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How to order PCBs for manufacturing

Surely you have ever wondered what TG130-140 means, what choice to choose between HASL with lead, HASL lead free, immersion in gold, hard gold, OSP, or what to choose between tenting vias, plugged vias or vias not covered, etc. 

After all the questions you ask us by email, we have written this post to try to clarify all the questions that normally arise when requesting to manufacture your printed circuit boards. In addition, we will update this entry if we receive new inquiries, so do not hesitate to ask us.

 

PCB capabilities

An important step before starting to design our PCB is to take into account the requirements and capabilities of the manufacturer. It is worth spending a bit of time at the beginning, and thus not having to make modifications to our design once finished to adapt to the capabilities of our PCB manufacturer. At pcbGO we offer you this information on our manufacturing capabilities page.

 

Getting started

To begin, we will take as a reference our instant quote form, in which you will know the cost of your PCBs immediately. We know that time is worth a lot, that's why we believe that we should not make you wait for you to receive a quotation by email several hours or days after each time you want to place an order.

 

Type of board

The first option we have available to choose is how our PCBs will be manufactured. If we choose "Single pieces" they will be manufactured individually. If on the contrary we choose "Panel by Customer" or "Panel created by pcbGO" means that there will be a matrix formed by one or different PCBs. This option is the most appropriate if these boards are subsequently assembled.

If we have chosen the option to panelize, we will have to choose the route process. This procedure will be carried out in the contour of each board, so that later we can separate them. We have "Panel as V-Scoring", "Panel as Tab Route" or "Both, V-Scoring & Tab-Routing". The option "X-out Allowance in Panel" lets us indicate if we want to allow the existence of defective boards in said panel.

If we choose "Panel created by pcbGO", we must also indicate if there will be edge rails and how we want the PCBs to be distributed in the panel (eg. 4x3), the size of the break-away rail, how many panels will be manufactured and the total number of boards.

If you want to know how to order your PCB panel online click here.

 

Different design in panel

Here we will indicate how many different designs there are in the panel. If the panel has different designs, an extra charge may be added.

 

Size

Width per maximum length of each individual PCB in millimeters.

 

Quantity

Number of individual PCBs to be manufactured.

 

Layers

Number of layers our plate will have. In case you have 4 or more layers, it is advisable to indicate which Gerber file corresponds to each layer. Here you could know more about multilayer PCBs.

 

Material

It is the type of material that will be used for manufacturing. You can choose between FR-4, aluminium or rigid-flexible.

 

TG

In case the chosen material is FR-4 or rigid-flexible, it will be necessary to indicate the value of the transition temperature of the PCB glass, called TG. This value indicates the temperature at which the material of the board begins to transform, changing its state from solid to liquid if the operating temperature exceeds this value. About this we will write an entry to go into detail.

 

Thickness

Indicates the thickness of the board, that depending on the value may have an extra charge. The thickness most used is 1.6mm.

 

Min track/spacing

It is the minimum width of the tracks and the space between tracks. The unit of measurement is one thousand (or mil, particularly in the United States), which corresponds to one thousandth of an inch and is equivalent to 0.0254 millimeters.

 

Min hole size

It is the diameter of the smallest hole in the plate. This includes holes for through-hole components, vias, etc. Here you can read how to design drilling holes for your PCBs.

 

Solder mask

As the name suggests, it is the colour of the solder mask. Some colours may have an extra cost.

 

Silkscreen

This is the colour of the silkscreen.

 

Gold fingers

Gold fingers are connectors plated in gold in the edges of the PCB. They receive this name because of their resemblance to the fingers, since they are long and narrow.

Some qualities of the golden fingers are:

  • They must be hard to allow the board to be inserted into a connector easily.
  • They are an excellent conductor that makes the connection very good.
  • They must also be very flat and smooth to allow easy insertion.

They are usually used in video cards, network adapter cards, etc.

 

Surface finish

There are many types of surface finish for printed circuit boards, which vary depending on the needs and performance of each board.

  • HASL (Hot Air Leveling) and HASL without lead: it is the most used. It consists of immersing the PCB in a pot with molten lead-tin alloy and then removing excess solder with hot air. It is the most economical option, but it is not suitable for fine-pitch components. If your PCBs require RoHS, this is not the best option. For this, you should consider the HASL option without lead.
  • Immersion gold (ENIG): it is becoming the most popular option in the industry due to the growth and implementation of the RoHS regulation.
  • Hard gold: consists of a layer of gold plated on a nickel barrier layer. Hard gold is extremely durable, and it is especially applied in areas of high wear, such as on the fingers of the edge connector and keyboards.
  • OSP (Organic Solderability Preservative): protects the copper surface from oxidation, since a very thin protective layer of material is applied over the exposed copper. As it uses a water-based organic compound, it is also extremely environmentally friendly compared to the other common lead-free finishes.

 

Via process

You can choose between the following options:

  • Tenting vias: this means covering the annular ring and the via hole with a solder mask. This is the easiest and cheapest process.
  • Plugged vias: this process is covered and sealed with a mask and the annular ring is covered. This is commonly used to prevent the solder from coming off the SMD pads during assembly.
  • Vias not covered: in this case, the vias are not covered, they are exposed and the surface finish is applied to the via. For the production phase, it is better to cover the vias.
An example of the different types of vias
Types of different vias

 

Finished copper

Copper with a thickness of 1 oz/ft2 is the most common and standard copper weight since most PCBs are manufactured for low power applications. Copper with a thickness of 2 oz/ft2 is usually more than what is required, while it costs much more, and copper of 0.5 oz/ft2 may not be enough, especially for the ground planes that must withstand higher currents. Therefore, copper with a thickness of 1 oz is usually the most appropriate option to meet the requirements taking into account the budget and design.

Copper layers of 3 or 4 oz are usually used mostly in PCBs for military applications or in situations where high current is required. In this post we explain you how to choose the copper weight of a PCB.

 

Finally, if you want to know how to optimize the cost when manufacturing your PCBs, you can see it in this post.

And with this we finalize this post. We hope you send us all your questions in the comments.

If you liked it, you can help us enormously by sharing it on Facebook, Twitter or Google+. Even you can subscribe to our newsletter!

 Roberto
 2018-04-27 10:11
 Help    Engineering   
First post
How to optimize cost when designing and manufacturing PCBs
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