Micro hole drilling
White Melamine Backup Board is a kind of new type of pcb drilling cushion for micro size hole. Then high density fibre board compound with paper phenolic solidity surface and stretchy midst core. It can be used for the hole on precise multilayer circuit board in pcb drill process. this backup material designed to replace the phenolic backup board in particular, especially for the pinhole aperture, multilayer board and flexible Board.
PCB drill hole is one of the important part for multilayer PCB. usually drilling cost account for 30% to 40% of the total cost in PCB fabrication.
In terms of function, micro hole drilling can divided into two categories. one used for electrical connection between each layers. The other used to fix or position the components.
In terms of technology in PCB manufacturing. the holes are generally divided into three categories. which are blind vias, buried vias and through holes. Blind via located at the top layer and bottom layer surface of the printed circuit board. which used for the connection between surface layer and inner layer. the depth of the hole is usually not exceed a certain ratio. Buried hole refers to connection hole that located in inner layer. of the printed circuit board. buried hole does not extend to the surface of the circuit board.
Through holes drilled through the whole printed circuit board. which can used for internal electrical interconnection. or used as a positioning hole to assemble components. Because the through holes are easier to achieve. in the pcb manufacturing process with lower cost. so most of printed circuit boards choose to use it rather than the other two holes (blind via and buried via).
In terms of pcb design, the hole is consist of two parts. one is the drill hole in the center area, the other is the pad around the drill hole. The size of these two parts determine the hole size. Obvious, in the design of a printed circuit board with high speed. and high density, the designers always hope that the holes the smaller the better. so that it can leave more space for circuit layout. But the hole size decrease will bring the increase of the pcb fabrication cost. moreover, the hole size is impossible to decrease.
because it's limited by the process of drilling and plating. The smaller hole size, the longer drill time required, and the easier off center position. When the depth of hole is more than 6 times of hole diameter, the copper plating process won't guarantee. that the hole wall could plate copper smoothly. For example, a standard 6 layer PCB with thickness (depth of the hole) about 50 mil. so the PCB manufacturer can provide the minimum hole diameter to 8 mil.
When it comes to obtaining the standard PCB drill holes sizes, it may be necessary that you follow certain rules to limit wastage. For instance, when the component is Xmm, you should drill a hole that is X+ 0.3mm. If the component is 0.4mm, then drilling a hole that is about 0.7- 0.8 mm may be necessary.
PCB vias plated through holes) come in all shapes and sizes, depending on the complexity of the circuit. You can use laser drills to make the small ones up to 0.006 inches, but most builds will require small “micro vias” cut from a CNC machine.
Holes smaller than 0.15mm can only be drilled by laser drill. Via with 0.6mm hole and a 1mm solder pad is the most common size that can be fud on most of the PCBs. 3.PCB aspect ratio. PCB’s aspect ratio can be defined as the ratio between the thickness of the board and the diameter of the drilled hole.
While designed-in features are the predominant driver of PCB manufacturing costs. the more subtle factor of panelization efficiency can also have a dramatic impact. One of the key things to understand about your PCB order is that the manufacturer. (some would say "fabricator") doesn't build individual boards. For the sake of automation and repeatability, their machinery. and processes are setup to handle uniformly-sized "panels" of material. Unless your board is large, or requires special processing. it's likely it will flow . through the manufacturing process on panels with other designs.
The second key thing to understand is that the cost of manufacturing panels. fixed for a given set of technology. This doesn't include non-reoccurring charges (i.e. the "one time" setup required for a new design). but it is the case for the actual fabrication processes. Other than the price of materials and labor, not much varies from panel to panel.
Working from a fixed panel cost, you can see that more boards packed into a set of panels. means more efficient (less costly) manufacturing. And, generally speaking, the more boards that fit on a panel the lower the per-board price. This works out well for both customers and fabricators. But, it's one of those things that seems to missed during PCB layout. Costs can skyrocket when your design differs from "what everyone else is doing". because your boards will need to be on panels all by themselves. Boards that done using "common" technology aggregated. meaning the cost of manufacturing the panel can spread among many customers. This can be a huge cost saver. But if you're boards are going to be on panels by themselves. you have to take a close look at panelization efficiency.
To make the best use of the available space on a panel (and thus lower your cost), choose the size of your board. Ask you manufacturer for the details of the panel sizes they prefer. and if possible pick board dimensions that are an integer divisors of the length and/or width of the panel size. Don't forget to account for the margin around the edge of the panel and spacing between the boards. Your manufacturer should be able to. provide specific instructions for sizing your board for maximal efficiency. if they can't (or won't), you may want to consider a more cooperative manufacturer.
