Problems and improvement methods in wave soldering operation1

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Problems and improvement methods in wave soldering operation

1. Poor tint POOR WETTING:

This situation is unacceptable. There is only a part of tin on the solder joint. The reason and improvement are as follows:

1-1. External pollutants such as oil, grease, wax, etc., such contaminants can usually be cleaned with solvents, such oils are sometimes stained when printing solder resists.

1-2. SILICON OIL is usually used for demoulding and lubrication. It is usually found on the substrate and parts. SILICON OIL is not easy to clean. Therefore, it should be very careful, especially when it is used as an antioxidant oil. Because it will evaporate on the substrate and cause poor soldering.

1-3. Occasionally, oxidation may occur due to poor storage conditions or problems in the substrate manufacturing process, and the flux may not be removed when the flux is removed. The secondary tin may solve the problem.

1-4. The fluxing method is incorrect. The cause is that the foaming pressure is unstable or insufficient, resulting in unstable or uneven foam, so that the substrate is not stained with flux.

1-5. Insufficient tin consumption time or insufficient tin temperature will cause poor tin staining, because molten tin needs sufficient temperature and time WETTING, usually the solder temperature should be higher than the melting point temperature between 50 ° C and 80 ° C, the total time of tinning is about 3 seconds.

2. Poor local tinning DE WETTING:

This situation is similar to the bad tin, except that the local tin is not exposed to the copper foil surface, only a thin layer of tin can not form a full solder joint.

3. Cold welding or solder joints are not bright. COLD SOLDER OR DISTURRED SOLDER JOINTS:

The solder joints seem to be broken and uneven. Most of the reason is that the parts are vibrated when the solder is cooling to form solder joints. Pay attention to whether the tin furnace is transported with abnormal vibration.

4. Solder joint crack CRACKS IN SOLDER FILLET:

This situation is usually caused by the expansion coefficient between solder, substrate, via, and part, which is not matched. It should be improved in substrate material, part material and design.

5. The solder joint tin volume is too large EXCES SOLDER:

Usually in the evaluation of a solder joint, I hope to be large, round and fat solder joints, but in fact too large solder joints may not help the conductivity and tensile strength.

5-1. Incorrect soldering angle will cause the solder joint to be too large. The tilt angle is from 1 to 7 degrees depending on the substrate design. The whole angle is about 3.5 degrees. The larger the angle, the thinner the tin is. The thicker the tin.

5-2. Increase the temperature of the tin bath, lengthen the soldering time, and then return the excess tin to the tin bath.

5-3. Increasing the preheating temperature can reduce the heat required for the substrate to be tinned, and has been added with the soldering effect.

5-4. Change the specific gravity of the flux, slightly reduce the specific gravity of the flux. Generally, the higher the specific gravity, the thicker the tin is, the easier it is to short-circuit. The lower the specific gravity, the thinner the tin, but the more likely it is to cause tin bridge and tin tip.

6. Tin Tip (Icicle) ICICLING:

This problem usually occurs on the DIP or WIVE soldering process, and ice-like tin is found on the top of the part or on the solder joint.

6-1. The solderability of the substrate is poor. This problem is usually accompanied by poor soldering. This problem should be discussed by the solderability of the substrate. It can be improved by increasing the specific gravity of the flux.

6-2. The area of the gold channel (PAD) on the substrate is too large, and the green (solderproof) paint line can be used to separate the gold channels to improve. In principle, the green (solderproof) paint line is divided into 5mm by 10mm on the Dajindao surface. Block.

6-3. The temperature of the tin bath is too short. The tinning time is too short. It can be used to increase the temperature of the tin bath and lengthen the soldering time, so that the excess tin is returned to the tin bath to improve.

6-4. The cooling airflow angle after the peak is not correct. It cannot be blown in the direction of the tin bath, which will cause the tin point to be rapid. The excess solder cannot be pulled back to the tin bath by gravity and cohesion.

6-5. Tin tip is generated during hand welding, usually the temperature of the soldering iron is too low, so the solder temperature is insufficient, and the solder joint cannot be immediately retracted due to cohesive force. Use a larger wattage soldering iron to lengthen the soldering iron in the preheating time of the object to be soldered. .

7. Retaining tin on the anti-weld green paint SOLDER WEBBING:

7-1. Some of the materials that are incompatible with the flux are left in the substrate. After overheating, the bismuth is viscous and the solder is formed into a tin wire. Acetone (*chemical solvent that has been banned by the Montreal Protocol) can be used. Solvents such as chlorinated olefins are cleaned. If it cannot be improved after cleaning, there is a possibility that the substrate layer CURING is incorrect. This accident should be promptly returned to the substrate supplier.

7-2. Incorrect substrate CURING will cause this phenomenon. It can be baked at 120 °C for two hours before the plug-in. This accident should be promptly returned to the substrate supplier.

7-3. The tin slag is pushed into the tin bath by PUMP and then sprayed out to cause the surface of the substrate to be stained with tin slag. This problem is relatively simple and good for tin furnace maintenance. The correct tin surface height of the tin bath (generally normal condition when tin) When the groove is not sprayed, the tin surface is 10mm away from the edge of the tin bath)

8. White residue WHITE RESIDUE:

After soldering or solvent cleaning, white residue is found on the substrate, usually a residue of rosin. Such substances do not affect the surface resistance, but the customer does not accept it.

8-1. Flux is usually the main cause of this problem, sometimes it can be improved by changing to another flux. Rosin flux often produces white shifts during cleaning. The best way to do this is to find a flux supplier. Assistance, the product is that they supply them more professionally.

8-2. Residual impurities in the process of substrate production, white spots will also be produced under long-term storage, and can be cleaned with flux or solvent.

8-3. Incorrect CURING will also cause white shifts, usually in a batch, which should be returned to the substrate supplier in time and cleaned with flux or solvent.

8-4. Flux used in the factory is not compatible with the substrate oxidation protection layer, which occurs when a new substrate supplier or a flux label is changed. Suppliers should be assisted.

8-5. The substrate material changes due to the solvent used in the substrate process, especially in the nickel plating process, which is often caused by the solution. It is recommended that the storage time be as short as possible.

8-6. The flux is used for a long time, and it is exposed to air to absorb water and gas. It is recommended to update the flux (usually the foaming flux should be updated weekly, the immersion flux is updated every two weeks, and the spray type is updated monthly. You can).

8-7. Using rosin-type flux, after the soldering furnace is parked for too long, it will be cleaned, resulting in a white shift. The time for soldering and cleaning can be shortened as much as possible.

8-8. The solvent moisture content of the cleaning substrate is too high, the cleaning ability is reduced and the white shift is generated. The solvent should be renewed.

9. Dark residue and etch marks DARK RESIDUES AND ETCH MARKS:

Usually black residue occurs at the bottom or top of the solder joint. This problem is usually caused by improper use of flux or cleaning.

9-1. Rosin-type flux is not cleaned immediately after welding, leaving dark brown residue, try to clean it as early as possible.

9-2. Acidic flux remains on the solder joints and causes black corrosion and can not be cleaned. This phenomenon is often found in hand soldering. Use a weaker flux and clean it as soon as possible.

9-3. Organic fluxes are burnt at higher temperatures to produce black shifts. Confirm the temperature of the tin bath and switch to a flux that is more resistant to high temperatures.

Wave soldering fixture