Burnt wax casting of electronic components 

Burnt wax casting technology: standards for electronic components

Burnt-wax casting (a process known internationally as Investment Casting or “lost-wax casting”) is the only method for producing housings and heat sinks for high-precision electronics. Unlike sand or chill casting, this technology makes it possible to produce parts with complex internal geometry and surface roughness Ra 1.6–3.2 microns without subsequent mechanical processing of critical areas. For the electronics sector, this means the ability to integrate liquid cooling channels directly into the aluminum or copper housing structure, reducing thermal resistance by 30-45% compared to composite solutions.

Our production line specializes in the production of batches from 50 to 5000 units in compliance with IT14-IT15 (GOST) tolerances and DIN ISO 8062 CT5-CT7 standards. We work primarily with aluminum alloys of the AK series (AlSi10Mg, AlSi7Mg) and copper alloys (BrAZh, BrKh), since these materials provide the necessary balance between electrical conductivity and mechanical strength when miniaturizing components. A key advantage of the method is that there are no mold parting lines, eliminating the risk of metal shavings getting inside sealed sensor housings or power modules—an issue we regularly encountered when using traditional injection molding on early projects.

Full production cycle: from 3D model to finishing

The process of manufacturing electronic cases using the lost wax casting method requires strict adherence to temperature conditions at each stage. Violation of technology even at the stage of assembling a cluster model leads to defects such as “underfilling” or gas holes that cannot be eliminated by post-processing. Below is a detailed algorithm that we use to ensure consistent batch quality.

1. Gating system development and 3D modeling.At this stage, engineers calculate the metal shrinkage for a specific alloy (for aluminum this is usually 1.3-1.5%, for copper - up to 2.1%). An error in calculating the shrinkage factor will result in the mounting holes not aligning with the printed circuit board. We use ProCAST software to simulate mold filling, which allows us to identify areas of metal stagnation in advance.Important:never design a gating system without taking into account the direction of heat dissipation; incorrect placement of feeders causes local overheating and warping of thin-walled housing elements.
2. Making wax models by injection.Wax copies of future parts are cast in silicone or metal molds under pressure. The wax temperature should be maintained in the range of 65-70°C; exceeding this threshold changes the rheological properties of the material and leads to a change in geometry. Each model undergoes visual inspection for flash.Common mistake:the use of recycled wax without preliminary filtration and degassing leads to the appearance of micropores on the surface of the casting, which is critical for sealed IP67 enclosures.
3. Assembly of clusters and application of ceramic shell.Wax models are assembled into a “tree” (cluster) and repeatedly dipped into a suspension of refractory filler (electrocorundum, zircon) and a binder. The process is repeated 6-9 times until the shell thickness is 6-8 mm. Drying between layers is carried out in controlled humidity. If you skip the drying stage of at least one layer, explosive vaporization will occur when pouring the metal, destroying the mold. We learned this rule after an incident in 2023, when a batch of 200 telecommunications equipment cases was rejected due to microcracks in the ceramics.
4. Burning wax and calcining molds.The clusters are placed in an autoclave, where the wax is removed with hot steam under pressure, and then the molds are calcined at a temperature of 850-950°C for 2-4 hours. This procedure not only removes carbon residues, but also activates the sintering of the ceramic material, giving the mold the necessary strength. An under-annealed mold may crack upon contact with molten metal at temperatures above 700°C. Control of residual carbon content (less than 0.05%) is a mandatory step before pouring.
5. Metal pouring and heat treatment.Molten metal is poured into heated molds either by gravity or under vacuum/pressure (to improve filling of thin walls). After cooling, the ceramic shell is removed hydraulically or by chemical etching. Parts are subjected to heat treatment (hardening + aging) to relieve internal stress. The final stage involves removing the sprues and shot blasting. Ignoring the aging regime for alloys of the AK7ch type leads to dimensional instability during operation under conditions of temperature changes.

Each stage is accompanied by input and output control. Finished products are checked against the drawing using coordinate measuring machines (CMM). For electronic components, we additionally carry out a leak test (helium leak detector) and measure the roughness of internal cavities. You may request a sample routing sheet for your specific product to evaluate the compatibility of your design with our capabilities.

Comparative Analysis: Investment Casting vs. Injection Casting

The choice of technology for producing electronics enclosures often becomes a stumbling block when planning a project budget. Many customers mistakenly believe that injection molding (HPDC) is always more profitable due to its high cycle speed. However, when working with complex electronics, where high precision and absence of porosity are required, savings at the casting stage result in huge costs for scrap and rework. Let's look at the key differences between the methods as applied to the production of electronic components.

In our practice, there was a case when a client tried to save money by ordering a batch of housings for medical sensors using injection molding. As a result, 40% of the batch had latent porosity, which only became apparent after sealing and pressure testing. The transition to lost wax casting technology increased the unit cost of production by 15%, but completely eliminated defects and warranty repair costs. If your project involves a series of less than 3000 units or requires non-standard radiator geometry, investment casting is the only correct technical solution.

