How to choose the material of substrate PCB circuit board?
The PCB circuit board with insulating board as base material, cut to size, at least with a conductive pattern, and distributed holes (such as component hole, the fastening hole metallized hole, etc.), used to replace the previous device for electronic components of the chassis, and realize the mutual connection between the electronic components.
Substrate material of PCB circuit board selection:
2 layers: layer thickness: 1.6mm line / space: 0.8mm/0.3mm material: FR-4 copper thickness: 1OZ aperture: 0.6mm process: oxidation resistance welding / character: white text on a dark green oil
1 spray tin
Because the cost is low, the solder is good, good reliability, compatibility of the strongest, but the welding characteristics of good HASL because of containing lead, so lead free process can not use. Another "tin silver copper tin spraying plate" because most of them are not using this process, the characteristics of data from difficulties.
2 gold plate
The processing cost of gold plate is the highest of all plates, but at present all the plate existing in the most stable, the most suitable for sheet also used in lead free process, especially electronic products requiring high reliability in some high price or recommend the use of this board as substrate.
3 gold plate
This kind of substrate the biggest problem point is "black pad" (BlackPad) problem, so in the lead-free process has a lot of Dachang is not agreed with the use of domestic manufacturers, but most of the use of the process.
4 heavy silver
Although the "silver" itself has the mobility is very strong, resulting in leakage happens, but "immersion silver" today is not the past pure metallic silver, but with organic co plating silver "organic" therefore has been able to meet the future lead-free process on demand, the weldability of the life more than OSP plate.
The lowest OSP process cost, convenient operation, but this process is due to the assembly plant to modify the equipment and process conditions and heavy poor popularity is still so poor, this kind of plates are used, after heating at high temperatures, the protective film is covered on the pre PAD is bound to damage, which led to the soldering tin reduction after two time, especially when the substrate after reflow situation more serious, so if the process has to undergo a DIP process, when the DIP terminal will face challenges on welding.
This substrate is easy to be polluted, scratched, coupled with process (FLUX) oxidation will occur discoloration, domestic manufacturers are mostly not using this process, the cost is relatively high.
Do PCB circuit board needs to provide what information?
Luen Hing Wah circuit is a professional production of rigid circuit board manufacturers, focusing on the Shenzhen circuit board factory, PCB board, LED aluminum plate, aluminum base circuit board and manufacturers of copper substrate, precision manufacturing factories (single panel, double sided board, multilayer board manufacturers) the highest layers can be up to 26 layers.
Do boards need to provide the following information:
1.PCB board (do circuit board drawing)
The 2 process:
Production process: surface spray tin, gold, immersion gold, nickel plating, antioxidant. (the election)
Color: dark green, light green resistance welding, blue oil, white oil, Red oil and so on (Qi Xuanyi)
The number of layers: the 1~26 layer
Thickness: 0.4~2.5mm (the election)
Plate: FR-4, aluminum plate, copper substrate, high frequency board, cam-1 (the election)
Copper thickness: 1oz=35um, 2oz=70um, 1.5oz=55um (the election)
The 3 number
4 method of payment
Note: if customers do is aluminum substrate that its coefficient of thermal conductivity in general can be divided into: general 1, guided, and high conductivity (the election)
Special requirements: impedance, BGA, minimum aperture is 0.2mm, the minimum line width / pitch 0.075mm
How to solve the common problems of the circuit board after welding
Can not use BGA package in the general design of the situation as far as possible not to use, the reason is that the BGA package is difficult to weld, solder situation cannot check package.
Level 10: thickness: 1.6mm minimum line width / pitch: 3.2mil minimum hole: 8mil color: green solder white differential impedance multi group: 90 ohm /100 ohm /110 ohm
Circuit board short: when the circuit board welding after took the aging process will find some circuit board outside short circuit, discharge circuit board design and electronic components of the problem, can from the following several aspects to find the circuit board solder tin time is too short, causing bad welding. Active flux itself is not strong, weakened the solder wettability and its extension. The circuit board into the tin tin wave direction and reverse direction, the welding surface oxide solder too much influence.
After the tin solder point dull dull: after soldering tin points found gray without Ze, from two aspects: one is the low degree of solder. Welding circuit board. Soldering tin containing more than 50% reach solder joints will have the gloss. On the other hand is the flux residue retention without cleaning and acid material corrosion it on the surface of tin solder point will also cause the tin point dull dull.
After the tin solder point surface is rough: Tin rough points on the surface of the first from the soldering quality, solder inside itself contains a small amount of a variety of metal elements, will affect the surface of tin point when the content of these metal elements exceeds its limit. When soldering tin liquid require no impurities surface, when the surface oxidation of liquid tin too much time to clean up or will affect the tin point form should be.
