The Via and hole conductive hole directing the through hole, in order to meet the requirements of customers, PCB vias must plug, after a lot of practice, change the traditional aluminum plug hole process, complete the line plate welding and Jack White net. The production is stable and the quality is reliable.
The role of Via hole in the connection and conduction of the through hole is also promoted by the development of the electronic industry. At the same time, it also promotes the development of PCB, and puts forward higher requirements for PCB manufacturing process and surface mount technology. Via hole came into being Jack process, at the same time should meet the following requirements:
(a) via hole in copper solder can be Saikebusai;
(two) conducting tin lead to hole, a certain thickness (4 microns), no solder resist ink into the hole, the hole caused by hidden solder;
(three) the vias must have solder resist ink hole is not transparent, there shall be no tin solder and flat circle, etc..
With the development of electronic products to "light, thin, short and small, PCB to high density and high difficulty of development, so the emergence of a large number of SMT, BGA PCB, and the customer requirements in the jack mount components, there are five main effects:
(a) to prevent PCB in wave soldering tin from the through-hole component side short-circuit; especially we put Kong Fang on BGA pad, you must first do Jack, and then plated, welding for BGA.
(two) avoid welding flux residue in the guide hole;
(three) after the surface mounting of the electronic plant and the assembly of the components, the PCB must absorb vacuum to form a negative pressure on the test machine.
(four) surface to prevent the solder paste into the holes caused by weld, impact mount;
(five) to prevent the wave soldering tin pops up, causing a short circuit.
The process of conducting hole hole
For surface mount board, especially installed via hole must be affixed to the formation of BGA and IC, and positive and negative 1mil, may not have holes on the edge of red tin; via Cangxi beads, in order to meet the requirements of customers, via hole process is all kinds of process, especially the long process it is difficult to control and often have resistance to soldering experiment in hot air leveling and green oil out of oil; oil explosion problem occurred after curing. According to the actual condition of production, a variety of PCB Jack process are summarized, some comparison and analysis of advantages and disadvantages in the process:
Note: the principle of hot air leveling is to remove the excess solder on the PCB surface and hole by hot air. The remaining solder is evenly covered on the pad and the solder wire and the surface package point. It is one of the ways of surface treatment of printed circuit boards.
A hot air leveling Jack process
This process is: the surface resistance welding - HAL - plug and curing. The production process of hot air leveling jack, with aluminum screen or ink retaining net to complete all customer requirements via Fort jack. Jack used photosensitive ink ink or thermosetting ink to ensure consistent color film, wet conditions, the best use of the same plate and Jack ink ink. This process can ensure the hot air leveling holes out of oil, but easy to cause pollution, uneven surface of ink hole. Customers in the mount due to the weld (especially in BGA). So many customers do not accept this method.
Two, before the hot air leveling Jack process
The 2.1 sheet aluminum plug hole, curing, grinding plate after pattern transfer
This process with CNC drilling machine, aluminum sheet, drilled hole shall be made to ensure the screen, jack via jack jack jack full ink ink, can also be used thermosetting ink features, have high hardness, resin shrinkage of small changes, and the hole wall with good adhesion. The process is: the pretreatment, Jack, grinding plate, pattern transfer, etching, surface resistance welding
This method can guarantee the via hole hole formation, no oil, hot air leveling blasting hole off oil and other quality problems, but this process requires a one-time thick copper, the hole wall copper thickness reached the standard client, so the whole plate copper demand is very high, and the performance of grinding machine is also very high the requirements, ensure that copper on the surface of the resin were completely removed, the copper surface clean, no pollution. Many PCB plants do not have a one-off copper thickening process, and the performance of the equipment can not meet the requirements. This process is not much used in the PCB plant.
2.2 hole sheet aluminum solder directly after printing plate
This process with CNC drilling machine, aluminum sheet, drilled hole shall be made of screen, screen printing machine installed in the hole, hole after completion of parking should not exceed 30 minutes, using 36T to screen the direct screen printing solder surface, the process is: the pretreatment of Jack - screen printing - pre drying - exposure developing - curing
Using this technology can guarantee the conduction oil hole, hole smooth, wet film color, hot air leveling can assure the via hole is on the tin ball, don't hide the hole, but it is likely to cause the pad after curing the ink in the hole, causing bad weldability; hot air leveling guide through hole edge foaming off the production process of oil, it is difficult to control the process, should be adopted by engineers and process parameters in order to ensure the quality of special jack.
2.3 aluminum plug hole, developing, pre curing and grinding plate after plate welding.
With CNC drilling machine, drill requirements of aluminum sheet, Jack made of screen, screen printing machine installed in the shift jack, Jack must be full, prominent on both sides of the better, after curing, grinding plate surface processing, the technological process is as follows: a pre drying pretreatment - Jack - developing - - Surface pre curing solder
Because this process can ensure HAL after curing by jack hole out of oil, but the oil burst, HAL, via Cangxi beads and vias Shangxi difficult to solve, so many customers do not receive.
The 2.4 board solder and Jack at the same time.
This method adopts the screen of 36T (43T), installed on screen printing machine, adopts the pad or nail bed, and completes all the holes in the same time while finishing the panel. The process flow is: pretreatment, screen printing, pre drying, exposure, development, solidification.
The process time is short, the equipment utilization rate, can guarantee the hole after the hot air leveling off oil, via hole is on the tin, but because of the adoption of printing Jack over holes in the memory of a large number of atmosphere, atmosphere, shrinkage in curing, breaking the solder mask, a vague, smooth, hot air there will be a large number of leveling via Cangxi. At present, a large number of the company after my test, and choice of different types of ink viscosity, pressure relief printing, basically for the empty hole pan and uneven, this technology has been adopted for mass production.
