IPC stands for Institute for circut board. IPC is followed by the tag – the Association Connecting Electronics Industries. Now, IPC is referred as Institute for Interconnecting and Packaging Electronic Circuits to take standards to bare boards, packaging and assemblies. This is a standard defined and followed by PCB designer and manufacturers for design, pcb manufacturing and assembly and packaging. If these standards do not comply with these or with equivalent requirements, the acceptance criteria shall be defined between the customer and supplier. In general, IPC standard III is specified for High Performance Electronic Products. These Includes products where continued high performance or performance-on-demand is critical, equipment downtime cannot be tolerated, end-use environment may be uncommonly harsh, and the equipment must function when required, such as life support or other critical systems. This is mostly used into multilayer PCB as they are mostly complex.
When this standard is contractually required following are the main points which are taken into accountability just for checking:
1. Procurement as agreed and documented between customer and supplier.
2. Master drawing or master assembly drawing reflecting the customer’s detailed requirements.
As we impose IPC-III standards into a PCB multilayer fabrication, we have to check design, fabrication, manufacturing, soldering circuits, etc, following are key points required for monitoring.
Primary side: This is mainly the side with most of the components and complex circuit. The compliance is associated with interconnecting structure (layers, components, etc) and packaging of PCB.
Secondary side: This is a side normally opposite to primary side. In case of through hole technology, it is referred as soldering side.
Solder source side: The solder source side is that side of the PCB to which solder is applied. The solder source side is normally the secondary side of the PCB when wave, dip, or drag soldering are used. The solder source side may be the primary side of the PCB when hand soldering operations are conducted.
Solder Destination Side
The solder destination side is that side of the PCB board that the solder flows toward in a through-hole application. The destination is normally the primary side of the PCB when wave, dip or drag soldering is used. The destination side may be the secondary side of the PCB when hand-soldering operations are conducted.
Cold Solder Connection: This is greyish porous solder, which is caused due to impurities in solder.
Electrical Clearance: spacing between non-common un-insulated conductors is referred to as minimum electrical clearance. It is defined in the applicable design standard or on the approved or controlled documentation. Insulating material needs to provide sufficient electrical isolation.
High Voltage, Intrusive solder, leaching, Mencius (Sealant or encapsulate on a lead, protruding from the seating plane of the component), inspection, verification, etc are also important compliances which should follow the IPC-III standards to avoid any conflict.
In case of multilayer routing, while the routing target is:
• Wire lay is parallel to the axis of the bundle with no crossover.
• Coaxial cable secured with tie wraps/straps.
It can be expected to Wires twist and crossover, but bundle is uniform in diameter. The defect arises as: Bundle is not uniform in diameter or excessive crossover is there.
Bend radius us also asn important parameter to be measured for defects. Bend radius is measured along the inside curve of the wire or wire bundles, Inside bend radius does not meet the criteria, then there is again conflict.