The solder joint is yellow to yellow in color: solder joint is a common problem, a lot of people do not know what reason. When solder appears generally in color temperature has a great relationship. When the yellow appearance of high temperature surface soldering tin liquid condition. Then to tin furnace temperature adjusting suitable operating temperature.
How to solve the problem of PCB copper clad laminate
A, how to search search
Want to make any number of PCB without having some problems is not possible, this is mainly attributable to the PCB copper clad laminate materials. Quality problems in the actual manufacturing process, often because of become the root cause problem of PCB substrate material. Even a carefully written and have been the effective implementation of PCB laminate technology specification, and there is no provision for determining PCB laminates is the result of the production process causes problems of test items must be carried out. Here is a list of some of the most commonly encountered PCB laminates problems and how to confirm their method.
Four layers: layer thickness: 1.6mm line / space: 0.8mm/0.3mm material: FR-4 copper thickness: 1OZ aperture: 0.6mm Technology: Gold
Once encountered PCB laminate problems, you should consider revised to specification PCB laminates to. Usually, if not for the technical specification of enrichment work, it will cause continually quality change, and the consequent product rejection.
In normal circumstances, problems of materials for changes of PCB laminate quality generation, occurred in the manufacturers use different batch of raw materials or by pressing load of different products made in. There are few users can hold large enough records, to make the processing sites distinguish specific pressing load or material batch. So they often happen: PCB constantly produced and installed components, but also in the solder bath continuous warp, thus wasting a lot of labour and expensive components.
If charging batch immediately available knowledge, PCB laminate maker can check out the batch number, batch number of the copper foil resin, curing cycle. That is to say, if the user cannot provide quality control system and PCB laminate manufacturers to maintain continuity, so will the user itself long-term losses. The following describes the PCB manufacturing process, the general problems associated with substrate materials.
Two, the surface of the problem
Symptom: ink adhesion is poor, poor adhesion of coating, some parts can not be etched away, and some part not soldering.
Can be used to the inspection method: usually visible watermark is formed on the plate surface visual inspection:
Possible reasons: because the release film caused by extremely dense and smooth surface, resulting in not copper surface too bright. Usually on one side of the laminate without copper clad laminate maker, without removing the release agent. Copper foil pinhole, resin resulting outflow, and accumulated in the surface of copper foil, which usually appear in the ratio 3/4 ounce weight specifications thin copper foil. Copper foil manufacturing put large amounts of antioxidants, coated on the copper foil surface. Laminate manufacturers changed resin system, demoulding thin, or brushing method.
Due to improper operation, there are many fingerprint or grease. In the stained with oil punching, blanking or drilling operation.
Possible solutions: suggest laminate manufacturers using a cloth like films or other release material. Contact and laminate maker, a method to eliminate the use of mechanical or chemical. Contact and laminate manufacturers, each batch of copper foil inspection unqualified; for removing resin grilled elite solution. Manufacturing to laminate for removing method. Often recommend the use of yansuan method, then by mechanical grinding brush removal. In the manufacture of laminates before any changes, with laminate manufacturing coordination, and the provisions of test items users.
All procedure of education personnel wearing gloves with copper clad laminate. To find out whether indeed laminates in transportation have suitable pad of paper or loaded in the bag, and a pad of paper and low sulfur content, packaging bags no dirt, pay attention to ensure that no one is using silicone containing detergent to contact with the copper foil, before plating or pattern transfer process for all laminates before degreasing treatment.
Online PCB circuit board sub board machine problem solving
Any online machine printed circuit board long signal pathway can be considered as a transmission line. If the line propagation delay time is too short rise time signal, then the signal generated by the rise reflects the LORD shall be drowned. No longer will overshoot and ringing, recoil, most of the existing MOS circuit, because the rise time line propagation delay time ratio is larger, so the alignment can be grown in meters without signal distortion. Logic circuit faster, especially high-speed emitter coupled logic.
Integrated circuit on-line machine, because of its high speed, no other measure of edge, track length must be shortened in order to maintain signal integrity.
Online machine there are two ways to make the high speed circuit in a relatively long line work without waveform distortion is serious, the falling edge of TTL fast Schottky diode clamp method, such as excessive is sandwiched between more than one diode drop below the level of the ground potential, thereby reducing the amplitude of the face after the rising edge of the head allows the recoil, slow down, but the circuit in the H level of the relative high output impedance, attenuation. In addition, due to the level of H of state immunity is large, the HCT series device recoil so the problem is not very prominent, the use of a Schottky diode clamp and a series resistor termination method combining the improved effect will be more obvious.
