Environmental protection PCB material selection

WDF-PCB-D-25,double-sided,wonderfulpcb.com

Surface metal layer

The industry mostly use green solder "silver copper tin" formula HASL (Sn Ag - 3.9-95.5 0.6 Cn) instead of pewter, environmentally friendly lead-free PCB surface coating layer should have high wetting liquid, smaller thermal stress, high temperature is not easy oxidation features, facilitate lead-free SMT processing.In addition, flux, a synchronization is required to adopt green HASL is poor, and they have mutual fusibility with SMT solder.

Ink

Ink on the PCB leaving include: solder resist ink, printing ink, jack inks, ink composition with plank, mainly containing resin, bromine flame retardants and curing agent, at present many brand ink has do not contain harmful, such as Japan, taizhou, the new Korean ink the sun.The choice of ink must not only conform to the requirements of environmental protection, and to withstand environmental protection lead-free SMT long time high temperature for many times, not hierarchical discoloration, peeling, crack phenomenon.

Control of lead-free materials

The management of raw materials is very important one link in green PCB production, such as tin, so long as has the lead article tin was mistakenly add pure tin bath will lead to disastrous consequences, and indirect materials such as flux residues also nots allow to ignore, specific countermeasures include: (1) establishing that the encoding rules of the halogen free lead-free materials;(2) using color logo, on the inner and outer packing printed with "green" label to be approved by IQA.(3) in the warehouse and production site, to separate storage for environmentally friendly raw materials, production site personnel to add;(4) to realize "green qualified suppliers" certification program.
The choice of lead-free process and control: the selection of lead-free PCB surface coating layer process include: Ni/Au plating, chemical immersion Ni/Au, OSP (organic run-off protection agent) chemical tin Sn and chemical heavy silver Ag.

The import of lead-free process steps

CAM design

Environmental protection engineering design of PCB is basic aspects, lead-free process after the CAM should take into account the SMT process influence on the function of the PCB.
Graphic design examples (wiring, welding area shape)
1. prevent immersion flow insert parts left, red eye diameter welding area a little bit small.
2. Prevent immersion flow QFP bridging QFP tilt 45%.A dummy welding area.
3. To prevent the soft melting chip separation illuminates the basic in the past.To make the protective film: opening near it.
Prevent substrate warp

Technology development

Process of the development and management is important link in the production of environmental protection PCB, specific countermeasures including:

(1) environmental protection and environmental protection materials do not collinear or mixed line production, such as: enhancement and finished products to clean.
(2) in the MI process of paper, with environmental protection product operators, and sign the MI confirmed its, lead-free process remind now field operation department staff.
(3) environmental protection product production facilities, tooling, visual management, with prominent logo distinguish.
(4) ink has to withstand environmental protection lead-free SMT long time high temperature for many times, so the pretreatment, substrate drying is a very important link, the printing ink after spray tin or lead free HASL SMT, the possible defects of the ink on the side of hole stripping is mainly hole, floor water residue, high temperature when inflation and make the ink and copper layer separation.
(5) solder resist ink is not allowed to add rare ze agent, which can avoid high temperature circumstances hole ink residue solvent volatilization sharply inflation caused by the blasting hole.6 HASL Cu content in the tin bath to control below 0.85%.

reliability assessment

Therefore, environmental protection PCB products reliable test compared to the environmental protection PCB, but also improved the following experiments:

(1)Solderability test.(solderability test furnace with lead-free solder environmental requirements of SMT solder or HASL consistent)
(2)thermal shock test.Condition: - 40 ℃ / 85 ℃ / 85 ℃, no crack after 3000 times.
(3)the thermal cycle test.No crack, shrinkage cavity appear.
(4)constant temperature and humidity test.Condition: 60 ℃ 90-95% RH, 500 hours, under high temperature and high humidity for a long time do not produce metal products.

