create Bridges over hole in TPH

[gauravkothari23]

Hi all,
I am trying to make a double sided PCB's using Dupont Photoresist dry film. my PCB manufacturing process is:
1) Drill the holes.
2) Make holes conductive.
3) Copper Electrolyte Plating.
4) Exposing photoresist film into UV Exposure.
5) Etching.
My problem is, when i expose the PCB to UV Exposure, the film over the holes does not gets harden creating a bridge over the holes, even if the holes are exposed to UV, the film over the holes peels out when the PCB is dipped into the developer solution after expose. due to which, while etching the copper inside the holes also gets etched out.
I am using 30 pieces of 0.50 watts of UV led for exposure. and exposing it for maximum 1 minute. Is it something wrong with my UV led's, do i need more watts UV led.

 

[expertengr]

If you move drilling from number 1 to number 5 than you would finish with etching using UV at least and then you can start drilling manually. In order to make via holes conductive you should drill them 0.8 mm diameter. Then use typical resistance lead which is 0.7 mm diameter and solder it on both sides. There is a trick when you pass the lead in the hole you should flatten it from one side and then cut the lead from other side and flatten it, make it like a toffee, in this way the lead will not leave the via while soldering,

 

[FvM]

The standard production process for through plated PCBs works differently. It applies a negative photoresist image after chemical through plating, leaving vias and traces exposed to galvanic plating. After copper plating, add a galvanic tin or nickel-gold plating which acts as etch resist after stripping the film.
See e.g. https://www.4pcb.com/media/presentation-how-to-build-pcb.pdf