayer PCB

14. Classification of PCBs According to Base Material PTFE Polyamide [Nylon] Epoxy Resin Phenolic Resin Silicon Resin

15. Characteristics of Base Materials of PCB (01) Poly Tetra Fluro Ethylene, PTFE Also known as Teflon. It has low dielectric constant, Chemically resistance and its properties do not change much even up to 330oC. It has low Dissipation Factor over large frequency range. They are used in modern day electronics at VHF and UHF frequencies

16. Characteristics of Base Materials of PCB (02) Polyamide Resin [Nylon] They have good mechanical properties, High volume and surface resistivities, and good dielectric strength. They are heat resistant. Copper binding strength is high. They are used in multilayer PCBs.

17. Characteristics of Base Materials of PCB (03) Epoxy Resin They have high resistivity. Low shrinkage, strong adhesion, low water absorption. Epoxy resin combined with glass forms base material for PCB. These have good mechanical and electrical properties.

18. Characteristics of Base Materials of PCB (04) Phenolic Resin They are cheap, non-toxic and harmless. They are not flame resistant. They are affected by acids and alkalis. Water absorption is also high. They are most popular and widely used by electronic hobbyists and educational institutions.

19. Characteristics of Base Materials of PCB (05) Silicon Resin They have high heat resistance. Silicon resin is combined with glass to form base material for PCB. Their mechanical properties are poor. Bonding strength for copper layer is also poor.

20. Properties of Copper Clad Laminate • Electrical: • (01) Volume Resistivity • (02) Surface Resistivity • (03) Dielectric Strength • (04) Dielectric Constant • (05) Dissipation Factor • (06) Dielectric Loss • (07) Loss Factor

21. Properties of Copper Clad Laminate • Mechanical: • (01) Glass Transition Temperature • (02) Flexural Strength • (03) Peel Strength • (04) Coefficient of Thermal Expansion • (05) Water Absorption • (06) Punchability • (07) Bow and Twist

22. Electrical Property of Copper Clad Laminate (01) Volume Resistivity: Ideally, resistance of base material must be infinite because it is an insulator. However, resistance practically is several Mega Ohms. Hence leakage currents flow through base material of copper clad laminate

23. Electrical Property of Copper Clad Laminate (01) Volume Resistivity [continued]: The volume resistance is resistance offered to leakage current and can be written as Where, ρv = Volume resistivity in ohm-metre l = length of current path in metre A = Cross sectional area of the current path in m2 perpendicular to direction of current

24. Electrical Property of Copper Clad Laminate (02) Surface Resistivity: The resistance offered by base material to flow of surface component of current (Is)

25. Electrical Property of Copper Clad Laminate Factors on which resistivity depends More the humidity, lesser the resistivity. This is undesirable. More the temperature, lesser the resistivity. This is undesirable.

26. Electrical Property of Copper Clad Laminate (03) Dielectric Strength: It is ability of material to resist the passage of disruptive voltage produced by electric stress. Its unit is kV/mm. The laminate (without copper layer) is placed between two electrodes and 50 Hz AC supply is given. Voltage is gradually increased. The voltage at which laminate ruptures is its break down voltage

27. Electrical Property of Copper Clad Laminate (03) Dielectric Strength [continued: More humidity and temperature, lesser the breakdown voltage. This is undesirable.

28. Electrical Property of Copper Clad Laminate (04) Dielectric Constant or Permittivity: It is ratio of capacitance with dielectric material to capacitance with air as dielectric. It is denoted by Єr . It does not have any unit.

29. Electrical Property of Copper Clad Laminate (04) Dielectric Constant [continued]: Lesser the value of dielectric constant, lesser will be dielectric loss

30. Electrical Property of Copper Clad Laminate (04) Dielectric Loss: In pure capacitor phase angle Ф is 90o. Hence real power loss P = V*I*cosФ will be zero. However, since dielectric has finite high resistance (instead of infinite resistance). Hence phase angle will be a bit less than 90o.