Materials Science: Selecting an Alloy for Heat Sink and Shielding

Electronic components operate under severe temperature conditions, so the choice of housing material directly affects the reliability of the entire system. In the investment casting process, we work with a wide range of alloys, but for electronics there are three groups of materials that are most in demand. Understanding their properties will help you avoid design mistakes.

Aluminum alloys (AK7ch, AlSi10Mg, AlSi7Mg).This is the most popular choice due to the combination of low density and good thermal conductivity (150-180 W/mK). AK7ch alloy (silumin) has excellent fluidity, which makes it possible to fill thin radiator fins with a thickness of 1 mm or more. However, pure aluminum is difficult to solder without special surface preparation. For power electronics packages, we recommend the use of modified alloys containing titanium and boron, which increase ductility and reduce the risk of hot cracking during casting. It is important to remember that the thermal conductivity of cast aluminum is always lower than that of its deformable counterpart due to the characteristics of the grain structure.

Copper alloys (BrAZh, BrKh, CuCrZr).When heat dissipation requirements are extreme (such as in laser diodes or high-power microwave amplifiers), aluminum is not sufficient. Copper provides thermal conductivity up to 380 W/mK. Lost wax casting of copper is technologically more difficult due to the high melting point and tendency to oxidize. We use protective atmospheres (nitrogen or argon) during casting to prevent the formation of oxide films inside the casting. The main disadvantage is the high weight and cost. In addition, copper cases require nickel plating or tinning to prevent corrosion and ensure solderability of the leads.

Special alloys and composites.Electromagnetic compatibility (EMC) applications sometimes require packages with magnetic properties or a specific coefficient of thermal expansion (CTE) matched to ceramic substrates. In such cases, iron-based alloys or special aluminum composites are used. For example, an alloy with a CTE close to silicon prevents the chip from detaching from the body during cyclic heating. The selection of such material requires individual calculation and trial melting.

When choosing a material, consider not only thermal physics, but also operating conditions. If the device will operate in an aggressive environment (sea water, chemical vapors), aluminum cases will require high-quality anodizing (layer thickness 20-25 microns), which reliably adheres to the surface obtained using the lost-wax method. We conduct a spectral analysis of each heat and provide a test report along with the batch, which complies with the requirements of the ISO 9001:2015 standard.

Experience of Wuxi Kaisheng LLC: from energy to precision electronics

The in-depth expertise in working with non-ferrous and refractory metals required for the production of high-precision electronic housings is based on many years of experience in heavy industrial sectors. A striking example of such competence is the company’s activitiesWuxi Kaisheng Electric Power and Petrochemical Equipment Co., Ltd.. Specializing in the design and manufacture of complex heat transfer equipment, the company has developed unique expertise in the casting and processing of titanium, copper-nickel alloys (such as C70600), C46400 marine brass and high-alloy steels.

Wuxi Kaisheng's products, including titanium shell-and-tube heat exchangers, 316 stainless steel corrugated tube bundles and air coolers, are certified to the strictest international ASME and PED standards. These standards require impeccable sealing, resistance to extreme pressures and temperatures, and the highest corrosion resistance—qualities that are also critical for modern electronics operating in harsh environments. Quality control technologies developed in the creation of components for oil refining, shipbuilding and water desalination have now been successfully adapted for the production of miniature components. Using virgin alloys and complying with regulations to ensure the absence of secondary impurities allows us to offer solutions that combine industrial-grade reliability with the precision required by microelectronics.

Quality control and certification in accordance with GOST and ISO

In the electronics supply industry, trust is built on documents and repeatability of results. Our production is certified according to the ISO 9001 quality management system, which guarantees the traceability of each casting from the heat number to the specific operator. However, to work in the EAEU markets and export to Europe, it is necessary to take into account the specifics of industry standards.

For the electronics industry, the key document is GOST R IEC 60068 (a series of standards for testing for environmental influences). Our enclosures are tested for vibration resistance and thermal shock in accordance with these standards. Particular attention is paid to monitoring internal cleanliness. According to internal regulations based on the requirements of IPC-A-610, the level of surface contamination should not exceed 10 µg/cm² chloride ions. Exceeding this threshold leads to migration of metals and short circuits under voltage.

We use non-destructive testing (NDT) for critical batches. X-ray inspection (RT) allows you to identify hidden holes and cracks inside massive parts of the body that cannot be detected visually. Ultrasonic testing (UT) is used to check the integrity of walls in zones of thickness transition. Statistics show that the introduction of 100% X-ray inspection for critical batches reduces the number of complaints by 98%. One of our clients, an avionics manufacturer, was faced with gyroscope failure due to a microcrack in the housing that was missed by visual inspection. After the introduction of mandatory RT for all products in this series, the incidents stopped.

