Copper Traces

The copper traces on your PCB are easily the most important part of the design so it is important to understand what they’re doing and what limitations you should consider.
As I mentioned earlier, copper traces are created by removing copper from the solid sheet that sits on top of the base material.
This means that the traces on your board are in fact just thin layers of copper. I don’t know about you, but when I discovered that it came as a bit of a surprise (relax I didn’t just find this out). For the longest time I assumed that PCBs were manufactured by pouring copper into a mold, letting it cool, and then somehow melting an insulator around the copper.
The thin sheet nature of these traces mean that there are some constraints to consider when routing your traces, most importantly, size considerations. All of these nuances will be discussed in detail in part 2.

Following will be continued in next chapter.

Shirley Xia
Oversea sales
Wonderful PCB

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PCB Applications

Classic applications for Printed Circuits are General Electronics PCB assembly, Dedicated Service Electronics Class, high Reliability Electronics.

Consumer Electronics – Digital Wrist Watch, CD Player, Am/FM/Radio/Alarm Clock, television, Calculator, Digital Coffee Pot, Microwave Oven, Home Alarm Systems, Cellular Telephone, Home Computer, Home Theater/Stereo Surround Sound System, Cable Television Converter Box, Hand Held Video Games, Remote control electronic toy, LOJACK auto recovery system etc. Telecommunications – Point to Point Microwave Transceivers, Police/ Fire/ Rescue Radios, Digital Network Equipment, SATCOM transceivers, Commercial and Private Aircraft Radios and Instrumentation, Cell Telephone Relay Stations, CB Radio/2 Way Talkie Talkies, etc. Industrial Electronics and Instrumentation – Weather Radar and Weather related Telemetry, Oscilloscopes, Network Analyzers, Ohm Meters, Temperature meters, Strain Gauges, Environmental Chambers and Ovens, Spectrum Analyzers, Solar Photo voltaic Power Co generation equipment, DC to AC Power Inverts, Switcher Power Supplies, CCD Telescopes. Military Electronics – IFF transponders, IR detectors, Night Vision Goggles, Military grade Computers with encryption, Fire Control circuits, Satellite Navigation instrumentation, Encrypted Frequency Hopping VHF Radios, Direction Finding Equipment, Missile Guidance Systems, FLIR Pod Test equipment, etc. Aerospace Electronics – Satellite systems, Space Shuttle controls and system, Aircraft communications and controls, etc…
Automotive Electronics – Automotive Ignition Controls, Emission monitoring and controls, Fuel Air Mixture, Fuel Injection, Climate controls, Dash Instrumentation, Radio/TV entertainment accessories, etc. Medical Electronics – Heart Monitors, Automated Medicine dispensing equipment, Breathing machine, Dialysis machine, Laser assisted tooth whitening machine, Laser optical corrective surgery machine LASIX, X-ray or CAT Scan equipment, MRI Imaging equipment, etc…

According to IPC-2221 1.6 Printed board assemblies are classified by intended end item use. The Performance Classes are listed as follows: Class 1 - General Electronics Products - Includes consumer products, some computer or computer peripherals, and general military hardware suitable for applications where cosmetic defects are not as important, and the major requirement of the board is its functionality. Class 2 - Dedicated Service Electronics – Includes Communication Equipment, sophisticated business machines, instruments and military equipment where high performance and extended life are required, and for which uninterrupted service is desired but not critical. Certain Cosmetic imperfections are allowed.
Class 3 – High Reliability Electronics – Includes Military and Commercial equipment where continued performance or performance on demand is critical. Equipment failure or down time is not tolerated and must function when required in the case of life support systems, or critical weapons systems. As for applications where high levels of assurance are required and service is essential.

Cleaner production technology of production process in PCB production

PCB is a printed circuit board (Printed Circuit Board) abbreviation, is a substrate for the electronic parts assembly. Its main function is to enable the various electronic components forming a predetermined circuit connection, starting relay transmission function, is the key of electronic interconnection of electronic products.

The rapid development of PCB industry, to bring economic development and at the same time also has brought serious influence to environment protection. Printed circuit board production and processing process, material type, energy consumption, water consumption, pollutant generation, as well as some poisonous and harmful or toxic substance use, all for the PCB industry as a " heavy polluting industries " hat. With the strengthening of enterprise and government awareness of environmental protection, pollution status of enterprises has improved, but the PCB industry is more and more big, lead to the entire Aluminum pcb industry pollution is still very big.
Cleaner production is to continually taken to improve the design, use of clean energy and raw materials, adopt advanced technology and equipment, improve the management, utilization and other measures, from the source to reduce pollution, improve resource utilization efficiency, reduce or avoid the generation and emission of pollutants during the process of production, services and products to use, in order to reduce or eliminate the hazards on human health and the environment. Cleaner production is a new kind of creative thought, the thought will be the overall preventive environmental strategy applied to production processes, products and services, to improve ecological efficiency and reduce human and environmental risks. For the production process, saving raw materials and energy requirements, eliminating toxic raw materials, reduce the quantity and toxicity of all waste. The product requires reducing adverse impacts from raw material extraction to final disposal of the entire life cycle. Also, requirements of environmental factors go into the design and services.
In recent years, a lot of research on China's PCB clean production for domestic surgery, in this paper, clean production technology of PCB throughout the production process uses were summarized, from product design, material selection, production process and equipment, energy and resources comprehensive utilization and management mechanism and other aspects of narrative, with a view to the enterprise, researchers and decision makers to grasp the situation, continue to promote clean production technology in China PCB industry.

