Manufacturing Printed Circuit Boards(PCB)
PCB : an electronic circuit consisting of thin strips of a conducting material such as copper, which have been etched from a layer fixed to a flat insulating sheet called a printed circuit board, and to which integrated circuits and other components are attached.
A PCB has 2 parts to it :
- Base material
- Conductor or High Purity Copper foil
While the coductor layer is ust that, the base material can vary. We explore this next.
Base Materials
| Name | Design | Use | Contour |
|---|---|---|---|
| FR2 | Paper-base laminate, phenolic resin Cu single- and double-sided, 18, 35, 70 µm | Single- and double-sided PCBs, non-plated through PCBs | Routing / scoring, can be punched at room temperature |
| CEM1 | Core: Paper, epoxy resin Exterior: Glass fibre epoxy resin, Cu single- and double-sided, 18, 35, 70 µm | Single- and double-sided PCBs, double-sided, non-plated through PCBs | Routing / scoring |
| CEM3 | Core: Paper, epoxy resin Exterior: Glass fibre epoxy resin, Cu single- and double-sided, 18, 35, 70 μm | Single- and double-sided PCBs, double-sided, non-plated through PCBs | Routing / scoring, can be punched at room temperature |
| FR4 | Glass fibre, epoxy resin Cu single- and double-sided, 18, 35, 70, 105 µm (others on request) | Single- and double-sided PCBs, double-sided, non-plated through PCBs, multilayer | Routing / scoring |
| FR4 High Tg (FR5) | Glass fibre, epoxy resin Cu single- and double-sided, 18, 35, 70, 105 µm (others on request) | Single- and double-sided PCBs, double-sided, non-plated through PCBs, multilayer | Routing / scoring |
| Teflon | Teflon, glass fibre Cu single- and double-sided, 18, 35, 70 µm (others on request) | Single- and double-sided PCBs, double-sided, plated through PCBs, multilayer, high-frequency PCBs >1 GHz | Routing / scoring |
| Polyimid | Cu single- and double-sided, 18, 35 µm | Single- and double-sided PCBs, double-sided, plated through PCBs, multilayer, rigid-flex PCBs, high temperature PCBs | Routing / laser cutting, can be punched at room temperature |
For reference routing and scoring are as the following :
Routing :
Scoring :
Standard thicknesses of rigid material:
0,5 mm / 0,8 mm / 1,0 mm / 1,2 mm / 1,6 mm / 2,0 mm / 2,4 mm / 3,2 mm / other thicknesses on request.
Polyimide can also be used as a rigid base material when reinforced with glass fibre, thickness 1,6 mm, other thicknesses on request.
Base materials and their technical properties
| Property | Unit | Pre-treatment | FR2 | CEM1 | CEM3 | FR4 | FR4 High Tg | Teflon | Polyimide |
|---|---|---|---|---|---|---|---|---|---|
| Glass transition temperature Tg | °C | – | 30 | 60/90 | 125 | 135 | 150/170/210 | 160 | > 250 |
| Adherence of CU foil | N/mm | – | 2,0 | 1,7 | 1,4 | 2,0 | > 1,4 | > 1,4 | 1,2 |
| Bending strength lengthwise 0,8 to 3,2 mm | N/mm | – | 160 | 400 | 480 | 600 | 600 | 600 | 110 |
| Bending strength crosswise | N/mm | – | 140 | 320 | 330 | 450 | 490 | 490 | 100 |
| Dielectric constant at 1MHz – | *D 24/23 | 4,1 | 4,2 | 5,0 | 4,2–4,8 | 4,5–5,4 | 2,5–2,8 | 3,8 | |
| Electric strength | kV | *D 48/50 | 15 | 40 | – | 40 | – | – | 90 |
| Surface resistance | Ohm | *C 96/35/90 | 109 | 1011 | 1011 | 1011 | 1011 | 1011 | 1011 |
| Volume resistivity | Ohm/cm | *C 96/35/90 | 1010 | 1013 | – | 1012 | – | – | 1014 |
| Solder-bath resistance | S | – | 15–20 | 30 | – | 120 | – | – | – |
| Combustibility UL 94 | – | – | V1 | V0 | V0 | V0 | V0 | V0 | V0 |
| Creepage formation DIN IEC 112 | CTI | – | 250 | – | – | 175–200 | – | – | 160–175 |
| Water-absorbation | % | *E 24/50 | 0,75 | – | – | – | – | – | 2,5 |
| Temperature limit | °C | – | 105 | – | – | – | – | – | – |
| Thermal expansion | Ppm/°K | *E 0/100 | 270–330 | 300 | 190 | 170 | 100–200 | 100–200 | – |
*C – Pre-treatment in humid air, *D – Pre-treatment in distilled water, *E – Storage in drying chamber