4 Layer High Frequency PCB Built On 2 Cores of 20mil RO4350B with Back Drill for GPS Tracker
This type of 4 Layer Rogers PCB is built on 2 core of 0.508mm (20mil) RO4350B for the application of GPS tracker. This board, we used back drilling technology to achieve the “blind via”. See the stack-up.

Back drilling can reduce noise interference and improve signal integrity. Using back drilling successfully reduced the difficulty of PCB fabrication and avoided the use of buried /blind via process.
The specifications of the PCB are as follows:
Base material: RO4350B 20 mil + RO4450B 4 mil
Layer count: 4 layers
Type: Mixed multiplier milled separately
Format: 70mm x 125mm = 1 piece
Surface finish: Immersion gold
Copper weight: Outer layer 35 um/ Inner layer 18 um
Solder mask / Legend: Green / white
Final PCB height: 1.42 mm
Standard: IPC 6012 Class 2
Packing: Each 25 panels are packed for shipment.
Lead time: 12 working days
Shelf life: 6 months
Features and benefits
1) Excellent high frequency performance due to low dielectric tolerance and loss;
2) Low thermal coefficient of dielectric constant;
3) Back drilling reducing noise interference;
4) ISO9001, ISO14001, UL certified manufacturing factory;
5) 30000 square meter month capability;
We can see their applications in multiplexer, video transmission gear, low noise block, power divider etc.

Parameter and data sheet
| PCB SIZE | 70mm x 125mm = 1 piece | 
| BOARD TYPE | Multlayer PCB | 
| Number of Layers | 4 Layers | 
| Surface Mount Components | YES | 
| Through Hole Components | YES | 
| LAYER STACKUP | Copper -----Signal 18um(0.5 oz)+plate TOP layer | 
| RO4350B 0.508 mm | |
| Copper -----Plain 0.018 mm | |
| Prepreg RO4450F X 3, 0.305mm | |
| Copper ----- Plain 0.018 mm | |
| RO4350B 0.508 mm | |
| Copper ------- 18um(0.5oz) + plate BOT Layer | |
| TECHNOLOGY | |
| Minimum Trace and Space: | 4 mil / 5 mil | 
| Minimum / Maximum Holes: | 0.4 mm / 5.6 mm | 
| Number of Different Holes: | 12 | 
| Number of Drill Holes: | 121 | 
| Number of Milled Slots: | 0 | 
| Number of Internal Cutouts: | NA | 
| Impedance Control: | N/A | 
| Number of Gold finger: | N/A | 
| BOARD MATERIAL | |
| Base Material: | RO4350B Tg280℃, er<3.48, Rogers Corp. | 
| Final foil external: | 1 oz | 
| Final foil internal: | 0.5 oz | 
| Final height of PCB: | 1.42 mm ±10% | 
| PLATING AND COATING | |
| Surface Finish | Immersion gold | 
| Solder Mask Apply To: | N/A | 
| Solder Mask Color: | N/A | 
| Solder Mask Type: | N/A | 
| CONTOUR/CUTTING | Routing | 
| MARKING | |
| Side of Component Legend | N/A | 
| Colour of Component Legend | N/A | 
| Manufacturer Name or Logo: | N/A | 
| VIA | Plated through hole(PTH), minimum size 0.4mm. | 
| FLAMIBILITY RATING | UL 94-V0 Approval MIN. | 
| DIMENSION TOLERANCE | |
| Outline dimension: | 0.0059" | 
| Board plating: | 0.0029" | 
| Drill tolerance: | 0.002" | 
| TEST | 100% Electrical Test prior shipment | 
| TYPE OF ARTWORK TO BE SUPPLIED | email file, Gerber RS-274-X, PCBDOC etc | 
| SERVICE AREA | Worldwide, Globally. |