31. Electrical Property of Copper Clad Laminate (04) Dielectric Loss [continued]: The dielectric loss is expressed as Where angle δ is known as ‘dielectric loss angle’. tan δ is known as Dissipation Factor of the insulator

32. Electrical Property of Copper Clad Laminate • (05) Dissipation Factor • In an insulating material, Dissipation Factor is ratio of total power loss in the material to the product of voltage and current in a capacitor in which that material is a dielectric • Dissipation Factor = tan δ • Lesser the dissipation factor, lesser will be dielectric loss. • Higher the temperature, more the dissipation factor • Higher the frequency lesser the dissipation factor. • More humidity, more the disspation factor.

33. Electrical Property of Copper Clad Laminate (05) Dissipation Factor (continued)

34. Electrical Property of Copper Clad Laminate Variation of Dissipation Factor and Dielectric Constant with Frequency

35. Electrical Property of Copper Clad Laminate (06) Loss Factor It is product of Dielectric Constant and Dissipation Factor of insulator Єr * tan δ

36. Electrical Properties of Copper Clad Laminates

37. Properties of Copper Clad Laminate • Mechanical: • (01) Glass Transition Temperature • (02) Flexural Strength • (03) Peel Strength • (04) Coefficient of Thermal Expansion • (05) Water Absorption • (06) Punchability • (07) Bow and Twist

38. Mechanical Property of Copper Clad Laminate (01) Glass Transition Temperature It is the temperature at which the laminate looses its solid-brittle property and turns in to semi-liquid (rubbery) state

39. Mechanical Property of Copper Clad Laminate (02) Flexural Strength This is load that the laminate strip can bear without getting fractured when supported at ends and loaded at its centre

40. Mechanical Property of Copper Clad Laminate (03) Peel Strength This is force needed to remove copper layer from base material. Its unit is N/mm. More the value, better the bonding.

41. Mechanical Property of Copper Clad Laminate (04) Coefficient of Thermal Expansion CTE More the heat, laminate length increases. With lower temperature, its length decreases. CTE is measured in mm/oC per metre. Epoxy Resin has high CTE 35 to 45 Fibreglass has low CTE 5 to 6

42. Mechanical Property of Copper Clad Laminate (05) Water Absorption It is defined as the ratio of weight of water absorbed to weight of dry laminate. More water absorption, more will be the weight of the laminate

43. Mechanical Property of Copper Clad Laminate (06) Punchability The PCB is drilled / punched for mounting components. A hole should have smooth edges, smooth from its inside and without cracks. For this, the laminate must be soft and free from warp and twist

44. Mechanical Property of Copper Clad Laminate (07) Bow and Twist Copper and base material have different properties. This bends the laminate. Warpage along edges is known as Bow. Warpage along diagonal is known as Twist. Both pull the sheet and it looses flatness

45. Properties of Copper Clad Laminates

46. Manufacturing Process for Copper Clad Laminates Copper clad laminate is made up of base material + copper layer. Base material is composed of Paper + Phenolic Resin or Glass + Epoxy Resin. Combine Filler and Resin Deposit copper layer

47. Manufacturing Process for Copper Clad Laminates

48. Manufacturing Process for Copper Clad Laminates Step- 01: Preparation of Copper Foil A stainless steel rotating drum is used as cathode and copper plate as anode. Copper gets deposited by electrolysis

49. Manufacturing Process for Copper Clad Laminates Step-02: Preparation of Prepreg The filler (e.g. paper) is coated with resin This material passes through squeeze rollers and through drying oven. The resin gets polymerized. This is known as Prepreg The prepreg is stored in room at 70oC at 35% humidity Paper + Phenolic Resin gives prepreg for paper phenolic base material Glass cloth + Epoxy Resin gives prepreg for paper phenolic base material

50. Manufacturing Process for Copper Clad Laminates Step-02 (continued): Preparation of Prepreg