I have in the past hand soldered SOIC packages for prototypes using a microscope and a soldering pencil. But now I am faced with a chip that is only available in an LCC package - the kind with the contacts under the chip. It only has 8 pins. Is there any hope that I can solder this chip using hobbyist's tools?
Robert Scott Ypsilanti, Michigan
Sure. Put solder paste on the pcb (very little), place the part, and use the iron to reflow each pad.
Or, use a hotplate to get all the top-side SMD parts, then an iron for everything else. I have some leadless resonators I soldered with a hotplate.
I have been able to solder these with a good Pace "mini wave" tip if the lands extend out far enough. For IPC-7851 lands there might not be enough land. For IPC-782 you should be good. The problem is that LLC parts usually have a ground power pad. This is for thermal dissipation. Sometimes you can get away with not soldering it, sometimes you can't.
Some of your ability to hand solder this depends on the PCB finish. If it is HASL or Immersion silver you will have better luck than Immersion Gold.
Hawker
On 3/8/2007 2:00 PM, The digits of Robert Scott's hands composed the following:
microscope
Well, the land is under my control because I have not yet laid out the PCB. I intend to use Advanced Circuits in Colorado to make my prototypes. Should I order the bare-bones board without soldermask?
I Robert Scott Ypsilanti, Michigan
Excuse my ignorance, but what is a hotplate? Are you talking about a kitchen utensil?
Robert Scott Ypsilanti, Michigan
No your going to definitely want solder mask on this one. Is this a typical 0.5mm pitch LLC?
I had assumed you already had a PCB. If you can afford it do Immersion Silver for this board as HASL, even though it solders better, is often nto flat enough for good LLC soldering. The biggest problems I have had with LLCs is opens due to the part not laying flat. For just a few you should be able to make HASL work, but I wouldn't use it for production on any board with LLCs, BGAs, or .65mm pitch or finer.
As to your hot plat comment. They are basically industrial versions of the home hot plate with metal table. Often chemistry folks have these for keeping things warm. People also have had good success using convection toaster ovens, especially when used with processes like the SIPAD process (google SIPAD).
Me I have access to a fully stocked contract manufacture for my stuff so I only get to the kind of stuff your talking about when I am putzing in the lab late night and I can't pawn if off on someone else who does it all day long. My soldering is getting worse and worse as I get lazy.
Hawker
On 3/8/2007 6:01 PM, The digits of Robert Scott's hands composed the following:
LCC (Ceramic Leadless Chip Carrier) isn't the kind with contacts only under the chip. The pads extend up to the side, and there is no center pad. Are you talking about Analog iMEMS devices?
Perhaps you mean QFN or LFCSP, but I don't think those go down to 8 pin. An LCC land pattern looks huge compared to QFN.
-- Ben Jackson AD7GD http://www.ben.com/
Yup. You know how your stove has, say, four "burners" on it? So you can cook four things at once? I've got a single-burner electric hotplate, normally used in dorms or apartments for cooking one thing at a time. I just cook circuit boards on it. I have a syringe of solder paste, and either manually dab it onto all the pads, or etch a brass stencil to squeegee the paste on.
Hotplate experiments:
microscope
I'm soldering a QFN68 pin package by hand:
I'm playing around with IR reflow using a toaster oven but I need to get some extra flux to add to the solder paste as it doesn't seem to flow too well and lots of small balls of unflowed solder paste show under the microscope. The IR oven shows promise but always needs reworking at present.
How did you know? Yes, it is an accelerometer.
Robert Scott Ypsilanti, Michigan
Yes, it's essentially a 1- or 2-burner stove that plugs in, and sits on the countertop (or benchtop ;-) ) Careful - this will probably wrap:
Hope This Helps! RIch
Yeah, a stove "burner" with a flat metal surface.
portable Single burner hotplates are available if your kitchen ventilation isn't upto the task of removing the smell of hot resin.
Bye. Jasen
PLEASE don't use your regular kitchen stuff (or even the kitchen itself) for PCB work. The chemicals involved in PCB work should never come in contact with the same utensils you cook food with.
My hotplate is dedicated to PCB assembly, and lives in my office next to the soldering iron.
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