Considerations for Making a High Temperature PCB

Considerations for Making a High Temperature PCB
5 min read
25 December 2022

There are a number of things to take into account before you begin if you wish to create a high-temperature printed circuit board. Substrates, laminates, die-attach materials, and the test procedure used in your lab oven are a few examples.

metals used in bond-pad and wire metallization

In electric drive power modules, a metallized ceramic baseplate is a crucial component. Compared to a typical ceramic baseplate, it performs better thermally. In addition, compared to a traditional ceramic base, a metalized baseplate offers more dependability and is more affordable.

Different metallizations and techniques may be utilised, depending on the application. This is particularly valid for bond-pad and wire metallization. The development and dependability of these linkages are influenced by a variety of circumstances.

The composition of the metallization material is one of the key elements influencing the compatibility of wire and bond-pad metallization. To discover which materials will work best in a specific application, numerous studies are now being conducted.

The compatibility of the metallization substance with the solder paste is a significant issue. For instance, alloys made of gold and aluminium are incompatible. Alkaline chemistries can also damage the metallization by penetrating through the wire bond pad sidewalls.

The bonding procedure might not work if the metallization and solder paste are incompatible. The issue of diffusion is another.

Considerations for Making a High Temperature PCB

Materials and laminations

Materials such as substrates and laminates determine the mechanical, electrical, and thermal properties of a PCB. They can be built specifically to fit the needs of a given application. The ideal material can be difficult to choose, though. Before making a choice, you might want to think about the temperature, frequency, and environmental requirements of your product. You can choose wisely with the aid of a qualified PCB maker.

Substrates and laminates can be made from a diverse range of materials. The most widely used ones include fibreglass, FR-4, and polyimide. These materials have outstanding dielectric qualities. Which of these solutions is best for you should be known if you need to design a high temperature PCB.

A PCB's surface layer is frequently made out of fibreglass. For circuits that need insulation, the material can also be employed as a hard, insulating substrate. It also makes a perfect board support.

The most typical substrate used for printed circuit boards is FR4. This substance is woven fibreglass cloth that has been coated in epoxy resin. It is flame-resistant and has excellent electrical insulating qualities.

Die-attach components

For attaching semiconductor devices to diverse substrates, die-attach materials are utilised. For instance, printed circuit boards, leadframes, multichip modules, and so forth. They provide connectivity, security, and dependability. Solder, conductive adhesives, and thermosetting adhesives are examples of common die-attach materials.

Low viscosity pastes with electrically conductive additives are known as conductive epoxies. These materials are simple to work with and have a wide range of uses. Fillers that transfer heat well, like alumina or boron nitride, are frequently used.

Die-attach materials that are electrostatically conductive can be processed using standard microelectronic machinery. At assembly companies, copper-filled adhesives are currently undergoing testing.

PCB applications requiring high temperatures can use die-attach materials. Materials like silver, nano silver, and copper can all be taken into consideration.

Ion scavengers and free radical inhibitors are present in a few of these compounds. Work can be done on thermally reworkable die-attach materials up to 250 degrees Celsius. As a result, the device can be attached to the die-attach layer before being significantly cooled.

Considerations for Making a High Temperature PCB

Oven testing in a lab 

Thermal testing of high temperature printed circuit boards (PCBs) is a crucial phase in the manufacturing process in the electronics manufacturing sector. This guarantees the components' long-term viability. Defects and faults can be found using this method, which is crucial.

Many times, thermal cycling tests are carried out in an oven equipped with a unique cycling mechanism. With this method, the oven's temperature gradients are fewer than two degrees Celsius.

Consider the specifications of a laboratory oven before buying one. The chamber's  dimensions and capacity are crucial considerations. They will have an impact on productivity and expense.

Other qualities to consider are consistency and a quick temperature recovery time. For great accuracy, these characteristics are essential.

A variety of setups, including Gravity Convection, Forced Air Convection, and Natural Air Convection, are available for lab ovens. There are various degrees of uniformity offered by each setup.

Better insulation is provided by double-wall ovens. Laboratory ovens frequently have interiors made of stainless steel. Galvanized steel or steel with a plating is also used in some versions.

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