PCB Building Help

[Ranger14]

I am currently working on upgrading my small work bench with ability to make one off pcb's  but have a couple questions.. To drill the holes I picked up a standard dewalt drill with drill press adapter and not sure if I would be able to use tungsten carbide bits because of the low speeds of the drill?? Also has anyone good luck with Chinese tungsten carbide sets ?? Has anyone had problems with liquid tin and smd parts

[Rerouter]

in the scheme of things, FR4 fibreglass is about as hard to drill through as pine timber, its just wears the bits faster because of the glass content,

as such just about any drill bit will work, and unless your drill press is very firm and unable to move, your likely going to be breaking a bit every 200 holes or so, equally the softer the material of the drill bit, the more forgiving it is before it snaps / shatters / chips

Tungsten carbide will certainly drill through fibreglass, likely without ever abraiding from the glass content, however it is extremely brittle so likely to chip if either the board or the drill shifts while in the hole.

Next up, liquid tin is a few microns thick layer, a drill bit will not care in the slightest, same with nickel platings of those thicknesses,

SMD parts? do you mean like drilling your own via's, if so that just comes down to if your deburing the holes or not, as there will be a raised edge on any hole you drill in a foil,

[KL27x]

Chinese pcb drills are great. Just figure out the smallest ones that work in your setup, and use steel bits from there.

A lot of people ditch liquid tin in the end. For me, it is easier to just rub the board with rosin flux. If it needs to stand up to, say, repeated contact with skin/sweat, after populating, tin plating isn't particularly helpful. I will clean the board with alcohol and paint it with conformal coat, lately. Although regular laquer works, too. Tin just doesnt do all that much for the amount of trouble. It provides only moderate corrosion resistance and esthetic appearance.

[M4trix]

A lot of people ditch liquid tin in the end. For me, it is easier to just rub the board with rosin flux. If it needs to stand up to, say, repeated contact with skin/sweat, after populating, tin plating isn't particularly helpful. I will clean the board with alcohol and paint it with conformal coat, lately. Although regular laquer works, too. Tin just doesnt do all that much for the amount of trouble. It provides only moderate corrosion resistance and esthetic appearance.

This is what worries me. I recently made a bunch of PCBs and coated the pads with immerse tin ( Seno 3211 ) and stored them cuz I'm not going to assemble them in couple of months. I never used liquid tin before. These days I found some articles and datasheets about the liquid tin shelf life which is only couple of months if pads are left unsoldered ! This means, the board will be useless and no solder flux will help ! After reading all these negative downsides, I stopped making boards for some time until these things with liquid tin are sorted out.  Guys, what is your experience with liquid tin ?

Seno 3211

http://www.tme.eu/gb/details/seno-3211/materials-for-pcb-production/

[Rerouter]

In the past for raw copper board i just coated them in sewing oil, and seperate them with wax paper, when i did need to solder i just wiped them down with isopropyl and they where good to go,

If its a more complex board, e.g. 4 layer, i generally just go enig to save myself the trouble as the boards already costing me something, if not that complex i just rely on the hasl to do its job and bake the board with a very thin layer of flux to clean it up before i use it.

[Buriedcode]

I just used to tin them with a soldering iron.  With liquid flux on the board - after cleaning the copper with steel wool - you can get a surprisingly thin layer of solder.

As for drilling, if there is *any* side loading on a carbide bit, it will break, and they can be expensive. Standard HSS bits have quite a bit of flex in them, and will tolerate any side-side movement or run-out better but as pointed out here, they will dull rather quickly.  Ultimately, if you're making a couple of PCB's a week, with only 20-30 holes in each, its much cheaper and easier to buy up packs of HSS drills.  They'll probably last about 20-30 holes but they're so cheap it doesn't matter.

If, on the other hand you have boards with lots and lots of holes of the same size, same 0.8mm and 1mm, then carbide bits start to be come more economical, but unless you have a very sturdy hobby drill that's rock steady as the bit is lowered (I haven't found a drill press than hasn't got some degree of this) you'll just end up shattering bits.

Also, whilst instinctively people 'go slow' on spindle speed, for such small diameters as PCB holes it needs to be quite fast.  Industrial PCB drilling machines are >20k rpm, which is clearly ridiculous for home use but a minimum of 8k rpm should be fine.  I broke less bits, and had better holes with a 12k rpm 12V drill. With that said, if I had a board with <10 holes I would just use a pin-vice and do them by hand - tedious, but with a sharp drill bit, it took a couple of minutes, quicker than it was to set up the drill press and calibrate it.