PCB assembly for electronics manufacturing of medical devices

Introduction

Developing a medical product with electronics involves a wide range of companies working seamlessly together, including the product owner, designers, consultants, regulators, and the manufacturer. While medical devices involve innovations in sensors and algorithms for processing collected data, the beating heart of the device is a Printed Circuit Board (PCB) assembly.


The PCB assembly connects sensors to the cloud, manages displays and the user interface, stores backup data in local memory and safely controls the administration of any actuating outputs, such as radiation, heat, lasers and so forth. Reliable operation of the electronics in a medical device is thus critical to successful product development.


This article highlights some of the key issues that product developers should think about when considering how best to develop and manufacture the PCB assembly.


PCB Assembly

The most important consideration for medical device PCB assemblies is the quality of the soldering used in a PCB Assemble. The PCB is a non-conductive substrate made from a resin laminate with copper signal traces interwoven, often in several connected layers. The electronic components such as microprocessors, resistors, capacitors etc are then mounted on the board, usually with a high-speed pick and place machine.


The type and amount of solder used to attach and electrically connect the components to the PCB can vary. The IPC-A-610 standard sets out the options and includes three classes of quality relating to the Acceptable Quality limit, acceptance/rejection of individual PCB assemblies.


IPC Class 3 relates to “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 for life support or other critical systems”.


A key difference between Class 2 and Class 3 is the level of inspection undertaken to assure the necessary level of quality. For Class 3, each soldered connection is inspected to ensure the right level of soldering has been applied.


It is important to note the difference between IPC classification and the general medical device classification system, which unfortunately has a similar number of levels and should not be confused. In Australia, the TGA classifies medical devices 1 to 3 (including subclasses), according to the level of risk to the patient and operators of the device. In the US, there a similar number of classifications but they are based on a predicate system whereby devices are classified by its similarity to other devices that have previously been assessed.


The classification of the medical device will thus guide the choice of IPC quality required for the device. The main thing to consider for PCB assembly is to ensure you contract electronics manufacturer has the quality systems in place to deliver the required level of quality control.


Quality Systems

While many electronics manufacturers have an ISO 9001 quality system, medical device manufacture requires a higher level of quality set out in the ISO 13485 standard. The product developer usually relies on the contract electronics manufacturer to help it comply with the requirements of this standard. If the contractor does not have ISO 13485 then the compliance burden on the product developer is much greater.


There are many things involved in implementing an ISO 13485 system but as a minimum, make sure your electronics manufacturer has the following:

  • An integrated software system to seamless move information to where it is needed and efficiently handle the necessary documentation

  • An effective risk management system to identify and address issues, such as component availability, before they impact delivery

  • Inspection systems for adherence to the Acceptable Quality Limit

  • Traceability systems for tracking where every component has come from and went to.

Traceability is particularly important, as the entire supply chain of medical devices must be assured. Electronics manufacturers must not only track components within their facility but must also audit suppliers to ensure components have been traced from their original creation. For most medical devices, implementing traceability at the batch level is sufficient.

However, for applications where correct operation of the device is critical to sustaining or supporting a patient’s life (Class III), product manufacturers may ask for traceability at the individual board/device level. If this is required, check to ensure your electronics manufacturer can manage this laborious process in an automated way.


Testing and box build

Once the PCB Assembly has been manufactured, it still must be electrically and functionally tested, then assembled into the final housing. Many product developers overlook this vitally important step in their initial planning and costing of the product. Development of a test jig for advanced medical devices is an entire project in its own right, with many of the same rigorous quality controls as required for the device itself.


For medical devices, the testing, assembly, labelling and packaging procedures need to be rigorously documented, with revision control, along with any reporting requirements and any certificates that need to be issued. These reports usually need to be supplied to quality auditors such as an ISO certification body and may be used to validate both the manufacturing process or the product itself.


Process reports include records of environmental conditions of virtually any parameter during the manufacturing process, such as the temperatures in the reflow ovens through to humidity levels at which components were stored. Product reports cover the result of tests, including automated optical inspection reports and x-ray results.


There are many more aspects to optimising PCB assembly that apply to products in all industries, not just MedTech. You can read more about this by downloading our 44 point Electronics Manufacturing Checklist.

Circuitwise Electronics Manufacturing, Sydney Australia

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