Conflict Between Thermal and SI/EMC PCB Design Requirements

Software simulation company Flomerics has released a new survey highlighting the conflict that often occurs between meeting thermal, electromagnetic compatibility (EMC) and signal integrity (SI) design requirements in the development of new PCB designs. 59% of recipients agreed that thermal and EMC requirements are usually in conflict in PCB design while only 23% disagreed. An even higher 60% agreed that thermal and signal integrity requirements are usually in conflict in PCB design while 23% disagreed.

However, the survey reveals a positive picture regarding the communication and collaboration between electronic and mechanical design engineers at most companies. 64% of respondents described communication as “good” or “very good”, 31% as “needs to improve”, and just 4% as “very poor”. 56% of respondents stated that “better software interfaces between electronic and mechanical software would greatly improve collaboration between electronic design engineers and mechanical design engineers”, while 28% said “software is not the issue – good management, human interaction, etc. are more important”.

Respondents were also asked to identify the percentage of new designs that overran time and cost budgets, and the most common causes of such overruns. Most respondents (50%) said that 10-30% of new PCB designs overran time and cost budgets, while 28% said less than 10%, 18% said 30-50% and 4% said more than 50%. The most common causes of time and budget overruns were: design requirement changes (59%); circuit design (39%); thermal problems (34%); EMC problems (32%); signal integrity problems (30%); physical layout problems (22%); and routing problems (19%). Note that respondents were allowed to specify more than one cause so the numbers total more than 100%.

The survey also provides insights into typical PCB design flows and processes. The average design cycle time for a new PCB design from concept to final testing and manufacturing signoff was specified at 6-12 weeks by 50% of respondents, more than 12 weeks by 29% and less than 6 weeks by 21%. When asked what generates the greatest pressure on the PCB design function, 54% said “functionality and performance”, 30% said “time to market” and 14% said “cost”. When asked about the design flow, 62% of respondents said there is “lots of interaction” between design stages such as concept design, detailed design, design verification, etc, while 38% said that design flow is performed in sequential stages with “little interaction between stages”. Regarding thermal design, 61% of respondents said that “a person or group with clear responsibility for thermal aspects of PCB design exists”, while 39% said there was “no such person or group”.

The industry sectors most represented among survey respondents were telecommunications (23%), power electronics (18%), aerospace and defense electronics (17%), and automotive and transportation electronics (11%). For a copy of the complete survey, please contact Flomerics at