Prototype Stencils step-by-step Tutorial

Step 4 - Reflow your PCB

Before reflowing starts, turn the oven on to heat up, a minimum of five minutes. Set the oven to bake and set the temperature to the highest baking temperature setting (450 to 500 degs F).

Before placing the PCB in the oven cut a piece of the Temperature Marker (413 degs F) with a blade or a sharp knife and place it on the surface of the board next to a large component (PLCC or QFP). Insure you can see the Temperature Marker through the oven door.

When the Temperature Marker melts remove the board from the oven. Be careful not to disturb the molten solder joints. Place the board on a surface and let it cool to near room temperature. Inspect the solder joints. Use your solder joint inspection criteria or the IPC 610 requirements. If any of the solder joints did not reflow, place a piece of the Temperature Marker next to the location that did not reflow. Use this location to control the reflow length.

If you have more than one board, place the next board in the oven with a piece of the Temperature Marker in the location determined from above. Remove the PCB after the Temperature Marker melts, let cool and inspect the solder joints. Repeat the above step until all the boards are reflowed.

Turn Oven off.
Repair any solder defects with a solder iron. Use a fine tip on the solder iron and do not let the tip touch the body of the SMT parts. The solder iron temperature should be set as low as possible. A solder iron that is set to a high temperature can thermal shock SMT components.

NOTE: If the PCB has SMT components on both sides of the board, process the side with the smallest SMT components first. When processing the second side of the PCB, it has to be held off the oven shelf with standoffs. The SMT solder joints from the first reflow will be disturbed if placed directly on the oven shelf.

IPC 610

The IPC 610 is an industry SMT solder joint quality standard. It can be ordered from the Institute for Interconnecting and Packaging Electronic Circuits (IPC). Their address is:

   2215 Sanders Road
   Northbrook, Illinois 60062-6135
   Tel (847) 509-9700

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