Technical Information
Base materials / Characteristics
Richter Elektronik – Specifications for FR4 printed circuit boards:Base material:
Standard FR4 materials:The standard FR4 base material for single-sided and double-sided printed circuit boards is based on FR4 epoxy glass weave laminate with a TG value of at least 130° C and a CTI value of 175.
The standard FR4 base material for multilayer boards is based on FR4 epoxy glass weave laminate with a TG value of at least 150° C and a CTI value of 175.
All base materials are specified by their manufacturers for flammability class UL 94 V0.The base materials are specified according to DIN EN 60249 Part 1 and IPC 4101.
Special FR4 materials:
Special FR4 materials like halogen-free, filled, high thermal stability or other materials can also be produced with UL approval.
Non-FR4 materials:
IMS boards on aluminium base
Polyimide (flex) for flexible boards
High frequency boards made of Rogers 4000
High frequency multilayer boards made of Rogers 4000 combined with FR4
FR4 base material thicknesses and tolerances
| Nominal thickness mm | Thickness tolerance mm |
| 0,30 | + / - 0,10 |
| 0,40 | + / - 0,10 |
| 0,50 | + / - 0,10 |
| 0,60 | + / - 0,10 |
| 0,80 | + / - 0,125 |
| 1,00 | + / - 0,125 |
| 1,20 | + / - 0,125 |
| Standard: 1,55* | + / - 0,125 |
| 2,00 | + / - 0,15 |
| 2,40 | + / - 0,20 |
| 3,00 | + / - 0,30 |
| 3,20 | + / - 0,30 |
Some base material, board thickness and copper thickness combinations are not available directly ex stock.
*There is no distinction between the nominal thicknesses 1.5, 1.55 and 1.6 mm.
Copper layer thicknesses and tolerances
The copper foils we use meet the HTE quality requirements (elasticity grade).Single-sided PCBs and inner layers of ML boards
In the normal manufacturing process, single sided PCBs and inner layers of ML boards are produced exclusively by etching and are not reinforced by plating. Thus, in terms of the final copper thickness of the board only the laminated copper thickness is considered.
| Final Cu thickness = base Cu thickness = nominal thickness | Nominal thickness tolerance |
| 12µ | -3µ / +1µ |
| 18µ | - 4µ / + 2µ |
| 35µ Standard | - 5µ / + 3µ |
| 70µ | - 9µ / + 6µ |
| 105µ | -13µ /+10µ |
| 140µ | -16µ /+14µ |
| 175µ | -19µ /+17µ |
| 210µ | -23µ /+21µ |
Double-sided plated-through PCBs and outer layers of ML boards
In the manufacturing process the outer layers are generated in semi-additive technology. The final copper thickness includes the base copper plus the plated copper reinforcement.
| Final Cu thickness = | Base Cu thickness | Note: Our functional specification which is available on request contains information about plated copper reinforcement and special copper reinforcement. |
|
| nominal thickness | nominal | minimum actual | |
| µ | µ | min. µ | |
| 35 | 12* | 9 | |
| Standard 35 | 18 | 16 | |
| 55 | 35 | 32 | |
| 70 | 50 | 45 | |
| 85 | 70 | 63 | |
| 105 | 105 | 94 | |
| 140 | 140 | 126 | |
| 175 | 175 | 157 | |
| 210 | 210 | 189 | |
*) 12 µ base copper thickness is-used for special purposes only.
Some base material, board thickness and copper thickness combinations are not available directly ex stock.
Additionally, the plated layer thickness and thus the final thickness depend on the copper pattern and its distribution and homogeneity as this determines the deposition rate of the copper plating process.
Copper thickness in plated-through holes
The plated-through barrel is generated during the copper plating process and must achieve a minimum wall thickness to withstand all subsequent mechanical, electrical and thermal stresses.
| Design | or | |
| Plated-through holes | Min. diameter | Aspect ratio |
| d (mm) | max. | |
| Through holes | 0,20 | 1:10 |
| 0,30 | 1:8 | |
| 0,40 | 1:6 | |
| 0,50 | 1:5 | |
| 0,60 | 1:4 | |
| Holes for press-in mounting | 0,70 | 1:5 |
| Microvia holes | 0,150 | 1:10 |
| Buried holes | 0,20 | 1:6 |
| Blind holes | 0,125 | 1:1 |
| Slots (nibbled, milled) | 0,60 | ---- |
| Plated milled contour | 1,6 | ---- |