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How to ensure the quality of PCB produced by the circuit

The supply of raw materials should be strictly controlled to prevent the use of inferior materials, IPC inspection of incoming materials, points of attention for discussion at pre-production engineering technical quality meetings, first confirmation of each process, quality inspection and monitoring by departments, and 100% inspection and shipment.
PCB manufacturers interpret color codes for printed circuit boards

In this colorful world, there are a lot of colors, and these colors affect our preferences and moods, so the resistance of PCB welding can also affect our preferences, each according to their own different hobbies to choose different colors of PCB resistance welding, today we focus on the circuit board resistance often Colors and advantages and disadvantages!

       When you recall what color you usually see on a circuit board, yes, there are many common circuit board colors, such as: green and white characters, white and black characters, blue and white characters, red and white characters, black and white characters and so on, and there are some unusual such as: butter and white characters, purple and white characters, you have not found a common point these There's a common word "oil" behind the different colors. You've finally found this little detail. These different colors of PCBs are the common paints in our lives. So the colors on PCBs are the effects of different paints.So you need what color of the circuit board, the circuit board manufacturers just need to use different paint can be produced, so there is no need to use different colors to make different circuit boards, from a cost point of view, only the large amount of conventional ink procurement costs, so the conventional color circuit boards do not need to add. Color cost,
       But in the actual production, black oil and white oil circuit board manufacturers will be charged extra, what is the reason? Today I will tell you, black is a very dark color, this color made out of the circuit board is a big challenge to the circuit board, because the dark look is not fine, need to spend A lot of labor costs to check for defects such as appearance, resulting in low labor efficiency, which increases labor costs, which leads to black oil circuit boards a little more expensive than green oil.After talking about black and white, you must say that black is not bright enough to produce more labor costs we can accept, why white is a bright color is also more expensive, there is a question that people explain that the IQ is quite high, listen to me slowly, white is a bright color system, does not affect the artificial Increase, but you should remember that white is a very easy to yellowing color, so in order to make a pure white circuit board, need to increase the white curing uniform, so as to ensure that the white oil does not yellowing, the increase of this addition uniform increases the cost, so it is expensive, if you do not mind the white oil yellowing is not. It will increase the cost. Everyone knows it here.
      Okay, today to popularize this knowledge to everyone here, next time in the analysis, surface treatment of the problem!

What happens to white spots or white spots in PCB panels?

In the process of making PCB board, we often encounter whiteboard or white spots in PCB board. These white spots or white spots are mainly caused by some external environment such as temperature, humidity and other factors. These problems will have a certain impact on the PCB material, will cause great trouble to the use of PCB board, so we must solve this problem before copying board. The following are the causes and solutions of white spots or leukoplakia in the PCB board.

PCB sheet may appear white spots or white spots when it is affected by external environment, which cause great trouble to many PCB sheet users. So what is the cause of the occurrence and how to solve it?

There are three main reasons for this.

①Improper thermal stress will also cause white spots and leukoplakia.

②The plate is subjected to improper mechanical impact resulting in the separation of local resin and glass fibers into white spots.

③The local wrench material is eroded by the chemical Yao containing fluorine and forms regular white spots (which can be seen as square when more serious).

In view of this situation, technological measures can be taken to solve the problem.

①Especially hot air leveling, infrared hot melting, such as control failure, will cause thermal stress and lead to defects in the substrate.

②Measures should be taken to minimize or reduce the excessive vibration in machining to reduce the effect of external mechanical force.

③Especially when the tin-stripping lead alloy coating is used, it is easy to occur between the gold-plated plug piece and plug piece.
How to solve common problems after welding circuit boards?

In general design can not use BGA packaging as far as possible, because BGA packaging is difficult to weld, can not check the solder inside the package.

Layer: 10 Layer Thickness: 1.6mm Minimum Linewidth / Line Spacing: 3.2mil Minimum Hole: 8mil Resistance Welding Color: Green Oil White Character Differential Impedance Multiple Group: 90 Ohm / 100 Ohm / 110 Ohm  

Circuit Board Short Circuit Circuit: When the circuit board after welding aging process will find some circuit boards short circuit, discharged from the circuit board design and electronic components of the original problems, can be found from the following aspects when the soldering time is too short, resulting in poor soldering. The flux itself is not strong enough to weaken the wettability and expansion of solder. The direction of the circuit board entering the tin is opposite to the direction of the tin wave, and the excessive oxide on the liquid surface of the solder affects the welding.

After soldering, the solder spot is gray and glossy. After soldering, it is found that the solder spot is gloomy and glossy. In two ways, the solder degree is too low. Circuit board welding. Soldering tin reaches more than 50% solder joints will have luster. On the other hand, the residue of flux stays on the surface of the solder spot without cleaning and its acid corrodes the solder joint, which will cause the solder spot to be gray and glossy.

