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Anyone here doing SMD projects at home (not in a pro lab), in India ?

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jayachar88

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Hi,

Context of the question is my current location, i.e. Bangalore - India. I know that there are lot of folks in other countries who have semi-professional (or professional grade) lab / bench at home, but I can ill afford that luxury here, both due to cost and availability.

So wondering if there are other folks here, from India, who work/worked on projects involving SMD components ? Would love to hear about their experience. What tools they use, where they purchased those tools, at what cost ? Where do you source your SMD components (in small quantities, esply) ? How do you do soldering ? etc.

cheers,
jay
 

poorchava

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SMT soldering is no different than THT soldering. The only real difference for an amateur is that you need a fine tweezer for operating parts. All you really need is solder wire, any flux-like substance (ordinary rosin is good, simple and cheap) and soldering iron (actually any soldering iron will do unless you want to solder fine pitch components). Nice thing is to have a solder wick. It's a kind of braided wire soaked with flux. When heated up it sucks solder inside itself allowing for easy desoldering and removal of excess solder. You can manufacture it at home from any coaxial cable (like the one that you use for connecting TV to antenna of your roof). Just peel the outer insulation, and pull out the inner wire+insulation. You are left with copper braided wire. then u soak it in rosin or whatever flux you have handy. Works like a charm.

Nice thing about smd is that you actually don't need many holes drilled which eliminates nescessity of buying a precision drill, which is usually quite expensive, as well as replacing drill bits on regular basis (because epoxy laminate makes drill bits dull very fast)

As for sourcing components and tool this is difficult thing. I think tweezers you can buy from pharmacy (at least that's what i do in Poland, medical ones are like 5x cheaper for some reason). Solder wire, rosin and soldering iron you can get from a tool store, hardware store, construction market, etc.

As for sourcing components in small quantities I recommend ebay. there are numerous sellers from Hongkong/China/etc who ship stuff worldwide for free (you can buy one screw and get it shipped for free from China). This is nice since in case of smd components the handling and shipping can get like 10x the price of actual parts ordered.

The bad side of using SMT is that you rarely can use universal boards, because of the pitch of elements. This means that you need to manufacture your own pcb everytime. This also means that you cannot draw traces on pcb's with nail polish or permanent marker, because you need much higher precision than that. You need at least a laser printer and cloth iron for that purpose.
 
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jayachar88

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Thanks @poorchava. Your explanation is quite encouraging, but having attempted some 0402 soldering, I've come to believe that you need better tools, since I don't have an excellent eyesight, and the cheap magnifier (purchased for about $15) I use, just sucks. It says 10x mag, but I think it's more like 2x-3x, at most, and hands need to be really very steady.

Without solder-mask, I've found the solder-pad affinity to be lacking and removing the bridges is so painful and timeconsuming (almost 4x the time taken with THT). I've not tried the braided desolder wicks, but plan to try them. They could make a lot of difference. So far, I'd be taking the approach of overusing liquid flux, but I guess that method works only on high quality PCB with good soldermask.
 

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jayachar88
You don't need any special tools at all just the stuff you already use in your workshop/home
Here is a video you may find useful and show's you how easy it is

EEVblog #186 – Soldering Tutorial Part 3 – Surface Mount | EEVblog - The Electronics Engineering Video Blog

wizpic


Thanks for the reply @wizpic. This is roughly the procedure I've been using, although I did learn a few useful tricks and will try to do a better job next time. My main problem, I think is lack of solder-mask on DIY or el-cheapo PCBs. In that case, the bridging, run-off etc. are quite extensive.
 

poorchava

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but having attempted some 0402 soldering
Dude... 0402 is kind of extreme for homemade circuits. They are solderable, but it's tough since they are so small and heat transfers very rapidly across resistor melting the opposite joint. I'm trying to stick to 0805 with 0603 being an exception. I can't recall using 0402 on homemade PCB.

So far, I'd be taking the approach of overusing liquid flux, but I guess that method works only on high quality PCB with good soldermask.
Right and wrong at the same time. Using lots of flux helps alot. Of course soldermask is very helpful, but not mandatory at all. For your homemade pcb to solder easily you need to get it very clean. After etching you should clean the laser printer toner with acetone or nitro paint thinner. First you can buy in cosmetics store and the second in construction market or wherever you buy household cleaning stuff. Then you can use some very fine sandpaper (i mean like 1500-2000 grit) to remove any remaining oxidation. On the other hand cleaning powder (like the one you use to clean badly burnt remains of food in the pot) also works and it saves more of you copper thickness. While sanding/powdering you need to pay attention not to rip out the pads or tracks. Then with generous dose of flux and small dose of solder your SMDs will solder fine.

This is a pcb I've made yesterday. IC's are ordinary so-8, small caps and resistors are 0805 size and large caps are tantalum size B.
 
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