The signal line when a fan, online machine at a higher bit rate and the advantage of speed ratio, the method described above is not always enough TTL shape. Because there is a reflected wave line, they will often synthesis at high rates, leading to severe distortion of the signal and interference reduction. Therefore, the online trigger in order to solve the reflection problem, emitter coupled logic system, commonly used another method: the line impedance matching method. In this way, the control can reflect the signal integrity assurance.
Strictly speaking, the online trigger a slower speed, the traditional TTL edge and CMOS equipment, power transmission line is not very necessary. There is a faster speed of the edge of the emitter coupled logic devices, transmission line is not always needed. However, when the transmission line use, they must forecast advantage and oscillating connection delay and control impedance reflect.
PCB board warpage prevention and treatment method
As the production personnel department technology circuit board factory, everyone will see or meet warping phenomenon of circuit board, circuit board warpage cause component positioning, plate bending in the SMT, THT, component pin is not the whole, will give the assembly and installation work to bring a lot of difficulties, so how to prevent the circuit board warpage, below Shenzhen Lianxing Hua circuit board factory's excellent technical staff to give you a detailed description!
: four layers of laminate thickness: 0.8mm line / space: 0.08mm/0.35mm material: FR-4 copper thickness: 1OZ aperture: 0.1mm Technology: Gold
IPC-6012, the SMB--SMT circuit board maximum warpage or distortion of 0.75%, other board warpage is generally not more than 1.5%; electronic assembly plant allows the warping degree (double sided / multilayer) is usually 0.70---0.75%, (1.6mm thickness) actually many boards such as SMB, BGA board requires warping degree is less than 0.5%; some factories even less than 0.3%.
Warping degree calculation method = warpage height / curved edge length
Prevention circuit board warpage:
1 Engineering design:
The interlayer prepreg arrangement should correspond with;
The multilayer board core plate and semi solidified sheet should use the same suppliers products;
The outer layer of C/S surface area as close as possible to the graphics, can be used for independent grid.
2 before blanking plate drying:
General 150 degree 6--10 hours, excluding plate in water vapor, further curing the resin completely, eliminate the stress in the plate; open material pre baking board, regardless of the inner layer or double need!
3 multilayer laminated plate should be noted before in longitude and latitude direction plate curing piece:
Warp shrinkage ratio, semi solidified sheet material laminated preattentive distinguish between warp and weft directions; core plate also should pay attention to the latitude and longitude direction; the general plate curing sheet rolling direction for the warp; copper clad laminate direction for the meridional length.
4 drilling pre baking plate: 150 degrees 4 hours.
5 laminated thick cold stress eliminating pressure platen, pruning burr.
The best 6 sheet without the mechanical grinding brush, recommend the use of chemical cleaning; electroplating using special fixture, to prevent the plate bending fold.
The 7 tin spraying in the rear flat plate cleaning marble or natural cooling to room temperature or air bed after cooling.
The warping board processing:
150 degrees or pressing 3--6 hours, with smooth steel weight, 2-3 baking.
How to check the multilayer problem occurs in where?
Prevention of multilayer board problems, the author suggested from the following aspects:
One, with red brown, metal organic film, black oxide process improvement of chemical TIN model process or after the post leaching
The customer can accept and production equipment, funds permitting, recommend the use of red brown, metal organic film and chemical tin and other new technology, currently on the market has many mature products in the promotion of the use of customers, in recent years the use effect of the market reflect the effect of good. Can also increase the leaching process in the production process in the. After processing the excess film acicular structure reduction off, but will increase the cost of production, as the novel process has cost competitiveness;
Six layers: layer bonding sheet thickness: 1.6mm line / space: 0.15mm/0.15mm material: FR-4 copper thickness: 1OZ aperture: 0.2mm process: the method of making gold multilayer board generally consists of the inner layer image to do first, and then to the printing etching into single-sided or double-sided substrate, and incorporated into the specified in the interlayer, and then through heating, pressurizing and be binding, as after drilling and plated through hole double side plate of the same. These basic production methods and go back to the 1960's method does not change much, but with the development of material and process technology (for example: pressing adhesive technology, to solve the drilling produce glue residue, film improve) the more mature, attached to the characteristics of multilayer is more diversified.