For more information, pls email: wonderful11@wonderfulpcb.com

Printed Circuit Board

A printed circuit board, or PCB, is a self-contained module of interconnected electronic components found in devices ranging from common beepers, or pagers, and radios to sophisticated radar and computer systems. The circuits are formed by a thin layer of conducting material deposited, or "printed," on the surface of an insulating board known as the substrate. Individual electronic components are placed on the surface of the substrate and soldered to the interconnecting circuits. Contact fingers along one or more edges of the substrate act as connectors to other PCBs or to external electrical devices such as on-off switches. A printed circuit board may have circuits that perform a single function, such as a signal amplifier, or multiple functions.

There are three major types of printed circuit board construction: single-sided, double-sided, and multi-layered. Single-sided boards have the components on one side of the substrate. When the number of components becomes too much for a single-sided board, a double-sided board may be used. Electrical connections between the circuits on each side are made by drilling holes through the substrate in appropriate locations and plating the inside of the holes with a conducting material. The third type, a multi-layered board, has a substrate made up of layers of printed circuits separated by layers of insulation. The components on the surface connect through plated holes drilled down to the appropriate circuit layer. This greatly simplifies the circuit pattern.

Components on a printed circuit board are electrically connected to the circuits by two different methods: the older "through hole technology" and the newer "surface mount technology." With through hole technology, each component has thin wires, or leads, which are pushed through small holes in the substrate and soldered to connection pads in the circuits on the opposite side. Gravity and friction between the leads and the sides of the holes keeps the components in place until they are soldered. With surface mount technology, stubby J-shaped or L-shaped legs on each component contact the printed circuits directly. A solder paste consisting of glue, flux, and solder are applied at the point of contact to hold the components in place until the solder is melted, or "reflowed," in an oven to make the final connection. Although surface mount technology requires greater care in the placement of the components, it eliminates the time-consuming drilling process and the space-consuming connection pads inherent with through hole technology. Both technologies are used today.

Two other types of circuit assemblies are related to the printed circuit board. An integrated circuit, sometimes called an IC or microchip, performs similar functions to a printed circuit board except the IC contains many more circuits and components that are electrochemically "grown" in place on the surface of a very small chip of silicon. A hybrid circuit, as the name implies, looks like a printed circuit board, but contains some components that are grown onto the surface of the substrate rather than being placed on the surface and soldered.

Wonderful PCB (HK) Limited, with over 15 years experience of producing PCB, fabricates printed circuit boards for customers in many industries worldwide, including communications/telecom/IT, medical electronics, consumer electronics (mobile phones, computers, LED lighting, etc.), and the automobile industry. We supply high-precision, high-density, double-sided and multilayer custom PCBs and PCBA services for customers in many countries.

PCB Repair

As we know, PCB Is customized product. Manufacturers produce PCBs based on customer’s Gerber Design. No matter how good electronic contract manufacturers become at producing ever-smaller and more complex circuit boards, every now and then, a defect  will be produced. In batch production, maybe it will not be a major issue. Due to it’s common when a certain small percentage of loss is expected. However, in a small order even sample order, what if the circuit board is unique? In this case, you could be looking at huge costs to recreate it, or even larger costs if you move forward anyway. To resolve these fails, it uses a PCB repair service.

PCB Repair Process:

1. Repair

When a component which was working has failed and you don’t know why, commonly this is the most common reason you might need to use repair service. Luckily, electronics experts can analyze both the original schematics and the resulting board to discover the underlying problem. Often, it's something as simple as a single broken bit of circuit wiring or a single failed component that can be fixed for far less than it would cost to recreate the board.

2. Rework

Sometimes, it's the initial design that's flawed. A capacitor cannot handle the charge it needs, or a particular computer chip proves to be incompatible with the board. In this case, PCB board repair services can take a look at the original design specs, compare them to the finished product, and uncover which component(s) are causing the issue.
From there, it's a relatively simple matter to find suitable replacements which can meet your original specifications.

