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Electronic Design PDF Print E-mail
Friday, 05 September 2008 20:48

Many consumer or industrial products have of course more areas involved than electronics only, like chemistry (sensors, displays), mechanics (housing, moving parts) and programming (firmware and applications).

The electronic part of this, the electronic design project, is typically divided into two main sections:

  1. The prototype
  2. Final product

For each of these sections, one or more circuit board(s) are produced. For the prototype, typically five PCB's are produced but only one or two populated for testing. When the prototype has been tested (and any necessary patches applied) the final product is produced. The number of populated PCB's may then vary, but a typical number is 20/year for an industrial product or 100/year for a commercial product.

The Prototype

Before the work on the prototype may begin, a few decisions must be made:

  • Which CAD system should be used for the design?
  • Is the design cost sensitive?
  • What are the input signals and output signals?
  • What connectors are to be used for the i/o signals?
  • What on-board sensors/displays/electro mechanical/power source parts should be used?
  • What are the mechanical restrictions?
  • What is the power source?
  • What programming and documentation is required?

Schematic and footprintscircuit

When all this has been specified, the schematic is drawn in the preferred CAD system. At this time we also select parts and design footprints for them if necessary. The circuit design and schematic takes typically one week for small projects. The schematic must pass a design review to proceed to the PCB layout stage.

 

 

PCB layoutRouting

When all involved parts has been verified to be available and all footprints has been drawn, we draw the PCB in the preferred CAD system. At this point the number of layers and technology (1206, 0805 or 0603) can be decided, considering the mechanical restraints. The design rules are set up to best match the mechanical restraints and keep the production cost low. All coating needs to be decided as well (gold, organic, tin for metals).

The time it takes depends on the complexity, but typically placing of the parts is 70% of the time while routing usually does not take that much time. For small projects one week is usually enough.

We do not auto-route.

PCB manufacturing

When the PCB has passed design rule check it is sent for production. The recommended time is one working week or more. Shorter time give higher production cost. By default all PCB's are electrically tested.

While the PCB is being manufactured, we order the parts necessary for the assembly of the boards. We also generate assembly lists and/or pick & place files. If any programming is required we also work on programming and documentation.

PCB assembly

For smaller volumes the boards are typically assembled "by hand" using an assembly list. For the prototype leaded tin / non-RoHs processe(s) might be used.

Larger volumes are typically produced in pick-and-place machines. Environmental requirements must be specified prior production start.

The assembly usually takes one day. For smaller volumes, the board is typically assembled and tested at the same time.

Testing

What has not been tested does not work. This is especially true for a prototype. For smaller volumes we need to allocate at least one day for testing. For prototypes this usually involves some patching to reach customer requirements which may have changed during the project.

The tested boards are then sent to the customer for evaluation.

The final Product

The production of the final product is similar to that of the prototype. First any patches are implemented in the CAD files, and then new production files are generated for the PCB.

After PCB manufacturing and assembly, the final product is tested and shipped to the customer.

 

Board example

Last Updated on Tuesday, 30 June 2009 17:13