Electric Griddle Reflow Soldering

Overview:

This page explains how I used an electric skillet to reflow solder a project of mine that used all surface mount components, including one QFN-28 leadless PIC18F2520!

Note: Reflow soldering, by the way, is the method of soldering by: first applying solder to the board, secondly placing components, and finally heating the solder and components so that the solder joins the component to the circuit board.

Mission:

Bare Circuit Boards

In designing a controller for an electronic paintball gun, I needed to build everything with SMT components to save space. The board has to fit into the grip frame the paintball gun, so it has to be small. This is all fine and dandy, but I had never soldered SMT components before.

I knew about the "normal" ways to solder: such as hot air reflow stations, soldering irons -- but more impressively (and cost effectively:) I had read about people soldering SMT with toaster ovens and electric skillets! (from Seattle Robotics Society, and more recently -- Spark Fun Electronics).

As my design had to be small, and surface mount components are appropriately small -- I knew SMT was the way to go, and I figured the hot-plate reflow method could take me there. Below are the steps I took.

Tools:

For my reflow heater, I used an electric griddle that I picked up from Wal-Mart for around $20 (Presto 07047 Cool Touch Electric Griddle). Meanwhile, if you want to order online -- Amazon has the Presto 07039 Professional 22-Inch Jumbo Electric Griddle for about $30.

Tools Used in Electric Griddle Reflow

Why did I go with the griddle? I looked at the other electric skillets and appliances they had, but got the griddle because I believed it had the largest heating element. I decided that if the griddle didn't get hot enough (i.e. because of cold spots farthest from the element,) then I at least I could put a lot of boards directly on the heating element.

I used Wahl silver solder paste for the SMT components, and regular solder & rosin paste flux for the larger through-hole components.

Note: Solder flux is the greatest thing ever. I've been soldering circuits well enough for years using just regular 60/40 rosin core solder, but let me tell you -- dabbing standalone flux on the circuit board where I need to solder a component makes it 10x easier, faster and cleaner! (minus the extra rosin that is now on the board -- but that generally can be scraped off or removed with acetone). So I strongly recommend solder flux to everyone for soldering through-hole components.

Additionally, I used bent nose tweezers to position the surface mount components on the board, a metal scribing tool to apply flux and scratch flux off, and cherry coke for energy.

Tools Used	Cost
Presto 07047 Cool Touch Electric Griddle	$20
Kester Rosin Paste Flux (SP 44)	$3
Wahl Silver Solder Paste	$5
Regular Solder	$5
Bent Nose Tweezers	borrowed
Metal Scribing Tool	borrowed
Wire Cutters	borrowed
Caffeinated Cherry Coke	priceless

Up next: the Reflow Process! -- click here to continue

project added: 5/4/2006

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