3. Modification

Or, perhaps your PCB works, but just not quite up to par. Perhaps it fails to meet a necessary requirement, such as FCC feedback shielding standards. If this is the problem, much as with rework efforts, your PCB repair service can take the working design and improve on it so it meets your needs.

4. The Protection Process

Finally, there is the highly important process of making sure all of those components can work in extreme conditions. A special type of coating is either done by dipping the components into a solution or spraying them, allowing the coating to protect the entire board from extreme heat, cold, possible corrosion or leakage, and even helps prevent shortages should condensation accumulate.

Concluded, as the development of PCB repairmen, the defects of PCB are decreasing in the finished production. Of course, it may cost some more time to find out these problems and repair them. But all we do are for better quality and better functions of PCB.

Printed Circuit Board Words

01、基准尺寸：reference dimension
02、参考尺寸：reaerence dimension
03、直接量定尺寸：direct dimensioning
04、基准图：datum feature
05、基准边：reference edge
06、导线设计距离：design space of conductor
07、导线设计宽度：design width of conductor
08、中心距：center to center spacing
09、线宽/间距：conductor width/space
10、节距：pitch
11、精细节距：fine pitch
12、层：layer
13、层间距：layer-to-layer spacing
14、边距：edge spacing
15、外形线：trim line
16、截面积：crossection area
17、真实值表测量：truth table test
18、准确位置：true position tolerance
19、精确位置：accuracy
20、精确位置误差：cumulative tolerance
21、精确度：accuracy
22、累积误差：cumulative tolerance
23、焊垫：footprint
24、外层：external layer
25、内层：internal layer
26、接地层：ground plane
27、接地层隔离：ground plane clearance
28、电压层：voltage plane
29、电源层隔离：voltage plane clearance
30、电源层：power plane, bus plane
21、导通网络：basic grid
22、导通网格：track grid
23、导通孔网格：via grid
24、连通盘网格：pad (land) grid
25、定位偏差：positional tolerance
26、对准靶标：bornb sight
27、梳状图形：comb pattern
28、对准标记：register mark
29、散热层：heat sink plane
30、端接:termination
Sophie Deng
_______________________________________
Wonderful PCB Limited
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1.Booth: L32,Expo Electronic 2013,Apr.10-12th in CROCUS EXPO,Moscow,Russia
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Repairing printed circuit boards - tips by Exception PCB

PCBs, or printed circuit boards, have revolutionised the electronic industry; however they lack the robustness of the earlier, steel-chassis, hardwired equipment, driving them to be much easier to crack. Restoring a circuit board needs a particular level of analytical ability, along with the skill to handle each element in the correct way.

Without having a thorough knowledge of the way a circuit board works, experts from Exception PCB express that diagnosing the trouble will be a problem. For PCBs that are especially complex, you might also need an oscilloscope to discover signals at different points, so as to discover the section which is creating the problem. Once this component has been discovered, it will then have to be replaced. Here, Exception PCB provides you with a brief guide on how to do this.

As outlined by Exception PCB, with the majority of passive (and occasionally active) components, a similar, as opposed to an exact copy of the broken element can be used as a replacement. You will find, for example, several unique versions of voltage regulators available, and one version can easily be swapped for another in a PCB. However, broken active components that have a very specific function (for example, audio amplifier chips) must be replaced with an exact copy.

After you have acquired the right replacement, you'll have to place the PCB on a flat surface for the fix. Exception PCB says that you might use tape to stick the board on both sides to the surface, to ensure that it doesn't move whilst you are carrying out the replacement. Pull the damaged component off the board very delicately, using tweezers. Next, switch on your soldering iron and set it to about 400 degrees Celsius.

Take some copper wire and put it on the pads of the PCB where the component was, and use the soldering iron to heat it. Wonderful pcb that any surplus solder remaining on these pads could be absorbed by the copper. Get in line the leads of the replacement component with the board's pads, taking a look at to make sure that the element is aligned as it needs to be. Then, use the soldering iron and the solder to join the leads with the corresponding pads on the board.