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Review – standard- and predefined build-ups

Standard and predefined build-ups

A few months ago, prepreg construction 2125 was removed from the available prepreg list of 370HR and IS400, 2 of our main FR4 material types.  We exchanged this prepreg type with construction 2116.  The thickness of 2116 differs from the 2125 with approximately 20 µm.  At first we assumed it wouldn’t have much influence on the final thickness of the boards.

Only, some of our standard build-ups contained many sheets of this type – our standard 6-layer board contained 7 of these –  which resulted in an unexpected final thickness, often too thick.

So, we had some work to do: checking out and updating all the build-ups our customers can chose from using the build-up selector.

We take the opportunity now to explain a bit more on how to read and understand the values we show in our PCB Configurator tool, referring to this subject.

The thickness label

This is the value we show in the selection box: Board thickness

This is not the final thickness of the board but a part of the name of a certain build-up.  We try to keep the thickness of the actual build-up situated in a range of +/- 10 percent of the label value.

If not, probably due to selection of high Cu thickness, it will be shown.

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The Total material thickness

Here we show the sum of all theoretical thicknesses of the used base material:

  • Core thickness
  • Prepreg thickness
  • Cu layers (inner and outer)

NO plated Cu thickness is included.

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The final board thickness

The calculated final board thickness is the material thickness + the plating thickness and the thickness of all additional layers, such as soldermask, legend… This calculated value should be within 10 percent from the measured value.

How to measure?

Measure on a spot without Cu, adding the thickness of the Cu from the outer-layers and the Cu plating and, if any, additional layers.

Details of the build-up construction

we show in the PCB Configurator tool can be discovered using the mouse-over function integrated in the buildup image.

You can see the core thicknesses, Cu thicknesses and the used prepregs appearing.

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Material selection

In Standard Pool, all our standard and predefined build-ups are constructed using these cores and prepreg types: check our download page with the list of used material types and their datasheets.

  • Core: 100, 200, 360, 710 µm (with Cu foil: 12/12,18/18, 35/35 or 70/70 µm)
  • Prepreg: PR1080 (70 µm), PR2116 (120 µm) and PR7628 (180 µm)
  • Other available core thicknesses: 510 µm, 1000 µm and 1200µm (stock not guaranteed and only used in “special Build-up”; add the build-up construction in your dataset in this case)

In RF Pool, we have 3 additional material types available. (Be aware that not all thicknesses have guaranteed stock)

  • RO4350B: 100, 168, 254, 338, 508, 762, 1524 µm (18/18)
    • Bold ones are used in standard RF buildups and are also available in 35/35 and have guaranteed stock
  • RO4003C: 203, 305, 406, 501, 813 and 1524 µm (18/18)
  • Prepreg RO4450F: 100 µm
  • I-Tera: 254, 360 and 508 µm (18/18)
    • Bold ones are used in standard RF buildups and have guaranteed stock

In IMS Pool, we selected Polyterm TC-Lam 1.3.: 1500/100/35 (Aluminum alloy/dielectric/Cu thickness)