[Syzygies]

Would it be easier to assemble a project using many surface mount components, if we could clamp a laser-cut frame over the PCB, drop in the components like a kid filling in a wooden puzzle of the fifty states, solder, and remove the frame?

"Caching" and "Precomputing" are key concepts for computers. We can't all afford $100,000 robotic assembly machines, this would be like precomputing the benefits of having such a machine, for easy distribution for home DIY use.

I'm thinking that each cutout would be shaped to keep the component from wiggling around, while at the same time providing openings to reach in to solder. The frame would be no thicker than necessary, with a legend to help remember what goes where.

A variant would be to have the holes fit the parts closely, and dab in some kind of glue as scaffolding that wouldn't hurt the component, solder, or operator.

I've noticed various references to laser cutting here, and also to a general distaste for surface mount soldering. Doobooloo's laser cut case blew me away, and she ran the job herself at school. A mostly surface mount PIMETA using discrete diamond buffers would beg for some kind of hand assembly assist like I'm proposing.

 

[jefemeister]

This is a common technique. If you order a PCB you can get a matching mask with all pad locations cut out. You lay the mask over the board, lay down some solder, place the components on top, and stick it in a little toaster-oven looking thing. you usually put a little piece of waxy stuff on top of the board so it melting is an indication to take the board from the oven. A little while later you have a perfectly assembled board. There's a name for this process but i can't remember it. It's usually only done for larger Flat Packs or BGAs.

edit: add a link: http://www.stencilsunlimited.com/?source=PCB123

 

[Syzygies]

That's a great link. As I read it, they use a $150 stencil to place the solder paste in what is similar to silk screen printing, then place the components by tweezer, flowing the solder in a "reflow toaster oven".

I was proposing a $6 stencil (in quantity) for the actual surface mount components themselves (like a wooded frame for the "fifty states" jigsaw puzzle). Place a speck of superglue between each pair of solder pads, drop in all the components, let dry, lift up the stencil, ventilate, and solder all the components.

First take-away message from this link: I've heard of the toaster oven method, but not the warning to dedicate it to solder paste, never use it again for food.

Second take-away message from this link: The solder paste and toaster oven method looks easier, even by hand, than any of the other methods described here in recent months.

Along the same lines, people moan about the non-photographic etch resist methods for making home boards, but no one who gets the photographich method to work once ever even thinks of going back. It sounds harder but it works better, making it effectively easier.

Is the solder paste, toaster oven method the same story?

 

[drewd]

Maybe it's just because I've done a lot of them, but hand soldering surface mount components seems pretty easy to me, compared with the (perceived) hassle of aligning the stencil, putting the glue down and then going back and soldering everything. I just put a drop of solder on one pad, then place the component with tweezers, heat and do the other side. I've done this with TSSOP parts and 0402's and it actually goes faster than through-hole parts because I don't have to stop and cut leads. For 1206 and SOIC parts, it's even easier!

Even the reflow process seems slower and more cumbersome to me. Also, solder paste has a relatively short shelf life. Unless it's for BGA type parts where you can't solder by hand, it's faster to do it with an iron, at least for me.

You do need to use pretty fine gauge solder!

-Drew

 

[Syzygies]

Thanks!

For etching my own boards, I can see two other advantages: Not drilling the holes, and more room for the traces on the other side.

 

[braillediver]

“hand soldering surface mount components seems pretty easy”

It’s best to learn how to do it and do it right then you can accomplish any task. Otherwise you’ll always need training wheels and only be able to do a limited number of boards.

Get some tweezers, fine tip iron, small diameter solder and some scrap or cheap components and practice.


Mitch

 

[aeriyn]

SMD devices are relatively easy for me to solder. I use the same method that drewd explained. Although when it comes to SOIC opamps and whatnot, I tend to put a tiny drop of adhesive under the chip to get it aligned perfectly with the pads before soldering, so my shaky hands don't knock the chip all skewed.

Getting them off the board is another story entirely... >.>;

 

[n_maher]

I had my first real experience with SMD parts the other night putting together a couple of MINT boards. I found that using scotch tape to hold the chip in place, with half of the legs exposed worked pretty well. I did not feel comfortable laying down any solder on the board and trying to hand-hold the chip in place.

We'll see how it sounds when I get one finished tonight (hopefully).

N