Each project is divided into five phases, Design, Breadboard, PC Layout, Prototype, and Compliance Testing. The product to be designed is divided into logical subassemblies. Each subassembly more or less goes through each design phase. Following is a discussion of each phase.
The design phase begins with an evaluation of alternative approaches. An approach is selected, and a paper design is done. Analog circuits with frequency domain considerations are usually simulated on PSPICE. If there is a microprocessor in the circuit a basic set of software is written that will exercise the hardware functions. An engineering notebook is started for each project. Rational and justification for component selection is recorded along with stress calculations. Emphasis is given to testability and manufacturability early in the design process. We realize that making a hundred or a thousand of something is very different than making one. The result of the design phase is to generate schematics that will be used in the next phase.
In the breadboard phase any new circuitry is built and tested. An attempt is made to prove, (or disprove) the integrity of the design. Circuits are built on prototype plug-boards, wirewrap boards, perfboards, or, old PC boards are
modified to the new configuration. Every attempt is made to test the design thoroughly. The cost to make a change in the design increases exponentially as the design process proceeds. We want to find all the problems now, and finalize all values, so the rest of the process will run smoothly. When there are subassemblies involved each one is tested independently, and then they are integrated into a complete system that is tested further. Testing is done in two steps. First functional testing is done to insure that the circuit performs as expected, then stress testing is done which usually involves temperature extremes under various circuit conditions. Finally, the documentation is updated to reflect any changes.
At this point we hold a design review with the customer. The design is reviewed in detail, as well as the results of the testing conducted on the breadboard. The customer is asked to approve the design by signing off on all documentation. This authorizes moving on to the next phase which is committing to printed circuit boards. This is an important milestone. Changes made at this point will still incur extra charges but changes made after this will be much more costly.
Printed Circuit Board Layout:
Board layout is an important part of the design process. Our board layouts are typically done by design engineers rather than draftsman. We find that their technical insight enables them to avoid problems that draftsmen would not see. Surface Mount Technology will be used wherever it makes sense. We have 3 PCAD workstations and often run 2 shifts in this department to insure quick turn around. Check plots will be provided to you for approval before phototools are made.
It is during this phase that the main software is written, and material procurement gets underway.
The purpose of this phase is to test the primary deliverable; Documentation. The design has already been thoroughly tested. In the prototype phase we build and test actual hardware using only deliverable documentation. We build two complete boards and keep one bare board as a reference. We try to duplicate the actual production process as close as possible in order to find any subtle problems. This includes testing the documentation by ordering parts from the actual Bill of Materials rather than from the engineer's notebook, and having the boards built by unfamiliar technicians using only documentation. This is all done toward the goal of smooth transition to manufacturing. Each subassembly is functionally tested, then the system is integrated and re-tested.
This phase involves testing the system to verify compliance with the specification. All the final hardware and packaging are tested under worse case conditions. This is intended to be only a verification process. Our intention is to have found all problems during previous phases. At this time we will deliver one of the two prototype systems to the customer to conduct his own testing.