What does the customer liaison at a test-and-assembly house do?

The customer liaison at a test-and-assembly house is the person in the middle whose job is to make things clear. They take what the customer wants, the specs, the dates, the revisions, and pass it to the factory correctly. They take what is happening in the factory, the yield, the problems, whether this batch can ship, and explain it to the customer in words the customer can use. The job has no single title, and each company divides the work differently. This article describes the general picture.

Why does a test-and-assembly house need a customer liaison?

First, assembly and test is the stage after the wafer fab: the chips are tested, cut apart, put into a package and tested again before they can be soldered onto a circuit board. For why chips need a package at all, see What is chip packaging?.

Many chip companies have no test-and-assembly house of their own, so they send this stage to a factory that specializes in it (see What is an OSAT?). One house often runs work for several customers at once, and each has its own products, specs and packing.

The customer won't go around to Test, Assembly and QA one by one, and each station on the line won't call the customer on its own. Someone has to stand in between: when the customer needs something, that person knows whom to ask; when the factory has news, it goes to that person first.

Think of the front of house in a restaurant. A diner says "no cilantro, and we need it by eight", and the server passes that to the kitchen word for word. The kitchen says "this dish needs another twenty minutes", and the server goes back to the table, tells them, and asks whether they'd like something else.

How do the customer's requirements reach the factory?

Most of what the customer wants is written in the specs:

• What to test: which items to measure on every chip, and what counts as a pass. This goes into the test program, which the tester follows.
• How to pack it: what to print on the package, how many parts go on each reel of tape and reel, and how parts that fear moisture get a dry pack.
• When it's needed: which day, and how many.

The liaison has to understand all of this first, then make sure every station is working from the right copy.

The riskiest moment is a revision. When the customer changes a spec or a drawing, the new version has to reach every station and the old one has to be withdrawn, or someone will keep working from the old one. The international quality management standard also requires version control when documents change.

It works the other way too. If the factory wants to change a material or a method, and the change could affect form, fit, function, quality or reliability, industry standards require formal notice to the customer. It can't be changed quietly.

How does the factory's status get explained to the customer?

The customer isn't on the floor and doesn't need to hear about every tool. What they usually want to know comes down to three things: quantity, time and quality.

What the factory says	What the customer hears
Final test yield is below target	This week's shipment will be a little smaller than planned; we're looking into why and will update you tomorrow afternoon
One wire bonder is down for readjustment	Part of this batch will be a day late; the rest is on schedule
A few trays are being held back	A few trays won't ship until we've checked them

One example is yield, the share of finished chips that are good (see What does "yield" mean in chip news?). When a customer hears the yield has dropped, what they really want to know is how many parts they'll be short, when that can be made up, and whether anything already shipped is affected. The liaison should have those three answers ready.

Parts that fail are sorted by how they failed into different groups called bins. Which bin is growing is a clue the customer will want to see. For how testing works, see How are chips tested?.

What has to be checked before a shipment goes out?

Before shipping, there is usually a checklist to go through item by item:

1. Are the records complete? What each station did and measured can be looked up.
2. Do the counts add up? How many went into each station, how many came out, how many were scrapped: together they must equal what came in at the start. Even one missing part needs an explanation of where it went.
3. Is the quality there? Is the final test yield above target? Is any lot still on hold and not yet cleared?
4. Reliability. For some products a sample is run hot with power applied for a while, to see whether the batch has early-life failures, chips that fail soon after they go into use (see What is burn-in?).
5. Packing and labels. The reels, the dry pack and the lot numbers are all correct, so every reel can be traced back to its batch.

If one item doesn't fully meet the spec, there are roughly three paths: fix it, retest it or screen it again before shipping; scrap it; or explain the situation and ask the customer whether they'll take it. Quality management standards call the last one a concession: an out-of-spec product can be released only with that permission, and usually only for a set quantity, a set period or a specific use.

The point is that nobody ships something because it "should be fine". Accepting it is the customer's decision; the liaison's job is to explain the situation well enough that the customer can make it. For how QA guards that gate, see What does QA (quality assurance) do in a chip fab?.

When something goes wrong, how do you tell the customer?

A problem isn't always a broken chip. The industry standard for handling component quality problems also counts the wrong quantity, parts facing the wrong way, and errors on labels or paperwork. So a count that doesn't add up deserves the same care as a part that won't power on.

The usual approach:

• Tell them early. As soon as you know there's a problem, tell the customer what happened, which batches are affected, what has already been done, and when the next update will come. The full report can follow.
• Stop the damage first. Hold back whatever hasn't shipped, and check whether other batches have the same problem. This is containment.
• Say only what is certain. Keep apart what was checked, what was seen and what isn't known yet. If the cause isn't confirmed, say it's still being investigated; don't jump to a conclusion.
• Put it in a report. Once the cause is clear, write an incident report. A common format is the 8D: describe the problem, contain it, find the root cause, choose a fix, prevent it from happening again. The report is there to make the cause clear, not to find someone to blame.

Parts the customer sends back usually get a return form first, an RMA, and then failure analysis to find where and why they failed.

Why does explaining things clearly matter most?

Because the customer can't see inside the factory. Whether to change their own line's schedule, whether to warn their own customers, whether to order extra stock: all of it rests on what the liaison tells them. One unclear sentence can lead both sides to do the wrong thing.

Bad news that comes early and clearly is often better than good news that later turns out to be wrong. The numbers have to match the records, and anything uncertain is said to be uncertain.

The same goes for colleagues in the factory. When the customer is in a hurry, the liaison explains why it's urgent and how urgent, instead of passing the pressure straight down the line. When both sides lay things out calmly and clearly, problems get solved faster.

In fab24hr

In fab24hr, the customer liaison is one of the roles at the test-and-assembly house: tap "Clock in", choose "A day in the fab", tap "Test-and-assembly house" on the "Your role today" card and swipe to the customer liaison. All four shifts fall on the day before shipping. On the late-night shift, the customer's line calls in the middle of the night to say our packing drawing doesn't match their machine's setting; when you compare the two, pin 1 on our drawing (where the pin numbering starts; the machine uses it to tell which way a chip faces) is turned half a turn. On the morning shift, an engineering sample comes back because it won't power on, and you go through it item by item in the reliability lab, then decide whether to reply now or wait for the full report. On the afternoon shift, the counts from every station come up a few short, and you decide whether to ship short and say so, or fill the order from the next batch. The evening shift is chapter 12 of the main story, The life of a chip, "The Night Before Shipping": after you go through the pre-shipment checklist with Mei-Hua from QA, the customer asks whether it can ship tomorrow, and you decide whether to run a two-day early-life failure sample and ship the whole batch a week late, or ship tomorrow as planned. The test-and-assembly house, the customer, the people and the numbers in the game are fictional; what the role does follows public, general sources, and every factory divides the work differently.