PCB Manufacturing

Understanding Via in Pad Plated Over (VIPPO): An In-Depth Overview

Via in Pad Plated Over

What is VIPPO (Via in Pad Plated Over)?

VIPPO is short for Via in Pad Plated Over. It means the via should be plugged and plated over. These vias basically fall under BGA or SMT pads to minimize board area. In the VIPPO process, the vias fall on the middle of BGA pads. The PCB manufacturer will fill those vias with epoxy and plate them shut. After this process, the vias are hidden under the BGA and are not visible on the plain surface of the BGA. The VIPPO is also called POFV (plated over for vias).   

How did VIPPO Come into Being?

As time went on, more and more complex PCBs came into existence; earlier, we used computers that were very big in size. But nowadays, they have become more and more compact and also execute thousands of tasks. So, how is it possible? It is possible through the revolution in electronic systems. The size of the electronics product becomes smaller and to make a smaller electronics product PCB become smaller in size. So, the complex process of PCB comes into existence due to the revolution in electronics. 

VIPPO is the small part of that complex system of PCB, which allows Increased signal speeds and many connections with very little space. These vias fall under BGA and SMD components, which reduce the solderable area of components. To achieve full connection of pads, we use the VIPPO (Via in Pad Plated Over) process. In which the circuit board manufacturers fill those vias with epoxy resin and plated shut. 

Via in Pad Plated Over

When to use VIPPO?

Should we always use Via in Pad? No! There are some reasons to do Via in Pad pated over. So, if you doing a basic board and you don’t have a really high density of components, then you should not use Via in Pad. As the Via in Pad process is expensive and also has reliability issues like the temperature up-down effect on epoxy resin, which we fill in vias, sometimes Via in Pad may cause failure. 

So, if your board is not complex and has enough spacing, it is good to avoid Via in Pad. But, if you build a complex board that has a fine pitch BGA (smaller than 0.8mm pitch BGA), you should use a Via in Pad. For example, if we use fine pitch BGA, it does not have enough space between pads, so if we place via between those pads, then it is possible the solder of BGA pads can enter into that via hole and go to the other side of PCB and short something. 

So, VIPPO is a very good process to eliminate this type of issue. Some more complex BGAs like 0.4 mm pitch don’t have enough space to place via between BGA pads; in that case, there are no other options other than Via in Pad. 

Advantages and Disadvantages of Via in Pad Plated Over (VIPPO) 

VIPPO are commonly used in HDI circuit boards. Should use VIPPO  technology in our products? Before making the decision, we should know the pros and cons of this technology. Here are some advantages and disadvantages of the Via in Pad Plated Over (VIPPO) process. 

Advantages: 

  1. Via in Pad Plated Over process reduces the board area. (Via placed in the BGA pad so the area of that region is saved)  
  2. Via in Pad Plated Over process convenient in HDI and fine pitch BGA (0.8mm or lesser pitch BGA) board. 
  3. Conductive Via in Pad provides better conductivity of pad and heat absorbent properties, as the filling material used in this is conductive material and conductive material has good conductivity and heat absorbent properties. 
  4. Due to Via in Pad Plated Over process and technology, fine pitch BGA can set into the small size board.  
  5. Via in Pad (VIPPO) process allows the usage of smaller size of holes in PCBs.  

Disadvantages: 

  1. Via in Pad Plated Over (VIPPO) process is expensive. 
  2. Some time non-conductive epoxy filling can lead via failure due to excess temperature on that area. As the temperature increase the epoxy resin expand and this will cause the via failure. To eliminate this issue conductive via filling required. But the conductive via filling is 5x costlier than non-conductive via filling. 

VIPPO PCB

Different Kinds of Vias & Via Filling Technologies

To understand the VIPPO (Via in Pad Plated Over) better, we should have a basic understanding of vias. Via allows the connection from one layer to multiple layers, to achieve connections among electronic components. There are several basic different types of vias like through via, micro vias, blind vias, buried vias, and the Via in Pad Plated Over which is a special type.

Through vias: Through vias are the vias which fall on top to bottom of the PCB. It is mechanically drilled on the entire width of printed circuit boards. Basic PCBs normally use these vias. 

Micro vias: Micro vias are basically laser vias that allow connection from the top or bottom layer to one to two layers deep, depending on the PCB thickness and layer structure. 

Blind vias: Blind vias are micro vias which fall from the top or bottom layer to any inner layer of the PCB; they can be drilled with mechanical or laser. 

Buried vias: Buried vias allow connection between the middle of the PCBs. For example, a 10-layer PCB has L2 to L5 vias provided. It means those are buried vias.

To enhance the reliability of the PCBs, these vias may need to be plugged by via filling materials. The following are the different types of filling material for via filling and there differences.: 

Via Filling TypesSolder Mask FillingNon-conductive FillingConductive Filling
Suitable forPTH viasPTH vias, blind vias, buried viasPTH vias, blind vias, buried vias
CostLowHighMedium

 

Solder mask filling: Filling performed by fill the solder mask in the holes. Generally, this technique is not used in Via in Pad; it is only used for the through-hole vias filling. 

Non-conductive vias: Vastly used in the Via in Pad Plated Over technique is non-conductive material filling due to its cost-effectiveness. Only some cases like thermal conducting heat and signal. Conductive filling is only used in special types of PCBs which require heat management of components. The non-conductive material should always match the CTE of the surrounding laminate to avoid fractures as hating allows the non-conductive material to expand, and expansion causes a fracture between the pad and the hole wall. 

Conductive filling: Basically, Via in Pad filling is performed using conductive and non-conductive material filling. Silver and copper are used as conductive materials for the via filling. The heat absorbent capacity of conductive filling is very high; that is why special types of PCBs prefer conductive via the filling process as special PCBs have different types of components, and some components may require conductive via filling for heat absorption. The conductive fill of vias is much more expensive than non-conductive vias fill.

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