FPC Assembly

Nowadays, technology is already very mature to rigid Printed circuit board, however, many problem may be faced by operator during SMT to FPC.
1 False soldering, short soldering,Tin beads.
2.The Reason is due to the hardness of  raw material of FPC(Flexible printed circuit) caused, FPC is out of shape when meet the hot air and high temperature in reflew machine. Lead the wave shape to FPC, and the slop to FPC pads, then cause the flow of molten tin (liquid tin under high temperature), which cause False soldering, short soldering,Tin beads.(The main reason is the hardness of FPC). So if make the hardness of FPC into the same situation as rigid printed circuit board, and all soldering problem to FPC can be solved. The condition is you should know the SMT process to PCB. And then improve the hardness of Flexible Printed circuit into with the same hardness as rigid PCB, and then FPC SMT can be realized. And some problem, like no fix hole, no mark point, or the FPC is over long, which are the fault of designer, and it is also hard to be solved even to rigid PCB SMT. And NG rate can be only reduced based on personal experience or device independence.

According to above comment, the main solution is to improve the hardness of FPC the same as hardness of Rigid-flex pcb.

B. How to realize stable soldering to FPC
How to get the stable FPC (flexible circuit board) to the rigid PCB welding effects depends on the degree of hardness.
Methods: using jigs(carrier, handling plate) to make FPC perform as rigid board during SMT.

Below is the instruction of Magnetic reflow soldering tray
The material
1. Choose imported alloy material: good flatness, stable performance under high temperature
2. High temperature resistant magnet (300 degrees) to ensure permanent magnet during reflow soldering process.
3.The special steel, with magnetic treatment and good elasticity, and no deformation under high temperature.
4.Performance
(1) Because the flatness to FPC surface cause from the steel pressure l, it can reduce the flow of solder tin during reflow, which can ensure the good quality of soldering and reduce the NG soldering at meanwhile.
(2) Ensure the life of tray when choosing tray material.
(3) Easy and convenient operation with high stability.
(4) Heat insulation, prevent the FPC from deformation
There’s no special requirement to the composition of solder paste of FPC, the size of the tin ball particles and the amount of metal content, etc will be subject to if there is narrow space of IC pins on FPC, BUT FPC has high performance requirements to the solder paste printing, solder paste should has good thixotropy, solder paste should be able to easily be printed , demoulding and can be firmly adhere to the surface of FPC, there will be no mold release lead the hole in stencil filled with tin or such as collapse after printing.

Because FPC fixed on the pallet before SMT,  and the FPC with high temperature heat-resistant pressure-sensitive adhesive tapes for purpose of location, which make its planar inconsistencies, thus FPC printing surface is unlikely to be as smooth as rigid PCB and the same consistent on thickness and hardness, so operator should not use a metal scraper, and should use the polyurethane scraper which with hardness of 80-90 degree.

Solder paste printing machine is best to be with the best optical positioning system, otherwise will have great influence to printing quality, FPC although fixed on the load board, however, there always be small space between FPC and the load board, this is the biggest difference as rigid PCB board, thus the equipment parameters’s setting will also has great influence to the printing effect.

Printing stations is also the key location to prevent FPC from being smudgy, need to wear glove then can go ahead for operation, at meanwhile,  workstation should be kept clean, stencil should be frequently wiped to be clean, to prevent the solder paste to pollute the gold fingers and gold plated key button.

Control of FPC SMT

According to the properties of the products, components quantity and efficiency of mounting, it is OK to adopt high-speed placement machine for SMT. Because every piece of FPC has positioning with fiducial MARK, therefore, there’s no big difference on surface mounting technology between FPC SMD mounting and rigid PCB SMD mounting. It is important to note that although the FPC are fixed on the load board, but its surface can’t be the same flatness like rigid PCB board surface, local space must  exist between FPC and load board, so, the height of suction nozzle’s dropping, compression of blowing should be exactly setted.  On other side, most bare FPC performance as panel; format, and the rate of good finished product relatively low, so it if normal that there’re part of pieces with not good quality, which request recognition function on BAD MARK to SMT machine, otherwise, when mounting FPC panel with the status of not all pieces are good, will show low efficiency.