How Does FPC Patch Point Adhesive Reinforcement

More and more FPC soft board factory received the customer request point glue to strengthen the order, at the beginning do not know how to do, in fact this is not so complicated.First of all, choose a good dispensing machine.The foreign brands of glue dispenser include Musashi, EFD, Asymtek, CAMALOT, Sejong, Korea Alpa, IEI and LILE.Domestic brands are AXXON axis, Dongguan Anda, Shenzhen Huhaida and other brands, dispensing machine has controller dispensing machine, desktop dispensing machine, semi-automatic dispensing machine, automatic dispensing machine and other types.These models vary widely in price depending on the degree of automation.Each factory according to their own capacity, personnel and order status to choose the right model.

After choosing the glue machine, is to choose the appropriate glue.One - component epoxy resin adhesive is usually used for this adhesive.Epoxy resin itself is a liquid, which will not cure by itself, so curing agent should be added.Curing agent does not cross link with epoxy resin at room temperature. Only when heated to a certain temperature, can cross link reaction occur. At the same time, a certain amount of heat is released to promote the curing of glue.Epoxy resin adhesive after curing has high bonding strength, long time high temperature resistance 200-250℃, instant resistance (400℃) impact resistance, vibration resistance;Good acid and alkaline resistance, moisture-proof, water-proof, oil-proof and dustproof, moisture and heat resistance and atmospheric aging;The cured product has good electrical and physical properties of insulation, compression resistance, high bonding strength.

The glue should be kept at a low temperature and returned to the heat for about 2 hours before use.Before bonding, the bonding site should be cleaned with a cleaning agent to enhance bonding strength.

The most common problem of IC reinforcement glue in FPC is air bubbles and gas pits. Here, explain the reasons and solutions.

1, epoxy resin adhesive defoaming has two ways, one is autonomous defoaming (through the role of defoaming agent), the other is passive defoaming (through external forces such as grinding, vacuum, etc.), is generally used in combination of the two ways.

2, bubbles divided into two types: a "needle eye" (shallow, such as the size of needle head), a "gas hole" (about 1mm, deep, some can even see the substrate or gold thread, generally a glue point only one air hole);

"Pinhole" is generally the glue itself contains bubbles vacuum and not clean, or the improper selection of antifoaming agent or improper proportion, so that it cannot completely eliminate bubbles and other reasons.Epoxy resin adhesive industry in our country have developed for more than 20 years, this situation has a high probability of the glue market has basically eliminated it.

So today I will focus on the formation of "gas pit" mechanism and solutions.

First of all, we need to understand the curing principle of epoxy resin adhesives: generally, the curing agent used in single-component epoxy resin adhesives has a curing temperature of 110 degrees, which means that almost all single-component epoxy resin adhesives are cured by heating.From room temperature to 110 degrees, it is also the process of thickening to thinning the epoxy resin (without curing agent, the epoxy resin can be heated to be as thin as water).When it reaches about 110 degrees, the curing agent in the adhesive starts to work, enters the vitrification process (hardening process), and continues to heat until it is completely cured. The curing process is also an exothermic reaction, which in turn accelerates and promotes the curing reaction.

So where did the "air hole" come from?How does the air get into the glue?

The mechanism of gas hole is to encapsulate air to the inside of the point, the heated air expands, the heated air break through the rubber surface to surface tension, rushed out of the (" Fried ") of glue, and glue maybe just at this time in the glass transition temperature, reason of glue cannot be blasted to recover, and holes (that is, "crater").

In contrast, there are several situations in which air may be enclosed:

A. The glue is coarse and dry, and the particle size of the filler is large, so it is directly "placed" on the line, blocking the penetration of the glue;(Problems of glue manufacturers)

B. If the glue is applied in the wrong way, click once to seal the air inside.

C. The preheating of the glue solution is not enough, which is relatively thick and cannot penetrate;

Therefore, to solve the problem of "air pit" is to control, improve and improve from the above points.

Gum manufacturers to improve, the automatic foam elimination ability of the gum is strong, will certainly eliminate part of the air, although this is not reliable, can not guarantee 100% elimination of air, but "air pit" type defective rate can be greatly reduced.

The user of glue should also take corresponding measures, namely (1) from the point of glue way: this has a lot to do with the point of glue way, it is recommended to point IC around when linking point, and first point one side, point the full version and then point the other side, so that the front point of glue penetration holes will force out the air.

(2), from the perspective of the dispensing after baking way: after dispensing toasted sectional to soft board, 70 first bake for a period of time, then, in more than 120 degrees bake for a period of time, the principle is to low temperature baking of sealed air heat expansion and ran out from under the adhesive solution, the glue isn't as critical temperature to the glass, will appear holes backfilling, then 120 degrees bake when no air inside, glue solidified no bubbles formed holes appearance.