FREQUENTLY ASK QUESTION
At Venture Electronics, clients asked us a multitude of questions. Below we have listed some of the most common questions we receive and those aspects which are common discussion topics. Hopefully, this list will help, be a reference source, or perhaps the trigger for a more in-depth discussion.
According to the IPC-2226 definition, it is a hole diameter of up to 0.15mm. It is usually a blind hole drilled with a laser.
It is a hole that runs from an outer layer but not through the entire PCB. These holes can be drilled mechanically or using laser technology.
That is a hole that runs between one or more inner layers. They usually are mechanically drilled.
The graphic below shows the different structures available for mass production and prototype.
That varies from manufacturer to manufacturer, but in general, you can say that the majority of manufacturers can produce them as follows:
A = 0.15 mm
B = 0.20 mm
C = 0.30 mm
For tighter constructions, please ask one of NCAB’s technicians for advice.
It represents the relationship between the diameter of the hole and its length. When a manufacturer states that their product 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.
The thicker the copper base, the wider the track should be. One rule of thumb is that with an 18 µm copper base, the track should not be narrower than 0.1 mm (4 mils), and with a 105 µm copper base, the track should not be more limited than 0.25 mm (10 mils).
The preferred type of plugging for the standard product (not including capped via hole) is IPC”4761 type VI filled and covered, with the target being complete fill. The image below shows type VI with liquid solder mask coverage. Single-sided plugging is not recommended (including type II tented and covered) due to concerns over entrapment of chemistry or the likelihood of solder balls being present with HASL finishes (LF and SnPb).
No, not necessarily. There are many factors to be considered. e.g., how many layers, the width, and the general complexity of the PCB. Some research has shown that a material with a “standard” Tg value performs better than some materials with a higher Tg value. Note that even with “leaded” soldering, the Tg value is exceeded. What is of most importance is how the material behaves at temperatures above the Tg value (post-Tg).
A more excellent Td value is preferable, especially if the board is technically complex and exposed to several remelting solderings.
Dicy (Dicyandiamine) is by far the most common hardening system for this epoxy; it usually gives a Td value of about 300–310°C, while a “non Dicy,” i.e., a Phenolic Cured Epoxy has a Td value of about 330–350°C and can therefore better resist the higher temperature.
CAF (Conductive Anodic Filament) means that there will be an electrochemical reaction between the copper anode and cathode, which may result in an internal short circuit in the material.
No, but for practical reasons, PCBs with lead-free HASL should be marked stating their RoHS compatibility due to the risk of confusion with leaded HASL.
No, not necessarily. The RoHS directive prohibits two types of bromide flame retardants. The PBB (polybrominated biphenyl) and the PBDE (polybrominated diphenyl ethers). A bromide flame retardant called TBBP-A (tetrabromo-bisphenol A) is typically used in PCBs.
There is no “best surface”; all surfaces have pros and cons. Which one you should choose depends on many factors. Please consult our technicians or review the information on surface finishes within this website section.
No, the investigation found that it is, for practical reasons -not possible to ban.
Reactive flame retardant is chemically bound to the epoxy and will not dissolve at waste deposit.
It is hard to give a precise answer, but we have made tests on Dicy and noisy-material with up to 22 reflows, four of which have a peak temperature of 270C°. The stress after 22 reflows is considerable, but all connections stick together. We recommend choosing a high Tg material with more than six layers and thicker than 1.6mm. The picture to the right shows a nondictatorial, and the left photo is a Dicymaterial.
SMD means surface mount device and can cover such components as resistors, capacitors, and transistors. Such elements do not have legs for through-hole assembly and can be very small – down to 0.41 x 0.20mm (footprint).
QFP stands for quad plat package, and this is a surface mount integrated circuit package with leads on all four sides.
The image below shows a basic QFP and the associated footprint on the PCB.
BGA stands for ball grid array, and this is an integrated circuit package with one face covered (or partly covered) with pins in a grid pattern. These pins conduct electrical signals from the integrated
circuit to the printed circuit board (PCB) on which it is placed. In a BGA, the solder balls stuck to the bottom of the package replaced the pins.