PCB manufacturers have a maximum size board they can handle. this is also their panel size. The PCB fabrication house's panel size is also important when mass producing boards. In this situation one would want to fit as many boards as possible on a panel with. as little wasted board space as possible (to reduce costs). Normal board spacing for routing (how boards separated on a panel) is 0.3". plus there is a 1.0" to 2.0" border on the board for handling it during processing.
Board thickness may also specified. A standard thickness and type of board is .062" FR4. Other typical board thickness are .010", .020", .031", and .092".
diameter of holes to drilled on a printed circuit board. as specified by the client’s files, called the smallest drill size. Technical limitations in the manufacturing process, including plating. and available drill bits, limit the smallest size a drilled hole can be through a PCB. At Bittele Electronics, our smallest drill hole diameter is 0.15mm for standard holes. and 0.1mm for laser drilled holes. This means that we cannot manufacture boards with holes smaller than these sizes.
The leads of through hole components are always above the smallest drill size. thus only when choosing a size for your vias should the smallest drill size considered. Most PCB designers should not need to worry about these minimums. But, if your design has a high density and you reqneede smallest possible via holes. then you may specify your holes down to our smallest size.
Another design parameter to consider is the aspect ratio of your holes. For thick boards with many layers or holes with very small diameters. there is a limit on the ratio between a hole’s depth and its diameter. At Bittele Electronics we permit a greatest aspect ratio of 10:1 for regular holes and 1:1 for laser drilling. This limitation is the reason why micro vias drilled one layer at a time. and cannot go through a multi-layer board in one drill.
One more specification to keep in mind. when designing your board is the smallest clearance. between your drilled holes and other copper features which it is not meant to connect to. This clearance varies based on the number of layers as
Most PCB manufacturers have a wide selection of drill (hole) sizes available. Some charge per drill size used, others offer a standard set of drill sizes for no charge. and then charge for any non-standard drill sizes. AP Circuits uses the latter approach. When choosing a hole size remember that the plate-through will cause the hole to be more narrow. The plate-through thickness varies from .001" to .003". AP Circuits' plate-through thickness is approximately .015" (meaning the "finished hole" diameter. is 3 mils smaller).
PCB via sizes
Advanced PCB fabrications need advanced routing techniques, including innovative use of vias. With all the different via structures available. and all the different placement options. your PCB design software should make it easy to keep track of your vias. Keeping track of smallest guidelines as well as enabling circuits. and boards to adapt as you see fit will be paramount. A strong PCB editor will enable you to check and inform your design from schematic to PCB layout.
You’ll need to define drilling steps for your vias, conductive. and non-conductive fill options, and layer stackup. Altium Designer has all the tools you need to define your via structures. and includes the fabrication and drill holes in your manufacturing outputs. Keeping your information clear, precise,. and documented will keep your production process running forward.
the most important routing features in a multilayer PCB are vias. Your vias are what let you route between each layer in your board. Whether you’re placing via-in-pad, through-hole vias, blind vias. or buried vias, you will need to define drill diameter and depth in each layer. Altium Designer gives you all the tools you need to customize your via sizes. and specify how you want them placed in your board.
As vias are hole most of the manufacturers can handle any of the standard drill sizes. But it is important to note that the production process will be efficient. if all the vias in the boards are of the same size. This will make the drilling process easier. and saves a considerable time thus saving production cost. Vias from drills start from 0.15mm with 0.3mm solder pad and can drill as big as requested. but different sizes may need manual drilling which increases the production cost. Holes smaller than 0.15mm can only drilled by laser drill. Via with 0.6mm hole and a 1mm solder pad is the most common size that can be fud on most of the PCBs
PCB pad Size
The biggest issues with pad size are solder ability and manufacturability. Solder ability is a matter of skill and will not discussed here. Manufacturability concerned with. whether the pad will broken when the hold drilled in it. This is a function of the accuracy of the PCB manufacturer's drilling. If a drill hole is off center the pad may broken at one edge leading to an open in the circuit. A standard need for pad sizes is a 5 mil annulus. This means there must be .005" all around the hole (i.e. a 28 mil hole would need a 38 mil pad). Something a little larger than this (10 mils) recommended for solder ability. AP Circuits states they have had consistent. success with a 2.5 mil annulus (i.e. a 20 mil hole with only a 25 mil pad), but they don't recommend it.
