PCB vias are the electrical connections between layers. Vias are handled in the following ways:
PCB vias be covered:
Standard: Over-line holes must be covered, normal screen-printed solder resisted, no special plug-hole treatment;
Plug, part of the hole is not plugged, must accept the mouth of the yellow, but does not receive the ring exposed copper.
Project Document Requirements: Normal Solder Mask
PCB vias be covered and not filled
Standard: Over-line holes must be covered, normal screen-printed solder resisted, no special plug-hole treatment;
Plug, part of the hole is not plugged, must accept the mouth of the yellow, but does not receive the ring exposed copper.
Project Document Requirements: Normal Solder Mask.
PCB vias be covered in pad not covered the vias
Standard: The wire holes must be covered, the normal whole board should be silk screened, no special plug holes should be handled; some holes must be plugged, some holes should not be plugged, and the hole ring should be exposed to copper ±2mils after opening the window according to the customer’s documents.
Project Document Requirements: Normal Solder Mask
PCB vias be not covered
Standard: All the wire holes are opened for window processing; some oil holes and plug holes are allowed in the holes, but holes are not allowed.
There is ink on the ring.
Project Document Requirements: Normal Solder Mask
PCB vias partially be covered
Standard: The area must be covered with a guideline, normal screen printing and soldering, no special plugging;
Part of the hole in the area of the hole is covered and part of the hole is not plugged. The hole must be yellowed, but not
Receiver ring exposed copper.
Project Document Requirements: Normal Solder Mask.
PCB vias partially be filled
Standard: It is necessary to make a hole in the designated area wire hole; in this area, the via hole is not allowed to transmit white light (allowing green light to pass through), but part of the hole mouth must be yellowed, but the copper ring is not received. .
Project Document Requirements: filled vias film
PCB vias filling
We can produce 2 types of channel fills:
- Through hole filling resin
- Through-hole filling solder resist.
Through hole filling resin
Use a special machine ITC THP 30 to fill the special hole blocking resin TAIYO THP-100 DX1 heat-curing permanent hole filling material. The additional production steps required for resin via filling are performed before the 2-layer PCB production process. In the case of multiple layers, this is after pressing.
Process overview:
- Only drill holes that need to be blocked
- Clean: Plasma and brushing
- Black hole
- Apply dry resist
- Only through hole imaging
- Through Hole Plating (PTH)
- Stripping resist
- If you need to brush your teeth
- Baking: 150°C 1 hour
- Blocked by resin
- Baking: 150°C 1.5 hours
- Brush your teeth
After these steps, the normal PCB production process begins or continues: drilling other PTH holes, as well as a normal outer production process.
IPC-4761 is classified by protection type. This resin-filled Via fill process always results in “Type VII – Fill and Cap” vias.
Note: This via fill resin type is suitable for Via-in-Pad applications.
Through-hole filling solder resist
The solder paste to be filled is filled with the solder resist as the filling material. This Via Filling technology uses a drilled ALU plate to push common solder mask ink in through holes to the filler. This is a screen printing process. This is a step before the normal solder mask process.
important:
Filling is always done from the top of the board
Solder vias filled with solder mask always give a reverse solder mask pad, and dimensions are added by tool size + 0.10mm.
In other words, this type of Via Filling will always cover the solder mask at the top and bottom.
Note: This pass-through with solder mask type fillers is not suitable for use on pads.