Copper wrap is a continuous deposit of plated copper that is deposited within the barrel of the hole and extends onto the surface of the PCB (or the surface of the innerlayer core if part of a HDI structure) by a minimum of 25 um. For class 2 demands the thickness of the surface deposit of the copper wrap is minimum 5um, but for class 3 demands this will vary dependant upon where this feature is situated within the build. Please consult our technicians for further information on class 3 demands.

TERMINOLOGY Archives

Q: What is the "aspect ratio"?

The relationship between the diameter of the hole and its length. When a manufacturer states that their production has an “aspect ratio” of 8:1 it means, for example, that the hole's diameter is 0.20 mm in a 1.60 mm thick PCB. For HDI structures, the aspect ratio for microvia is limited to 1:1, but 0.7-0.8:1 is preferable to easy the plating.

Q: What is meant by a thermal pad?

For SMD components, especially the smaller ones, use thermal relief pads to simulate the same thermal mass on both terminations to avoid tombstoning, twisted components or even in worst case broken components. For hole mounted (HMD) components we use thermal relief pads on inner layer planes to help wetting in the hole barrel. Formulas for thermal relief pads can be found in IPC-2220 series.

Q: Should approval for addition of teardrops be added in the procurement documentation?

According to new IPC-6012D section 3.4.2 it is allowed to add teardrops to the tracking when boards shall comply to classes 1 & 2. If you do not want tear-drops, highlight that in the procurement documentation. But add enough annular ring.

Q: What is back-drilling technology?

For high frequency applications we need to prevent signal loss and therefore when one layer is connected to another and the signal travels from one layer to another it must pass through a via hole that connects the layers. If the signal is to pass layer one to layer two in a 20 layer board, for example, then part of the via structure is considered as ‘excess’ and for this application it is best to remove the excess copper from this hole as it acts as an antenna and impacts the signal. We use back-drilling (controlled depth in z-axis) to drill out the ‘excess’ copper in the hole in order to get better signal stability. Ideally the shorter the stub (‘excess’ copper) then the better the result. Back-drill size should be typically 0.2mm larger than corresponding via. BACK DRILLING / COUNTER BORE (mm) A: Depth tolerance +/-0.20 +/-0.15 +/-0.10 B: Min. remain thickness and tolerance 0.5+/-0.25 0.35+/-0.1 0.3+/-0.1

Q: What does “UL marking” mean?

Security is key in the electronics industry. It is vital that users can rely on the finished product when considering factors such as fire and electrical safety, which means that both the PCB and the materials they contain must measure up to the highest standards. To ensure that the boards do conform, it has become common practice to UL certify the constituent materials or the PCB itself. To start with, what is UL? The letters UL stand for Underwriters Laboratories. Why is UL recognition important? UL is a major authority and enjoys a good reputation in the PCB industry. The company is irreplaceable for testing fire and electrical safety. Customers from around the world – including well-known Chinese companies – demand factories that can achieve UL recognition. Having UL recognition is therefore very important for PCB factories to produce secure boards and be able to access the international market.

Q: What is thermal resistance?

In this video you can learn about thermal resistance and thermal conductivity. https://youtu.be/baNnMwHstMQ

TERMINOLOGY

What is thermal resistance?

What does “UL marking” mean?

What is back-drilling technology?

Should approval for addition of teardrops be added in the procurement documentation?

What is meant by a thermal pad?

Is there more than one type of controlled impedance?

What is controlled impedance?

What is a copper coin PCB?

What is copper wrap?

What is the “aspect ratio”?