Melamine backup board Specification
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Melamine backup board feature
1. It’s the surface hardness is the same as the phenolic backup board but stabilize dimension and not easy to distort. so as to elinimate the PCB drill burr,anti- drill bit wear out and breakage
2. It’s easy to treat with after using and accord with environmental protection standard.
how to drill holes in a pcb board
X-ray drill of reference holes
Now we drill the holes for leaded components and the via holes that link the copper layers together. First we use an X-ray drill to locate targets in the copper of the inner layers. The machine drills registration holes to ensure that we will drill. through the centre of the inner layer pads.
Prepare the stacks for drillng
To set up the drill the operator first puts a panel of exit material on the drill bed. This stops the drill tearing the copper foil as it comes through the PCB. Then he loads one or more PCB panels, and a sheet of aluminium entry foil.
The drilling machine is computer-controlled. The operator selects the right drill program. This tells the machine which drill to use and the X Y co-ordinates of the holes. Our drills use air-driven spindles which can rotate up to 150,000 revolutions per minute. High speed drilling ensures clean hole walls to provide a secure base for good plating on the hole walls.
pcb drill hole size Use Tool
Resistors, disc caps, small diodes. ICs, transistors, reed switches, DIP switches, encoders, PCB relays, DIP sockets, LEDs. and SIP resistors will all fit fine in any hole greater than 0.0292".
Odd capacitors - 0.0394 or greater
Large wire diodes - 0.0394 or greater
small PCB switches - 0.0360 or greater
large PCB switches - 0.040 or greater
2N3771 TO-3 - 0.0595 or greater
Molex KK connectors - 0.036 or greater
7809 - 0.036 or greater
Drilling is a slow process as each hole must drilled . So depending on the drill size we drill a stack of one to three PCB panels together. We can drill holes down to 100 microns in diameter. To give you an idea of the size, the diameter of a human hair is about 150 microns. Drill change is automatic. The machine selects the drill to use from the drill rack. checks that it is the correct size, and then loads it into the drill head.
Once all the holes drilled the operator unloads the panels. from the drilling machine and discards the entry and exit material.
To achieve high quality results from laser micro machining. an greatest laser process must chosen. This starts with the choice of the laser itself. The process optimization comes from many parameters, including laser wavelengths, power, pulse fluence. and duration, and beam size. More considerations include work area to covered, acceptable process time. and handling the debris that generated by the ablation.
Each material to be laser micro machined has its own unique response. Thus, the processsteps must tailored for each material to processed. For example, one material might be much more impervious to heat than another. This will impact both power and pulse duration. For materials that are sensitive to heat buildup, an ultra-fast laser may be the only option.
Today’s multilayer PCBs feature both through holes and via holes. Through holes have diameters of 5mils or larger. and they are the deepest holes; hence they have high aspect ratios and are most drilled. Via holes are either blind vias or buried vias. Blind vias exposed to one side of the board and stop at the next underlying copper layer. Buried vias start out as blind vias. and are thereafter embedded in the multilayer PCB . connecting the two copper layers intermittent. in the multilayer PCB structure.
This accomplished by stacking multilayers together. The challenge for any via is to drill through the first copper layer. then drill through the underlying composite material. for example (FR4) without damaging the next copper layer. NSI Laser has developed a dual-head UV/CO2 system to address this exact challenge. The UV laser drills though the first copper layer, but only into the FR4. The CO2 laser is the most suitable for the FR4, and many other composite materials used in PCBs. The most unique feature with the CO2 laser light is that it stops at the second copper layer. The two lasers can operate on different parts of the panel PCB panel. reducing the drilling process time.
Creating via holes by conventional mechanical drilling technology . can only done by careful control of the height. The less the hole diameter, the more difficult mechanical drilling becomes. Another challenge is the aspect ratio (hole diameter to hole depth). Mechanical drilling is suitable for for deep holes with aspect ratios much larger than 1:1. But, when the hole diameter goes below 4mils (100microns), mechanical drilling becomes impossible.
By comparison, with laser drilling the smaller the hole diameter, the deeper the hole. This is valuable as today’s high density PCBs need smaller and smaller via holes. Thus, laser drilling has gaining in popularity. And this trend is growing as even higher density PCBs. become necessary to accommodate. even more electronic circuitry over a small area. Laser drilling offers a long pathway of opportunities with many more parameters. which can impact the drilling. Not until hole diameters. and PCB layer thicknesses approach the micron level will. today’s laser drilling reach its physical limits.
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