Environmental protection PCB material selection

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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

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.

High PCB Design----Wonderful PCB (hk) Limited

In the field of telecommunications , the design is very complex , the transmission speed in the transmission of application data , voice and image of the
Has been far higher than 500Mbps, people in the communications field in pursuit of higher performance and faster to launch production

Goods, and the cost is not the first. They will use more board layers, sufficient power and ground planes, any problems that may arise in the high-speed signal lines will be implemented using discrete components match. They have
SI (signal integrity) and EMC (electromagnetic compatibility) experts to simulate and analyze the wiring before each
an internal design engineers follow strict design requirements. So the field of communication design engineers through
this design is often used excessive speed PCB design strategy.

Home computer motherboard design area is the other extreme, the cost and effectiveness above all , the design
Teachers are always using the fastest, the best , highest-performance CPU chips, memory and graphics processing module technology
To form increasingly complex computer . The home computer motherboards are usually four shelves , some high-speed PCB

Design technology is difficult to apply to this area , so engineers in the field of home computers generally have adopted over
Research methods to design high-speed PCB board, they are designed to fully study the specific circumstances of those who truly resolved
The existence of high-speed circuit problem.

Introduction on flux and Tin paste for PCB assembly

FLUX
A. The function of Flux
1. Remove the oxide on the surface of part and substrate
2.Reduce the surface tension of the solder and promote the flow of the solder
3.To protect the surface of the metal, avoid it to be oxidized under the environment of high temperature.

B. The main ingredients of flux
1.Rosin: it is refined from the grease of pine tree.
2.surfactant : Because of the gentle characteristics of rosin, it is not easy to remove the oxide, thus must add surfactant in order to enhance its effect.
3. Solvent: Dissolve and blend solid state material like rosin and surfactant, general multi-purpose isopropyl alcohol or ethylene glycol.
4. In addition, there are interface active agent, foaming agent and other ingredients

C. Variety of PCBA manufacturer.
(1) Rosin flux :
1. R grade : Inactive rosin flux
2 . RMA : Weak activity rosin flux
3 . RA : Strong activity of rosin flux
4 . RSA : Super Strong activity of rosin flux

(2) Synthesis of active flux : This kind of flux is developed by DUPONT company, it’s advantage is can make the residue which caused after soldering can become liquid state, easily for cleaning.
Based on activity, it can be divided into: 
SR–No active synthetic flux
SMAR – Weak active synthetic flux
SSAR – Strong active synthetic flux
SAR – Super strong active synthetic flux

(3). Water-soluble flux: The flux of organic acids, performs best help on welding, but must pay attention to the cleaning situation of the base board of welding after washing. If there’s residues, it will cause corrosion of substrate material, military and aerospace industry are banning the use of water-soluble flux process of substrate

(4). Disposable flux
Rosin kind improved flux: solid content 5-20%, residues will not cause corrosion to the base plate.

Low content of solid flux: solid content at 5%,  disposable flux disposable because its residue in the residues of substrate could not cause corrosion of substrate, but solid content in about 5% of the flux its residue is too much less than the flux with solid content of 5-20%, so if product with high requirements on cleanliness and appearance, you must use the solid content at 5% disposable flux.

TIN PASTE
(5). VOC-FREE disposable flux :
Does not contain volatile organic solvents of disposable flux, the above all flux contain volatile organic solvent, the solvent flammable (dangerous). Not easy to control (quality) is volatile harmful to human body and the environment (toxic), in order to avoid such problems, so developed the pure water as the solvent of disposable flux.
(1).The main ingredients of Tin solder paste
Tin powder: Can realize the electrical conduction between parts and base board, and can joint the parts and boards.
Flux: compromise the tin powder and other solid substance into paste.
Its main ingredients are as follows:
A.Solvent : mix all flux element into homogeneous liquid thickens.
B. Flux : can prevent the PCB board surface to be oxide again after welding, and can pack the surfactant to improve the SIR, to enhance the trustworthiness of the base board.
C. Thixotropic Agent: avoid separation of powder and flux, and improve the printability of tin and protect tin from collapse.
D.Active agent: The main function is to eliminate the solder joints and lead oxide substrate, common active agent is: organic ammonia hydrochloride, ammonia, organic acids, etc. 

(2). Kinds of Tin Paste
1 . Water type of Tin paste: Use water to clean the flux residue on PCB board                    Water temperature 50 – 60 degree,
water pressure 2 – 3 kg / cm 2 ,
Water low: 11 – 15 l / min
2 . Resin type of Tin paste:
a . Use solvent ( CFC or HCFC Cleaner ) to clean the flux residue on PCB board.
b . Because resin kind substance does not dissolve in water, using saponification agent to make it become the material which can be soluble in water,  then use it to clean the flux residues on board.
c . Semi-wash, use EC – 7R Axarel 32 to clean the flux residue on PCB board.
3 . Free wash kinds Tin Paste : no need to be cleaned after soldering.



Ms Grace Zhang
________________________________
Oversea sales
Wonderful PCB
A Floor 6, Nanyuan Fengye Mansion, Nanshan Avenue, Nanshan District, Shenzhen City 518054, China

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