Insight Technology – Finished PCB Thickness Tolerances

Definition of Tolerance for Manufacturing

Manufacturing tolerances are the amount of variation that is allowed in a measurement or other characteristic of an object.

Ref: Collins English Dictionary

We continue with our series on Understanding Tolerances on a PCB with our 5th guide:

Finished PCB Thickness Tolerances

As with all manufacturing processes the Finished PCB Thickness is influenced by various factors and thus there is a tolerance applied to the final thickness.

The process of manufacturing a PCB starts with the Base Materials (e.g. FR4) and these are available in various thicknesses.

Base material thicknesses have a tolerance as defined by the manufacture, for example for FR4 this is ±10%.

Added to this are the various other tolerances accumulated throughout the manufacturing process and this is where the Final PCB Thickness Tolerance is derived from.

We always comply with the IPC-A-600 Acceptability of Printed Boards (Industrial products) standards for PCB thickness measurement and tolerance.

The thickness of a PCB must be measured on an area of laminate that is free of Soldermask, copper and legend.

To read more on how and why these factors influence the Finished PCB Thickness, simply click on the button below.

 

 

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Insight Technology – Finished Slot Size Tolerances

Definition of Tolerance for Manufacturing

Manufacturing tolerances are the amount of variation that is allowed in a measurement or other characteristic of an object.

Ref: Collins English Dictionary

We continue with our series on Understanding Tolerances on a PCB with our 4th guide:

Slot Size Tolerances

The definition of a slot is “a narrow-elongated slit or aperture”.

We define a slot or cut-out as an aperture inside of the PCB profile but differentiate between them from a production point of view.

A slot is simply an elongated hole whereas a cut-out, is another hole of any shape, see image below.

Slots are very common on PCB’s and like holes they can be plated (PTH) or non-plated (NPTH).

The purpose of slots varies, the most common use is for component mounting.

Other uses are for cable pass throughs, ventilation, electrical isolation etc.

The Finished Slot Size like holes are influenced by various factors during the manufacturing process as below:

  • Type of Slot – Plated or Non-Plated.
  • Nominal Slot Size vs available tool sizes.
  • Tool Size Tolerance.
  • Tool Wear during use.
  • Slot Cleaning (Desmear).
  • The Plating Process and Copper Balance.
  • The Final Surface Finish of the PCB.

We use our knowledge of the PCB manufacturing process to ensure that the finish slot size is within the accepted tolerance.

We produce all our boards according to the IPC-A-600 Acceptability of Printed Boards (Industrial products).

To read more and view our video on how and why these factors influence the finished hole size on a PCB simply click on the button below.