Two, still using multilayer PCB production process of old, occur check prevention multilayer board the issues of how to control? The author, after many years of practical experience in production and processing of multilayer board, it is recommended to be controlled from the following aspects:
1 multilayer board inner layer of black oxide, pay attention to the following several parameters that control the blackening process:
A. micro etching thickness, generally in the range of 1.5-2.5um, through the slot liquid analysis and micro erosion thickness measurement control;
The B. prepreg temperature blackening pre immersion temperature could increase to about 30-40 degrees, the processing time of 1-2 minutes, not at room temperature, the change can effectively guarantee the uniformity of the blackening plate color, reduce because of color blackening uneven colors bring;
And the concentration of AB solution C. black oxidation of the proportion of AB, processing time, bath aging condition: different liquid ratio and concentration will influence the generation of melanization of blackening film density and color uniformity, physical properties and crystallization tank liquid layer and the length of treatment time and bath ageing condition will affect the blackening film crystallization the.
2 when laminating attention control process parameters, to ensure the flow of glue fully, while avoiding excessive flow of glue, lack of plastic production, fully guarantee between the resin and the blackening layer fully penetrate each other, produce the best adhesion; through metallographic observation of PCB multilayer circuit board after lamination situation, have no direct serious glass fiber contact the inner copper surface conditions, so as to judge whether the flow of glue excessive or inadequate phenomenon;
The 3 hole, pay attention to not feed speed and retracting speed is too fast, the same turn mill, pay attention to drill in the cleaning, taking, guarantee the drilling and cutting edge good effect, reduce the bit due to aging and passivation on the hole wall tear pull and other adverse mechanical effect, reduce the multi laminate tear production, but also to avoid a effective measures of pink ring produced!
4 multilayer board in desmear (Desmear) process, should pay attention to strengthening the control of the glue removal process conditions, minimize the glue removing excessive, because the Yao of water on the inner blackening layer and semi solidified insulating layer between the parts of a strong offensive, the tank liquid infiltration in the easy, easy to make the Kong Tong fracture or fold in the coating, resulting in pink ring; it can also cause copper impregnated glass fiber bundle (wicking) result in lower insulation performance reliability of possible Yao water infiltration and interlayer;
In the process of 5 chemical copper has as far as possible the use of alkaline degreasing, salt based colloid palladium or palladium ion, avoid acid based Colloid Palladium, also note that the prepreg and activation in the liquid content should not be too high, because the prepreg and activation solution with aggressive and corrosive strong ability of copper oxide; chemical precipitation of copper the alkali content is not too high, the copper deposition time shoulds not be too long, because the results: copper deposition liquid attack on the copper layer is the strongest in all wet process, while under alkaline conditions, the stability of oxidized copper is very good, but in the presence of a strong reducing agent formaldehyde and new generation active chemical copper especially by-products generated strong reducing agent of active hydrogen and the existence conditions of copper deposition reaction time, they can attack the copper oxide layer, the reduction of copper oxide layer, resulting in pink ring;
6 during electroplating electroplating technology especially liusuan copper electroplating process, the liusuan content should not be too high, generally not more than 230 g / L, while for small hole of deep hole electroplating, now generally use low current, long time of plating, should maintain a normal current electroplating 3-5 minutes to ensure that the copper plating layer chemical copper surface osteoporosis can timely coverage a layer of compact panel charged under the groove, reduce the bath liusuan infiltration, should pay attention to is the multilayer board production and processing in the process of content;
7 for can bake after drilling in multilayer board WIP occurrence pink circle, 150 degrees, bake for 4 hour, can effectively reduce the generation of subsequent pink ring.
White spots or white spots appear in the PCB plate?
In the process of making PCB circuit board, often encounter a whiteboard or white spots appear printed circuit board in the case of PCB, these white spots or white spots is mainly due to the PCB plate resulting in the effect received some external environment such as temperature, humidity and other factors. These issues will have a certain impact on the PCB material, will give PCB slabs caused great distress, therefore on the plate before must first solve the problem. The following is caused by a board of PCB white spots or white spot specific reasons and countermeasures.
PCB sheet may appear white spots or white spots in the affected by the external environment, this caused great distress to many users of PCB sheet, then what is the causes of it, should be how to solve?
There are three main reasons for this situation:
The plate by improper thermal stress can also cause white spots, vitiligo.
The separation plate subjected to inappropriate external mechanical forces caused by the impact of local resin and glass fiber and leukoplakia.
The local pull material containing fluorine chemical products by Yao infiltration and woven point etching of glass fiber cloth, white spot formation regularity of the (more serious when can see square).
In view of this situation, we can take measures from the process to solve:
The particularly hot air leveling, such as infrared hot control failure, will cause the action of thermal stress leads to defects in substrate.
Second, take measures from the process, to minimize or reduce the vibration phenomenon of excessive mechanical processing to reduce the mechanical external force.
Third, especially in tin lead alloy coating, easy to occur between gold-plated plug piece and the plug piece, must pay attention to choose from a tin lead Yao water and suitable operation process.