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• Engineering Implementation of High Performance PCB Design
• 来源：EDADOC     作者：Hans Axiao Bridge Tang     发布时间：2008-07-23 08:12:01    评论(0条)  
  

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• III. Challenges of the design of high-performance PCB

  The design of PCB is a kind of art with endless improvement. An excellent design of PCB will be faced with the following challenges:

  1.Challenge of the R&D cycle

  It has been revealed that for notebook computers, generally it takes half a year to come into the market from item declaration. However, for mobile phones, it takes only three months on average. Therefore, as part of product research and development, the time for design of PCB is increasingly reduced. 
  In April 1985, Toshiba Corporation designs a mini-machine named T1100 which gives an impetus to the industry of computer. Since then, the R&D cycle for main board of computer is improved greatly.
    
  Figure 1: Change of design cycle for main board of computer

  In EDADOC, the design time for PCB of notebook is basically confined within 3 weeks, and the design time for mobile phone PCB is generally 10 ten days as expected by customers.

  How do PCB engineers deal with the challenge that the R&D cycle decreases continuously due to market competition?

  First, Use top-ranking EDA design software

  High-effect EDA tool software brings not only a rise in efficiency but also a brand-new design concept. Among all types of EDA tool software, series of SPB from Cadence undoubtedly take the lead in the industry. From design by a single engineer ten years ago, to subsequent “sub-drawing” and to today’s “partition”, Cadence Allegro provides the parallel design by multiple engineers, which enables the formerly impossible R&D cycle to become reality. In EDADOC, the parallel design is adopted for 92% of PCB design.  

  For instance, EDADOC once completes SI simulation, placement and routing for one XDSL PCB board with 20000PIN in 6 days, which mainly owes its success to the parallel design.

  Take PCB design for main board of common notebook as an example, and let us compare the main PCB design data between traditional work mode of “design by one PCB engineer”, 3-shift work mode adopted by some companies, and the work mode of parallel design:
  

  Work Modes	Design by one engineer	Three shifts by three engineers	Parallel Design
  Design Time	30 days	18 days	15 days
  Advantage	Single engineer in charge, without having to hand over work halfway, with low communication cost	Short delivery time, and wisdom from multiple engineers	Short delivery time, with multiple engineers working together, easy communication, and wisdom from multiple engineers
  Disadvantage	long cycle, and limited by personal knowledge	It is difficult for engineers to accept the work mode, low efficiency in night shift, inconvenient communication with surrounding resources	Asking for a certain scale of team, with a slightly low efficiency
  Scope of application	For small companies of simple single boards	For complicated boards without having to communicate with surrounding resources. In combination with parallel design in some special cases	For complicated or relatively complicated boards, with a short design cycle. Widely used for large and middle-sized EDA teams

   
  Second, Advanced R&D process , reduced redo work

  At the stage of overall plan design, PCB engineers step into the research and development, mainly including design and demonstration of system structure of products. At the stage of overall design, they evaluate the feasibility of earlier PCB design. At the stage of detailed design, they work out a plan of Synchronization schematic design and participate in choosing components, structural design and thermal design, so that, when starting the design of PCB, they can simplify the main work, and at the same time reduce the redo work which due to oversized component, insufficient driving capacity and infeasible topology plan and structural heat dispersion etc in the course of PCB design.

  Third. Design concept for “succeed in the first time”

  Senior consultants of IBM once point out the problems in some domestic R&D team, “you have no time to do the work well with one time but have time to do it again and again”. Against the background of market competition, experienced PCB design engineers, together with a well-rounded design flow and top-class EDA tools, will ensure the commonly-called “succeed in the first time”, which would save not only the cost for PCBs but also the whole R & D design Period. Therefore, in order to win the opportunity for market, both PCB designer and PM shall keep in mind the concept of “succeed in the first time”.        .     

  Finally, Reusing Modules, Technology accumulation.

  Many domestic well-known companies the author got in touch with pay great attention to the module reuse so they achieve a sound technological accumulation and effectively reduce the design time for PCB at the same time.

  All in a word, we shall, in the design concept, participate in R&D in advance, adopt the work mode of parallel design and “succeed in the first time”, reduce the cycle of R&D and use such advanced software as Cadence Allegro. We can solve the problem of R&D cycle of PCB without excessive overtime work, two-shift and three-shift work modes.
  

  
  
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