The surface of the solder spot is rough after soldering: the roughness of the surface of the solder spot first depends on the quality of the solder, the solder itself contains a variety of small amounts of metal elements, when the content of these metal elements exceeds its limit will affect the surface of the solder spot. Tin soldering requires no impurities on the surface of the liquid tin, when the surface of the liquid tin oxidation is too much to clean up in time, otherwise it will affect the surface whisker of the tin spot.

The color of solder joints is yellow: the color of solder joints is yellow, which is a common problem. Many people do not know why. When solder appears color, it is generally related to temperature. When the solder temperature is too high, the surface of tin liquid appears yellowing. At this time, the temperature of the tin stove should be adjusted.
Problem solving of PCB circuit board on line Slitter

The long signal path of any printed circuit board can be regarded as a transmission line. If the line propagation delay is a much shorter rise time signal, then the rise of the signal reflects that the Lord must be submerged. No longer will overshoot, recoil and ring, most existing MOS circuits, because the rise time line propagation delay ratio is greater, so alignment can grow in meters without signal distortion. Faster logic circuits, especially high speed emitter coupled logic.

On-line sub-board integrated circuit, because of its high speed, no other measures of edge tracking length must be shortened to maintain signal integrity.

There are two ways to make the high-speed circuit work on a relatively long line without serious waveform distortion. The TTL drops along the fast Schottky diode clamp method, which is excessively clamped on more than one diode below the ground potential level, thus reducing the amplitude of the back recoil and slowing the rise edge overhead allowed, but in H water. The attenuation of a flat state circuit relative to the high output impedance.In addition, since the level H state exemption is large, so the problem is not prominent backlash of the H CT series equipment, the use of a Schottky diode clamp and series resistor termination method combined with the improved effect will be more obvious.

When a fan's signal line, an on-line sub-board at a higher bit rate and speed advantage rate, the methods described above are often inadequate for TTL shaping. Because there is a reflected wave line, they tend to be synthesized at high rates, resulting in serious signal distortion and interference reduction. Therefore, in order to solve the reflection problem of the on-line splitter, the emitter coupling logic system, another method commonly used: line impedance matching method. In this way, control can reflect the assurance of signal integrity.

Strictly speaking, on-line sub-boards have a slower speed, traditional TTL edges and CMOS devices, and transmission lines are not necessary. There is a faster edge speed, high speed emitter coupled logic device, and transmission lines are not always needed. However, when using transmission lines, they must predict connection delays and control the advantages and oscillations reflected by impedance.
How to select the substrate material of PCB PCB?

PCB circuit boards are made of insulating boards and cut to a certain size. At least one conductive pattern is attached to the PCB circuit boards with holes (such as component holes, fastening holes, metallizing holes, etc.) to replace the chassis of electronic components of previous devices and to realize the interconnection between electronic components.

Selection of substrate material for PCB PCB:

Layer number: 2 ply thickness: 1.6mm linewidth / line spacing: 0.8mm / 0.3mm material: FR-4 copper thickness: 1OZ pore diameter: 0.6mm process: oxidation resistance welding / character: dark green oil white character

Because of the low cost, good soldering, good reliability, the strongest compatibility, but this solder spray plate with good soldering characteristics because of lead, so lead-free process can not be used. There are also tin silver copper sprayed tin plates, because most of them do not use this process, so the characteristic data are difficult to obtain.

2.Gold plated plate
Gold-plated sheet is the most expensive of all sheets, but it is the most stable of all available sheets and is most suitable for lead-free processing, especially in some high-cost or high-reliability electronic products.

3.Gold plate
The biggest problem with this type of substrate is the "black pad" problem, so there are many large factories in the lead-free process are not willing to use, but most domestic manufacturers use this process.

4.Silver plate
Although "silver" itself has a strong migration, resulting in leakage of electricity, but today's "silver dip" is not pure metal silver, but with organic co-plated "organic silver" has been able to meet the future lead-free process requirements, its solderability life is longer than OSP plate.

OSP process costs the lowest, easy to operate, but the process has to be modified equipment and process conditions and poor heavy workability, so the popularity is still poor, the use of this kind of plate, after high temperature heating, pre-coated on the PAD protective film is bound to be damaged, resulting in reduced solderability, especially when the substrate passes through the second time. The situation is more serious after backwelding, so if the DIP process needs to go through again, then the DIP end will face the welding challenge.

6.Immersion Tin
This kind of substrate is easy to be contaminated, scratched, coupled with the process (FLUX) will oxidize pornography, most domestic manufacturers do not use this process, the cost is relatively high.

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