In PCB manufacturing and assembly industry, we often hear low volume PCB manufacturing, high volume PCB manufacturing, high-mix low volume PCBA and high volume low-mix PCBA concepts.
If you are looking for the above PCB manufacturing & assembly service, you can contact us directly to get a quote. On the other hand, if you don’t know much about the above, this article will introduce you in detail.
High-mix low-volume PCBA products are commonly used for industrialized products, such as medical, telecom infrastructure, industrial control, aerospace, military, and other fields, with many product types and SKUs. However, a single kind of production volume is relatively small.
There are no clear standards of the complexity and quantity of High Mix Low Volume PCBA. those applications are for business customers mainly, especially the application of medium and large equipment. Mostly, the demand or order frequency of these PCBAs is to be placed on a quarterly basis, and the quantity of each order is usually hundreds of pcs level. In addition. The demand for each electronic product will be composed of a series of PCBAs, such as the main control board, power board, connection board, power board, LED board, communication board, etc.
Complex Manufacturing Process
High-Mix Low-Volume PCB Assembly requires multi-manufacturing technologies, including SMT, DIP, wiring harness assembly, case assembly, etc. Regarding DIP, There are two solutions: automated equipment such as selective wave soldering machine and manual inserting. But for most industries, a selective wave soldering machine is not an economical option. So far, manual inserting is still the best solution for most industries. But whatever automated or manual work, the result should meet the below criteria:
– A certain ratio of components needs performing process before production.The height of the lead on the welding surface of the insert components is 1.5 to 2.0 mm, the solder joints should be smooth without burrs and slightly arc-shaped, and the solder should exceed 2/3 of the height of the soldering end but should not exceed the height of the soldering end.
– Height of solder joints The height of solder climbing pins should not be less than 1mm for a single panel, not less than 0.5mm for a double panel, and need to penetrate in.
– The shape of the solder joint It is conical and covers the entire pad.
– Solder joint surface Smooth and bright, no black spots, flux and other debris, no spikes, pits, pores, exposed copper, and other defects.
– Solder joint strength Fully wetted with pads and pins, without false soldering.
– Cross-section of solder joints The cutting lead of the components should not be cut to the soldered part as much as possible, and there is no cracking phenomenon on the contact surface between the pins and the solder. There are no spikes and barbs at the cross-section.
– Connector welding: The Connector needs to be inserted into the bottom board, and the position and direction are correct. After the connector is welded, the bottom floating height should not exceed 0.5mm, and the seat body should not be skewed beyond the silk screen frame. The rows of needle seats should also be kept neat, and no dislocation or unevenness is allowed.
So a large number of trained employees is needed in the DIP process. For some mega EMS, the DIP procedure is a challenge they cannot complete. Cause it needs a high standard quality control system and spot management capabilities to reduce human errors.
Additional Engineering Requests
In addition to general X-RAY, AOI, ICT, FCT testing, HMLM PCBA always have additional request on testing and engineer capability, these are:
Some of the above requests require customized equipment, some require joint development with customers, while the rest need the factory to have strong software systems like MES.
Supply chain challenges are everywhere, and many supply chain costs appear as hidden costs rather than direct costs：
There are diverse materials in the BOM of High-Mix Low-Volume PCBA, including electrical and electronic components, connectors, cable and wire harnesses, mechanical and plastic parts, etc., and the volume varies greatly. Each type of material needs to have corresponding incoming inspection standards and storage methods. It requires several times more storage space than ordinary consumer electronic products. automated kitting methods often do not work. More, The warehouse laborers need to reserve scrap for each PCBA build because the scrap ratio of Hign Mix Low Volume PCBA is much higher than that of High Volume Low Mix PCBA; at the same time, there are a large number of mantissa items that need to be counted and managed.
An electronic product is assembled from a series of PCBAs. It is necessary to consider the cadence issues between sub-level PCBAs. Even though there are individual PCBAs with simple requirements in the list, such as LED light PCBA, the overall schedule can’t be expedited easily. Customers still evaluate the manufacturing cycle time according to the full series.
Material cost is divided into two types; the purchase unit price determines the direct material cost. Because the purchase batch of High Mix Low Volume PCBA is usually not large, it isn’t easy to obtain a competitive price, In the case of direct cost, the unit price of the material may be acceptable. But when we count the total inventory amount of all raw materials purchased for this batch, that is, the hidden material cost, we may be shocked by the total amount purchased for that batch build. There is a MOQ minimum order quantity. For example, for a single FPGA chip mounted on PCBA of equipment, the product demand is 500PCS, Unit price is $10, but we have to buy a reel 2000PCS, rest of 1500PCS will become slow-moving inventory, with amount is $15000, and have to wait at least several quarters to consumed. The worst may be excess or obsolete after demand changes.