All products are accompanied by a quality certificate, which indicates: the alloy grade (with a breakdown of the chemical composition), the results of mechanical tests (tensile strength, relative elongation), hardness data and a leak-tightness report. For export deliveries to the countries of the Customs Union, a declaration of conformity with the CU TR is issued. We are also willing to audit your technical department to ensure our processes meet your internal quality standards.

Cost-effectiveness and delivery times

Calculating the cost of an order for investment casting consists of several variables: the complexity of the geometry, the weight of the metal, the type of alloy and the batch size. Unlike injection molding, where most of the cost is in expensive steel tooling, here the costs are more evenly distributed. The cost of a silicone mold for making wax models is 10-15 times lower than a steel mold, which makes the method ideal for development work (R&D) and small-scale production.

The production time for the first pilot batch is 14-20 working days. This period includes time for 3D modeling, making a master model, creating a silicone mold, casting wax, building up ceramics and the actual casting. For regular deliveries, the cycle is reduced to 7-10 days, since master models and technologies have already been developed. Logistics of finished products is carried out in compliance with the requirements for electronics packaging: antistatic protection, shock absorption and humidity control.

The minimum order quantity (MOQ) in our workshop starts from 50 pieces. This is due to the economic feasibility of starting a kiln and preparing ceramic materials. When ordering over 500 pieces, there is a progressive scale of discounts, reaching 20% due to the optimization of the layout of models in the cluster and the automation of some post-processing stages. We do not impose unnecessary services: if sand casting is sufficient for your project, we will be honest about this and redirect you to partners, but for precision electronics our offer will be the most cost-effective in the long term.

Frequently Asked Questions

What is the maximum dimensional accuracy that can be achieved in electronic package molding?

The standard accuracy of investment casting is ±0.05 mm for the first 25 mm of length and ±0.002 mm for each subsequent millimeter. For electronic components where slots for connectors are critical, we recommend placing a machining allowance of 0.2-0.3 mm only on critical bases, leaving the remaining surfaces in a cast state. Достижение более высоких допусков (IT12 и выше) возможно, но требует применения специальных керамических составов и увеличивает стоимость процесса на 30-40%.

Можно ли сразу после литья наносить гальванические покрытия на алюминиевые корпуса?

Да, поверхность отливок, полученных по технологии lost-wax, идеально подходит для гальваники благодаря низкой шероховатости и отсутствию пор. Однако перед нанесением цинка, никеля или хрома обязательна подготовка поверхности: обезжиривание, травление и цинкатная обработка (нанесение подслоя цинка). Без цинкатного подслой адгезия покрытия к алюминию будет слабой, и оно начнет отслаиваться при термоциклировании. Мы выполняем всю цепочку предварительной обработки на своем участке, гарантируя адгезию не менее 10 МПа по методу решетчатого надреза.

Какие ограничения существуют по минимальной толщине стенки корпуса?

Технологически возможно отлить стенку толщиной до 0.5 мм для алюминиевых сплавов и до 1.0 мм для медных. Однако на практике для обеспечения надежности и отсутствия недоливов мы рекомендуем проектировать стенки не тоньше 1.5-2.0 мм для алюминия и 2.5-3.0 мм для меди. Попытка уменьшить толщину ниже этих значений без изменения конструкции литниковой системы приведет к росту брака. Если ваша конструкция требует сверхтонких стенок, рассмотрите возможность использования разделенных деталей или диффузионной сварки.

Как долго хранятся силиконовые формы для восковых моделей?

Ресурс одной силиконовой фо рмы составляет в среднем 50-70 циклов инжекции воска, в зависимости от сложности конфигурации и агрессивности режима эксплуатации. После этого форма подлежит замене, что занимает 2-3 дня. Для долгосрочных проектов объемом свыше 1000 штук мы изготавливаем несколько дублирующих форм, что позволяет вести непрерывное производство без простоев. Хранение форм осуществляется в специальных контейнерах при комнатной температуре, исключающей деформацию.

Do you work with customer-supplied raw materials?

Мы принимаем давальческое сырье только при условии предоставления сертификата качества на каждую плавку и проведения входного спектрального анализа в нашей лаборатории. Однако мы настоятельно рекомендуем использовать наши материалы, так как мы гарантируем происхождение слитков (первичный алюминий/медь) и отсутствие вторичных примесей, которые могут ухудшить литейные свойства. Использование нашего сырья дает полную гарантию на механические свойства готового изделия в рамках договора поставки.

Производство электронных корпусов методом литья по выжигаемым восковым моделям — это сложный инженерный процесс, требующий глубокой экспертизы в материаловедении и термодинамике. Правильный выбор технологии на этапе проектирования сэкономит вам месяцы отладки и значительные финансовые средства. Мы готовы обсудить ваш проект, провести бесплатный анализ чертежей на технологичность и рассчитать точную стоимость партии.

Contact us today, чтобы получить консультацию ведущего технолога и запросить коммерческое предложение. Мы обеспечиваем полный цикл работ от 3D-моделирования до поставки готовых изделий с полным пакетом сопроводительной документации.Узнать больше о возможностях литья для электроники.