Welcome to Project 15 - Surface Mount Oven

1.1 Project Overview

The School of EECS at Oregon State has requested that we create a new surface mount technology (SMT) oven. The oven will need to be designed to ensure that a uniform heating pattern is applied to the board and no "hotspots" are created during the heating process. This is to ensure that SMT components do not "tombstone", a process in which smaller SMT components can stand upright on one solder pad. The SMT oven must also slowly heat up and cool off in order to prevent components from cracking. Another necessary feature is a "dwell" time in the heating profile. During this time, the oven will be held at a medium temperature lower than the melting point of the solder to burn off moisture that could cause imperfections in the reflow process. The interface must be presented at a basic level with a display that shows the status of the oven, the set temperature of the oven, an indicator that shows when the oven has completed the heating cycle, and when the PCB has transformed into a printed circuit assembly (PCA).

The oven has to accept a 9 inch by 9 inch PCB. If an extra tray is included for ease of access, this tray must still allow the 9 inch by 9 inch PCB square and not cut into the previously stated 2d size requirement. There will be a vertical height clearance as well to allow the PCB to have 1 inch high components. The device will require the boards to be extracted and then reinserted into the surface mount oven in the event of a duel sided PCA production, but there will be a selectable profile to select this feature.

Leaded and lead free soldering profiles will be made possible as well as a reflow temperature solder setting for dual sided boards. The primary soldering profile will be the industry standard of ROHS soldier (lead free solder) for ease of access and industry convenience. The Oven will be simple to use and include an instruction manual in order to easily accommodate new users.

1.2 Project Requirements

Reliability: The oven must be reliable and able to successfully reflow solder the SMT components on a PCB very consistently.

Heating Profiles: The oven must include basic built-in heating profiles for both leaded and unleaded solder.

Limited Temperature Variation: The oven must keep the temperature surrounding the PCB stable with a small amount of variation.

Maximum PCB Dimensions: The oven must be able to handle PCB sizes of up to 9" by 9".

Dwell Period: The oven must maintain a temperature below the solder melting point to burn off any unwanted moisture before soldering begins.

Controlled Heating/Cooling Rates: The oven must both increase and decrease the temperature of the board at a sufficient rate to avoid damage to the components.

Cost: The oven must be fairly inexpensive, preferably < $400.

User Interface: The oven must have a user friendly interface.

Indicator Light: The oven must have an led light that turns on when the oven is on.

No Shock Hazard: During normal use, the oven must not pose as an electrical shock hazard.

No Burn Hazard: The oven does not create a fire hazard during use.

2 Background Research
3 System Requirements and Desired Features
4 Design Solutions
5 Top Level Block Design

5.1 Power Supply
5.2 Microcontroller
5.2a Microcontroller(hardware)
5.2b Microcontroller(code)
5.3 Temperature Sensors
5.4 User Interface
5.5 Heating Block
5.6 Oven Body

6 Testing
7 Project Timeline
8 System Test Evidence
9 Expo Material

Team Members

From left to right:

Group Video Presentation

Team Sponsors

Team Mentors

References

[1] D. Graffox. (2009, Sept). IEEE Citation Reference [Online]. Available: http://www.ieee.org/documents/ieeecitationref.pdf

Attachments