Low Manufacturing Efficiency
The production line for High-Mix Low Volume PCBA is completely different from HVLM PCBA’s. In the latter’s production line, planning managers do not need to issue production change orders frequently, and the production takt remains constant over time. It is not feasible for a factory producing HMLV PCBA to arrange a few parallel lines for each PCBA in a series of Products. A dynamic balance must be maintained between switch line efficiency and production efficiency; Since each manufacturing procedure of each PCBA is variant on takt, the arrangement of the production line must create sufficient flexibility to deploy resources and switch products to build enough PCB Assembly for a whole series. But overall, the output ratio is still low compared to High-Volume Low-Mix PCBA.
EASHUB’s factories have the ability and experience to produce High-Mix, Low-Volume PCBAs. Our standard manufacturing procedures are incoming material inspection, warehouse, and storage management, material kitting, SMT and reflow welding, DIP and Wave sold welding, ICT, FCT, conformal coating, wire harness assembly, and box assembly. Our factories have dozens of SMT lines, DIP wave solder lines, X-Ray and Online AOI, and a few box assembly lines.
We also have a selective conformal coating line and manual coating line, an aging chamber, and a test lab. Our testing equipment is majorly from global leader equipment suppliers like Teradyne, Takaya, and NI Software. Lastly, our strategy factory also has barcode scanning and traceability systems SAP and MES system.
Eashub’s production method is more flexible and efficient. First, we do not configure redundant production lines to solve the simultaneous production of multiple PCBAs. Each line and section is produced as much as possible. Still, through our effective training, in the back-end process, Our employees own the capability of handling multiple processes, such as component performing, DIP, box assembly, and back-end welding, which makes our technicians in the back-end more flexible. A few of our production lines use the cell line production method to level the rhythm between each procedure and ensure that the production process can use the shortest time and the least personnel changes to minimize the loss of line change. We recommend suitable automated production solutions, such as selective DIP machines for some large-scale and mature products.
Unlike other EMS, we will calculate the unit price and inventory costs for each batch of High-Mix, Low-Volume PCBA. We had developed a self-owned smart sourcing tool; In the PCBA Prototype stage, we will purchase by prototype need rather than buying the whole package. After mass production, we will simulate the inventory cost of the product life cycle based on the frequency of demand and the quantity of a single batch, then purchase based on MPQ to achieve maximum sales with the minimum hidden inventory cost. The 2nd price benefit from Eashub is as a leading PCB Assembly solutions provider, we have a better contract price after we consolidate customers’ demand.
If you have a demand for high volume low, mixed electronics products, where those products have special requirements like component packages, component specifications, assembly technologies, levels of density, and manufacturing environments is required, Eashub is your ideal candidate, and As a reliable contract manufacturer, we are proficient in providing the PCB assembly services on high mix low volume products, our major facilities own decades years of building complex PCBA for automotive, industrial control customers
We don’t have a minimum order quantity request and favor the most complex design to continue enhancing our capability. Everybody shares the same goals of on-demand order fulfillment and lower costs of goods sold, but the ability to realize giants from the supply chain is not the same with totally different product mix and volume ratios. You must fix more challenges both on technology and supply chain on high mix low volume products than other products. Eashub is a professional who helps customers to fix challenges in the supply chain. Our expectation is to help small and middle-size companies, where most are providing high mix low, volume portfolios, to enjoy the leading supply chain services. You can quickly check Eashub’s capability on high mix low volume PCB Assembly as below：
|Features||High Mix Low Mix Volume||Eashub’s Capability or Solutions|
|Order Quantity by batch||<500pcs/order||Eashub’s facility has decades of manufacturing experience on variant high mix low volume electronics products.|
|Order Frequency||demand by quarter||Eashub normally reviews the frequency and figures out the best business model.|
|Trial Run Order Quantity||<100pcs/order||Eashub’s NPI capability supports demand starting from 1 pcs.|
|Application Area||Industrial Electronics||Multi facilities own both consumer and industrial electronics assembly experience.|
|Specialty||High Power, High Frequency||Eashub owns experience in manufacturing high power, high-frequency products for industrial control for Automotive and Telcom PCB Assmebly.|
|Application Requirement||High reliability, Safety||Eashub can meet the product application’s reliability, safety and environmental requirements.|
|Package Design||Yes||Eashub owns the capability of packaging design including recycle packages and one-time packages.|
|Certification||ISO9001, TF16949, TS13485, ESD2.0||Our core facility pass IATF16949, ISO13485, ESD2.0.|
|SMT||Down to 0201 size||Our SMT supports 01005 size|
