12 Problemi riscontrati da un produttore di schede PCB nell'area asciutta Pcb | Cina2020-04-14
A Comprehensive printed circuit board solutions Guide
Why produttore della scheda pcb should plug BGA soldering of PCB?
Answer: First of all, a produttore della scheda pcb installs the solder stopper hole to protect the service life of the via hole.
Because the hole diameter of the plug required for the BGA position is generally relatively small, between 0.2-0.35mm. And some of the potion in the hole is not easy to be processed during post-processing Drying or evaporating.
Generally, it is easy to leave residues. If there is no plug hole or full plug in the solder mask, there will be residual foreign objects or tin beads in the subsequent processes such as:
- spraying tin and
- immersion gold.
When a produttore della scheda pcb heats it during high-temperature soldering, foreign materials or tin beads in the hole will flow out. And adhere to the component, causing defects in the performance of the component, such as:
- open, short circuit.
- The BGA is located in the solder mask hole
- It must be full.
- There must be no redness or false copper.
- It must not be too full.
What is the difference between the tabletop glass of the exposure machine and ordinary glass?
Answer: The tabletop glass of the exposure machine will not produce light refraction when it passes through. A produttore della scheda pcb should keep in mind that if the reflector of the exposure lamp is flat and smooth, then the light shines on it.
According to the principle of light, it forms only one reflected light shining on the board to be exposed. According to the light in principle, the light that hits the recess and the light that hits the protrusion will form countless scattered light rays. Moreover, forming an irregular but uniform light to the board to be exposed to improve the exposure effect.
What is side development for produttore della scheda pcb ?
Answer: The width area of the bottom of the part where the green oil on one side of the solder resist window is developed is called side development.
When the side development is too large, it means that the green oil area of the developed part that contacts the substrate. Similarly, the processing in subsequent processes such as:
- tin spray
- sink tin
- Immersion gold and
- other side development parts are subject to high temperature
- pressure and some potions that are more aggressive against green oil, and oil will form.
If the IC part has a green oil bridge, it will be dropped when the customer attaches the soldering component. Furthermore, it will cause a short circuit in the bridge.
What is poor solder mask exposure according to produttore della scheda pcb ?
A: After produttore della scheda pcb processes the solder mask, it is exposed to the pads. During the solder mask alignment / exposure process, it causes the cross-linking reaction. Moreover, during development, this part of the green oil will not be dissolved by the solution. And the outside of the pad will not expose. This is called welding.
Poor exposure. Poor exposure in the post-process will lead to failure to mount components, poor soldering, and severe open circuit.
Why do produttore della scheda pcb need to pre-treat the grinding board for the circuit and solder resist?
Answer: 1. The circuit board surface includes a foil-clad substrate and a copper-plated substrate. In order to ensure the firm adhesion of the dry film to the substrate surface, it is required that the substrate surface has no:
- oxide layer
- oil stains
- fingerprints and
- other dirt
- no drilling burrs and
- no rough plating.
Simultaneously, to increase the contact area between the dry film and the substrate surface, it is also required that the substrate has a micro-rough surface. Moreover, to meet the above two requirements, a pcb board manufacturer must treat substrate carefully before filming. The treatment methods can be summarized as mechanical cleaning and chemical cleaning.
- The same is true for the same solder mask. Before the solder mask is ground, some:
- oxide layers
- oil stains
- fingerprints and
- other contaminants are removed from the board surface.
In order to increase the contact area of the solder mask ink and the board surface and make it stronger, it also requires a micro-rough surface. Furthermore, if a pcb board manufacturer doesn’t process the board before solder mask, it will directly separate the solder mask. And the circuit film from the board surface.
What is viscosity? How does the viscosity of solder resist ink affect the production of pcb boards?
Answer: Viscosity is a measure to prevent or resist flow. The viscosity of solder resist ink has a considerable influence on the production of PCB. Similarly, when the viscosity is too high, it is easy to cause no oil or sticky net.
