PCB News - Comment and Analysis of Cost Saving in PCB Design

Question 1: The resistance value of these pull-up/pull-down resistors does not matter much, so choose an integer 5K.

Comment: There is no resistance value of 5K in the market, the closest is 4.99K (accuracy 1%), followed by 5.1K (accuracy 5%), and its cost is 4 times and 2 times higher than that of 4.7K with an accuracy of 20%. . The resistance values of 20% precision resistors are only 1, 1.5, 2.2, 3.3, 4.7, 6.8 (including integer multiples of 10); similarly, 20% precision capacitors have only the above values, if you choose other types The value must use higher precision, and the cost will be doubled several times, but it will not bring any benefits.

Question 2: What color should the indicator light on the panel choose? I think blue is more special, so choose it

Comment: Other red, green, yellow, orange and other colors, regardless of size (under 5MM), have been mature for decades, and the price is generally below 50 cents, while blue is something that was invented in the past three or four years. Technology maturity and supply stability are poor, but the price is four or five times more expensive. At present, the blue indicator light is only used in occasions that cannot be replaced by other colors, such as displaying video signals.

Question three: 74XX gate circuits can also be used for this logic, but it is too earthy, so use CPLD, which looks much more high-end

Comment: 74XX gate circuit is only a few cents, and CPLD is at least dozens of dollars, (GAL/PAL is only a few dollars, but the company does not recommend it). Not to mention the increase in cost by N times, it also adds several times of work to production and documentation.

Question 4: Our system requirements are so high, including MEM, CPU, FPGA and all chips must choose the fastest

Comment: Not every part of a high-speed system works at high speed, and every time the device speed increases by one level, the price almost doubles, and it also has a great negative impact on signal integrity problems.

Question 5: The PCB design requirements of this board are not high, just use a thinner thread and automatically arrange it.

Comment: Automatic wiring will inevitably take up a larger PCB area, and at the same time it will produce many times more vias than manual wiring. In a large batch of products, the factors that PCB manufacturers consider for reducing prices are line width and overpass, in addition to business factors. The number of holes, which respectively affect the yield of PCB and the number of consumption of drill bits, saves the cost of the supplier, and finds a reason for the price reduction.

Question 6: As long as the program is stable, the code is longer and lower efficiency is not the key

Comment: CPU speed and memory space are both bought with money. If you spend a few more days to improve the efficiency of the program when writing code, the cost savings from reducing the CPU frequency and reducing the memory capacity are definitely worthwhile. The CPLD/FPGA design is similar.

The above is an introduction to the analysis of cost saving issues in PCB design. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology.