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
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Oversea sales
Wonderful PCB
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Nice blog. You described everything about how copper plates used in PCB. Electroless plating is widely used in the printed circuit board (PCB) production and processing which has holes on that and it can also be called PTH(Plated Through Hole), the main purpose is to deposit a layer of copper through a series of chemical treatment methods in the conductive substrate, and then increasing the thickness of the copper layer through subsequent electroplating methods to its specific thickness of design which is usually 1 mil (25.4 um) or more thicker, and sometimes even directly increasing the thickness of copper of the whole printed circuit board by using the special chemical methods.
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