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mar 31 2021
Datum: den 31 mars 2021 11:51
The capped vias technology with hole filling with resin aims to increase the density of the interconnections in printed circuit boards by using the space occupied by through holes as SMD assembly points. This technique consists in filling the holes after plating them, with copper thicknesses on the walls, normally >25µm, and, in any case, defined with the customer.
The resins adopted for "filled and capped vias” have specific insulation properties and dimensional variation with temperatures, they are treated with heat for the relative polymerization and consequent hardening, and, subsequently, are first planarized and then covered with a layer of copper with a thickness of at least 15µm.
This technique can be applied for the realization of different types of printed circuits and with multiple application variants which for this reason are in strong expansion:
- pads used for µBGA, "ball on via technology" and SMD assembly: "Via in Pad Assembly Technology"
- pads used as test points, "Via in Pad Test Technology”
- heat dissipation pads under the cases of the components for "heat management”
- SBU - sequential build up" construction with laser stacked holes on buried holes treated as capped vias
The fundamental operations for filling the holes with resin are carried out in two distinct phases: in the first, the holes are filled with variable pressure and vacuum to allow perfect filling of the holes without the risk of gaps in the resin, while, in the second phase, a surface cleaning of the panel is performed to eliminate the excess resin, facilitating its subsequent planarization.
Whatever the final technology chosen, after complete polymerization, the resin is removed by a mechanical brushing action, called planarization, which can be performed with specific machines that work with cup brushes or with horizontal brushing machines.
The target is to remove the excess resin and create a uniform surface: this operation is a prerequisite for the subsequent over-plating of the filled vias with copper to allow ideal soldering of electronic components. (inserisci disegno).
The knowledge of "capped vias" technology is fundamental today to create compliant pcbs to market and regulations standards required, especially relating to the growing HDI technology demand.
feb 25 2021
Datum: den 25 februari 2021 16:08
This trend is imposed by the market demand for increasingly portable devices, therefore of low weight, and capable of integrating many functions: the real challenge is to reduce the size of the devices, miniaturizing them, and, at the same time, to increase their performance.
The target can be reached basically by working on the structure of the printed circuit board by increasing the density of the components on the surface and the number of connections between the layers that make it up: this need has therefore led to the birth and diffusion of " HDI - High Density Interconnection" structures.
All circuits with pitches’ density per surface with values greater than 20 pitches/cm² greater than traditional printed circuit boards (PCBs) are defined as high interconnection density PCBs (HDI). This therefore results in smaller size for design parameters such as tracks less than 100 ?m/4mils wide, laser holes with a diameter less than 150 ?m/6mils and pitches with a diameter less than 400 ?m/16mils.
feb 9 2021
Datum: den 9 februari 2021 07:52
In particular, we have highlighted that the moisture absorbed by the base material can generate delamination during the assembly of PCBs.
With this second article, relating to the risks generated on PCBs by the presence of humidity, we deepen the subject and deal, in particular, with the impact of humidity on the Tg of the base materials and the consequences on the quality of PCBs and PCBAs.
The Tg of a polymeric material (laminates and pre-impregnates are partially made of resin) represents the temperature value at which the glass transition begins which we could define as the temperature at which the resin changes its mechanical characteristics starting to soften: for this reason it is important to choose the base material in relation to the expected conditions of use of each PCB.
To read all the article, click here
jan 25 2021
Datum: den 25 januari 2021 07:39
nov 28 2020
Datum: den 28 november 2020 23:00