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complex assemblies

Metal BGA

Electronics have become essential to daily life. Everything from refrigerators to military aircraft contains electronics. Today’s critical advanced assembly challenges mainly fall into three categories: performance, usability and productivity. To build and visualise product designs quickly and economically, engineers must address all these challenges.

On the other hand, manufacturing techniques are becoming more advanced and aesthetics are increasingly in demand. Project lifecycles and budgets are constrained. Sometimes, these constraints mean that DFM standards are overlooked in PCB design. For example, if the PCB has to fit in a box of fixed dimensions, the PCB design has to be tweaked accordingly. Or, components with different reflow profiles may be used on the same sid

Newer design houses or inexperienced engineers and designers may be prone to these mistakes. But not validating designs with tool and industry standards is bad practice. Here are just a few examples:

Pad mismatch

 If the copper termination pad separates partially or completely from the board, it can be hard to identify the fault; the pad may look intact as the solder usually remains attached to the component. The cause is usually mechanical strain that begins during testing, manufacturing, vibration while being transported or even when connectors are attached. PCB performance is impaired and performance is inconsistent. Extensive or even destructive testing may be required to positively identify the cause. Podrain follows a painstaking process to minimise the risk of damage from pad mismatch at each step.

No silkscreen. 

The silkscreen does not impact the electrical functionality of a PCB, but it is still extremely valuable as it provides essential information when assembling the PCB. It provides simple visual feedback that helps to catch deeper problems. It is not merely for aesthetic purposes. It is information that should not be separated from the board. Unique ID numbers, warning symbols, certifications etc. should be displayed on the board. At Podrain, we treat correct and comprehensive silkscreens as an integral part of the PCB.

THT vs. SMT components. 

When SMTs were developed in the 1980s they were expected to completely replace THTs. But THTs and SMTs are not always interchangeable. THTs offer reliable and useful in test and prototyping applications where frequent manual adjustments and replacements are needed. But SMTs are almost always more efficient and cost-effective. Podrain’s extensive experience in a wide range of applications gives us the expertise to know which type of components to use for a given project.

Incorrect polarity marking. 

To prevent polarised component packages from being inverted during assembly machine setup or manual soldering, accurate polarity marking is critical. It is only necessary for land patterns that have a specific rotation during assembly. Incorrect polarity markings can cause equipment damage, short-circuiting, serious injury, fires or even explosions. Podrain follows stringent Post Assembly Inspection Process protocols to visually validate that assembly insertion is done correctly

Incorrect component separation. 

Most designers are used to PCB clearance rules for spacing between traces in a single layer. However, many design houses overlook PCB clearance between layers. Today’s circuit designs often involve a single PCB with power and controls on the same substrate. This may put high-voltage traces close to low-voltage signals, creating a risk of arcing. The resulting sparks can permanently damage the port of the low-voltage component. Podrain designers and engineers keep ourselves up to date on the latest IPC-2221B design standards to ensure optimum manufacturability with minimum risk.

Podrain’s customers have brought us some interesting design challenges.

A top manufacturer of electric vehicle charging stations found that the PCBA yield was below 90%, lower than expected. The company approached Podrain to investigate. The issue was all the more challenging because the assembly was ROHS. Planning and finding the right profile, especially on a PCB that uses BGA + LGA, is an art.  By devoting our experienced people to solve this, we iterated through a range of 11 temperature profiles in a reflow oven within just 2 days to find the solution.

Another customer set us the challenge of setting the right profile for a board designed with a heavy BGA connector having multiple ceramic BGAs, including micro BGAs, on a 2mm thick PCB. The issue is these kind of connectors use very high temperature for soldering. 265 degree Celsius plus is needed for soldering but a normal BGA can tolerate only 245 to 255 degree Celsius. We designed and conducted multiple trials by changing the solder paste for each profile. After 15-20 trials supported by some fixtures, we were able to determine the best profile for the customer’s board.

Podrain has solved many such complex assembly design challenges for our customers.