|Performing||Yes||10% of Eashub’s components need performing before wave solder process|
|DIP||Majority needs DIP||All our facilities have DIP lines|
|ICT||Yes||Eashub’s standard process|
|FCT||Yes||Eashub’s standard process.|
|Aqueous Washing||Seldom needs Aqueous Washing Process||Eashub has Aqueous Washing capability.|
|Pin Insertion||Majority needs Pin Insertion Process||Eashub has Pin Insertion capability.|
|Crimping||Majority needs Crimping Process||Eashub has Crimping process.|
|ORT Test||Majority needs ORT Test||Eashub has ORT Test capability.|
|Aging Test||Majority needs Aging Test||Eashub can support aging test with or without loading.|
|Conformal Coating||Majority needs Conformal Coating||Eashub can support manual coating or auto coating.|
|Glue Process||Majority needs glue process||Eashub can support a few Glue process.|
|Assembly||Yes||Our standard process.|
|Fixture capability||Yes||Eashub can in-house design or outsource.|
|Quality Standard||IPC 2, IPC 3||Quality standards meet up to IPC 3.|
|NPI management||Yes||Dedicate Project manager for each customer, and regular gate review process coverage whole product life cycle time.|
|Warranty||Yes||1 year free warranty on PCBA.|
|Cost||Rational price||Recommend low cost sources, Consolidate demand to get a lower value-added cost, Eashub eliminates excess by supporting buy for demand.|
|Demand fulfillment||Response to order in short cycle time||Eashub has BTO model.|
|Quality||High yield pass ratio, tractability on key components||MES system|
|Tractability||Majority need||Eashub has bar code system.|
|Sourcing||Reliable supply bases support||Strictly AVL control by system driving and a quick process on vendors with qualification on vendors with qualification.|
|Gating Parts||Yes||Critical buffer or quick source fix the risk.|
|Excess||Big excess pressure causes by demand less than MOQ||Eashub buy based on actual demand quantity, Eashub has a leading intelligent supply chain tool to fix it.|
Compared with high volume PCBA, high mix low volume PCBA production efficiency is low, and the procurement cost is high. Moreover, it is difficult to achieve complete automation; the production plan and organization are more complex and usually encounter many difficulties, requiring PCBA manufacturers with rich experience.
EASHUB often uses the following methods to continuously improve low-volume PCB production and control the quality of PCB assembly. Next, let’s look at the steps that EASHUB takes to maintain PCB quality.
Low volume PCBA quality control steps
Low volume PCBA quality control can help reduce production costs and improve the accuracy of PCB development. To improve the qualification rate of SMT chip processing and the reliability of production sample quality, EASHUB will conduct PCB design, component procurement, process flow, and Production equipment and staffing are tracked and controlled throughout the process.
Among these control measures, SMT patch control is essential in the PCB manufacturing process. If there is a defect in SMT, let us cause bad results for our subsequent production. We can avoid it by ensuring that the SMT patch is qualified, so how does EASHUB make it?
EASHUB first uses inspection methods to control the quality of SMT patches, including incoming inspection, processing inspection and surface assembly board inspection.
SMT patch incoming inspection
Material inspection before SMT chip processing is a prerequisite to ensuring the quality of the chip. The quality of the PCB board, components, and SMT chip processing materials directly affect the quality of the PCB board. Therefore, we strictly check the below items according to the relevant regulations.
PCB board incoming inspection
1) Check whether the layout of the pad pattern, size, silk screen, solder mask, and via hole on the PCB design meets the SMT PCB board design specification requirements. (For example: check whether the silkscreen is printed on the pad, whether the distance between the pads is reasonable, whether the via hole is made on the pad, etc.).
2) The external dimensions of the PCB should be the same, and the dimensions of the positioning holes and datum marks of the PCB should meet the requirements of the production equipment.
3.) PCB allowable warpage size:
a) Upward/convex: max 0.2mm/5Omm length max 0.5mm/length direction of the whole PCB.
b) Downward/Concave: Maximum 0.2mm/5Omm length and maximum 1.5mm/length direction of the entire PCB.
4.) Inspect the PCB for improper transportation or storage damage.
SMT chip processing components incoming inspection
For the incoming inspection of components, we can conduct a sampling inspection through the quality inspection part. The inspection items mainly include pin coplanarity, usability and solderability.
First, the solderability of components is usually detected by using stainless steel tweezers to clamp the component body and immerse it in a tin pot at 230±5℃ or 235±5℃, take it out after 3±0.5s or 2±0.2s, and then put it under a 20 times microscope.
Next, check the soldering end’s soldering condition, and ensure that more than 90% of the soldering end of the component is tinned to be considered qualified.
The SMT workshop can do the following visual inspections:
1) Check whether the components’ marked value, specification, model, precision, external dimension, etc., are in line with the production process requirements.
2) Use a magnifying glass or visual inspection to check whether the component’s soldering end or lead surface is oxidized or contaminated.
