High temperature drilling electronics
A printed circuit board assembly (PCBA) for downhole applications has a printed circuit board (PCB) and a plurality of electronic components installed on the PCB. The PCB comprises a polyimide substrate, a lead-free surface finish, a plurality of traces, a plurality of surface mount pads, and a plurality of VIAs. The ratio between the width of one of the plurality of surface mount pads to the width of the trace connected thereto is 2 or less.
1. A printed circuit board assembly (PCBA) for downhole applications, comprising:
a printed circuit board (PCB) and a plurality of electronic components installed on the PCB;
wherein the PCB comprises a polyimide substrate, a lead-free surface finish, a plurality of traces, a plurality of surface mount pads, and a plurality of VIAs, and
wherein a ratio between a width of one of the plurality of surface mount pads to a width of the trace connected thereto is 2 or less,
wherein X/Y ranges from 0.8 to about 0.86, wherein X is a minimum trace width of the plurality of traces and Y is the minimum spacing between the two adjacent traces amongst the plurality of traces.
2. The printed circuit board assembly (PCBA) of claim 1 , wherein the polyimide substrate is polyimide 35N or polyimide 85N.
3. The printed circuit board assembly (PCBA) of claim 2 , wherein the polyimide substrate is polyimide 85N.
4. The printed circuit board assembly (PCBA) of claim 1 , wherein the lead-free surface finish is electroless nickel immersion gold (ENIG), electroless gold, electroless palladium, immersion silver, immersion tin (ENEPIG), organic solder-ability preservatives (OSP), or direct gold on copper (DIG).
5. The printed circuit board assembly (PCBA) of claim 1 , wherein the lead-free surface finish is electroless nickel immersion gold (ENIG).
6. The printed circuit board assembly (PCBA) of claim 1 , wherein the plurality of traces have a width of 0.5 mm or higher.
7. The printed circuit board assembly (PCBA) of claim 1 , wherein the plurality of VIAs comprises one or more microVlAs, one or more blind VIAs, and one or more buried VIAs.
8. The printed circuit board assembly (PCBA) of claim 1 , wherein the plurality of VIAs each has a diameter of 0.30 mm or larger.
9. The printed circuit board assembly (PCBA) of claim 1 , wherein the PCB further comprises one or more plated thru-holes for mounting the plurality of electronic components.
10. The printed circuit board assembly (PCBA) of claim 1 , wherein the plurality of electronic components has a distance to an edge of the PCB that follows the following relation, when a height of the electronic component is less than 3 mm, the distance is at least 2.0 mm; and when a height of the electronic component is 3 mm or higher, the distance is at least 2.5 mm.
11. The printed circuit board assembly (PCBA) of claim 1 , wherein the PCBA is operable at up to 200° C. for more than 500 hrs.
12. The printed circuit board assembly (PCBA) of claim 1 , wherein the PCB has a copper thickness of 2 oz or less.
13. The printed circuit board assembly (PCBA) of claim 1 , wherein the width of the trace is 0.5 mm or higher.