When the viscosity is too low, the fluidity of the ink on the board surface will increase, which will easily cause oil to enter the hole. And local oil books. Relatively speaking, when etching the outer copper thicker (≥1.50Z), it is necessary to control the viscosity of the ink to be lower.
If the viscosity is too high, a pcb board manufacturer will reduce the fluidity of the ink. Then the bottom of the line and the corner will not form oil, dew line.
What are the similarities and differences between pcb board poor development and poor exposure?
Answer: The same point: a is that there is solder resist oil remaining on the surface of the copper / gold to be welded after solder mask resistance. The reasons caused by b are basically the same:
- the time
- exposure time, and
- energy of the baking board.
The area formed by poor exposure is large, the residual solder resist oil is from outside to inside. Similarly, most of them appear on the non-porous pads. Mainly because the ink in this part has been exposed to ultraviolet light.
The remaining solder resist oil is not a relatively thin layer of oil at the bottom of the development. Its area is not large. But it forms a thin film state. This part of the ink is mainly due to different curing factors. It generally appears on the pad with holes.
Why are there bubbles in the pcb board solder mask? How to prevent it?
Answer: (1) A produttore della scheda pcb generally prepares the solder oil by mixing:
The solder resist oil is generally prepared by mixing:
- the main agent of the ink
- + curing agent
- + diluent.
During the mixing and stirring, there will be some air remaining in the liquid. When they encounter strong light or a relatively high temperature in a short time, the gas in the ink will rapidly evaporate outward as the ink accelerates each other.
- The line spacing is too narrow
- the line is too high
- the solder resist ink cannot be printed on the substrate during screen printing.
It will result in the presence of air or moisture between the solder resist ink and the substrate.
The single line is mainly caused by the high line. When the blade contacts the line, the angle between the blade and the line increases. So that a pcb board manufacturer cannot print the solder resist ink. And there is gas between the side of the. After heating, a small bubble will form.
Prevention: a. The prepared ink is still for a certain period of time before printing. B. The printed board is also still for a certain period of time. The gas in the ink on the surface of the board gradually volatilizes with the flow of the ink. Bake at temperatures.
Why do produttore della scheda pcb need to suck vacuum when exposing machine?
Answer: In the non-parallel light exposure operation the degree of vacuum suction is a major factor affecting the exposure quality. Air is also a medium layer. There is air between the suction film, which will cause light refraction and affect the effect of exposure.
Vacuuming is not only to prevent light refraction. But also, to prevent the gap between the film and the board surface from expanding, ensuring alignment.
What are the advantages of using volcanic ash grinding plates for pcb board pretreatment?
Answer: Advantages: A. The combination of abrasive pumice powder particles and nylon brushes wipes with cotton cloth tangentially. Which can remove all dirt and expose fresh and pure copper.
- B. It can form completely sanded, rough, uniform the multi-peaked surface has no cultivated grooves.
C-The connection between the surface. And the hole will not be damaged due to the ease of the nylon brush.
What is the impact if the pcb board developing point is too large or too small?
Answer: A produttore della scheda pcb determines the correct development time point. The development point must be maintained at a constant percentage of the total length of the development section.
If the development point is too close to the exit of the development section, the unpolymerized resist film cannot be sufficiently cleaned and developed. And the residue of the resist may be left on the surface of the plate to cause undeveloped development.
If the developing point is too close to the entrance of the developing section, the polymerized dry film may be eroded by Na2C03. Due to prolonged contact with the developing solution and become hairy. And the film will be lost and the gloss will cause excessive development.
What role does solder resist ink play on pcb board?
Answer: Solder resist ink: It is a kind of protective layer. A produttore della scheda pcb coats it on the substrate. The purpose is to prevent bridging between the lines during soldering. While providing a permanent electrical environment and a protective layer that is resistant to:
- heat, and
- giving the PCB an aesthetic appearance.
There are two major systems of solder resist ink:
- Thermosetting epoxy ink
- Liquid photosensitive imaging ink.