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Access to capital: the Msme money maze

Capital Access that looks easy on paper is difficult in practice

The government’s Make in India strategy demonstrates how important MSMEs are to India’s growth story, but capital is still hard to get. If you are considering launching a startup, here are some things to keep in mind:

KEEP FRIENDS, FAMILY AND FOREIGN FUNDS CLOSE

Most credit schemes are aimed at MSMEs that are at least three years old. If your company is newer, informal sources like family and friends must be part of your fundraising strategy. Quite often, this means looking abroad for help. Even if you are looking at a VC / PE funding, the Indian ecosystem is in its infancy and you are likely to go beyond India’s borders. But this can lead to a problem. Indian financial institutions need at least 75% Indian ownership to qualify you for most of their loan products. This is intended to encourage Indian entrepreneurs, but as a startup that might be considering all options for support – make sure foreign investors hold less than 25%.

CAUTION: COLLATERAL AHEAD!

Typically, financial institutions ask for collateral that equals (or exceeds) the loan amount. This can be a term deposit or a mortgage on your home. Indian financial organizations are very cautious about lending. Read the loan terms carefully and include all supporting documentation with your application. 

PLEASE MIND THE GAP

The Small Industries Development Bank of India (SIDBI) was established to bring MSMEs and capital together. This is excellent news for MSMEs but the execution is not perfect. Rules can be unclear and confusing. Decision-making does not always follow the on-paper criteria. If your application is rejected, you may not know why.

Government schemes to support MSMEs working on Covid-19-related projects face similar challenges. Companies that qualify for credit on paper may still be rejected without an explanation.

WHAT CAN CHANGE

Podrain’s experience has taught us that patience is key. It also helps to have an experienced, trusted financial advisor or mentor who understands the options and provides guidance on processes and documentation. Some signposts and directions from financial institutions will make navigating easier.

MSMEs should be able to quickly and easily understand what each regulator is responsible for. Clearly stated eligibility rules for each scheme and a simple explanation of the risks and benefits of each option will help entrepreneurs who are not always financial experts make the right choice. A single-window approach to clearances will make MSMEs’ search for capital much easier. Regulators can also help to match MSMEs with the right funding source for their needs. We can then rely on financial institutions and their lending officers for guidance on the right capital products and schemes. 

Financial institutions also need to look beyond traditional collateral-based criteria. Very often these show only the borrower’s existing financial strength and not the intent to repay. To help new MSMEs get started, lenders may consider performance-based criteria to approve loans. For example, whether a startup pays its employees’ salaries, its taxes, and its statutory dues (GST, PF, etc.) on time is a good indication of its intent to pay. Market-based criteria used by PE/VC funds may also be used with modifications that reflect the lower risk appetite of the lender. These forward-looking strategies are consistent with the idea of financial institutions as partners in the Indian MSME growth story.

By adopting a partnership mindset, financial institutions can make capital more easily accessible to MSMEs who want to Make in India.

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Solder Paste

Solder Paste Choice

Solder paste printing attaches surface mount devices to printed circuit boards. Over 70% of Surface Mount Technology defects are driven by solder problems.* The choice of solder paste can make a huge difference. As devices and their components become smaller, the solder connections are also correspondingly finer. Its hard to fill apertures for these small devices with coarser type 3 solder paste. Type 2 solder paste is almost never used on Printed Circuit Boards. Rather, it features in power and industrial products where the chip package is bigger.  

 

Until 2017, India had easy access only to type 3 solder paste which has 25-45 microns powder size. While it is possible to use type 3 solder paste for lead pitch between 0.3mm and 0.02mm , the reliability and durability of the boards reduces. Type 4 solder paste yields better results in our experience. We also use a Solder Paste Inspection system to ensure the right amount has been used.

 

Podrain has been sourcing and utilising type 4 solder paste, even though it entails a 20%-30% higher cost for the past 4 years. Now, we see an across the industry move to Type 4 solder paste  and even the manufacture of Type 3 solder paste is coming down. We are currently evaluating switching to type 5 solder paste which has a powder size of 15-25 microns for components that need to go on the smallest PCB’s. 

 

So when you are looking for a provider to make your PCBA’s, go beyond looking at the machines on the assembly line, and ask what solder paste is used. 

 

*Biemans. 2011. “5D solder paste inspection merits beyond 3D technology.” Global SMT and Packaging 8-13 

References

https://blog.gotopac.com/2020/03/13/solder-paste-types-powder-sizes-for-smt-dispensing/

https://scholarworks.rit.edu/cgi/viewcontent.cgi?article=10208&context=theses

 

 

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