3) The pins of SOT and SOIC cannot be deformed. Therefore, for multi-lead QFP devices with a lead spacing of less than 0.65mm, the coplanarity of the pins should be less than 0.1mm.
4) For components that need to be cleaned, we must ensure the components marked do not fall off after cleaning and do not affect the performance and reliability of the components.
SMT processing inspection
SMT chip processing and welding inspection is a comprehensive inspection of welded products. Generally, the items that need to be tested include: whether the spot welding surface is smooth and clean, whether there are holes, holes, etc.;
In SMT chip processing, to ensure the soldering quality of the printed circuit board, we must focus on whether the reflow soldering process parameters are reasonable. If the parameters are set incorrectly, it cannot guarantee the soldering quality of the printed circuit board. Therefore, we must conduct two furnace temperature tests and one low-temperature test daily under normal conditions.
By constantly improving the temperature curve of welding products and setting the temperature curve of welding products, we will ensure the quality of processed products.
Light reflection distribution measurement method
The welding part detects the decoration, the light is incident inward from the oblique direction, the TV camera is installed above, and it is inspected. The most important thing about this detection method is understanding the SMT solder’s surface angle, especially the illumination luminosity information. We must obtain the angle information through various light colors. Conversely, if it is irradiated from above, the angle measured is the reflected light distribution, and it is sufficient to check the inclined surface of the solder.
That is the method used to check the three-dimensional shape. Although there are already triangle-based, the observed results will be different since the triangulation method requires using different light incidents and directions.
Surface Mount Board Inspection
In addition to SMT incoming inspection and processing inspection, EASHUB will also carry out a strict quality inspection after the SMT patch is completed In the low volume PCB assembly process. Our common inspection methods include the triangulation method, light reflection distribution measurement method, transformation angle inspection, focus detection utilization method, etc.
Transform angle check
This detection method must have an auxiliary system with changing angles. This system generally has at least 5 cameras and multiple LED lighting equipment, which can be inspected with multiple images, and the reliability is relatively high.
Focus detection method
For some high-density circuit boards, the above three methods are difficult to detect whether the product has defects, so we usually need to use the focus detection and utilization method. This method can achieve detection through the multi-segment focus method. For example, we can directly detect the solder surface’s height, set 10 focal plane detections simultaneously, obtain the focal plane by finding the maximum output, and detect the position of the solder surface.
EASHUB adopted the above detection method to ensure the excellent quality of SMT in the PCB assembly process. From this, we know that after the quality problem is found in the inspection of incoming materials, solder paste printing and pre-soldering tempering, it can correct according to the rework situation. Therefore, it is a low impact on the reliability of electronic products.
However, after SMT welding, the detection of problems will cause huge losses. Furthermore, unqualified post-soldering repairs need to be re-soldered after desoldering. In addition to working time and materials, it will also damage components and circuit boards. Therefore, the best thing is that the material inspection and processing inspection before the SMT patch can effectively reduce the defect rate, reduce the cost of rework and maintenance, and avoid the occurrence of quality hazards from the source.
Therefore, We can ensure the reliability of SMT patch quality through strict quality inspection. After the SMT inspection, we often use the following high mix low volume production and quality management systems to obtain maximum benefits.
Reduced scrap rates during commissioning
Due to the different production product types, it must frequently modify the equipment’s parameters, replace the tools and fixtures, and compile or call the numerical control program to produce better products. If it does not match, substandard products will be produced, resulting in product scrap and loss.
Most failed products in low volume PCB production are caused by product changeover and debugging equipment. Therefore, reducing the scrap rate during the commissioning process for the high mix low volume production is very important. Furthermore, EASHUB can reduce the loss as much as possible by establishing detailed work instructions and standard operating procedures for the commissioning stage.
Our production work instructions include the required CNC programs, fixture numbers, inspection methods, and adjusting parameters. Therefore, before low volume production, fully consider various factors and prepare operation instructions, which can improve the accuracy and feasibility of debugging, effectively reduce the time for model change and debugging, and improve equipment utilization rate.
Advanced management concept
If PCB production is only regarded as a production workshop and other parts are not involved, it will be not easy to establish an effective quality management system. Therefore, high-quality PCB production requires the cooperation of various departments, strict quality control is needed for each process, and it must not bring the one failed process to the next.
EASHUB adopts a prevention-oriented strategy through a strict whole-process tracking supervision and management system to ensure that each PCB production process, equipment operation specifications, and quality inspection measures are recorded.
Furthermore, the managers continuously implement advanced management concepts and follow the existing rules and regulations to improve the existing deficiencies.
From the above, although the quality control of products is more difficult due to the low volume PCB manufacturing characteristics, it still can ensure the product quality by establishing detailed operation instructions, introducing advanced management concepts, and optimizing production steps.