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<wpwrak>
xiangfu: did you scrub the pcb with steel wool and then clean it with alcohol before the toner transfer ?
<xiangfu>
wpwrak, only wool. (no steel wool, no alcohol)
<xiangfu>
use only wool do some clean.
<wpwrak>
xiangfu: you also don't seem to have sufficient clearance between traces and some bga pads. so unless you expect them to connect or you don't care, you should move the trace exactly in the middle between the pads
<xiangfu>
yes. I am still improving the design now.
<wpwrak>
you'll need the steel wool. first, it removes oxides, which other methods can't touch. second, it leaves small scratches that improve adhesion
<xiangfu>
got it. thanks
<xiangfu>
wpwrak, now I understand more on pcbnew. I have a question on those layers btw.
<wpwrak>
and after the steel wool, you need alcohol to 1) remove the dust/dirt left behind by the steel wool, 2) remove any grease
<xiangfu>
ok.
<wpwrak>
the steel wool should be the fine type, with the steel about at thick as human hair. not the more coarse steel wool where the steel is about 1 mm (for scrubbing pots and such)
<wpwrak>
what's the trouble with the layers ?
<kristianpaul>
indeed clean is must
<xiangfu>
(with the steel about at thick as human hair.) got it.
<xiangfu>
the layer.. there are so many layers. like adhes, soldp, silks, mask, eco1/2,
<xiangfu>
what are those layers for. is there any document about them?
<wpwrak>
soldp is for solder paste. that's used when you do the smt at a fab.
<xiangfu>
I understand the 'comments' layer. which is print after solder mask.
<wpwrak>
adhes is adhesive, also used at the fab (for items that need to be glued to the board, e.g., if they're on the bottom side and would fall off during soldering)
<wpwrak>
mask is the solder mask. that's a protective layer applied on top of the copper when making the pcb (at a pcb fab)
<wpwrak>
silks is the silk screen, the white printing you get on top of the pcb (at a pcb fab)
<wpwrak>
none of these usually matter if you make the pcb at home, but solder mask and silk screen must be correct if you have the pcb made at a fab
<wpwrak>
not sure what eco1/2 stand for. i don't use them. i think they're basically for some sort of comment.
<wpwrak>
then you have "drawings" and "comments". one goes to the silk screen, the other is for things you use during design but that don't correspond to any structures on the physical pcb
<xiangfu>
ok. drawings goes to silk screen.
<wpwrak>
in the sense that things you draw on "drawings" are automatically propagated to the silk screen. you could also draw directly on the silk screen, though. using the "drawings" layer makes it easier to hide your drawings, when the pcb gets crowded and you want to display only the things you're working on at the time.
<xiangfu>
ok. I understand the adhes, mask now.
<xiangfu>
you just answer what I want ask. (can you read my mind?. that is scare :)
<wpwrak>
heh :) is noticed that my explanation was ambiguous
<xiangfu>
what is the soldp for? like some pad have tin, and some not? right?
<wpwrak>
solder paste is a cream that contains solder (tin)
<wpwrak>
at an smt fab, it is applied on top of smt pads before placing the components
<wpwrak>
then, when the pcb is put into the oven, the volatiles in the solder paste evaporate and the tin melts, making the solder bonds
<xiangfu>
yes. understand now.
<wpwrak>
you sometimes also use solder paste for manual smt, but most things can be done without it (it's a bit messy to handle manually)
<wpwrak>
e.g., it's useful for soldering crystals. not sure if you need it for bga, too. i never tried to hand-solder bga.
<xiangfu>
ok.
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<xiangfu>
I will try hand-solder bga without solder paste this week. :)
<xiangfu>
I already have 5 slx9-ftg256 chips on my desk.
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